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Diffstat (limited to 'Modules/zlib/examples/zran.c')
| -rw-r--r-- | Modules/zlib/examples/zran.c | 404 |
1 files changed, 0 insertions, 404 deletions
diff --git a/Modules/zlib/examples/zran.c b/Modules/zlib/examples/zran.c deleted file mode 100644 index 8c7717e..0000000 --- a/Modules/zlib/examples/zran.c +++ /dev/null @@ -1,404 +0,0 @@ -/* zran.c -- example of zlib/gzip stream indexing and random access - * Copyright (C) 2005 Mark Adler - * For conditions of distribution and use, see copyright notice in zlib.h - Version 1.0 29 May 2005 Mark Adler */ - -/* Illustrate the use of Z_BLOCK, inflatePrime(), and inflateSetDictionary() - for random access of a compressed file. A file containing a zlib or gzip - stream is provided on the command line. The compressed stream is decoded in - its entirety, and an index built with access points about every SPAN bytes - in the uncompressed output. The compressed file is left open, and can then - be read randomly, having to decompress on the average SPAN/2 uncompressed - bytes before getting to the desired block of data. - - An access point can be created at the start of any deflate block, by saving - the starting file offset and bit of that block, and the 32K bytes of - uncompressed data that precede that block. Also the uncompressed offset of - that block is saved to provide a referece for locating a desired starting - point in the uncompressed stream. build_index() works by decompressing the - input zlib or gzip stream a block at a time, and at the end of each block - deciding if enough uncompressed data has gone by to justify the creation of - a new access point. If so, that point is saved in a data structure that - grows as needed to accommodate the points. - - To use the index, an offset in the uncompressed data is provided, for which - the latest accees point at or preceding that offset is located in the index. - The input file is positioned to the specified location in the index, and if - necessary the first few bits of the compressed data is read from the file. - inflate is initialized with those bits and the 32K of uncompressed data, and - the decompression then proceeds until the desired offset in the file is - reached. Then the decompression continues to read the desired uncompressed - data from the file. - - Another approach would be to generate the index on demand. In that case, - requests for random access reads from the compressed data would try to use - the index, but if a read far enough past the end of the index is required, - then further index entries would be generated and added. - - There is some fair bit of overhead to starting inflation for the random - access, mainly copying the 32K byte dictionary. So if small pieces of the - file are being accessed, it would make sense to implement a cache to hold - some lookahead and avoid many calls to extract() for small lengths. - - Another way to build an index would be to use inflateCopy(). That would - not be constrained to have access points at block boundaries, but requires - more memory per access point, and also cannot be saved to file due to the - use of pointers in the state. The approach here allows for storage of the - index in a file. - */ - -#include <stdio.h> -#include <stdlib.h> -#include <string.h> -#include "zlib.h" - -#define local static - -#define SPAN 1048576L /* desired distance between access points */ -#define WINSIZE 32768U /* sliding window size */ -#define CHUNK 16384 /* file input buffer size */ - -/* access point entry */ -struct point { - off_t out; /* corresponding offset in uncompressed data */ - off_t in; /* offset in input file of first full byte */ - int bits; /* number of bits (1-7) from byte at in - 1, or 0 */ - unsigned char window[WINSIZE]; /* preceding 32K of uncompressed data */ -}; - -/* access point list */ -struct access { - int have; /* number of list entries filled in */ - int size; /* number of list entries allocated */ - struct point *list; /* allocated list */ -}; - -/* Deallocate an index built by build_index() */ -local void free_index(struct access *index) -{ - if (index != NULL) { - free(index->list); - free(index); - } -} - -/* Add an entry to the access point list. If out of memory, deallocate the - existing list and return NULL. */ -local struct access *addpoint(struct access *index, int bits, - off_t in, off_t out, unsigned left, unsigned char *window) -{ - struct point *next; - - /* if list is empty, create it (start with eight points) */ - if (index == NULL) { - index = malloc(sizeof(struct access)); - if (index == NULL) return NULL; - index->list = malloc(sizeof(struct point) << 3); - if (index->list == NULL) { - free(index); - return NULL; - } - index->size = 8; - index->have = 0; - } - - /* if list is full, make it bigger */ - else if (index->have == index->size) { - index->size <<= 1; - next = realloc(index->list, sizeof(struct point) * index->size); - if (next == NULL) { - free_index(index); - return NULL; - } - index->list = next; - } - - /* fill in entry and increment how many we have */ - next = index->list + index->have; - next->bits = bits; - next->in = in; - next->out = out; - if (left) - memcpy(next->window, window + WINSIZE - left, left); - if (left < WINSIZE) - memcpy(next->window + left, window, WINSIZE - left); - index->have++; - - /* return list, possibly reallocated */ - return index; -} - -/* Make one entire pass through the compressed stream and build an index, with - access points about every span bytes of uncompressed output -- span is - chosen to balance the speed of random access against the memory requirements - of the list, about 32K bytes per access point. Note that data after the end - of the first zlib or gzip stream in the file is ignored. build_index() - returns the number of access points on success (>= 1), Z_MEM_ERROR for out - of memory, Z_DATA_ERROR for an error in the input file, or Z_ERRNO for a - file read error. On success, *built points to the resulting index. */ -local int build_index(FILE *in, off_t span, struct access **built) -{ - int ret; - off_t totin, totout; /* our own total counters to avoid 4GB limit */ - off_t last; /* totout value of last access point */ - struct access *index; /* access points being generated */ - z_stream strm; - unsigned char input[CHUNK]; - unsigned char window[WINSIZE]; - - /* initialize inflate */ - strm.zalloc = Z_NULL; - strm.zfree = Z_NULL; - strm.opaque = Z_NULL; - strm.avail_in = 0; - strm.next_in = Z_NULL; - ret = inflateInit2(&strm, 47); /* automatic zlib or gzip decoding */ - if (ret != Z_OK) - return ret; - - /* inflate the input, maintain a sliding window, and build an index -- this - also validates the integrity of the compressed data using the check - information at the end of the gzip or zlib stream */ - totin = totout = last = 0; - index = NULL; /* will be allocated by first addpoint() */ - strm.avail_out = 0; - do { - /* get some compressed data from input file */ - strm.avail_in = fread(input, 1, CHUNK, in); - if (ferror(in)) { - ret = Z_ERRNO; - goto build_index_error; - } - if (strm.avail_in == 0) { - ret = Z_DATA_ERROR; - goto build_index_error; - } - strm.next_in = input; - - /* process all of that, or until end of stream */ - do { - /* reset sliding window if necessary */ - if (strm.avail_out == 0) { - strm.avail_out = WINSIZE; - strm.next_out = window; - } - - /* inflate until out of input, output, or at end of block -- - update the total input and output counters */ - totin += strm.avail_in; - totout += strm.avail_out; - ret = inflate(&strm, Z_BLOCK); /* return at end of block */ - totin -= strm.avail_in; - totout -= strm.avail_out; - if (ret == Z_NEED_DICT) - ret = Z_DATA_ERROR; - if (ret == Z_MEM_ERROR || ret == Z_DATA_ERROR) - goto build_index_error; - if (ret == Z_STREAM_END) - break; - - /* if at end of block, consider adding an index entry (note that if - data_type indicates an end-of-block, then all of the - uncompressed data from that block has been delivered, and none - of the compressed data after that block has been consumed, - except for up to seven bits) -- the totout == 0 provides an - entry point after the zlib or gzip header, and assures that the - index always has at least one access point; we avoid creating an - access point after the last block by checking bit 6 of data_type - */ - if ((strm.data_type & 128) && !(strm.data_type & 64) && - (totout == 0 || totout - last > span)) { - index = addpoint(index, strm.data_type & 7, totin, - totout, strm.avail_out, window); - if (index == NULL) { - ret = Z_MEM_ERROR; - goto build_index_error; - } - last = totout; - } - } while (strm.avail_in != 0); - } while (ret != Z_STREAM_END); - - /* clean up and return index (release unused entries in list) */ - (void)inflateEnd(&strm); - index = realloc(index, sizeof(struct point) * index->have); - index->size = index->have; - *built = index; - return index->size; - - /* return error */ - build_index_error: - (void)inflateEnd(&strm); - if (index != NULL) - free_index(index); - return ret; -} - -/* Use the index to read len bytes from offset into buf, return bytes read or - negative for error (Z_DATA_ERROR or Z_MEM_ERROR). If data is requested past - the end of the uncompressed data, then extract() will return a value less - than len, indicating how much as actually read into buf. This function - should not return a data error unless the file was modified since the index - was generated. extract() may also return Z_ERRNO if there is an error on - reading or seeking the input file. */ -local int extract(FILE *in, struct access *index, off_t offset, - unsigned char *buf, int len) -{ - int ret, skip; - z_stream strm; - struct point *here; - unsigned char input[CHUNK]; - unsigned char discard[WINSIZE]; - - /* proceed only if something reasonable to do */ - if (len < 0) - return 0; - - /* find where in stream to start */ - here = index->list; - ret = index->have; - while (--ret && here[1].out <= offset) - here++; - - /* initialize file and inflate state to start there */ - strm.zalloc = Z_NULL; - strm.zfree = Z_NULL; - strm.opaque = Z_NULL; - strm.avail_in = 0; - strm.next_in = Z_NULL; - ret = inflateInit2(&strm, -15); /* raw inflate */ - if (ret != Z_OK) - return ret; - ret = fseeko(in, here->in - (here->bits ? 1 : 0), SEEK_SET); - if (ret == -1) - goto extract_ret; - if (here->bits) { - ret = getc(in); - if (ret == -1) { - ret = ferror(in) ? Z_ERRNO : Z_DATA_ERROR; - goto extract_ret; - } - (void)inflatePrime(&strm, here->bits, ret >> (8 - here->bits)); - } - (void)inflateSetDictionary(&strm, here->window, WINSIZE); - - /* skip uncompressed bytes until offset reached, then satisfy request */ - offset -= here->out; - strm.avail_in = 0; - skip = 1; /* while skipping to offset */ - do { - /* define where to put uncompressed data, and how much */ - if (offset == 0 && skip) { /* at offset now */ - strm.avail_out = len; - strm.next_out = buf; - skip = 0; /* only do this once */ - } - if (offset > WINSIZE) { /* skip WINSIZE bytes */ - strm.avail_out = WINSIZE; - strm.next_out = discard; - offset -= WINSIZE; - } - else if (offset != 0) { /* last skip */ - strm.avail_out = (unsigned)offset; - strm.next_out = discard; - offset = 0; - } - - /* uncompress until avail_out filled, or end of stream */ - do { - if (strm.avail_in == 0) { - strm.avail_in = fread(input, 1, CHUNK, in); - if (ferror(in)) { - ret = Z_ERRNO; - goto extract_ret; - } - if (strm.avail_in == 0) { - ret = Z_DATA_ERROR; - goto extract_ret; - } - strm.next_in = input; - } - ret = inflate(&strm, Z_NO_FLUSH); /* normal inflate */ - if (ret == Z_NEED_DICT) - ret = Z_DATA_ERROR; - if (ret == Z_MEM_ERROR || ret == Z_DATA_ERROR) - goto extract_ret; - if (ret == Z_STREAM_END) - break; - } while (strm.avail_out != 0); - - /* if reach end of stream, then don't keep trying to get more */ - if (ret == Z_STREAM_END) - break; - - /* do until offset reached and requested data read, or stream ends */ - } while (skip); - - /* compute number of uncompressed bytes read after offset */ - ret = skip ? 0 : len - strm.avail_out; - - /* clean up and return bytes read or error */ - extract_ret: - (void)inflateEnd(&strm); - return ret; -} - -/* Demonstrate the use of build_index() and extract() by processing the file - provided on the command line, and the extracting 16K from about 2/3rds of - the way through the uncompressed output, and writing that to stdout. */ -int main(int argc, char **argv) -{ - int len; - off_t offset; - FILE *in; - struct access *index; - unsigned char buf[CHUNK]; - - /* open input file */ - if (argc != 2) { - fprintf(stderr, "usage: zran file.gz\n"); - return 1; - } - in = fopen(argv[1], "rb"); - if (in == NULL) { - fprintf(stderr, "zran: could not open %s for reading\n", argv[1]); - return 1; - } - - /* build index */ - len = build_index(in, SPAN, &index); - if (len < 0) { - fclose(in); - switch (len) { - case Z_MEM_ERROR: - fprintf(stderr, "zran: out of memory\n"); - break; - case Z_DATA_ERROR: - fprintf(stderr, "zran: compressed data error in %s\n", argv[1]); - break; - case Z_ERRNO: - fprintf(stderr, "zran: read error on %s\n", argv[1]); - break; - default: - fprintf(stderr, "zran: error %d while building index\n", len); - } - return 1; - } - fprintf(stderr, "zran: built index with %d access points\n", len); - - /* use index by reading some bytes from an arbitrary offset */ - offset = (index->list[index->have - 1].out << 1) / 3; - len = extract(in, index, offset, buf, CHUNK); - if (len < 0) - fprintf(stderr, "zran: extraction failed: %s error\n", - len == Z_MEM_ERROR ? "out of memory" : "input corrupted"); - else { - fwrite(buf, 1, len, stdout); - fprintf(stderr, "zran: extracted %d bytes at %llu\n", len, offset); - } - - /* clean up and exit */ - free_index(index); - fclose(in); - return 0; -} |