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-rw-r--r--src/lib/formats/img_dsk.cpp378
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diff --git a/src/lib/formats/img_dsk.cpp b/src/lib/formats/img_dsk.cpp
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+// license:BSD-3-Clause
+// copyright-holders: F. Ulivi
+/*********************************************************************
+
+ img_dsk.cpp
+
+ "IMG" disk format
+
+ This format is just a raw image of every sector on SSDD 8" floppy
+ disks as used in Intel MDS-II systems.
+ Files with this format have no header/trailer and are exactly
+ 512512 bytes in size (52 sectors, 1 head, 77 tracks,
+ 128 bytes per sector).
+
+*********************************************************************/
+
+#include "emu.h"
+#include "img_dsk.h"
+
+// Debugging
+#define VERBOSE 0
+#define LOG(...) do { if (VERBOSE) printf(__VA_ARGS__); } while (false)
+
+constexpr unsigned CELL_SIZE = 1200; // Bit cell size (1 µs)
+constexpr uint8_t INDEX_AM = 0x0c; // Index address mark
+constexpr uint8_t ID_AM = 0x0e; // ID address mark
+constexpr uint8_t DATA_AM = 0x0b; // Data address mark
+constexpr uint8_t AM_CLOCK = 0x70; // Clock pattern of AM
+constexpr unsigned PREIDX_GAP = 45; // Size of pre-index gap
+constexpr unsigned SYNC_00_LEN = 18; // 00's in sync (gaps 1, 2, 3)
+constexpr unsigned SYNC_FF_LEN = 10; // FF's in sync (gaps 1, 2, 3)
+constexpr int ID_DATA_OFFSET = 35 * 16; // Nominal distance (in cells) between ID & DATA AM
+// Size of image file
+constexpr unsigned IMG_IMAGE_SIZE = IMG_TRACKS * IMG_HEADS * IMG_SECTORS * IMG_SECTOR_SIZE;
+constexpr uint16_t CRC_POLY = 0x1021; // CRC-CCITT
+
+img_format::img_format()
+{
+}
+
+int img_format::identify(io_generic *io, uint32_t form_factor)
+{
+ uint64_t size = io_generic_size(io);
+
+ if (((form_factor == floppy_image::FF_8) || (form_factor == floppy_image::FF_UNKNOWN)) &&
+ size == IMG_IMAGE_SIZE) {
+ return 50;
+ } else {
+ return 0;
+ }
+}
+
+bool img_format::load(io_generic *io, uint32_t form_factor, floppy_image *image)
+{
+ uint64_t size = io_generic_size(io);
+ if (size != IMG_IMAGE_SIZE) {
+ return false;
+ }
+ image->set_variant(floppy_image::SSDD);
+
+ // Suck in the whole image
+ std::vector<uint8_t> image_data(size);
+ io_generic_read(io, (void *)image_data.data(), 0, size);
+
+ for (unsigned cyl = 0; cyl < IMG_TRACKS; cyl++) {
+ std::vector<uint32_t> track_data;
+
+ write_gap(track_data, 0 , PREIDX_GAP);
+ write_mmfm_byte(track_data , INDEX_AM , AM_CLOCK);
+
+ // Compute interleave factor and skew for current track
+ unsigned il_factor;
+ unsigned skew;
+ if (cyl == 0) {
+ il_factor = 1;
+ skew = 51;
+ } else if (cyl == 1) {
+ il_factor = 4;
+ skew = 48;
+ } else {
+ il_factor = 5;
+ skew = (47 + 45 * (cyl - 2)) % 52;
+ }
+ std::vector<uint8_t> sector_list = interleaved_sectors(il_factor);
+
+ for (unsigned sector = 0; sector < IMG_SECTORS; sector++) {
+ unsigned real_sector = sector_list[ (sector + skew) % IMG_SECTORS ];
+ unsigned offset_in_image = (real_sector - 1 + cyl * IMG_SECTORS) * IMG_SECTOR_SIZE;
+ write_sector(track_data , cyl , real_sector , &image_data[ offset_in_image ]);
+ }
+ fill_with_gap4(track_data);
+ generate_track_from_levels(cyl , 0 , track_data , 0 , image);
+ }
+ return true;
+}
+
+bool img_format::save(io_generic *io, floppy_image *image)
+{
+ for (int cyl = 0; cyl < IMG_TRACKS; cyl++) {
+ uint8_t bitstream[ 21000 ];
+ int bitstream_size;
+ generate_bitstream_from_track(cyl , 0 , CELL_SIZE , bitstream , bitstream_size , image , 0);
+ int pos = 0;
+ unsigned track_no , sector_no;
+ uint8_t sector_data[ IMG_SECTOR_SIZE ];
+ while (get_next_sector(bitstream , bitstream_size , pos , track_no , sector_no , sector_data)) {
+ if (track_no == cyl && sector_no >= 1 && sector_no <= IMG_SECTORS) {
+ unsigned offset_in_image = (cyl * IMG_SECTORS + sector_no - 1) * IMG_SECTOR_SIZE;
+ io_generic_write(io, sector_data, offset_in_image, IMG_SECTOR_SIZE);
+ }
+ }
+ }
+ return true;
+}
+
+const char *img_format::name() const
+{
+ return "img";
+}
+
+const char *img_format::description() const
+{
+ return "MDS-II floppy disk image";
+}
+
+const char *img_format::extensions() const
+{
+ return "img";
+}
+
+bool img_format::supports_save() const
+{
+ return true;
+}
+
+std::vector<uint8_t> img_format::interleaved_sectors(unsigned il_factor)
+{
+ std::vector<uint8_t> out(IMG_SECTORS);
+ unsigned idx = 0;
+ for (unsigned s = 0; s < IMG_SECTORS; s++) {
+ while (out[ idx ] != 0) {
+ if (++idx >= IMG_SECTORS) {
+ idx = 0;
+ }
+ }
+ out[ idx ] = s + 1;
+ idx += il_factor;
+ if (idx >= IMG_SECTORS) {
+ idx -= IMG_SECTORS;
+ }
+ }
+ return out;
+}
+
+void img_format::write_mmfm_bit(std::vector<uint32_t> &buffer , bool data_bit , bool clock_bit)
+{
+ bool had_transition = buffer.size() < 2 ? false : bit_r(buffer, buffer.size() - 1) || bit_r(buffer , buffer.size() - 2);
+ clock_bit = !data_bit && (clock_bit || !had_transition);
+ bit_w(buffer , clock_bit , CELL_SIZE);
+ bit_w(buffer , data_bit , CELL_SIZE);
+
+ if (BIT(m_crc , 15) ^ data_bit) {
+ m_crc = (m_crc << 1) ^ CRC_POLY;
+ } else {
+ m_crc <<= 1;
+ }
+}
+
+void img_format::write_mmfm_byte(std::vector<uint32_t> &buffer , uint8_t data , uint8_t clock)
+{
+ for (int i = 7; i >= 0; i--) {
+ write_mmfm_bit(buffer , BIT(data , i) , BIT(clock , i));
+ }
+}
+
+void img_format::write_sync(std::vector<uint32_t> &buffer)
+{
+ write_gap(buffer , SYNC_00_LEN , SYNC_FF_LEN);
+}
+
+void img_format::write_crc(std::vector<uint32_t> &buffer , uint16_t crc)
+{
+ // Note that CRC is stored with MSB (x^15) first
+ for (unsigned i = 0; i < 16; i++) {
+ write_mmfm_bit(buffer , BIT(crc , 15 - i) , 0);
+ }
+}
+
+void img_format::write_gap(std::vector<uint32_t> &buffer , unsigned size_00 , unsigned size_ff)
+{
+ for (unsigned i = 0; i < size_00; ++i) {
+ write_mmfm_byte(buffer, 0);
+ }
+ for (unsigned i = 0; i < size_ff; ++i) {
+ write_mmfm_byte(buffer, 0xff);
+ }
+}
+
+void img_format::write_sector(std::vector<uint32_t> &buffer , uint8_t track_no , uint8_t sect_no , const uint8_t *sect_data)
+{
+ // **** On-disk format of a sector ****
+ //
+ // | Offset | Size | Value | Content |
+ // |--------+------+-------+----------------------|
+ // | 0 | 18 | 00 | Gap 1/3 |
+ // | 18 | 10 | ff | Gap 1/3 |
+ // | 28 | 1 | 0e | ID AM (clock = 70) |
+ // | 29 | 1 | xx | Track no. |
+ // | 30 | 1 | 00 | N/U |
+ // | 31 | 1 | xx | Sector no. |
+ // | 32 | 1 | 00 | N/U |
+ // | 33 | 2 | xx | ID CRC |
+ // | 35 | 18 | 00 | Gap 2 |
+ // | 53 | 10 | ff | Gap 2 |
+ // | 63 | 1 | 0b | Data AM (clock = 70) |
+ // | 64 | 128 | xx | Sector data |
+ // | 192 | 2 | xx | Data CRC |
+ // | 194 | | | |
+
+ // Gap1
+ write_sync(buffer);
+ // ID AM
+ m_crc = 0;
+ write_mmfm_byte(buffer , ID_AM , AM_CLOCK);
+ // Track #
+ write_mmfm_byte(buffer , track_no);
+ write_mmfm_byte(buffer , 0);
+ // Sector #
+ write_mmfm_byte(buffer , sect_no);
+ write_mmfm_byte(buffer , 0);
+ // ID CRC
+ write_crc(buffer , m_crc);
+ // Gap 2
+ write_sync(buffer);
+ // Data AM
+ m_crc = 0;
+ write_mmfm_byte(buffer , DATA_AM , AM_CLOCK);
+ for (unsigned i = 0; i < IMG_SECTOR_SIZE; i++) {
+ // Data
+ write_mmfm_byte(buffer , sect_data[ i ]);
+ }
+ // Data CRC
+ write_crc(buffer , m_crc);
+}
+
+void img_format::fill_with_gap4(std::vector<uint32_t> &buffer)
+{
+ // Cell count in a track (1 µs cells in a 1/6 s track)
+ unsigned cell_count = (500000 * 120) / 360;
+ unsigned cells_in_buffer = buffer.size();
+ // Size of gap 4
+ unsigned gap_4 = (cell_count - cells_in_buffer) / 16;
+ // Gap 4
+ write_gap(buffer , gap_4 , 0);
+ // Last cell to round everything up to 2E+8
+ if (buffer.size() * CELL_SIZE < 200000000) {
+ bit_w(buffer , false , 200000000 - buffer.size() * CELL_SIZE);
+ }
+}
+
+std::vector<uint8_t> img_format::get_next_id_n_block(const uint8_t *bitstream , int bitstream_size , int& pos , int& start_pos)
+{
+ std::vector<uint8_t> res;
+ uint8_t data_sr;
+ uint8_t clock_sr;
+
+ // Look for either sync + ID AM or sync + DATA AM
+ do {
+ unsigned cnt_trans = 0;
+ while (pos < bitstream_size && cnt_trans < 34) {
+ bool bit = BIT(bitstream[ pos >> 3 ] , ~pos & 7);
+ pos++;
+ if (cnt_trans < 32) {
+ if (!(BIT(cnt_trans , 0) ^ bit)) {
+ cnt_trans++;
+ } else {
+ cnt_trans = 0;
+ }
+ } else if (cnt_trans == 32) {
+ if (!bit) {
+ start_pos = pos;
+ cnt_trans++;
+ } else {
+ cnt_trans = 0;
+ }
+ } else if (!bit) {
+ cnt_trans++;
+ } else {
+ cnt_trans = 32;
+ }
+ }
+
+ if (pos == bitstream_size) {
+ // End of track reached
+ return res;
+ }
+
+ // Get AM
+ data_sr = clock_sr = 0;
+ for (unsigned i = 0; i < 7; ++i) {
+ bool bit = BIT(bitstream[ pos >> 3 ] , ~pos & 7);
+ pos++;
+ clock_sr = (clock_sr << 1) | bit;
+ bit = BIT(bitstream[ pos >> 3 ] , ~pos & 7);
+ pos++;
+ data_sr = (data_sr << 1) | bit;
+ }
+ if (pos >= bitstream_size) {
+ return res;
+ }
+ } while (clock_sr != AM_CLOCK);
+
+ // ID blocks: Track no. + 0 + sector no. + 0 + CRC
+ // Data blocks: Sector data + CRC
+ res.push_back(data_sr);
+ unsigned to_dump;
+ if (data_sr == ID_AM) {
+ to_dump = 4;
+ } else if (data_sr == DATA_AM) {
+ to_dump = IMG_SECTOR_SIZE;
+ } else {
+ to_dump = 0;
+ }
+
+ pos++;
+ for (unsigned i = 0; i < to_dump && pos < bitstream_size; i++) {
+ data_sr = 0;
+ unsigned j;
+ for (j = 0; j < 8 && pos < bitstream_size; j++) {
+ bool bit = BIT(bitstream[ pos >> 3 ] , ~pos & 7);
+ pos += 2;
+ data_sr = (data_sr << 1) | bit;
+ }
+ if (j == 8) {
+ res.push_back(data_sr);
+ }
+ }
+ return res;
+}
+
+bool img_format::get_next_sector(const uint8_t *bitstream , int bitstream_size , int& pos , unsigned& track , unsigned& sector , uint8_t *sector_data)
+{
+ std::vector<uint8_t> block;
+ while (true) {
+ // Scan for ID block first
+ int id_pos = 0;
+ while (true) {
+ if (block.size() == 0) {
+ block = get_next_id_n_block(bitstream , bitstream_size , pos , id_pos);
+ if (block.size() == 0) {
+ return false;
+ }
+ }
+ if (block[ 0 ] == ID_AM && block.size() >= 5) {
+ track = block[ 1 ];
+ sector = block[ 3 ];
+ break;
+ } else {
+ block.clear();
+ }
+ }
+ // Then for DATA block
+ int data_pos = 0;
+ block = get_next_id_n_block(bitstream , bitstream_size , pos , data_pos);
+ if (block.size() == 0) {
+ return false;
+ }
+ if (block[ 0 ] == DATA_AM && block.size() >= (IMG_SECTOR_SIZE + 1) && abs((data_pos - id_pos) - ID_DATA_OFFSET) <= 64) {
+ break;
+ }
+ }
+
+ memcpy(sector_data , block.data() + 1 , IMG_SECTOR_SIZE);
+
+ return true;
+}
+
+const floppy_format_type FLOPPY_IMG_FORMAT = &floppy_image_format_creator<img_format>;