zlib——compress.c檔案分析

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include "zlib.h"
#if
#  include <fcntl.h>
#  include <io.h>
#  define
#else
#  define
#endif
#define
/* Compress from file source to file dest until EOF on source.
   def() returns Z_OK on success, Z_MEM_ERROR if memory could not be
   allocated for processing, Z_STREAM_ERROR if an invalid compression
   level is supplied, Z_VERSION_ERROR if the version of zlib.h and the
   version of the library linked do not match, or Z_ERRNO if there is
   an error reading or writing the files. */
int def(FILE *source, FILE *dest, int level)
{
    int ret, flush;
    unsigned have;
    z_stream strm;
    unsigned char in[CHUNK];
    unsigned char out[CHUNK];
    /* allocate deflate state */
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    ret = deflateInit(&strm, level);
    if (ret != Z_OK)
        return ret;
    /* compress until end of file */
    do {
        strm.avail_in = fread(in, 1, CHUNK, source);
        if (ferror(source)) {
            (void)deflateEnd(&strm);
            return Z_ERRNO;
        }
        flush = feof(source) ? Z_FINISH : Z_NO_FLUSH;
        strm.next_in = in;
        /* run deflate() on input until output buffer not full, finish
           compression if all of source has been read in */
        do {
            strm.avail_out = CHUNK;
            strm.next_out = out;
            ret = deflate(&strm, flush);    /* no bad return value */
            assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
            have = CHUNK - strm.avail_out;
            if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                (void)deflateEnd(&strm);
                return Z_ERRNO;
            }
        } while (strm.avail_out == 0);
        assert(strm.avail_in == 0);     /* all input will be used */
        /* done when last data in file processed */
    } while (flush != Z_FINISH);
    assert(ret == Z_STREAM_END);        /* stream will be complete */

    /* clean up and return */
    (void)deflateEnd(&strm);
    return Z_OK;
}

/* Decompress from file source to file dest until stream ends or EOF.
   inf() returns Z_OK on success, Z_MEM_ERROR if memory could not be
   allocated for processing, Z_DATA_ERROR if the deflate data is
   invalid or incomplete, Z_VERSION_ERROR if the version of zlib.h and
   the version of the library linked do not match, or Z_ERRNO if there
   is an error reading or writing the files. */
int inf(FILE *source, FILE *dest)
{
    int ret;
    unsigned have;
    z_stream strm;
    unsigned char in[CHUNK];
    unsigned char out[CHUNK];
    /* allocate inflate state */
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    strm.avail_in = 0;
    strm.next_in = Z_NULL;
    ret = inflateInit(&strm);
    if (ret != Z_OK)
        return ret;
    /* decompress until deflate stream ends or end of file */
    do {
        strm.avail_in = fread(in, 1, CHUNK, source);
        if (ferror(source)) {
            (void)inflateEnd(&strm);
            return Z_ERRNO;
        }
        if (strm.avail_in == 0)
            break;
        strm.next_in = in;
        /* run inflate() on input until output buffer not full */
        do {
            strm.avail_out = CHUNK;
            strm.next_out = out;
            ret = inflate(&strm, Z_NO_FLUSH);
            assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
            switch (ret) {
            case Z_NEED_DICT:
                ret = Z_DATA_ERROR;     /* and fall through */
            case Z_DATA_ERROR:
            case Z_MEM_ERROR:
                (void)inflateEnd(&strm);
                return ret;
            }
            have = CHUNK - strm.avail_out;
            if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                (void)inflateEnd(&strm);
                return Z_ERRNO;
            }
        } while (strm.avail_out == 0);
        /* done when inflate() says it's done */
    } while (ret != Z_STREAM_END);
    /* clean up and return */
    (void)inflateEnd(&strm);
    return ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR;
}

/* report a zlib or i/o error */
void zerr(int ret)
{
    fputs("zpipe: ", stderr);
    switch (ret) {
    case Z_ERRNO:
        if (ferror(stdin))
            fputs("error reading stdin\n", stderr);
        if (ferror(stdout))
            fputs("error writing stdout\n", stderr);
        break;
    case Z_STREAM_ERROR:
        fputs("invalid compression level\n", stderr);
        break;
    case Z_DATA_ERROR:
        fputs("invalid or incomplete deflate data\n", stderr);
        break;
    case Z_MEM_ERROR:
        fputs("out of memory\n", stderr);
        break;
    case Z_VERSION_ERROR:
        fputs("zlib version mismatch!\n", stderr);
    }
}

/* compress or decompress from stdin to stdout */
int main(int argc, char **argv)
{
    int ret;
    /* avoid end-of-line conversions */
    SET_BINARY_MODE(stdin);
    SET_BINARY_MODE(stdout);
    /* do compression if no arguments */
    if (argc == 1) {
        ret = def(stdin, stdout, Z_DEFAULT_COMPRESSION);
        if (ret != Z_OK)
            zerr(ret);
        return ret;
    }
    /* do decompression if -d specified */
    else if (argc == 2 && strcmp(argv[1], "-d") == 0) {
        ret = inf(stdin, stdout);
        if (ret != Z_OK)
            zerr(ret);
        return ret;
    }
    /* otherwise, report usage */
    else {
        fputs("zpipe usage: zpipe [-d] < source > dest\n", stderr);
        return 1;
    }
}      

/* compress.c -- compress a memory buffer */
#define
#include "zlib.h"
/* ===========================================================================
     Compresses the source buffer into the destination buffer. The level
   parameter has the same meaning as in deflateInit.  sourceLen is the byte
   length of the source buffer. Upon entry, destLen is the total size of the
   destination buffer, which must be at least 0.1% larger than sourceLen plus
   12 bytes. Upon exit, destLen is the actual size of the compressed buffer.

     compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
   memory, Z_BUF_ERROR if there was not enough room in the output buffer,
   Z_STREAM_ERROR if the level parameter is invalid.
*/
int ZEXPORT compress2 (dest, destLen, source, sourceLen, level)
    Bytef *dest;
    uLongf *destLen;
    const Bytef *source;
    uLong sourceLen;
    int level;
{
    z_stream stream;
    int err;
    const uInt max = (uInt)-1;
    uLong left;
    left = *destLen;
    *destLen = 0;
    stream.zalloc = (alloc_func)0;
    stream.zfree = (free_func)0;
    stream.opaque = (voidpf)0;

    err = deflateInit(&stream, level);
    if (err != Z_OK) return err;

    stream.next_out = dest;
    stream.avail_out = 0;
    stream.next_in = (z_const Bytef *)source;
    stream.avail_in = 0;

    do {
        if (stream.avail_out == 0) {
            stream.avail_out = left > (uLong)max ? max : (uInt)left;
            left -= stream.avail_out;
        }
        if (stream.avail_in == 0) {
            stream.avail_in = sourceLen > (uLong)max ? max : (uInt)sourceLen;
            sourceLen -= stream.avail_in;
        }
        err = deflate(&stream, sourceLen ? Z_NO_FLUSH : Z_FINISH);
    } while (err == Z_OK);

    *destLen = stream.total_out;
    deflateEnd(&stream);
    return err == Z_STREAM_END ? Z_OK : err;
}

int ZEXPORT compress (dest, destLen, source, sourceLen)
    Bytef *dest;
    uLongf *destLen;
    const Bytef *source;
    uLong sourceLen;
{
    return compress2(dest, destLen, source, sourceLen, Z_DEFAULT_COMPRESSION);
}

/* ===========================================================================
     If the default memLevel or windowBits for deflateInit() is changed, then
   this function needs to be updated.
 */
uLong ZEXPORT compressBound (sourceLen)
    uLong sourceLen;
{
    return sourceLen + (sourceLen >> 12) + (sourceLen >> 14) +
           (sourceLen >> 25) + 13;
}