mirror of
https://git.do.srb2.org/STJr/SRB2.git
synced 2024-12-01 16:52:25 +00:00
51 lines
2.7 KiB
C
51 lines
2.7 KiB
C
/* 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);
|