diff options
Diffstat (limited to '3rdparty/zlib/examples/zran.h')
-rw-r--r-- | 3rdparty/zlib/examples/zran.h | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/3rdparty/zlib/examples/zran.h b/3rdparty/zlib/examples/zran.h new file mode 100644 index 00000000000..ebf780d0c1f --- /dev/null +++ b/3rdparty/zlib/examples/zran.h @@ -0,0 +1,51 @@ +/* zran.h -- example of deflated stream indexing and random access + * Copyright (C) 2005, 2012, 2018, 2023 Mark Adler + * For conditions of distribution and use, see copyright notice in zlib.h + * Version 1.3 18 Feb 2023 Mark Adler */ + +#include <stdio.h> +#include "zlib.h" + +// Access point. +typedef struct point { + off_t out; // offset in uncompressed data + off_t in; // offset in compressed file of first full byte + int bits; // 0, or number of bits (1-7) from byte at in-1 + unsigned char window[32768]; // preceding 32K of uncompressed data +} point_t; + +// Access point list. +struct deflate_index { + int have; // number of access points in list + int mode; // -15 for raw, 15 for zlib, or 31 for gzip + off_t length; // total length of uncompressed data + point_t *list; // allocated list of access points +}; + +// Make one pass through a zlib, gzip, or raw deflate compressed stream and +// build an index, with access points about every span bytes of uncompressed +// output. gzip files with multiple members are fully indexed. span should be +// chosen to balance the speed of random access against the memory requirements +// of the list, which is about 32K bytes per access point. The return value is +// the number of access points on success (>= 1), Z_MEM_ERROR for out of +// memory, Z_BUF_ERROR for a premature end of input, Z_DATA_ERROR for a format +// or verification error in the input file, or Z_ERRNO for a file read error. +// On success, *built points to the resulting index. +int deflate_index_build(FILE *in, off_t span, struct deflate_index **built); + +// Use the index to read len bytes from offset into buf. Return the number of +// bytes read or a negative error code. If data is requested past the end of +// the uncompressed data, then deflate_index_extract() will return a value less +// than len, indicating how much was actually read into buf. If given a valid +// index, this function should not return an error unless the file was modified +// somehow since the index was generated, given that deflate_index_build() had +// validated all of the input. If nevertheless there is a failure, Z_BUF_ERROR +// is returned if the compressed data ends prematurely, Z_DATA_ERROR if the +// deflate compressed data is not valid, Z_MEM_ERROR if out of memory, +// Z_STREAM_ERROR if the index is not valid, or Z_ERRNO if there is an error +// reading or seeking on the input file. +ptrdiff_t deflate_index_extract(FILE *in, struct deflate_index *index, + off_t offset, unsigned char *buf, size_t len); + +// Deallocate an index built by deflate_index_build(). +void deflate_index_free(struct deflate_index *index); |