summaryrefslogtreecommitdiffstatshomepage
path: root/docs/source
diff options
context:
space:
mode:
author hap <happppp@users.noreply.github.com>2025-02-05 16:44:39 +0100
committer hap <happppp@users.noreply.github.com>2025-02-05 16:49:57 +0100
commitae474c5e7c79c19c01b3f5c2884bfa905d2df14b (patch)
treeb2201b3ceb21b720c8583e4bcb3e67d35b6c69de /docs/source
parentcea7758f4f5b4c26dde9646caeb0785607c817a5 (diff)
kim1: add view toggle for keypad
Diffstat (limited to 'docs/source')
0 files changed, 0 insertions, 0 deletions
a> 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286
// license:BSD-3-Clause
// copyright-holders:Aaron Giles
/***************************************************************************

    chd.c

    MAME Compressed Hunks of Data file format

***************************************************************************/

#include <assert.h>

#include "chd.h"
#include "avhuff.h"
#include "hashing.h"
#include "flac.h"
#include "cdrom.h"
#include "coretmpl.h"
#include <zlib.h>
#include <time.h>
#include <stddef.h>
#include <stdlib.h>
#include <new>
#include "eminline.h"


//**************************************************************************
//  CONSTANTS
//**************************************************************************

// standard metadata formats
const char *HARD_DISK_METADATA_FORMAT = "CYLS:%d,HEADS:%d,SECS:%d,BPS:%d";
const char *CDROM_TRACK_METADATA_FORMAT = "TRACK:%d TYPE:%s SUBTYPE:%s FRAMES:%d";
const char *CDROM_TRACK_METADATA2_FORMAT = "TRACK:%d TYPE:%s SUBTYPE:%s FRAMES:%d PREGAP:%d PGTYPE:%s PGSUB:%s POSTGAP:%d";
const char *GDROM_TRACK_METADATA_FORMAT = "TRACK:%d TYPE:%s SUBTYPE:%s FRAMES:%d PAD:%d PREGAP:%d PGTYPE:%s PGSUB:%s POSTGAP:%d";
const char *AV_METADATA_FORMAT = "FPS:%d.%06d WIDTH:%d HEIGHT:%d INTERLACED:%d CHANNELS:%d SAMPLERATE:%d";

static const uint32_t METADATA_HEADER_SIZE = 16;          // metadata header size

static const uint8_t V34_MAP_ENTRY_FLAG_TYPE_MASK = 0x0f;     // what type of hunk
static const uint8_t V34_MAP_ENTRY_FLAG_NO_CRC = 0x10;        // no CRC is present



// V3-V4 entry types
enum
{
	V34_MAP_ENTRY_TYPE_INVALID = 0,             // invalid type
	V34_MAP_ENTRY_TYPE_COMPRESSED = 1,          // standard compression
	V34_MAP_ENTRY_TYPE_UNCOMPRESSED = 2,        // uncompressed data
	V34_MAP_ENTRY_TYPE_MINI = 3,                // mini: use offset as raw data
	V34_MAP_ENTRY_TYPE_SELF_HUNK = 4,           // same as another hunk in this file
	V34_MAP_ENTRY_TYPE_PARENT_HUNK = 5,         // same as a hunk in the parent file
	V34_MAP_ENTRY_TYPE_2ND_COMPRESSED = 6       // compressed with secondary algorithm (usually FLAC CDDA)
};

// V5 compression types
enum
{
	///< codec #0
	// these types are live when running
	COMPRESSION_TYPE_0 = 0,
	///< codec #1
	COMPRESSION_TYPE_1 = 1,
	///< codec #2
	COMPRESSION_TYPE_2 = 2,
	///< codec #3
	COMPRESSION_TYPE_3 = 3,
	///< no compression; implicit length = hunkbytes
	COMPRESSION_NONE = 4,
	///< same as another block in this chd
	COMPRESSION_SELF = 5,
	///< same as a hunk's worth of units in the parent chd
	COMPRESSION_PARENT = 6,

	///< start of small RLE run (4-bit length)
	// these additional pseudo-types are used for compressed encodings:
	COMPRESSION_RLE_SMALL,
	///< start of large RLE run (8-bit length)
	COMPRESSION_RLE_LARGE,
	///< same as the last COMPRESSION_SELF block
	COMPRESSION_SELF_0,
	///< same as the last COMPRESSION_SELF block + 1
	COMPRESSION_SELF_1,
	///< same block in the parent
	COMPRESSION_PARENT_SELF,
	///< same as the last COMPRESSION_PARENT block
	COMPRESSION_PARENT_0,
	///< same as the last COMPRESSION_PARENT block + 1
	COMPRESSION_PARENT_1
};



//**************************************************************************
//  TYPE DEFINITIONS
//**************************************************************************

// ======================> metadata_entry

// description of where a metadata entry lives within the file
struct chd_file::metadata_entry
{
	uint64_t                  offset;         // offset within the file of the header
	uint64_t                  next;           // offset within the file of the next header
	uint64_t                  prev;           // offset within the file of the previous header
	uint32_t                  length;         // length of the metadata
	uint32_t                  metatag;        // metadata tag
	uint8_t                   flags;          // flag bits
};


// ======================> metadata_hash

struct chd_file::metadata_hash
{
	uint8_t                   tag[4];         // tag of the metadata in big-endian
	util::sha1_t            sha1;           // hash data
};



//**************************************************************************
//  INLINE FUNCTIONS
//**************************************************************************

//-------------------------------------------------
//  be_read - extract a big-endian number from
//  a byte buffer
//-------------------------------------------------

inline uint64_t chd_file::be_read(const uint8_t *base, int numbytes)
{
	uint64_t result = 0;
	while (numbytes--)
		result = (result << 8) | *base++;
	return result;
}


//-------------------------------------------------
//  be_write - write a big-endian number to a byte
//  buffer
//-------------------------------------------------

inline void chd_file::be_write(uint8_t *base, uint64_t value, int numbytes)
{
	base += numbytes;
	while (numbytes--)
	{
		*--base = value;
		value >>= 8;
	}
}


//-------------------------------------------------
//  be_read_sha1 - fetch a sha1_t from a data
//  stream in bigendian order
//-------------------------------------------------

inline util::sha1_t chd_file::be_read_sha1(const uint8_t *base)
{
	util::sha1_t result;
	memcpy(&result.m_raw[0], base, sizeof(result.m_raw));
	return result;
}


//-------------------------------------------------
//  be_write_sha1 - write a sha1_t to a data
//  stream in bigendian order
//-------------------------------------------------

inline void chd_file::be_write_sha1(uint8_t *base, util::sha1_t value)
{
	memcpy(base, &value.m_raw[0], sizeof(value.m_raw));
}


//-------------------------------------------------
//  file_read - read from the file at the given
//  offset; on failure throw an error
//-------------------------------------------------

inline void chd_file::file_read(uint64_t offset, void *dest, uint32_t length)
{
	// no file = failure
	if (m_file == nullptr)
		throw CHDERR_NOT_OPEN;

	// seek and read
	m_file->seek(offset, SEEK_SET);
	uint32_t count = m_file->read(dest, length);
	if (count != length)
		throw CHDERR_READ_ERROR;
}


//-------------------------------------------------
//  file_write - write to the file at the given
//  offset; on failure throw an error
//-------------------------------------------------

inline void chd_file::file_write(uint64_t offset, const void *source, uint32_t length)
{
	// no file = failure
	if (m_file == nullptr)
		throw CHDERR_NOT_OPEN;

	// seek and write
	m_file->seek(offset, SEEK_SET);
	uint32_t count = m_file->write(source, length);
	if (count != length)
		throw CHDERR_WRITE_ERROR;
}


//-------------------------------------------------
//  file_append - append to the file at the given
//  offset, ensuring we start at the given
//  alignment; on failure throw an error
//-------------------------------------------------

inline uint64_t chd_file::file_append(const void *source, uint32_t length, uint32_t alignment)
{
	// no file = failure
	if (m_file == nullptr)
		throw CHDERR_NOT_OPEN;

	// seek to the end and align if necessary
	m_file->seek(0, SEEK_END);
	if (alignment != 0)
	{
		uint64_t offset = m_file->tell();
		uint32_t delta = offset % alignment;
		if (delta != 0)
		{
			// pad with 0's from a local buffer
			uint8_t buffer[1024];
			memset(buffer, 0, sizeof(buffer));
			delta = alignment - delta;
			while (delta != 0)
			{
				uint32_t bytes_to_write = (std::min<std::size_t>)(sizeof(buffer), delta);
				uint32_t count = m_file->write(buffer, bytes_to_write);
				if (count != bytes_to_write)
					throw CHDERR_WRITE_ERROR;
				delta -= bytes_to_write;
			}
		}
	}

	// write the real data
	uint64_t offset = m_file->tell();
	uint32_t count = m_file->write(source, length);
	if (count != length)
		throw CHDERR_READ_ERROR;
	return offset;
}


//-------------------------------------------------
//  bits_for_value - return the number of bits
//  necessary to represent all numbers 0..value
//-------------------------------------------------

inline uint8_t chd_file::bits_for_value(uint64_t value)
{
	uint8_t result = 0;
	while (value != 0)
		value >>= 1, result++;
	return result;
}



//**************************************************************************
//  CHD FILE MANAGEMENT
//**************************************************************************

/**
 * @fn  chd_file::chd_file()
 *
 * @brief   -------------------------------------------------
 *            chd_file - constructor
 *          -------------------------------------------------.
 */

chd_file::chd_file()
	: m_file(nullptr),
		m_owns_file(false)
{
	// reset state
	memset(m_decompressor, 0, sizeof(m_decompressor));
	close();
}

/**
 * @fn  chd_file::~chd_file()
 *
 * @brief   -------------------------------------------------
 *            ~chd_file - destructor
 *          -------------------------------------------------.
 */

chd_file::~chd_file()
{
	// close any open files
	close();
}

/**
 * @fn  util::sha1_t chd_file::sha1()
 *
 * @brief   -------------------------------------------------
 *            sha1 - return our SHA1 value
 *          -------------------------------------------------.
 *
 * @return  A sha1_t.
 */

util::sha1_t chd_file::sha1()
{
	try
	{
		// read the big-endian version
		uint8_t rawbuf[sizeof(util::sha1_t)];
		file_read(m_sha1_offset, rawbuf, sizeof(rawbuf));
		return be_read_sha1(rawbuf);
	}
	catch (chd_error &)
	{
		// on failure, return nullptr
		return util::sha1_t::null;
	}
}

/**
 * @fn  util::sha1_t chd_file::raw_sha1()
 *
 * @brief   -------------------------------------------------
 *            raw_sha1 - return our raw SHA1 value
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_UNSUPPORTED_VERSION  Thrown when a chderr unsupported version error
 *                                          condition occurs.
 *
 * @return  A sha1_t.
 */

util::sha1_t chd_file::raw_sha1()
{
	try
	{
		// determine offset within the file for data-only
		if (m_rawsha1_offset == 0)
			throw CHDERR_UNSUPPORTED_VERSION;

		// read the big-endian version
		uint8_t rawbuf[sizeof(util::sha1_t)];
		file_read(m_rawsha1_offset, rawbuf, sizeof(rawbuf));
		return be_read_sha1(rawbuf);
	}
	catch (chd_error &)
	{
		// on failure, return nullptr
		return util::sha1_t::null;
	}
}

/**
 * @fn  util::sha1_t chd_file::parent_sha1()
 *
 * @brief   -------------------------------------------------
 *            parent_sha1 - return our parent's SHA1 value
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_UNSUPPORTED_VERSION  Thrown when a chderr unsupported version error
 *                                          condition occurs.
 *
 * @return  A sha1_t.
 */

util::sha1_t chd_file::parent_sha1()
{
	try
	{
		// determine offset within the file
		if (m_parentsha1_offset == 0)
			throw CHDERR_UNSUPPORTED_VERSION;

		// read the big-endian version
		uint8_t rawbuf[sizeof(util::sha1_t)];
		file_read(m_parentsha1_offset, rawbuf, sizeof(rawbuf));
		return be_read_sha1(rawbuf);
	}
	catch (chd_error &)
	{
		// on failure, return nullptr
		return util::sha1_t::null;
	}
}

/**
 * @fn  chd_error chd_file::hunk_info(uint32_t hunknum, chd_codec_type &compressor, uint32_t &compbytes)
 *
 * @brief   -------------------------------------------------
 *            hunk_info - return information about this hunk
 *          -------------------------------------------------.
 *
 * @param   hunknum             The hunknum.
 * @param [in,out]  compressor  The compressor.
 * @param [in,out]  compbytes   The compbytes.
 *
 * @return  A chd_error.
 */

chd_error chd_file::hunk_info(uint32_t hunknum, chd_codec_type &compressor, uint32_t &compbytes)
{
	// error if invalid
	if (hunknum >= m_hunkcount)
		return CHDERR_HUNK_OUT_OF_RANGE;

	// get the map pointer
	uint8_t *rawmap;
	switch (m_version)
	{
		// v3/v4 map entries
		case 3:
		case 4:
			rawmap = &m_rawmap[16 * hunknum];
			switch (rawmap[15] & V34_MAP_ENTRY_FLAG_TYPE_MASK)
			{
				case V34_MAP_ENTRY_TYPE_COMPRESSED:
					compressor = CHD_CODEC_ZLIB;
					compbytes = be_read(&rawmap[12], 2) + (rawmap[14] << 16);
					break;

				case V34_MAP_ENTRY_TYPE_UNCOMPRESSED:
					compressor = CHD_CODEC_NONE;
					compbytes = m_hunkbytes;
					break;

				case V34_MAP_ENTRY_TYPE_MINI:
					compressor = CHD_CODEC_MINI;
					compbytes = 0;
					break;

				case V34_MAP_ENTRY_TYPE_SELF_HUNK:
					compressor = CHD_CODEC_SELF;
					compbytes = 0;
					break;

				case V34_MAP_ENTRY_TYPE_PARENT_HUNK:
					compressor = CHD_CODEC_PARENT;
					compbytes = 0;
					break;
			}
			break;

		// v5 map entries
		case 5:
			rawmap = &m_rawmap[m_mapentrybytes * hunknum];

			// uncompressed case
			if (!compressed())
			{
				if (be_read(&rawmap[0], 4) == 0)
				{
					compressor = CHD_CODEC_PARENT;
					compbytes = 0;
				}
				else
				{
					compressor = CHD_CODEC_NONE;
					compbytes = m_hunkbytes;
				}
				break;
			}

			// compressed case
			switch (rawmap[0])
			{
				case COMPRESSION_TYPE_0:
				case COMPRESSION_TYPE_1:
				case COMPRESSION_TYPE_2:
				case COMPRESSION_TYPE_3:
					compressor = m_compression[rawmap[0]];
					compbytes = be_read(&rawmap[1], 3);
					break;

				case COMPRESSION_NONE:
					compressor = CHD_CODEC_NONE;
					compbytes = m_hunkbytes;
					break;

				case COMPRESSION_SELF:
					compressor = CHD_CODEC_SELF;
					compbytes = 0;
					break;

				case COMPRESSION_PARENT:
					compressor = CHD_CODEC_PARENT;
					compbytes = 0;
					break;

				default:
					return CHDERR_UNKNOWN_COMPRESSION;
			}
			break;
	}
	return CHDERR_NONE;
}

/**
 * @fn  void chd_file::set_raw_sha1(sha1_t rawdata)
 *
 * @brief   -------------------------------------------------
 *            set_raw_sha1 - set our SHA1 values
 *          -------------------------------------------------.
 *
 * @param   rawdata The rawdata.
 */

void chd_file::set_raw_sha1(util::sha1_t rawdata)
{
	// create a big-endian version
	uint8_t rawbuf[sizeof(util::sha1_t)];
	be_write_sha1(rawbuf, rawdata);

	// write to the header
	uint64_t offset = (m_rawsha1_offset != 0) ? m_rawsha1_offset : m_sha1_offset;
	assert(offset != 0);
	file_write(offset, rawbuf, sizeof(rawbuf));

	// if we have a separate rawsha1_offset, update the full sha1 as well
	if (m_rawsha1_offset != 0)
		metadata_update_hash();
}

/**
 * @fn  void chd_file::set_parent_sha1(sha1_t parent)
 *
 * @brief   -------------------------------------------------
 *            set_parent_sha1 - set the parent SHA1 value
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_INVALID_FILE Thrown when a chderr invalid file error condition occurs.
 *
 * @param   parent  The parent.
 */

void chd_file::set_parent_sha1(util::sha1_t parent)
{
	// if no file, fail
	if (m_file == nullptr)
		throw CHDERR_INVALID_FILE;

	// create a big-endian version
	uint8_t rawbuf[sizeof(util::sha1_t)];
	be_write_sha1(rawbuf, parent);

	// write to the header
	assert(m_parentsha1_offset != 0);
	file_write(m_parentsha1_offset, rawbuf, sizeof(rawbuf));
}

/**
 * @fn  chd_error chd_file::create(util::core_file &file, uint64_t logicalbytes, uint32_t hunkbytes, uint32_t unitbytes, chd_codec_type compression[4])
 *
 * @brief   -------------------------------------------------
 *            create - create a new file with no parent using an existing opened file handle
 *          -------------------------------------------------.
 *
 * @param [in,out]  file    The file.
 * @param   logicalbytes    The logicalbytes.
 * @param   hunkbytes       The hunkbytes.
 * @param   unitbytes       The unitbytes.
 * @param   compression     The compression.
 *
 * @return  A chd_error.
 */

chd_error chd_file::create(util::core_file &file, uint64_t logicalbytes, uint32_t hunkbytes, uint32_t unitbytes, chd_codec_type compression[4])
{
	// make sure we don't already have a file open
	if (m_file != nullptr)
		return CHDERR_ALREADY_OPEN;

	// set the header parameters
	m_logicalbytes = logicalbytes;
	m_hunkbytes = hunkbytes;
	m_unitbytes = unitbytes;
	memcpy(m_compression, compression, sizeof(m_compression));
	m_parent = nullptr;

	// take ownership of the file
	m_file = &file;
	m_owns_file = false;
	return create_common();
}

/**
 * @fn  chd_error chd_file::create(util::core_file &file, uint64_t logicalbytes, uint32_t hunkbytes, chd_codec_type compression[4], chd_file &parent)
 *
 * @brief   -------------------------------------------------
 *            create - create a new file with a parent using an existing opened file handle
 *          -------------------------------------------------.
 *
 * @param [in,out]  file    The file.
 * @param   logicalbytes    The logicalbytes.
 * @param   hunkbytes       The hunkbytes.
 * @param   compression     The compression.
 * @param [in,out]  parent  The parent.
 *
 * @return  A chd_error.
 */

chd_error chd_file::create(util::core_file &file, uint64_t logicalbytes, uint32_t hunkbytes, chd_codec_type compression[4], chd_file &parent)
{
	// make sure we don't already have a file open
	if (m_file != nullptr)
		return CHDERR_ALREADY_OPEN;

	// set the header parameters
	m_logicalbytes = logicalbytes;
	m_hunkbytes = hunkbytes;
	m_unitbytes = parent.unit_bytes();
	memcpy(m_compression, compression, sizeof(m_compression));
	m_parent = &parent;

	// take ownership of the file
	m_file = &file;
	m_owns_file = false;
	return create_common();
}

/**
 * @fn  chd_error chd_file::create(const char *filename, uint64_t logicalbytes, uint32_t hunkbytes, uint32_t unitbytes, chd_codec_type compression[4])
 *
 * @brief   -------------------------------------------------
 *            create - create a new file with no parent using a filename
 *          -------------------------------------------------.
 *
 * @param   filename        Filename of the file.
 * @param   logicalbytes    The logicalbytes.
 * @param   hunkbytes       The hunkbytes.
 * @param   unitbytes       The unitbytes.
 * @param   compression     The compression.
 *
 * @return  A chd_error.
 */

chd_error chd_file::create(const char *filename, uint64_t logicalbytes, uint32_t hunkbytes, uint32_t unitbytes, chd_codec_type compression[4])
{
	// make sure we don't already have a file open
	if (m_file != nullptr)
		return CHDERR_ALREADY_OPEN;

	// create the new file
	util::core_file::ptr file;
	const osd_file::error filerr = util::core_file::open(filename, OPEN_FLAG_READ | OPEN_FLAG_WRITE | OPEN_FLAG_CREATE, file);
	if (filerr != osd_file::error::NONE)
		return CHDERR_FILE_NOT_FOUND;

	// create the file normally, then claim the file
	const chd_error chderr = create(*file, logicalbytes, hunkbytes, unitbytes, compression);
	m_owns_file = true;

	// if an error happened, close and delete the file
	if (chderr != CHDERR_NONE)
	{
		file.reset();
		osd_file::remove(filename);
	}
	else
	{
		file.release();
	}
	return chderr;
}

/**
 * @fn  chd_error chd_file::create(const char *filename, uint64_t logicalbytes, uint32_t hunkbytes, chd_codec_type compression[4], chd_file &parent)
 *
 * @brief   -------------------------------------------------
 *            create - create a new file with a parent using a filename
 *          -------------------------------------------------.
 *
 * @param   filename        Filename of the file.
 * @param   logicalbytes    The logicalbytes.
 * @param   hunkbytes       The hunkbytes.
 * @param   compression     The compression.
 * @param [in,out]  parent  The parent.
 *
 * @return  A chd_error.
 */

chd_error chd_file::create(const char *filename, uint64_t logicalbytes, uint32_t hunkbytes, chd_codec_type compression[4], chd_file &parent)
{
	// make sure we don't already have a file open
	if (m_file != nullptr)
		return CHDERR_ALREADY_OPEN;

	// create the new file
	util::core_file::ptr file;
	const osd_file::error filerr = util::core_file::open(filename, OPEN_FLAG_READ | OPEN_FLAG_WRITE | OPEN_FLAG_CREATE, file);
	if (filerr != osd_file::error::NONE)
		return CHDERR_FILE_NOT_FOUND;

	// create the file normally, then claim the file
	const chd_error chderr = create(*file, logicalbytes, hunkbytes, compression, parent);
	m_owns_file = true;

	// if an error happened, close and delete the file
	if (chderr != CHDERR_NONE)
	{
		file.reset();
		osd_file::remove(filename);
	}
	else
	{
		file.release();
	}
	return chderr;
}

/**
 * @fn  chd_error chd_file::open(const char *filename, bool writeable, chd_file *parent)
 *
 * @brief   -------------------------------------------------
 *            open - open an existing file for read or read/write
 *          -------------------------------------------------.
 *
 * @param   filename        Filename of the file.
 * @param   writeable       true if writeable.
 * @param [in,out]  parent  If non-null, the parent.
 *
 * @return  A chd_error.
 */

chd_error chd_file::open(const char *filename, bool writeable, chd_file *parent)
{
	// make sure we don't already have a file open
	if (m_file != nullptr)
		return CHDERR_ALREADY_OPEN;

	// open the file
	const uint32_t openflags = writeable ? (OPEN_FLAG_READ | OPEN_FLAG_WRITE) : OPEN_FLAG_READ;
	util::core_file::ptr file;
	const osd_file::error filerr = util::core_file::open(filename, openflags, file);
	if (filerr != osd_file::error::NONE)
		return CHDERR_FILE_NOT_FOUND;

	// now open the CHD
	chd_error err = open(*file, writeable, parent);
	if (err != CHDERR_NONE)
		return err;

	// we now own this file
	file.release();
	m_owns_file = true;
	return err;
}

/**
 * @fn  chd_error chd_file::open(util::core_file &file, bool writeable, chd_file *parent)
 *
 * @brief   -------------------------------------------------
 *            open - open an existing file for read or read/write
 *          -------------------------------------------------.
 *
 * @param [in,out]  file    The file.
 * @param   writeable       true if writeable.
 * @param [in,out]  parent  If non-null, the parent.
 *
 * @return  A chd_error.
 */

chd_error chd_file::open(util::core_file &file, bool writeable, chd_file *parent)
{
	// make sure we don't already have a file open
	if (m_file != nullptr)
		return CHDERR_ALREADY_OPEN;

	// open the file
	m_file = &file;
	m_owns_file = false;
	m_parent = parent;
	m_cachehunk = ~0;
	return open_common(writeable);
}

/**
 * @fn  void chd_file::close()
 *
 * @brief   -------------------------------------------------
 *            close - close a CHD file for access
 *          -------------------------------------------------.
 */

void chd_file::close()
{
	// reset file characteristics
	if (m_owns_file && m_file)
		delete m_file;
	m_file = nullptr;
	m_owns_file = false;
	m_allow_reads = false;
	m_allow_writes = false;

	// reset core parameters from the header
	m_version = HEADER_VERSION;
	m_logicalbytes = 0;
	m_mapoffset = 0;
	m_metaoffset = 0;
	m_hunkbytes = 0;
	m_hunkcount = 0;
	m_unitbytes = 0;
	m_unitcount = 0;
	memset(m_compression, 0, sizeof(m_compression));
	m_parent = nullptr;
	m_parent_missing = false;

	// reset key offsets within the header
	m_mapoffset_offset = 0;
	m_metaoffset_offset = 0;
	m_sha1_offset = 0;
	m_rawsha1_offset = 0;
	m_parentsha1_offset = 0;

	// reset map information
	m_mapentrybytes = 0;
	m_rawmap.clear();

	// reset compression management
	for (auto & elem : m_decompressor)
	{
		delete elem;
		elem = nullptr;
	}
	m_compressed.clear();

	// reset caching
	m_cache.clear();
	m_cachehunk = ~0;
}

/**
 * @fn  chd_error chd_file::read_hunk(uint32_t hunknum, void *buffer)
 *
 * @brief   -------------------------------------------------
 *            read - read a single hunk from the CHD file
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_NOT_OPEN             Thrown when a chderr not open error condition occurs.
 * @exception   CHDERR_HUNK_OUT_OF_RANGE    Thrown when a chderr hunk out of range error
 *                                          condition occurs.
 * @exception   CHDERR_DECOMPRESSION_ERROR  Thrown when a chderr decompression error error
 *                                          condition occurs.
 * @exception   CHDERR_REQUIRES_PARENT      Thrown when a chderr requires parent error condition
 *                                          occurs.
 * @exception   CHDERR_READ_ERROR           Thrown when a chderr read error error condition
 *                                          occurs.
 *
 * @param   hunknum         The hunknum.
 * @param [in,out]  buffer  If non-null, the buffer.
 *
 * @return  The hunk.
 */

chd_error chd_file::read_hunk(uint32_t hunknum, void *buffer)
{
	// wrap this for clean reporting
	try
	{
		// punt if no file
		if (m_file == nullptr)
			throw CHDERR_NOT_OPEN;

		// return an error if out of range
		if (hunknum >= m_hunkcount)
			throw CHDERR_HUNK_OUT_OF_RANGE;

		// get a pointer to the map entry
		uint64_t blockoffs;
		uint32_t blocklen;
		util::crc32_t blockcrc;
		uint8_t *rawmap;
		uint8_t *dest = reinterpret_cast<uint8_t *>(buffer);
		switch (m_version)
		{
			// v3/v4 map entries
			case 3:
			case 4:
				rawmap = &m_rawmap[16 * hunknum];
				blockoffs = be_read(&rawmap[0], 8);
				blockcrc = be_read(&rawmap[8], 4);
				switch (rawmap[15] & V34_MAP_ENTRY_FLAG_TYPE_MASK)
				{
					case V34_MAP_ENTRY_TYPE_COMPRESSED:
						blocklen = be_read(&rawmap[12], 2) + (rawmap[14] << 16);
						file_read(blockoffs, &m_compressed[0], blocklen);
						m_decompressor[0]->decompress(&m_compressed[0], blocklen, dest, m_hunkbytes);
						if (!(rawmap[15] & V34_MAP_ENTRY_FLAG_NO_CRC) && dest != nullptr && util::crc32_creator::simple(dest, m_hunkbytes) != blockcrc)
							throw CHDERR_DECOMPRESSION_ERROR;
						return CHDERR_NONE;

					case V34_MAP_ENTRY_TYPE_UNCOMPRESSED:
						file_read(blockoffs, dest, m_hunkbytes);
						if (!(rawmap[15] & V34_MAP_ENTRY_FLAG_NO_CRC) && util::crc32_creator::simple(dest, m_hunkbytes) != blockcrc)
							throw CHDERR_DECOMPRESSION_ERROR;
						return CHDERR_NONE;

					case V34_MAP_ENTRY_TYPE_MINI:
						be_write(dest, blockoffs, 8);
						for (uint32_t bytes = 8; bytes < m_hunkbytes; bytes++)
							dest[bytes] = dest[bytes - 8];
						if (!(rawmap[15] & V34_MAP_ENTRY_FLAG_NO_CRC) && util::crc32_creator::simple(dest, m_hunkbytes) != blockcrc)
							throw CHDERR_DECOMPRESSION_ERROR;
						return CHDERR_NONE;

					case V34_MAP_ENTRY_TYPE_SELF_HUNK:
						return read_hunk(blockoffs, dest);

					case V34_MAP_ENTRY_TYPE_PARENT_HUNK:
						if (m_parent_missing)
							throw CHDERR_REQUIRES_PARENT;
						return m_parent->read_hunk(blockoffs, dest);
				}
				break;

			// v5 map entries
			case 5:
				rawmap = &m_rawmap[m_mapentrybytes * hunknum];

				// uncompressed case
				if (!compressed())
				{
					blockoffs = uint64_t(be_read(rawmap, 4)) * uint64_t(m_hunkbytes);
					if (blockoffs != 0)
						file_read(blockoffs, dest, m_hunkbytes);
					else if (m_parent_missing)
						throw CHDERR_REQUIRES_PARENT;
					else if (m_parent != nullptr)
						m_parent->read_hunk(hunknum, dest);
					else
						memset(dest, 0, m_hunkbytes);
					return CHDERR_NONE;
				}

				// compressed case
				blocklen = be_read(&rawmap[1], 3);
				blockoffs = be_read(&rawmap[4], 6);
				blockcrc = be_read(&rawmap[10], 2);
				switch (rawmap[0])
				{
					case COMPRESSION_TYPE_0:
					case COMPRESSION_TYPE_1:
					case COMPRESSION_TYPE_2:
					case COMPRESSION_TYPE_3:
						file_read(blockoffs, &m_compressed[0], blocklen);
						m_decompressor[rawmap[0]]->decompress(&m_compressed[0], blocklen, dest, m_hunkbytes);
						if (!m_decompressor[rawmap[0]]->lossy() && dest != nullptr && util::crc16_creator::simple(dest, m_hunkbytes) != blockcrc)
							throw CHDERR_DECOMPRESSION_ERROR;
						if (m_decompressor[rawmap[0]]->lossy() && util::crc16_creator::simple(&m_compressed[0], blocklen) != blockcrc)
							throw CHDERR_DECOMPRESSION_ERROR;
						return CHDERR_NONE;

					case COMPRESSION_NONE:
						file_read(blockoffs, dest, m_hunkbytes);
						if (util::crc16_creator::simple(dest, m_hunkbytes) != blockcrc)
							throw CHDERR_DECOMPRESSION_ERROR;
						return CHDERR_NONE;

					case COMPRESSION_SELF:
						return read_hunk(blockoffs, dest);

					case COMPRESSION_PARENT:
						if (m_parent_missing)
							throw CHDERR_REQUIRES_PARENT;
						return m_parent->read_bytes(uint64_t(blockoffs) * uint64_t(m_parent->unit_bytes()), dest, m_hunkbytes);
				}
				break;
		}

		// if we get here, something was wrong
		throw CHDERR_READ_ERROR;
	}

	// just return errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  chd_error chd_file::write_hunk(uint32_t hunknum, const void *buffer)
 *
 * @brief   -------------------------------------------------
 *            write - write a single hunk to the CHD file
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_NOT_OPEN             Thrown when a chderr not open error condition occurs.
 * @exception   CHDERR_HUNK_OUT_OF_RANGE    Thrown when a chderr hunk out of range error
 *                                          condition occurs.
 * @exception   CHDERR_FILE_NOT_WRITEABLE   Thrown when a chderr file not writeable error
 *                                          condition occurs.
 *
 * @param   hunknum The hunknum.
 * @param   buffer  The buffer.
 *
 * @return  A chd_error.
 */

chd_error chd_file::write_hunk(uint32_t hunknum, const void *buffer)
{
	// wrap this for clean reporting
	try
	{
		// punt if no file
		if (m_file == nullptr)
			throw CHDERR_NOT_OPEN;

		// return an error if out of range
		if (hunknum >= m_hunkcount)
			throw CHDERR_HUNK_OUT_OF_RANGE;

		// if not writeable, fail
		if (!m_allow_writes)
			throw CHDERR_FILE_NOT_WRITEABLE;

		// uncompressed writes only via this interface
		if (compressed())
			throw CHDERR_FILE_NOT_WRITEABLE;

		// see if we have allocated the space on disk for this hunk
		uint8_t *rawmap = &m_rawmap[hunknum * 4];
		uint32_t rawentry = be_read(rawmap, 4);

		// if not, allocate one now
		if (rawentry == 0)
		{
			// first make sure we need to allocate it
			bool all_zeros = true;
			const uint32_t *scan = reinterpret_cast<const uint32_t *>(buffer);
			for (uint32_t index = 0; index < m_hunkbytes / 4; index++)
				if (scan[index] != 0)
				{
					all_zeros = false;
					break;
				}

			// if it's all zeros, do nothing more
			if (all_zeros)
				return CHDERR_NONE;

			// append new data to the end of the file, aligning the first chunk
			rawentry = file_append(buffer, m_hunkbytes, m_hunkbytes) / m_hunkbytes;

			// write the map entry back
			be_write(rawmap, rawentry, 4);
			file_write(m_mapoffset + hunknum * 4, rawmap, 4);

			// update the cached hunk if we just wrote it
			if (hunknum == m_cachehunk && buffer != &m_cache[0])
				memcpy(&m_cache[0], buffer, m_hunkbytes);
		}

		// otherwise, just overwrite
		else
			file_write(uint64_t(rawentry) * uint64_t(m_hunkbytes), buffer, m_hunkbytes);
		return CHDERR_NONE;
	}

	// just return errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  chd_error chd_file::read_units(uint64_t unitnum, void *buffer, uint32_t count)
 *
 * @brief   -------------------------------------------------
 *            read_units - read the given number of units from the CHD
 *          -------------------------------------------------.
 *
 * @param   unitnum         The unitnum.
 * @param [in,out]  buffer  If non-null, the buffer.
 * @param   count           Number of.
 *
 * @return  The units.
 */

chd_error chd_file::read_units(uint64_t unitnum, void *buffer, uint32_t count)
{
	return read_bytes(unitnum * uint64_t(m_unitbytes), buffer, count * m_unitbytes);
}

/**
 * @fn  chd_error chd_file::write_units(uint64_t unitnum, const void *buffer, uint32_t count)
 *
 * @brief   -------------------------------------------------
 *            write_units - write the given number of units to the CHD
 *          -------------------------------------------------.
 *
 * @param   unitnum The unitnum.
 * @param   buffer  The buffer.
 * @param   count   Number of.
 *
 * @return  A chd_error.
 */

chd_error chd_file::write_units(uint64_t unitnum, const void *buffer, uint32_t count)
{
	return write_bytes(unitnum * uint64_t(m_unitbytes), buffer, count * m_unitbytes);
}

/**
 * @fn  chd_error chd_file::read_bytes(uint64_t offset, void *buffer, uint32_t bytes)
 *
 * @brief   -------------------------------------------------
 *            read_bytes - read from the CHD at a byte level, using the cache to handle partial
 *            hunks
 *          -------------------------------------------------.
 *
 * @param   offset          The offset.
 * @param [in,out]  buffer  If non-null, the buffer.
 * @param   bytes           The bytes.
 *
 * @return  The bytes.
 */

chd_error chd_file::read_bytes(uint64_t offset, void *buffer, uint32_t bytes)
{
	// iterate over hunks
	uint32_t first_hunk = offset / m_hunkbytes;
	uint32_t last_hunk = (offset + bytes - 1) / m_hunkbytes;
	uint8_t *dest = reinterpret_cast<uint8_t *>(buffer);
	for (uint32_t curhunk = first_hunk; curhunk <= last_hunk; curhunk++)
	{
		// determine start/end boundaries
		uint32_t startoffs = (curhunk == first_hunk) ? (offset % m_hunkbytes) : 0;
		uint32_t endoffs = (curhunk == last_hunk) ? ((offset + bytes - 1) % m_hunkbytes) : (m_hunkbytes - 1);

		// if it's a full block, just read directly from disk unless it's the cached hunk
		chd_error err = CHDERR_NONE;
		if (startoffs == 0 && endoffs == m_hunkbytes - 1 && curhunk != m_cachehunk)
			err = read_hunk(curhunk, dest);

		// otherwise, read from the cache
		else
		{
			if (curhunk != m_cachehunk)
			{
				err = read_hunk(curhunk, &m_cache[0]);
				if (err != CHDERR_NONE)
					return err;
				m_cachehunk = curhunk;
			}
			memcpy(dest, &m_cache[startoffs], endoffs + 1 - startoffs);
		}

		// handle errors and advance
		if (err != CHDERR_NONE)
			return err;
		dest += endoffs + 1 - startoffs;
	}
	return CHDERR_NONE;
}

/**
 * @fn  chd_error chd_file::write_bytes(uint64_t offset, const void *buffer, uint32_t bytes)
 *
 * @brief   -------------------------------------------------
 *            write_bytes - write to the CHD at a byte level, using the cache to handle partial
 *            hunks
 *          -------------------------------------------------.
 *
 * @param   offset  The offset.
 * @param   buffer  The buffer.
 * @param   bytes   The bytes.
 *
 * @return  A chd_error.
 */

chd_error chd_file::write_bytes(uint64_t offset, const void *buffer, uint32_t bytes)
{
	// iterate over hunks
	uint32_t first_hunk = offset / m_hunkbytes;
	uint32_t last_hunk = (offset + bytes - 1) / m_hunkbytes;
	const uint8_t *source = reinterpret_cast<const uint8_t *>(buffer);
	for (uint32_t curhunk = first_hunk; curhunk <= last_hunk; curhunk++)
	{
		// determine start/end boundaries
		uint32_t startoffs = (curhunk == first_hunk) ? (offset % m_hunkbytes) : 0;
		uint32_t endoffs = (curhunk == last_hunk) ? ((offset + bytes - 1) % m_hunkbytes) : (m_hunkbytes - 1);

		// if it's a full block, just write directly to disk unless it's the cached hunk
		chd_error err = CHDERR_NONE;
		if (startoffs == 0 && endoffs == m_hunkbytes - 1 && curhunk != m_cachehunk)
			err = write_hunk(curhunk, source);

		// otherwise, write from the cache
		else
		{
			if (curhunk != m_cachehunk)
			{
				err = read_hunk(curhunk, &m_cache[0]);
				if (err != CHDERR_NONE)
					return err;
				m_cachehunk = curhunk;
			}
			memcpy(&m_cache[startoffs], source, endoffs + 1 - startoffs);
			err = write_hunk(curhunk, &m_cache[0]);
		}

		// handle errors and advance
		if (err != CHDERR_NONE)
			return err;
		source += endoffs + 1 - startoffs;
	}
	return CHDERR_NONE;
}

/**
 * @fn  chd_error chd_file::read_metadata(chd_metadata_tag searchtag, uint32_t searchindex, std::string &output)
 *
 * @brief   -------------------------------------------------
 *            read_metadata - read the indexed metadata of the given type
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_METADATA_NOT_FOUND   Thrown when a chderr metadata not found error
 *                                          condition occurs.
 *
 * @param   searchtag       The searchtag.
 * @param   searchindex     The searchindex.
 * @param [in,out]  output  The output.
 *
 * @return  The metadata.
 */

chd_error chd_file::read_metadata(chd_metadata_tag searchtag, uint32_t searchindex, std::string &output)
{
	// wrap this for clean reporting
	try
	{
		// if we didn't find it, just return
		metadata_entry metaentry;
		if (!metadata_find(searchtag, searchindex, metaentry))
			throw CHDERR_METADATA_NOT_FOUND;

		// read the metadata
		output.assign(metaentry.length, '\0');
		file_read(metaentry.offset + METADATA_HEADER_SIZE, &output[0], metaentry.length);
		return CHDERR_NONE;
	}

	// just return errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  chd_error chd_file::read_metadata(chd_metadata_tag searchtag, uint32_t searchindex, std::vector<uint8_t> &output)
 *
 * @brief   Reads a metadata.
 *
 * @exception   CHDERR_METADATA_NOT_FOUND   Thrown when a chderr metadata not found error
 *                                          condition occurs.
 *
 * @param   searchtag       The searchtag.
 * @param   searchindex     The searchindex.
 * @param [in,out]  output  The output.
 *
 * @return  The metadata.
 */

chd_error chd_file::read_metadata(chd_metadata_tag searchtag, uint32_t searchindex, std::vector<uint8_t> &output)
{
	// wrap this for clean reporting
	try
	{
		// if we didn't find it, just return
		metadata_entry metaentry;
		if (!metadata_find(searchtag, searchindex, metaentry))
			throw CHDERR_METADATA_NOT_FOUND;

		// read the metadata
		output.resize(metaentry.length);
		file_read(metaentry.offset + METADATA_HEADER_SIZE, &output[0], metaentry.length);
		return CHDERR_NONE;
	}

	// just return errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  chd_error chd_file::read_metadata(chd_metadata_tag searchtag, uint32_t searchindex, void *output, uint32_t outputlen, uint32_t &resultlen)
 *
 * @brief   Reads a metadata.
 *
 * @exception   CHDERR_METADATA_NOT_FOUND   Thrown when a chderr metadata not found error
 *                                          condition occurs.
 *
 * @param   searchtag           The searchtag.
 * @param   searchindex         The searchindex.
 * @param [in,out]  output      If non-null, the output.
 * @param   outputlen           The outputlen.
 * @param [in,out]  resultlen   The resultlen.
 *
 * @return  The metadata.
 */

chd_error chd_file::read_metadata(chd_metadata_tag searchtag, uint32_t searchindex, void *output, uint32_t outputlen, uint32_t &resultlen)
{
	// wrap this for clean reporting
	try
	{
		// if we didn't find it, just return
		metadata_entry metaentry;
		if (!metadata_find(searchtag, searchindex, metaentry))
			throw CHDERR_METADATA_NOT_FOUND;

		// read the metadata
		resultlen = metaentry.length;
		file_read(metaentry.offset + METADATA_HEADER_SIZE, output, std::min(outputlen, resultlen));
		return CHDERR_NONE;
	}

	// just return errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  chd_error chd_file::read_metadata(chd_metadata_tag searchtag, uint32_t searchindex, std::vector<uint8_t> &output, chd_metadata_tag &resulttag, uint8_t &resultflags)
 *
 * @brief   Reads a metadata.
 *
 * @exception   CHDERR_METADATA_NOT_FOUND   Thrown when a chderr metadata not found error
 *                                          condition occurs.
 *
 * @param   searchtag           The searchtag.
 * @param   searchindex         The searchindex.
 * @param [in,out]  output      The output.
 * @param [in,out]  resulttag   The resulttag.
 * @param [in,out]  resultflags The resultflags.
 *
 * @return  The metadata.
 */

chd_error chd_file::read_metadata(chd_metadata_tag searchtag, uint32_t searchindex, std::vector<uint8_t> &output, chd_metadata_tag &resulttag, uint8_t &resultflags)
{
	// wrap this for clean reporting
	try
	{
		// if we didn't find it, just return
		metadata_entry metaentry;
		if (!metadata_find(searchtag, searchindex, metaentry))
			throw CHDERR_METADATA_NOT_FOUND;

		// read the metadata
		output.resize(metaentry.length);
		file_read(metaentry.offset + METADATA_HEADER_SIZE, &output[0], metaentry.length);
		resulttag = metaentry.metatag;
		resultflags = metaentry.flags;
		return CHDERR_NONE;
	}

	// just return errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  chd_error chd_file::write_metadata(chd_metadata_tag metatag, uint32_t metaindex, const void *inputbuf, uint32_t inputlen, uint8_t flags)
 *
 * @brief   -------------------------------------------------
 *            write_metadata - write the indexed metadata of the given type
 *          -------------------------------------------------.
 *
 * @param   metatag     The metatag.
 * @param   metaindex   The metaindex.
 * @param   inputbuf    The inputbuf.
 * @param   inputlen    The inputlen.
 * @param   flags       The flags.
 *
 * @return  A chd_error.
 */

chd_error chd_file::write_metadata(chd_metadata_tag metatag, uint32_t metaindex, const void *inputbuf, uint32_t inputlen, uint8_t flags)
{
	// wrap this for clean reporting
	try
	{
		// must write at least 1 byte and no more than 16MB
		if (inputlen < 1 || inputlen >= 16 * 1024 * 1024)
			return CHDERR_INVALID_PARAMETER;

		// find the entry if it already exists
		metadata_entry metaentry;
		bool finished = false;
		if (metadata_find(metatag, metaindex, metaentry))
		{
			// if the new data fits over the old data, just overwrite
			if (inputlen <= metaentry.length)
			{
				file_write(metaentry.offset + METADATA_HEADER_SIZE, inputbuf, inputlen);

				// if the lengths don't match, we need to update the length in our header
				if (inputlen != metaentry.length)
				{
					uint8_t length[3];
					be_write(length, inputlen, 3);
					file_write(metaentry.offset + 5, length, sizeof(length));
				}

				// indicate we did everything
				finished = true;
			}

			// if it doesn't fit, unlink the current entry
			else
				metadata_set_previous_next(metaentry.prev, metaentry.next);
		}

		// if not yet done, create a new entry and append
		if (!finished)
		{
			// now build us a new entry
			uint8_t raw_meta_header[METADATA_HEADER_SIZE];
			be_write(&raw_meta_header[0], metatag, 4);
			raw_meta_header[4] = flags;
			be_write(&raw_meta_header[5], (inputlen & 0x00ffffff) | (flags << 24), 3);
			be_write(&raw_meta_header[8], 0, 8);

			// append the new header, then the data
			uint64_t offset = file_append(raw_meta_header, sizeof(raw_meta_header));
			file_append(inputbuf, inputlen);

			// set the previous entry to point to us
			metadata_set_previous_next(metaentry.prev, offset);
		}

		// update the hash
		metadata_update_hash();
		return CHDERR_NONE;
	}

	// return any errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  chd_error chd_file::delete_metadata(chd_metadata_tag metatag, uint32_t metaindex)
 *
 * @brief   -------------------------------------------------
 *            delete_metadata - remove the given metadata from the list
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_METADATA_NOT_FOUND   Thrown when a chderr metadata not found error
 *                                          condition occurs.
 *
 * @param   metatag     The metatag.
 * @param   metaindex   The metaindex.
 *
 * @return  A chd_error.
 */

chd_error chd_file::delete_metadata(chd_metadata_tag metatag, uint32_t metaindex)
{
	// wrap this for clean reporting
	try
	{
		// find the entry
		metadata_entry metaentry;
		if (!metadata_find(metatag, metaindex, metaentry))
			throw CHDERR_METADATA_NOT_FOUND;

		// point the previous to the next, unlinking us
		metadata_set_previous_next(metaentry.prev, metaentry.next);
		return CHDERR_NONE;
	}

	// return any errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  chd_error chd_file::clone_all_metadata(chd_file &source)
 *
 * @brief   -------------------------------------------------
 *            clone_all_metadata - clone the metadata from one CHD to a second
 *          -------------------------------------------------.
 *
 * @exception   err Thrown when an error error condition occurs.
 *
 * @param [in,out]  source  Another instance to copy.
 *
 * @return  A chd_error.
 */

chd_error chd_file::clone_all_metadata(chd_file &source)
{
	// wrap this for clean reporting
	try
	{
		// iterate over metadata entries in the source
		std::vector<uint8_t> filedata;
		metadata_entry metaentry;
		metaentry.metatag = 0;
		metaentry.length = 0;
		metaentry.next = 0;
		metaentry.flags = 0;
		for (bool has_data = source.metadata_find(CHDMETATAG_WILDCARD, 0, metaentry); has_data; has_data = source.metadata_find(CHDMETATAG_WILDCARD, 0, metaentry, true))
		{
			// read the metadata item
			filedata.resize(metaentry.length);
			source.file_read(metaentry.offset + METADATA_HEADER_SIZE, &filedata[0], metaentry.length);

			// write it to the destination
			chd_error err = write_metadata(metaentry.metatag, (uint32_t)-1, &filedata[0], metaentry.length, metaentry.flags);
			if (err != CHDERR_NONE)
				throw err;
		}
		return CHDERR_NONE;
	}

	// return any errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  util::sha1_t chd_file::compute_overall_sha1(sha1_t rawsha1)
 *
 * @brief   -------------------------------------------------
 *            compute_overall_sha1 - iterate through the metadata and compute the overall hash of
 *            the CHD file
 *          -------------------------------------------------.
 *
 * @param   rawsha1 The first rawsha.
 *
 * @return  The calculated overall sha 1.
 */

util::sha1_t chd_file::compute_overall_sha1(util::sha1_t rawsha1)
{
	// only works for v4 and above
	if (m_version < 4)
		return rawsha1;

	// iterate over metadata
	std::vector<uint8_t> filedata;
	std::vector<metadata_hash> hasharray;
	metadata_entry metaentry;
	for (bool has_data = metadata_find(CHDMETATAG_WILDCARD, 0, metaentry); has_data; has_data = metadata_find(CHDMETATAG_WILDCARD, 0, metaentry, true))
	{
		// if not checksumming, continue
		if ((metaentry.flags & CHD_MDFLAGS_CHECKSUM) == 0)
			continue;

		// allocate memory and read the data
		filedata.resize(metaentry.length);
		file_read(metaentry.offset + METADATA_HEADER_SIZE, &filedata[0], metaentry.length);

		// create an entry for this metadata and add it
		metadata_hash hashentry;
		be_write(hashentry.tag, metaentry.metatag, 4);
		hashentry.sha1 = util::sha1_creator::simple(&filedata[0], metaentry.length);
		hasharray.push_back(hashentry);
	}

	// sort the array
	if (!hasharray.empty())
		qsort(&hasharray[0], hasharray.size(), sizeof(hasharray[0]), metadata_hash_compare);

	// read the raw data hash from our header and start a new SHA1 with that data
	util::sha1_creator overall_sha1;
	overall_sha1.append(&rawsha1, sizeof(rawsha1));
	if (!hasharray.empty())
		overall_sha1.append(&hasharray[0], hasharray.size() * sizeof(hasharray[0]));
	return overall_sha1.finish();
}

/**
 * @fn  chd_error chd_file::codec_configure(chd_codec_type codec, int param, void *config)
 *
 * @brief   -------------------------------------------------
 *            codec_config - set internal codec parameters
 *          -------------------------------------------------.
 *
 * @param   codec           The codec.
 * @param   param           The parameter.
 * @param [in,out]  config  If non-null, the configuration.
 *
 * @return  A chd_error.
 */

chd_error chd_file::codec_configure(chd_codec_type codec, int param, void *config)
{
	// wrap this for clean reporting
	try
	{
		// find the codec and call its configuration
		for (int codecnum = 0; codecnum < ARRAY_LENGTH(m_compression); codecnum++)
			if (m_compression[codecnum] == codec)
			{
				m_decompressor[codecnum]->configure(param, config);
				return CHDERR_NONE;
			}
		return CHDERR_INVALID_PARAMETER;
	}

	// return any errors
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  const char *chd_file::error_string(chd_error err)
 *
 * @brief   -------------------------------------------------
 *            error_string - return an error string for the given CHD error
 *          -------------------------------------------------.
 *
 * @param   err The error.
 *
 * @return  null if it fails, else a char*.
 */

const char *chd_file::error_string(chd_error err)
{
	switch (err)
	{
		case CHDERR_NONE:                       return "no error";
		case CHDERR_NO_INTERFACE:               return "no drive interface";
		case CHDERR_OUT_OF_MEMORY:              return "out of memory";
		case CHDERR_NOT_OPEN:                   return "file not open";
		case CHDERR_ALREADY_OPEN:               return "file already open";
		case CHDERR_INVALID_FILE:               return "invalid file";
		case CHDERR_INVALID_PARAMETER:          return "invalid parameter";
		case CHDERR_INVALID_DATA:               return "invalid data";
		case CHDERR_FILE_NOT_FOUND:             return "file not found";
		case CHDERR_REQUIRES_PARENT:            return "requires parent";
		case CHDERR_FILE_NOT_WRITEABLE:         return "file not writeable";
		case CHDERR_READ_ERROR:                 return "read error";
		case CHDERR_WRITE_ERROR:                return "write error";
		case CHDERR_CODEC_ERROR:                return "codec error";
		case CHDERR_INVALID_PARENT:             return "invalid parent";
		case CHDERR_HUNK_OUT_OF_RANGE:          return "hunk out of range";
		case CHDERR_DECOMPRESSION_ERROR:        return "decompression error";
		case CHDERR_COMPRESSION_ERROR:          return "compression error";
		case CHDERR_CANT_CREATE_FILE:           return "can't create file";
		case CHDERR_CANT_VERIFY:                return "can't verify file";
		case CHDERR_NOT_SUPPORTED:              return "operation not supported";
		case CHDERR_METADATA_NOT_FOUND:         return "can't find metadata";
		case CHDERR_INVALID_METADATA_SIZE:      return "invalid metadata size";
		case CHDERR_UNSUPPORTED_VERSION:        return "mismatched DIFF and CHD or unsupported CHD version";
		case CHDERR_VERIFY_INCOMPLETE:          return "incomplete verify";
		case CHDERR_INVALID_METADATA:           return "invalid metadata";
		case CHDERR_INVALID_STATE:              return "invalid state";
		case CHDERR_OPERATION_PENDING:          return "operation pending";
		case CHDERR_UNSUPPORTED_FORMAT:         return "unsupported format";
		case CHDERR_UNKNOWN_COMPRESSION:        return "unknown compression type";
		case CHDERR_WALKING_PARENT:             return "currently examining parent";
		case CHDERR_COMPRESSING:                return "currently compressing";
		default:                                return "undocumented error";
	}
}



//**************************************************************************
//  INTERNAL HELPERS
//**************************************************************************

/**
 * @fn  uint32_t chd_file::guess_unitbytes()
 *
 * @brief   -------------------------------------------------
 *            guess_unitbytes - for older CHD formats, take a guess at the bytes/unit based on
 *            metadata
 *          -------------------------------------------------.
 *
 * @return  An uint32_t.
 */

uint32_t chd_file::guess_unitbytes()
{
	// look for hard disk metadata; if found, then the unit size == sector size
	std::string metadata;
	int i0, i1, i2, i3;
	if (read_metadata(HARD_DISK_METADATA_TAG, 0, metadata) == CHDERR_NONE && sscanf(metadata.c_str(), HARD_DISK_METADATA_FORMAT, &i0, &i1, &i2, &i3) == 4)
		return i3;

	// look for CD-ROM metadata; if found, then the unit size == CD frame size
	if (read_metadata(CDROM_OLD_METADATA_TAG, 0, metadata) == CHDERR_NONE ||
		read_metadata(CDROM_TRACK_METADATA_TAG, 0, metadata) == CHDERR_NONE ||
		read_metadata(CDROM_TRACK_METADATA2_TAG, 0, metadata) == CHDERR_NONE ||
		read_metadata(GDROM_OLD_METADATA_TAG, 0, metadata) == CHDERR_NONE ||
		read_metadata(GDROM_TRACK_METADATA_TAG, 0, metadata) == CHDERR_NONE)
		return CD_FRAME_SIZE;

	// otherwise, just map 1:1 with the hunk size
	return m_hunkbytes;
}

/**
 * @fn  void chd_file::parse_v3_header(uint8_t *rawheader, sha1_t &parentsha1)
 *
 * @brief   -------------------------------------------------
 *            parse_v3_header - parse the header from a v3 file and configure core parameters
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_INVALID_FILE         Thrown when a chderr invalid file error condition
 *                                          occurs.
 * @exception   CHDERR_UNKNOWN_COMPRESSION  Thrown when a chderr unknown compression error
 *                                          condition occurs.
 *
 * @param [in,out]  rawheader   If non-null, the rawheader.
 * @param [in,out]  parentsha1  The first parentsha.
 */

void chd_file::parse_v3_header(uint8_t *rawheader, util::sha1_t &parentsha1)
{
	// verify header length
	if (be_read(&rawheader[8], 4) != V3_HEADER_SIZE)
		throw CHDERR_INVALID_FILE;

	// extract core info
	m_logicalbytes = be_read(&rawheader[28], 8);
	m_mapoffset = 120;
	m_metaoffset = be_read(&rawheader[36], 8);
	m_hunkbytes = be_read(&rawheader[76], 4);
	m_hunkcount = be_read(&rawheader[24], 4);

	// extract parent SHA-1
	uint32_t flags = be_read(&rawheader[16], 4);
	m_allow_writes = (flags & 2) == 0;

	// determine compression
	switch (be_read(&rawheader[20], 4))
	{
		case 0: m_compression[0] = CHD_CODEC_NONE;      break;
		case 1: m_compression[0] = CHD_CODEC_ZLIB;      break;
		case 2: m_compression[0] = CHD_CODEC_ZLIB;      break;
		case 3: m_compression[0] = CHD_CODEC_AVHUFF;    break;
		default: throw CHDERR_UNKNOWN_COMPRESSION;
	}
	m_compression[1] = m_compression[2] = m_compression[3] = CHD_CODEC_NONE;

	// describe the format
	m_mapoffset_offset = 0;
	m_metaoffset_offset = 36;
	m_sha1_offset = 80;
	m_rawsha1_offset = 0;
	m_parentsha1_offset = 100;

	// determine properties of map entries
	m_mapentrybytes = 16;

	// extract parent SHA-1
	if (flags & 1)
		parentsha1 = be_read_sha1(&rawheader[m_parentsha1_offset]);

	// guess at the units based on snooping the metadata
	m_unitbytes = guess_unitbytes();
	m_unitcount = (m_logicalbytes + m_unitbytes - 1) / m_unitbytes;
}

/**
 * @fn  void chd_file::parse_v4_header(uint8_t *rawheader, sha1_t &parentsha1)
 *
 * @brief   -------------------------------------------------
 *            parse_v4_header - parse the header from a v4 file and configure core parameters
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_INVALID_FILE         Thrown when a chderr invalid file error condition
 *                                          occurs.
 * @exception   CHDERR_UNKNOWN_COMPRESSION  Thrown when a chderr unknown compression error
 *                                          condition occurs.
 *
 * @param [in,out]  rawheader   If non-null, the rawheader.
 * @param [in,out]  parentsha1  The first parentsha.
 */

void chd_file::parse_v4_header(uint8_t *rawheader, util::sha1_t &parentsha1)
{
	// verify header length
	if (be_read(&rawheader[8], 4) != V4_HEADER_SIZE)
		throw CHDERR_INVALID_FILE;

	// extract core info
	m_logicalbytes = be_read(&rawheader[28], 8);
	m_mapoffset = 108;
	m_metaoffset = be_read(&rawheader[36], 8);
	m_hunkbytes = be_read(&rawheader[44], 4);
	m_hunkcount = be_read(&rawheader[24], 4);

	// extract parent SHA-1
	uint32_t flags = be_read(&rawheader[16], 4);
	m_allow_writes = (flags & 2) == 0;

	// determine compression
	switch (be_read(&rawheader[20], 4))
	{
		case 0: m_compression[0] = CHD_CODEC_NONE;      break;
		case 1: m_compression[0] = CHD_CODEC_ZLIB;      break;
		case 2: m_compression[0] = CHD_CODEC_ZLIB;      break;
		case 3: m_compression[0] = CHD_CODEC_AVHUFF;    break;
		default: throw CHDERR_UNKNOWN_COMPRESSION;
	}
	m_compression[1] = m_compression[2] = m_compression[3] = CHD_CODEC_NONE;

	// describe the format
	m_mapoffset_offset = 0;
	m_metaoffset_offset = 36;
	m_sha1_offset = 48;
	m_rawsha1_offset = 88;
	m_parentsha1_offset = 68;

	// determine properties of map entries
	m_mapentrybytes = 16;

	// extract parent SHA-1
	if (flags & 1)
		parentsha1 = be_read_sha1(&rawheader[m_parentsha1_offset]);

	// guess at the units based on snooping the metadata
	m_unitbytes = guess_unitbytes();
	m_unitcount = (m_logicalbytes + m_unitbytes - 1) / m_unitbytes;
}

/**
 * @fn  void chd_file::parse_v5_header(uint8_t *rawheader, sha1_t &parentsha1)
 *
 * @brief   -------------------------------------------------
 *            parse_v5_header - read the header from a v5 file and configure core parameters
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_INVALID_FILE Thrown when a chderr invalid file error condition occurs.
 *
 * @param [in,out]  rawheader   If non-null, the rawheader.
 * @param [in,out]  parentsha1  The first parentsha.
 */

void chd_file::parse_v5_header(uint8_t *rawheader, util::sha1_t &parentsha1)
{
	// verify header length
	if (be_read(&rawheader[8], 4) != V5_HEADER_SIZE)
		throw CHDERR_INVALID_FILE;

	// extract core info
	m_logicalbytes = be_read(&rawheader[32], 8);
	m_mapoffset = be_read(&rawheader[40], 8);
	m_metaoffset = be_read(&rawheader[48], 8);
	m_hunkbytes = be_read(&rawheader[56], 4);
	m_hunkcount = (m_logicalbytes + m_hunkbytes - 1) / m_hunkbytes;
	m_unitbytes = be_read(&rawheader[60], 4);
	m_unitcount = (m_logicalbytes + m_unitbytes - 1) / m_unitbytes;

	// determine compression
	m_compression[0] = be_read(&rawheader[16], 4);
	m_compression[1] = be_read(&rawheader[20], 4);
	m_compression[2] = be_read(&rawheader[24], 4);
	m_compression[3] = be_read(&rawheader[28], 4);

	m_allow_writes = !compressed();

	// describe the format
	m_mapoffset_offset = 40;
	m_metaoffset_offset = 48;
	m_sha1_offset = 84;
	m_rawsha1_offset = 64;
	m_parentsha1_offset = 104;

	// determine properties of map entries
	m_mapentrybytes = compressed() ? 12 : 4;

	// extract parent SHA-1
	parentsha1 = be_read_sha1(&rawheader[m_parentsha1_offset]);
}

/**
 * @fn  chd_error chd_file::compress_v5_map()
 *
 * @brief   -------------------------------------------------
 *            compress_v5_map - compress the v5 map and write it to the end of the file
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_COMPRESSION_ERROR    Thrown when a chderr compression error error
 *                                          condition occurs.
 *
 * @return  A chd_error.
 */

chd_error chd_file::compress_v5_map()
{
	try
	{
		// first get a CRC-16 of the original rawmap
		util::crc16_t mapcrc = util::crc16_creator::simple(&m_rawmap[0], m_hunkcount * 12);

		// create a buffer to hold the RLE data
		std::vector<uint8_t> compression_rle(m_hunkcount);
		uint8_t *dest = &compression_rle[0];

		// use a huffman encoder for 16 different codes, maximum length is 8 bits
		huffman_encoder<16, 8> encoder;
		encoder.histo_reset();

		// RLE-compress the compression type since we expect runs of the same
		uint32_t max_self = 0;
		uint32_t last_self = 0;
		uint64_t max_parent = 0;
		uint64_t last_parent = 0;
		uint32_t max_complen = 0;
		uint8_t lastcomp = 0;
		int count = 0;
		for (int hunknum = 0; hunknum < m_hunkcount; hunknum++)
		{
			uint8_t curcomp = m_rawmap[hunknum * 12 + 0];

			// promote self block references to more compact forms
			if (curcomp == COMPRESSION_SELF)
			{
				uint32_t refhunk = be_read(&m_rawmap[hunknum * 12 + 4], 6);
				if (refhunk == last_self)
					curcomp = COMPRESSION_SELF_0;
				else if (refhunk == last_self + 1)
					curcomp = COMPRESSION_SELF_1;
				else
					max_self = std::max(max_self, refhunk);
				last_self = refhunk;
			}

			// promote parent block references to more compact forms
			else if (curcomp == COMPRESSION_PARENT)
			{
				uint32_t refunit = be_read(&m_rawmap[hunknum * 12 + 4], 6);
				if (refunit == (uint64_t(hunknum) * uint64_t(m_hunkbytes)) / m_unitbytes)
					curcomp = COMPRESSION_PARENT_SELF;
				else if (refunit == last_parent)
					curcomp = COMPRESSION_PARENT_0;
				else if (refunit == last_parent + m_hunkbytes / m_unitbytes)
					curcomp = COMPRESSION_PARENT_1;
				else
					max_parent = std::max(max_parent, uint64_t(refunit));
				last_parent = refunit;
			}

			// track maximum compressed length
			else //if (curcomp >= COMPRESSION_TYPE_0 && curcomp <= COMPRESSION_TYPE_3)
				max_complen = std::max(max_complen, uint32_t(be_read(&m_rawmap[hunknum * 12 + 1], 3)));

			// track repeats
			if (curcomp == lastcomp)
				count++;

			// if no repeat, or we're at the end, flush it
			if (curcomp != lastcomp || hunknum == m_hunkcount - 1)
			{
				while (count != 0)
				{
					if (count < 3)
						encoder.histo_one(*dest++ = lastcomp), count--;
					else if (count <= 3+15)
					{
						encoder.histo_one(*dest++ = COMPRESSION_RLE_SMALL);
						encoder.histo_one(*dest++ = count - 3);
						count = 0;
					}
					else
					{
						int this_count = std::min(count, 3+16+255);
						encoder.histo_one(*dest++ = COMPRESSION_RLE_LARGE);
						encoder.histo_one(*dest++ = (this_count - 3 - 16) >> 4);
						encoder.histo_one(*dest++ = (this_count - 3 - 16) & 15);
						count -= this_count;
					}
				}
				if (curcomp != lastcomp)
					encoder.histo_one(*dest++ = lastcomp = curcomp);
			}
		}

		// compute a tree and export it to the buffer
		std::vector<uint8_t> compressed(m_hunkcount * 6);
		bitstream_out bitbuf(&compressed[16], compressed.size() - 16);
		huffman_error err = encoder.compute_tree_from_histo();
		if (err != HUFFERR_NONE)
			throw CHDERR_COMPRESSION_ERROR;
		err = encoder.export_tree_rle(bitbuf);
		if (err != HUFFERR_NONE)
			throw CHDERR_COMPRESSION_ERROR;

		// encode the data
		for (uint8_t *src = &compression_rle[0]; src < dest; src++)
			encoder.encode_one(bitbuf, *src);

		// determine the number of bits we need to hold the a length
		// and a hunk index
		uint8_t lengthbits = bits_for_value(max_complen);
		uint8_t selfbits = bits_for_value(max_self);
		uint8_t parentbits = bits_for_value(max_parent);

		// for each compression type, output the relevant data
		lastcomp = 0;
		count = 0;
		uint8_t *src = &compression_rle[0];
		uint64_t firstoffs = 0;
		for (int hunknum = 0; hunknum < m_hunkcount; hunknum++)
		{
			uint8_t *rawmap = &m_rawmap[hunknum * 12];
			uint32_t length = be_read(&rawmap[1], 3);
			uint64_t offset = be_read(&rawmap[4], 6);
			uint16_t crc = be_read(&rawmap[10], 2);

			// if no count remaining, fetch the next entry
			if (count == 0)
			{
				uint8_t val = *src++;
				if (val == COMPRESSION_RLE_SMALL)
					count = 2 + *src++;
				else if (val == COMPRESSION_RLE_LARGE)
					count = 2 + 16 + (*src++ << 4), count += *src++;
				else
					lastcomp = val;
			}
			else
				count--;

			// output additional data needed for this entry
			switch (lastcomp)
			{
				case COMPRESSION_TYPE_0:
				case COMPRESSION_TYPE_1:
				case COMPRESSION_TYPE_2:
				case COMPRESSION_TYPE_3:
					assert(length < (1 << lengthbits));
					bitbuf.write(length, lengthbits);
					bitbuf.write(crc, 16);
					if (firstoffs == 0)
						firstoffs = offset;
					break;

				case COMPRESSION_NONE:
					bitbuf.write(crc, 16);
					if (firstoffs == 0)
						firstoffs = offset;
					break;

				case COMPRESSION_SELF:
					assert(offset < (uint64_t(1) << selfbits));
					bitbuf.write(offset, selfbits);
					break;

				case COMPRESSION_PARENT:
					assert(offset < (uint64_t(1) << parentbits));
					bitbuf.write(offset, parentbits);
					break;

				case COMPRESSION_SELF_0:
				case COMPRESSION_SELF_1:
				case COMPRESSION_PARENT_SELF:
				case COMPRESSION_PARENT_0:
				case COMPRESSION_PARENT_1:
					break;
			}
		}

		// write the map header
		uint32_t complen = bitbuf.flush();
		assert(!bitbuf.overflow());
		be_write(&compressed[0], complen, 4);
		be_write(&compressed[4], firstoffs, 6);
		be_write(&compressed[10], mapcrc, 2);
		compressed[12] = lengthbits;
		compressed[13] = selfbits;
		compressed[14] = parentbits;
		compressed[15] = 0;

		// write the result
		m_mapoffset = file_append(&compressed[0], complen + 16);

		// then write the map offset
		uint8_t rawbuf[sizeof(uint64_t)];
		be_write(rawbuf, m_mapoffset, 8);
		file_write(m_mapoffset_offset, rawbuf, sizeof(rawbuf));
		return CHDERR_NONE;
	}
	catch (chd_error &err)
	{
		return err;
	}
}

/**
 * @fn  void chd_file::decompress_v5_map()
 *
 * @brief   -------------------------------------------------
 *            decompress_v5_map - decompress the v5 map
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_DECOMPRESSION_ERROR  Thrown when a chderr decompression error error
 *                                          condition occurs.
 */

void chd_file::decompress_v5_map()
{
	// if no offset, we haven't written it yet
	if (m_mapoffset == 0)
	{
		memset(&m_rawmap[0], 0xff, m_rawmap.size());
		return;
	}

	// read the reader
	uint8_t rawbuf[16];
	file_read(m_mapoffset, rawbuf, sizeof(rawbuf));
	uint32_t const mapbytes = be_read(&rawbuf[0], 4);
	uint64_t const firstoffs = be_read(&rawbuf[4], 6);
	util::crc16_t const mapcrc = be_read(&rawbuf[10], 2);
	uint8_t const lengthbits = rawbuf[12];
	uint8_t const selfbits = rawbuf[13];
	uint8_t const parentbits = rawbuf[14];

	// now read the map
	std::vector<uint8_t> compressed(mapbytes);
	file_read(m_mapoffset + 16, &compressed[0], mapbytes);
	bitstream_in bitbuf(&compressed[0], compressed.size());

	// first decode the compression types
	huffman_decoder<16, 8> decoder;
	huffman_error err = decoder.import_tree_rle(bitbuf);
	if (err != HUFFERR_NONE)
		throw CHDERR_DECOMPRESSION_ERROR;
	uint8_t lastcomp = 0;
	int repcount = 0;
	for (int hunknum = 0; hunknum < m_hunkcount; hunknum++)
	{
		uint8_t *rawmap = &m_rawmap[hunknum * 12];
		if (repcount > 0)
			rawmap[0] = lastcomp, repcount--;
		else
		{
			uint8_t val = decoder.decode_one(bitbuf);
			if (val == COMPRESSION_RLE_SMALL)
				rawmap[0] = lastcomp, repcount = 2 + decoder.decode_one(bitbuf);
			else if (val == COMPRESSION_RLE_LARGE)
				rawmap[0] = lastcomp, repcount = 2 + 16 + (decoder.decode_one(bitbuf) << 4), repcount += decoder.decode_one(bitbuf);
			else
				rawmap[0] = lastcomp = val;
		}
	}

	// then iterate through the hunks and extract the needed data
	uint64_t curoffset = firstoffs;
	uint32_t last_self = 0;
	uint64_t last_parent = 0;
	for (int hunknum = 0; hunknum < m_hunkcount; hunknum++)
	{
		uint8_t *rawmap = &m_rawmap[hunknum * 12];
		uint64_t offset = curoffset;
		uint32_t length = 0;
		uint16_t crc = 0;
		switch (rawmap[0])
		{
			// base types
			case COMPRESSION_TYPE_0:
			case COMPRESSION_TYPE_1:
			case COMPRESSION_TYPE_2:
			case COMPRESSION_TYPE_3:
				curoffset += length = bitbuf.read(lengthbits);
				crc = bitbuf.read(16);
				break;

			case COMPRESSION_NONE:
				curoffset += length = m_hunkbytes;
				crc = bitbuf.read(16);
				break;

			case COMPRESSION_SELF:
				last_self = offset = bitbuf.read(selfbits);
				break;

			case COMPRESSION_PARENT:
				offset = bitbuf.read(parentbits);
				last_parent = offset;
				break;

			// pseudo-types; convert into base types
			case COMPRESSION_SELF_1:
				last_self++;
			case COMPRESSION_SELF_0:
				rawmap[0] = COMPRESSION_SELF;
				offset = last_self;
				break;

			case COMPRESSION_PARENT_SELF:
				rawmap[0] = COMPRESSION_PARENT;
				last_parent = offset = (uint64_t(hunknum) * uint64_t(m_hunkbytes)) / m_unitbytes;
				break;

			case COMPRESSION_PARENT_1:
				last_parent += m_hunkbytes / m_unitbytes;
			case COMPRESSION_PARENT_0:
				rawmap[0] = COMPRESSION_PARENT;
				offset = last_parent;
				break;
		}
		be_write(&rawmap[1], length, 3);
		be_write(&rawmap[4], offset, 6);
		be_write(&rawmap[10], crc, 2);
	}

	// verify the final CRC
	if (util::crc16_creator::simple(&m_rawmap[0], m_hunkcount * 12) != mapcrc)
		throw CHDERR_DECOMPRESSION_ERROR;
}

/**
 * @fn  chd_error chd_file::create_common()
 *
 * @brief   -------------------------------------------------
 *            create_common - command path when creating a new CHD file
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_UNSUPPORTED_VERSION  Thrown when a chderr unsupported version error
 *                                          condition occurs.
 * @exception   CHDERR_INVALID_PARAMETER    Thrown when a chderr invalid parameter error
 *                                          condition occurs.
 * @exception   CHDERR_UNKNOWN_COMPRESSION  Thrown when a chderr unknown compression error
 *                                          condition occurs.
 *
 * @return  The new common.
 */

chd_error chd_file::create_common()
{
	// wrap in try for proper error handling
	try
	{
		m_version = HEADER_VERSION;
		m_metaoffset = 0;

		// if we have a parent, it must be V3 or later
		if (m_parent != nullptr && m_parent->version() < 3)
			throw CHDERR_UNSUPPORTED_VERSION;

		// must be an even number of units per hunk
		if (m_hunkbytes % m_unitbytes != 0)
			throw CHDERR_INVALID_PARAMETER;
		if (m_parent != nullptr && m_unitbytes != m_parent->unit_bytes())
			throw CHDERR_INVALID_PARAMETER;

		// verify the compression types
		bool found_zero = false;
		for (auto & elem : m_compression)
		{
			// once we hit an empty slot, all later slots must be empty as well
			if (elem == CHD_CODEC_NONE)
				found_zero = true;
			else if (found_zero)
				throw CHDERR_INVALID_PARAMETER;
			else if (!chd_codec_list::codec_exists(elem))
				throw CHDERR_UNKNOWN_COMPRESSION;
		}

		// create our V5 header
		uint8_t rawheader[V5_HEADER_SIZE];
		memcpy(&rawheader[0], "MComprHD", 8);
		be_write(&rawheader[8], V5_HEADER_SIZE, 4);
		be_write(&rawheader[12], m_version, 4);
		be_write(&rawheader[16], m_compression[0], 4);
		be_write(&rawheader[20], m_compression[1], 4);
		be_write(&rawheader[24], m_compression[2], 4);
		be_write(&rawheader[28], m_compression[3], 4);
		be_write(&rawheader[32], m_logicalbytes, 8);
		be_write(&rawheader[40], compressed() ? 0 : V5_HEADER_SIZE, 8);
		be_write(&rawheader[48], m_metaoffset, 8);
		be_write(&rawheader[56], m_hunkbytes, 4);
		be_write(&rawheader[60], m_unitbytes, 4);
		be_write_sha1(&rawheader[64], util::sha1_t::null);
		be_write_sha1(&rawheader[84], util::sha1_t::null);
		be_write_sha1(&rawheader[104], (m_parent != nullptr) ? m_parent->sha1() : util::sha1_t::null);

		// write the resulting header
		file_write(0, rawheader, sizeof(rawheader));

		// parse it back out to set up fields appropriately
		util::sha1_t parentsha1;
		parse_v5_header(rawheader, parentsha1);

		// writes are obviously permitted; reads only if uncompressed
		m_allow_writes = true;
		m_allow_reads = !compressed();

		// write out the map (if not compressed)
		if (!compressed())
		{
			uint32_t mapsize = m_mapentrybytes * m_hunkcount;
			uint8_t buffer[4096] = { 0 };
			uint64_t offset = m_mapoffset;
			while (mapsize != 0)
			{
				uint32_t bytes_to_write = (std::min<size_t>)(mapsize, sizeof(buffer));
				file_write(offset, buffer, bytes_to_write);
				offset += bytes_to_write;
				mapsize -= bytes_to_write;
			}
		}

		// finish opening the file
		create_open_common();
	}

	// handle errors by closing ourself
	catch (chd_error &err)
	{
		close();
		return err;
	}
	catch (...)
	{
		close();
		throw;
	}
	return CHDERR_NONE;
}

/**
 * @fn  chd_error chd_file::open_common(bool writeable)
 *
 * @brief   -------------------------------------------------
 *            open_common - common path when opening an existing CHD file for input
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_INVALID_FILE         Thrown when a chderr invalid file error condition
 *                                          occurs.
 * @exception   CHDERR_UNSUPPORTED_VERSION  Thrown when a chderr unsupported version error
 *                                          condition occurs.
 * @exception   CHDERR_FILE_NOT_WRITEABLE   Thrown when a chderr file not writeable error
 *                                          condition occurs.
 * @exception   CHDERR_INVALID_PARENT       Thrown when a chderr invalid parent error condition
 *                                          occurs.
 * @exception   CHDERR_INVALID_PARAMETER    Thrown when a chderr invalid parameter error
 *                                          condition occurs.
 *
 * @param   writeable   true if writeable.
 *
 * @return  A chd_error.
 */

chd_error chd_file::open_common(bool writeable)
{
	// wrap in try for proper error handling
	try
	{
		// reads are always permitted
		m_allow_reads = true;

		// read the raw header
		uint8_t rawheader[MAX_HEADER_SIZE];
		file_read(0, rawheader, sizeof(rawheader));

		// verify the signature
		if (memcmp(rawheader, "MComprHD", 8) != 0)
			throw CHDERR_INVALID_FILE;

		m_version = be_read(&rawheader[12], 4);

		// read the header if we support it
		util::sha1_t parentsha1 = util::sha1_t::null;
		switch (m_version)
		{
			case 3:     parse_v3_header(rawheader, parentsha1); break;
			case 4:     parse_v4_header(rawheader, parentsha1); break;
			case 5:     parse_v5_header(rawheader, parentsha1); break;
			default:    throw CHDERR_UNSUPPORTED_VERSION;
		}

		// only allow writes to the most recent version
		if (m_version < HEADER_VERSION)
			m_allow_writes = false;

		if (writeable && !m_allow_writes)
			throw CHDERR_FILE_NOT_WRITEABLE;

		// make sure we have a parent if we need one (and don't if we don't)
		if (parentsha1 != util::sha1_t::null)
		{
			if (m_parent == nullptr)
				m_parent_missing = true;
			else if (m_parent->sha1() != parentsha1)
				throw CHDERR_INVALID_PARENT;
		}
		else if (m_parent != nullptr)
			throw CHDERR_INVALID_PARAMETER;

		// finish opening the file
		create_open_common();
		return CHDERR_NONE;
	}

	// handle errors by closing ourself
	catch (chd_error &err)
	{
		close();
		return err;
	}
}

/**
 * @fn  void chd_file::create_open_common()
 *
 * @brief   -------------------------------------------------
 *            create_open_common - common code for handling creation and opening of a file
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_UNKNOWN_COMPRESSION  Thrown when a chderr unknown compression error
 *                                          condition occurs.
 */

void chd_file::create_open_common()
{
	// verify the compression types and initialize the codecs
	for (int decompnum = 0; decompnum < ARRAY_LENGTH(m_compression); decompnum++)
	{
		m_decompressor[decompnum] = chd_codec_list::new_decompressor(m_compression[decompnum], *this);
		if (m_decompressor[decompnum] == nullptr && m_compression[decompnum] != 0)
			throw CHDERR_UNKNOWN_COMPRESSION;
	}

	// read the map; v5+ compressed drives need to read and decompress their map
	m_rawmap.resize(m_hunkcount * m_mapentrybytes);
	if (m_version >= 5 && compressed())
		decompress_v5_map();
	else
		file_read(m_mapoffset, &m_rawmap[0], m_rawmap.size());

	// allocate the temporary compressed buffer and a buffer for caching
	m_compressed.resize(m_hunkbytes);
	m_cache.resize(m_hunkbytes);
}

/**
 * @fn  void chd_file::verify_proper_compression_append(uint32_t hunknum)
 *
 * @brief   -------------------------------------------------
 *            verify_proper_compression_append - verify that the given hunk is a proper candidate
 *            for appending to a compressed CHD
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_NOT_OPEN             Thrown when a chderr not open error condition occurs.
 * @exception   CHDERR_HUNK_OUT_OF_RANGE    Thrown when a chderr hunk out of range error
 *                                          condition occurs.
 * @exception   CHDERR_FILE_NOT_WRITEABLE   Thrown when a chderr file not writeable error
 *                                          condition occurs.
 * @exception   CHDERR_COMPRESSION_ERROR    Thrown when a chderr compression error error
 *                                          condition occurs.
 *
 * @param   hunknum The hunknum.
 */

void chd_file::verify_proper_compression_append(uint32_t hunknum)
{
	// punt if no file
	if (m_file == nullptr)
		throw CHDERR_NOT_OPEN;

	// return an error if out of range
	if (hunknum >= m_hunkcount)
		throw CHDERR_HUNK_OUT_OF_RANGE;

	// if not writeable, fail
	if (!m_allow_writes)
		throw CHDERR_FILE_NOT_WRITEABLE;

	// compressed writes only via this interface
	if (!compressed())
		throw CHDERR_FILE_NOT_WRITEABLE;

	// only permitted to write new blocks
	uint8_t *rawmap = &m_rawmap[hunknum * 12];
	if (rawmap[0] != 0xff)
		throw CHDERR_COMPRESSION_ERROR;

	// if this isn't the first block, only permitted to write immediately
	// after the previous one
	if (hunknum != 0 && rawmap[-12] == 0xff)
		throw CHDERR_COMPRESSION_ERROR;
}

/**
 * @fn  void chd_file::hunk_write_compressed(uint32_t hunknum, int8_t compression, const uint8_t *compressed, uint32_t complength, crc16_t crc16)
 *
 * @brief   -------------------------------------------------
 *            hunk_write_compressed - write a hunk to a compressed CHD, discovering the best
 *            technique
 *          -------------------------------------------------.
 *
 * @param   hunknum     The hunknum.
 * @param   compression The compression.
 * @param   compressed  The compressed.
 * @param   complength  The complength.
 * @param   crc16       The CRC 16.
 */

void chd_file::hunk_write_compressed(uint32_t hunknum, int8_t compression, const uint8_t *compressed, uint32_t complength, util::crc16_t crc16)
{
	// verify that we are appending properly to a compressed file
	verify_proper_compression_append(hunknum);

	// write the final result
	uint64_t offset = file_append(compressed, complength);

	// update the map entry
	uint8_t *rawmap = &m_rawmap[hunknum * 12];
	rawmap[0] = (compression == -1) ? COMPRESSION_NONE : compression;
	be_write(&rawmap[1], complength, 3);
	be_write(&rawmap[4], offset, 6);
	be_write(&rawmap[10], crc16, 2);
}

/**
 * @fn  void chd_file::hunk_copy_from_self(uint32_t hunknum, uint32_t otherhunk)
 *
 * @brief   -------------------------------------------------
 *            hunk_copy_from_self - mark a hunk as being a copy of another hunk in the same CHD
 *          -------------------------------------------------.
 *
 * @exception   CHDERR_INVALID_PARAMETER    Thrown when a chderr invalid parameter error
 *                                          condition occurs.
 *
 * @param   hunknum     The hunknum.
 * @param   otherhunk   The otherhunk.
 */

void chd_file::hunk_copy_from_self(uint32_t hunknum, uint32_t otherhunk)
{
	// verify that we are appending properly to a compressed file
	verify_proper_compression_append(hunknum);

	// only permitted to reference prior hunks
	if (otherhunk >= hunknum)
		throw CHDERR_INVALID_PARAMETER;

	// update the map entry
	uint8_t *rawmap = &m_rawmap[hunknum * 12];
	rawmap[0] = COMPRESSION_SELF;
	be_write(&rawmap[1], 0, 3);
	be_write(&rawmap[4], otherhunk, 6);
	be_write(&rawmap[10], 0, 2);
}

/**
 * @fn  void chd_file::hunk_copy_from_parent(uint32_t hunknum, uint64_t parentunit)
 *
 * @brief   -------------------------------------------------
 *            hunk_copy_from_parent - mark a hunk as being a copy of a hunk from a parent CHD
 *          -------------------------------------------------.
 *
 * @param   hunknum     The hunknum.
 * @param   parentunit  The parentunit.
 */

void chd_file::hunk_copy_from_parent(uint32_t hunknum, uint64_t parentunit)
{
	// verify that we are appending properly to a compressed file
	verify_proper_compression_append(hunknum);

	// update the map entry
	uint8_t *rawmap = &m_rawmap[hunknum * 12];
	rawmap[0] = COMPRESSION_PARENT;
	be_write(&rawmap[1], 0, 3);
	be_write(&rawmap[4], parentunit, 6);
	be_write(&rawmap[10], 0, 2);
}

/**
 * @fn  bool chd_file::metadata_find(chd_metadata_tag metatag, int32_t metaindex, metadata_entry &metaentry, bool resume)
 *
 * @brief   -------------------------------------------------
 *            metadata_find - find a metadata entry
 *          -------------------------------------------------.
 *
 * @param   metatag             The metatag.
 * @param   metaindex           The metaindex.
 * @param [in,out]  metaentry   The metaentry.
 * @param   resume              true to resume.
 *
 * @return  true if it succeeds, false if it fails.
 */

bool chd_file::metadata_find(chd_metadata_tag metatag, int32_t metaindex, metadata_entry &metaentry, bool resume)
{
	// start at the beginning unless we're resuming a previous search
	if (!resume)
	{
		metaentry.offset = m_metaoffset;
		metaentry.prev = 0;
	}
	else
	{
		metaentry.prev = metaentry.offset;
		metaentry.offset = metaentry.next;
	}

	// loop until we run out of options
	while (metaentry.offset != 0)
	{
		// read the raw header
		uint8_t raw_meta_header[METADATA_HEADER_SIZE];
		file_read(metaentry.offset, raw_meta_header, sizeof(raw_meta_header));

		// extract the data
		metaentry.metatag = be_read(&raw_meta_header[0], 4);
		metaentry.flags = raw_meta_header[4];
		metaentry.length = be_read(&raw_meta_header[5], 3);
		metaentry.next = be_read(&raw_meta_header[8], 8);

		// if we got a match, proceed
		if (metatag == CHDMETATAG_WILDCARD || metaentry.metatag == metatag)
			if (metaindex-- == 0)
				return true;

		// no match, fetch the next link
		metaentry.prev = metaentry.offset;
		metaentry.offset = metaentry.next;
	}

	// if we get here, we didn't find it
	return false;
}

/**
 * @fn  void chd_file::metadata_set_previous_next(uint64_t prevoffset, uint64_t nextoffset)
 *
 * @brief   -------------------------------------------------
 *            metadata_set_previous_next - set the 'next' offset of a piece of metadata
 *          -------------------------------------------------.
 *
 * @param   prevoffset  The prevoffset.
 * @param   nextoffset  The nextoffset.
 */

void chd_file::metadata_set_previous_next(uint64_t prevoffset, uint64_t nextoffset)
{
	uint64_t offset = 0;

	// if we were the first entry, make the next entry the first
	if (prevoffset == 0)
	{
		offset = m_metaoffset_offset;
		m_metaoffset = nextoffset;
	}

	// otherwise, update the link in the previous header
	else
		offset = prevoffset + 8;

	// create a big-endian version
	uint8_t rawbuf[sizeof(uint64_t)];
	be_write(rawbuf, nextoffset, 8);

	// write to the header and update our local copy
	file_write(offset, rawbuf, sizeof(rawbuf));
}

/**
 * @fn  void chd_file::metadata_update_hash()
 *
 * @brief   -------------------------------------------------
 *            metadata_update_hash - compute the SHA1 hash of all metadata that requests it
 *          -------------------------------------------------.
 */

void chd_file::metadata_update_hash()
{
	// only works for V4 and above, and only for compressed CHDs
	if (m_version < 4 || !compressed())
		return;

	// compute the new overall hash
	util::sha1_t fullsha1 = compute_overall_sha1(raw_sha1());

	// create a big-endian version
	uint8_t rawbuf[sizeof(util::sha1_t)];
	be_write_sha1(&rawbuf[0], fullsha1);

	// write to the header
	file_write(m_sha1_offset, rawbuf, sizeof(rawbuf));
}

/**
 * @fn  int CLIB_DECL chd_file::metadata_hash_compare(const void *elem1, const void *elem2)
 *
 * @brief   -------------------------------------------------
 *            metadata_hash_compare - compare two hash entries
 *          -------------------------------------------------.
 *
 * @param   elem1   The first element.
 * @param   elem2   The second element.
 *
 * @return  A CLIB_DECL.
 */

int CLIB_DECL chd_file::metadata_hash_compare(const void *elem1, const void *elem2)
{
	return memcmp(elem1, elem2, sizeof(metadata_hash));
}



//**************************************************************************
//  CHD COMPRESSOR
//**************************************************************************

/**
 * @fn  chd_file_compressor::chd_file_compressor()
 *
 * @brief   -------------------------------------------------
 *            chd_file_compressor - constructor
 *          -------------------------------------------------.
 */

chd_file_compressor::chd_file_compressor()
	: m_walking_parent(false),
		m_total_in(0),
		m_total_out(0),
		m_read_queue(nullptr),
		m_read_queue_offset(0),
		m_read_done_offset(0),
		m_read_error(false),
		m_work_queue(nullptr),
		m_write_hunk(0)
{
	// zap arrays
	memset(m_codecs, 0, sizeof(m_codecs));

	// allocate work queues
	m_read_queue = osd_work_queue_alloc(WORK_QUEUE_FLAG_IO);
	m_work_queue = osd_work_queue_alloc(WORK_QUEUE_FLAG_MULTI);
}

/**
 * @fn  chd_file_compressor::~chd_file_compressor()
 *
 * @brief   -------------------------------------------------
 *            ~chd_file_compressor - destructor
 *          -------------------------------------------------.
 */

chd_file_compressor::~chd_file_compressor()
{
	// free the work queues
	osd_work_queue_free(m_read_queue);
	osd_work_queue_free(m_work_queue);

	// delete allocated arrays
	for (auto & elem : m_codecs)
		delete elem;
}

/**
 * @fn  void chd_file_compressor::compress_begin()
 *
 * @brief   -------------------------------------------------
 *            compress_begin - initiate compression
 *          -------------------------------------------------.
 */

void chd_file_compressor::compress_begin()
{
	// reset state
	m_walking_parent = (m_parent != nullptr);
	m_total_in = 0;
	m_total_out = 0;
	m_compsha1.reset();

	// reset our maps
	m_parent_map.reset();
	m_current_map.reset();

	// reset read state
	m_read_queue_offset = 0;
	m_read_done_offset = 0;
	m_read_error = false;

	// reset work item state
	m_work_buffer.resize(hunk_bytes() * (WORK_BUFFER_HUNKS + 1));
	memset(&m_work_buffer[0], 0, m_work_buffer.size());
	m_compressed_buffer.resize(hunk_bytes() * WORK_BUFFER_HUNKS);
	for (int itemnum = 0; itemnum < WORK_BUFFER_HUNKS; itemnum++)
	{
		work_item &item = m_work_item[itemnum];
		item.m_compressor = this;
		item.m_data = &m_work_buffer[hunk_bytes() * itemnum];
		item.m_compressed = &m_compressed_buffer[hunk_bytes() * itemnum];
		item.m_hash.resize(hunk_bytes() / unit_bytes());
	}

	// initialize codec instances
	for (auto & elem : m_codecs)
	{
		delete elem;
		elem = new chd_compressor_group(*this, m_compression);
	}

	// reset write state
	m_write_hunk = 0;
}

/**
 * @fn  chd_error chd_file_compressor::compress_continue(double &progress, double &ratio)
 *
 * @brief   -------------------------------------------------
 *            compress_continue - continue compression
 *          -------------------------------------------------.
 *
 * @param [in,out]  progress    The progress.
 * @param [in,out]  ratio       The ratio.
 *
 * @return  A chd_error.
 */

chd_error chd_file_compressor::compress_continue(double &progress, double &ratio)
{
	// if we got an error, return an error
	if (m_read_error)
		return CHDERR_READ_ERROR;

	// if done reading, queue some more
	while (m_read_queue_offset < m_logicalbytes && osd_work_queue_items(m_read_queue) < 2)
	{
		// see if we have enough free work items to read the next half of a buffer
		uint32_t startitem = m_read_queue_offset / hunk_bytes();
		uint32_t enditem = startitem + WORK_BUFFER_HUNKS / 2;
		uint32_t curitem;
		for (curitem = startitem; curitem < enditem; curitem++)
			if (m_work_item[curitem % WORK_BUFFER_HUNKS].m_status != WS_READY)
				break;

		// if it's not all clear, defer
		if (curitem != enditem)
			break;

		// if we're walking the parent, we want one more item to have cleared so we
		// can read an extra hunk there
		if (m_walking_parent && m_work_item[curitem % WORK_BUFFER_HUNKS].m_status != WS_READY)
			break;

		// queue the next read
		for (curitem = startitem; curitem < enditem; curitem++)
			m_work_item[curitem % WORK_BUFFER_HUNKS].m_status = WS_READING;
		osd_work_item_queue(m_read_queue, async_read_static, this, WORK_ITEM_FLAG_AUTO_RELEASE);
		m_read_queue_offset += WORK_BUFFER_HUNKS * hunk_bytes() / 2;
	}

	// flush out any finished items
	while (m_work_item[m_write_hunk % WORK_BUFFER_HUNKS].m_status == WS_COMPLETE)
	{
		work_item &item = m_work_item[m_write_hunk % WORK_BUFFER_HUNKS];

		// free any OSD work item
		if (item.m_osd != nullptr)
			osd_work_item_release(item.m_osd);
		item.m_osd = nullptr;

		// for parent walking, just add to the hashmap
		if (m_walking_parent)
		{
			uint32_t uph = hunk_bytes() / unit_bytes();
			uint32_t units = uph;
			if (item.m_hunknum == hunk_count() - 1 || !compressed())
				units = 1;
			for (uint32_t unit = 0; unit < units; unit++)
				if (m_parent_map.find(item.m_hash[unit].m_crc16, item.m_hash[unit].m_sha1) == hashmap::NOT_FOUND)
					m_parent_map.add(item.m_hunknum * uph + unit, item.m_hash[unit].m_crc16, item.m_hash[unit].m_sha1);
		}

		// if we're uncompressed, use regular writes
		else if (!compressed())
		{
			chd_error err = write_hunk(item.m_hunknum, item.m_data);
			if (err != CHDERR_NONE)
				return err;

			// writes of all-0 data don't actually take space, so see if we count this
			chd_codec_type codec = CHD_CODEC_NONE;
			uint32_t complen;
			hunk_info(item.m_hunknum, codec, complen);
			if (codec == CHD_CODEC_NONE)
				m_total_out += m_hunkbytes;
		}

		// for compressing, process the result
		else do
		{
			// first see if the hunk is in the parent or self maps
			uint64_t selfhunk = m_current_map.find(item.m_hash[0].m_crc16, item.m_hash[0].m_sha1);
			if (selfhunk != hashmap::NOT_FOUND)
			{
				hunk_copy_from_self(item.m_hunknum, selfhunk);
				break;
			}

			// if not, see if it's in the parent map
			if (m_parent != nullptr)
			{
				uint64_t parentunit = m_parent_map.find(item.m_hash[0].m_crc16, item.m_hash[0].m_sha1);
				if (parentunit != hashmap::NOT_FOUND)
				{
					hunk_copy_from_parent(item.m_hunknum, parentunit);
					break;
				}
			}

			// otherwise, append it compressed and add to the self map
			hunk_write_compressed(item.m_hunknum, item.m_compression, item.m_compressed, item.m_complen, item.m_hash[0].m_crc16);
			m_total_out += item.m_complen;
			m_current_map.add(item.m_hunknum, item.m_hash[0].m_crc16, item.m_hash[0].m_sha1);
		} while (0);

		// reset the item and advance
		item.m_status = WS_READY;
		m_write_hunk++;

		// if we hit the end, finalize
		if (m_write_hunk == m_hunkcount)
		{
			// if this is just walking the parent, reset and get ready for compression
			if (m_walking_parent)
			{
				m_walking_parent = false;
				m_read_queue_offset = m_read_done_offset = 0;
				m_write_hunk = 0;
				for (auto & elem : m_work_item)
					elem.m_status = WS_READY;
			}

			// wait for all reads to finish and if we're compressed, write the final SHA1 and map
			else
			{
				osd_work_queue_wait(m_read_queue, 30 * osd_ticks_per_second());
				if (!compressed())
					return CHDERR_NONE;
				set_raw_sha1(m_compsha1.finish());
				return compress_v5_map();
			}
		}
	}

	// update progress and ratio
	if (m_walking_parent)
		progress = double(m_read_done_offset) / double(logical_bytes());
	else
		progress = double(m_write_hunk) / double(m_hunkcount);
	ratio = (m_total_in == 0) ? 1.0 : double(m_total_out) / double(m_total_in);

	// if we're waiting for work, wait
	// sometimes code can get here with .m_status == WS_READY and .m_osd != nullptr, TODO find out why this happens
	while (m_work_item[m_write_hunk % WORK_BUFFER_HUNKS].m_status != WS_READY &&
		m_work_item[m_write_hunk % WORK_BUFFER_HUNKS].m_status != WS_COMPLETE &&
		m_work_item[m_write_hunk % WORK_BUFFER_HUNKS].m_osd != nullptr)
		osd_work_item_wait(m_work_item[m_write_hunk % WORK_BUFFER_HUNKS].m_osd, osd_ticks_per_second());

	return m_walking_parent ? CHDERR_WALKING_PARENT : CHDERR_COMPRESSING;
}

/**
 * @fn  void *chd_file_compressor::async_walk_parent_static(void *param, int threadid)
 *
 * @brief   -------------------------------------------------
 *            async_walk_parent - handle asynchronous parent walking operations
 *          -------------------------------------------------.
 *
 * @param [in,out]  param   If non-null, the parameter.
 * @param   threadid        The threadid.
 *
 * @return  null if it fails, else a void*.
 */

void *chd_file_compressor::async_walk_parent_static(void *param, int threadid)
{
	work_item *item = reinterpret_cast<work_item *>(param);
	item->m_compressor->async_walk_parent(*item);
	return nullptr;
}

/**
 * @fn  void chd_file_compressor::async_walk_parent(work_item &item)
 *
 * @brief   Asynchronous walk parent.
 *
 * @param [in,out]  item    The item.
 */

void chd_file_compressor::async_walk_parent(work_item &item)
{
	// compute CRC-16 and SHA-1 hashes for each unit, unless we're the last one or we're uncompressed
	uint32_t units = hunk_bytes() / unit_bytes();
	if (item.m_hunknum == m_hunkcount - 1 || !compressed())
		units = 1;
	for (uint32_t unit = 0; unit < units; unit++)
	{
		item.m_hash[unit].m_crc16 = util::crc16_creator::simple(item.m_data + unit * unit_bytes(), hunk_bytes());
		item.m_hash[unit].m_sha1 = util::sha1_creator::simple(item.m_data + unit * unit_bytes(), hunk_bytes());
	}
	item.m_status = WS_COMPLETE;
}

/**
 * @fn  void *chd_file_compressor::async_compress_hunk_static(void *param, int threadid)
 *
 * @brief   -------------------------------------------------
 *            async_compress_hunk - handle asynchronous hunk compression
 *          -------------------------------------------------.
 *
 * @param [in,out]  param   If non-null, the parameter.
 * @param   threadid        The threadid.
 *
 * @return  null if it fails, else a void*.
 */

void *chd_file_compressor::async_compress_hunk_static(void *param, int threadid)
{
	work_item *item = reinterpret_cast<work_item *>(param);
	item->m_compressor->async_compress_hunk(*item, threadid);
	return nullptr;
}

/**
 * @fn  void chd_file_compressor::async_compress_hunk(work_item &item, int threadid)
 *
 * @brief   Asynchronous compress hunk.
 *
 * @param [in,out]  item    The item.
 * @param   threadid        The threadid.
 */

void chd_file_compressor::async_compress_hunk(work_item &item, int threadid)
{
	// use our thread's codec
	assert(threadid < ARRAY_LENGTH(m_codecs));
	item.m_codecs = m_codecs[threadid];

	// compute CRC-16 and SHA-1 hashes
	item.m_hash[0].m_crc16 = util::crc16_creator::simple(item.m_data, hunk_bytes());
	item.m_hash[0].m_sha1 = util::sha1_creator::simple(item.m_data, hunk_bytes());

	// find the best compression scheme, unless we already have a self or parent match
	// (note we may miss a self match from blocks not yet added, but this just results in extra work)
	// TODO: data race
	if (m_current_map.find(item.m_hash[0].m_crc16, item.m_hash[0].m_sha1) == hashmap::NOT_FOUND &&
		m_parent_map.find(item.m_hash[0].m_crc16, item.m_hash[0].m_sha1) == hashmap::NOT_FOUND)
		item.m_compression = item.m_codecs->find_best_compressor(item.m_data, item.m_compressed, item.m_complen);

	// mark us complete
	item.m_status = WS_COMPLETE;
}

/**
 * @fn  void *chd_file_compressor::async_read_static(void *param, int threadid)
 *
 * @brief   -------------------------------------------------
 *            async_read - handle asynchronous source file reading
 *          -------------------------------------------------.
 *
 * @param [in,out]  param   If non-null, the parameter.
 * @param   threadid        The threadid.
 *
 * @return  null if it fails, else a void*.
 */

void *chd_file_compressor::async_read_static(void *param, int threadid)
{
	reinterpret_cast<chd_file_compressor *>(param)->async_read();
	return nullptr;
}

/**
 * @fn  void chd_file_compressor::async_read()
 *
 * @brief   Asynchronous read.
 */

void chd_file_compressor::async_read()
{
	// if in the error or complete state, stop
	if (m_read_error)
		return;

	// determine parameters for the read
	uint32_t work_buffer_bytes = WORK_BUFFER_HUNKS * hunk_bytes();
	uint32_t numbytes = work_buffer_bytes / 2;
	if (m_read_done_offset + numbytes > logical_bytes())
		numbytes = logical_bytes() - m_read_done_offset;

	// catch any exceptions coming out of here
	try
	{
		// do the read
		uint8_t *dest = &m_work_buffer[0] + (m_read_done_offset % work_buffer_bytes);
		assert(dest == &m_work_buffer[0] || dest == &m_work_buffer[work_buffer_bytes/2]);
		uint64_t end_offset = m_read_done_offset + numbytes;

		// if walking the parent, read in hunks from the parent CHD
		if (m_walking_parent)
		{
			uint8_t *curdest = dest;
			for (uint64_t curoffs = m_read_done_offset; curoffs < end_offset + 1; curoffs += hunk_bytes())
			{
				m_parent->read_hunk(curoffs / hunk_bytes(), curdest);
				curdest += hunk_bytes();
			}
		}

		// otherwise, call the virtual function
		else
			read_data(dest, m_read_done_offset, numbytes);

		// spawn off work for each hunk
		for (uint64_t curoffs = m_read_done_offset; curoffs < end_offset; curoffs += hunk_bytes())
		{
			uint32_t hunknum = curoffs / hunk_bytes();
			work_item &item = m_work_item[hunknum % WORK_BUFFER_HUNKS];
			assert(item.m_status == WS_READING);
			item.m_status = WS_QUEUED;
			item.m_hunknum = hunknum;
			item.m_osd = osd_work_item_queue(m_work_queue, m_walking_parent ? async_walk_parent_static : async_compress_hunk_static, &item, 0);
		}

		// continue the running SHA-1
		if (!m_walking_parent)
		{
			if (compressed())
				m_compsha1.append(dest, numbytes);
			m_total_in += numbytes;
		}

		// advance the read pointer
		m_read_done_offset += numbytes;
	}
	catch (chd_error& err)
	{
		fprintf(stderr, "CHD error occurred: %s\n", chd_file::error_string(err));
		m_read_error = true;
	}
	catch (std::exception& ex)
	{
		fprintf(stderr, "exception occurred: %s\n", ex.what());
		m_read_error = true;
	}
}



//**************************************************************************
//  CHD COMPRESSOR HASHMAP
//**************************************************************************

/**
 * @fn  chd_file_compressor::hashmap::hashmap()
 *
 * @brief   -------------------------------------------------
 *            hashmap - constructor
 *          -------------------------------------------------.
 */

chd_file_compressor::hashmap::hashmap()
	: m_block_list(new entry_block(nullptr))
{
	// initialize the map to empty
	memset(m_map, 0, sizeof(m_map));
}

/**
 * @fn  chd_file_compressor::hashmap::~hashmap()
 *
 * @brief   -------------------------------------------------
 *            ~hashmap - destructor
 *          -------------------------------------------------.
 */

chd_file_compressor::hashmap::~hashmap()
{
	reset();
	delete m_block_list;
}

/**
 * @fn  void chd_file_compressor::hashmap::reset()
 *
 * @brief   -------------------------------------------------
 *            reset - reset the state of the map
 *          -------------------------------------------------.
 */

void chd_file_compressor::hashmap::reset()
{
	// delete all the blocks
	while (m_block_list->m_next != nullptr)
	{
		entry_block *block = m_block_list;
		m_block_list = block->m_next;
		delete block;
	}
	m_block_list->m_nextalloc = 0;

	// reset the hash
	memset(m_map, 0, sizeof(m_map));
}

/**
 * @fn  uint64_t chd_file_compressor::hashmap::find(crc16_t crc16, sha1_t sha1)
 *
 * @brief   -------------------------------------------------
 *            find - find an item in the CRC map
 *          -------------------------------------------------.
 *
 * @param   crc16   The CRC 16.
 * @param   sha1    The first sha.
 *
 * @return  An uint64_t.
 */

uint64_t chd_file_compressor::hashmap::find(util::crc16_t crc16, util::sha1_t sha1)
{
	// look up the entry in the map
	for (entry_t *entry = m_map[crc16]; entry != nullptr; entry = entry->m_next)
		if (entry->m_sha1 == sha1)
			return entry->m_itemnum;
	return NOT_FOUND;
}

/**
 * @fn  void chd_file_compressor::hashmap::add(uint64_t itemnum, crc16_t crc16, sha1_t sha1)
 *
 * @brief   -------------------------------------------------
 *            add - add an item to the CRC map
 *          -------------------------------------------------.
 *
 * @param   itemnum The itemnum.
 * @param   crc16   The CRC 16.
 * @param   sha1    The first sha.
 */

void chd_file_compressor::hashmap::add(uint64_t itemnum, util::crc16_t crc16, util::sha1_t sha1)
{
	// add to the appropriate map
	if (m_block_list->m_nextalloc == ARRAY_LENGTH(m_block_list->m_array))
		m_block_list = new entry_block(m_block_list);
	entry_t *entry = &m_block_list->m_array[m_block_list->m_nextalloc++];
	entry->m_itemnum = itemnum;
	entry->m_sha1 = sha1;
	entry->m_next = m_map[crc16];
	m_map[crc16] = entry;
}