example.c

一个国人自己实现图像库的程序（有参考价值）

/* example.c -- usage example of the zlib compression library
 * Copyright (C) 1995-1998 Jean-loup Gailly.
 * For conditions of distribution and use, see copyright notice in zlib.h 
 */

/* @(#) $Id$ */

#include <stdio.h>
#include "zlib.h"

#ifdef STDC
#  include <string.h>
#  include <stdlib.h>
#else
   extern void exit  OF((int));
#endif

#if defined(VMS) || defined(RISCOS)
#  define TESTFILE "foo-gz"
#else
#  define TESTFILE "foo.gz"
#endif

#define CHECK_ERR(err, msg) { \
    if (err != Z_OK) { \
        fprintf(stderr, "%s error: %d\n", msg, err); \
        exit(1); \
    } \
}

const char hello[] = "hello, hello!";
/* "hello world" would be more standard, but the repeated "hello"
 * stresses the compression code better, sorry...
 */

const char dictionary[] = "hello";
uLong dictId; /* Adler32 value of the dictionary */

void test_compress      OF((Byte *compr, uLong comprLen,
		            Byte *uncompr, uLong uncomprLen));
void test_gzio          OF((const char *out, const char *in, 
		            Byte *uncompr, int uncomprLen));
void test_deflate       OF((Byte *compr, uLong comprLen));
void test_inflate       OF((Byte *compr, uLong comprLen,
		            Byte *uncompr, uLong uncomprLen));
void test_large_deflate OF((Byte *compr, uLong comprLen,
		            Byte *uncompr, uLong uncomprLen));
void test_large_inflate OF((Byte *compr, uLong comprLen,
		            Byte *uncompr, uLong uncomprLen));
void test_flush         OF((Byte *compr, uLong *comprLen));
void test_sync          OF((Byte *compr, uLong comprLen,
		            Byte *uncompr, uLong uncomprLen));
void test_dict_deflate  OF((Byte *compr, uLong comprLen));
void test_dict_inflate  OF((Byte *compr, uLong comprLen,
		            Byte *uncompr, uLong uncomprLen));
int  main               OF((int argc, char *argv[]));

/* ===========================================================================
 * Test compress() and uncompress()
 */
void test_compress(compr, comprLen, uncompr, uncomprLen)
    Byte *compr, *uncompr;
    uLong comprLen, uncomprLen;
{
    int err;
    uLong len = strlen(hello)+1;

    err = compress(compr, &comprLen, (const Bytef*)hello, len);
    CHECK_ERR(err, "compress");

    strcpy((char*)uncompr, "garbage");

    err = uncompress(uncompr, &uncomprLen, compr, comprLen);
    CHECK_ERR(err, "uncompress");

    if (strcmp((char*)uncompr, hello)) {
        fprintf(stderr, "bad uncompress\n");
	exit(1);
    } else {
        printf("uncompress(): %s\n", (char *)uncompr);
    }
}

/* ===========================================================================
 * Test read/write of .gz files
 */
void test_gzio(out, in, uncompr, uncomprLen)
    const char *out; /* compressed output file */
    const char *in;  /* compressed input file */
    Byte *uncompr;
    int  uncomprLen;
{
    int err;
    int len = strlen(hello)+1;
    gzFile file;
    z_off_t pos;

    file = gzopen(out, "wb");
    if (file == NULL) {
        fprintf(stderr, "gzopen error\n");
        exit(1);
    }
    gzputc(file, 'h');
    if (gzputs(file, "ello") != 4) {
        fprintf(stderr, "gzputs err: %s\n", gzerror(file, &err));
	exit(1);
    }
    if (gzprintf(file, ", %s!", "hello") != 8) {
        fprintf(stderr, "gzprintf err: %s\n", gzerror(file, &err));
	exit(1);
    }
    gzseek(file, 1L, SEEK_CUR); /* add one zero byte */
    gzclose(file);

    file = gzopen(in, "rb");
    if (file == NULL) {
        fprintf(stderr, "gzopen error\n");
    }
    strcpy((char*)uncompr, "garbage");

    uncomprLen = gzread(file, uncompr, (unsigned)uncomprLen);
    if (uncomprLen != len) {
        fprintf(stderr, "gzread err: %s\n", gzerror(file, &err));
	exit(1);
    }
    if (strcmp((char*)uncompr, hello)) {
        fprintf(stderr, "bad gzread: %s\n", (char*)uncompr);
	exit(1);
    } else {
        printf("gzread(): %s\n", (char *)uncompr);
    }

    pos = gzseek(file, -8L, SEEK_CUR);
    if (pos != 6 || gztell(file) != pos) {
	fprintf(stderr, "gzseek error, pos=%ld, gztell=%ld\n",
		(long)pos, (long)gztell(file));
	exit(1);
    }

    if (gzgetc(file) != ' ') {
	fprintf(stderr, "gzgetc error\n");
	exit(1);
    }

    gzgets(file, (char*)uncompr, uncomprLen);
    uncomprLen = strlen((char*)uncompr);
    if (uncomprLen != 6) { /* "hello!" */
        fprintf(stderr, "gzgets err after gzseek: %s\n", gzerror(file, &err));
	exit(1);
    }
    if (strcmp((char*)uncompr, hello+7)) {
        fprintf(stderr, "bad gzgets after gzseek\n");
	exit(1);
    } else {
        printf("gzgets() after gzseek: %s\n", (char *)uncompr);
    }

    gzclose(file);
}

/* ===========================================================================
 * Test deflate() with small buffers
 */
void test_deflate(compr, comprLen)
    Byte *compr;
    uLong comprLen;
{
    z_stream c_stream; /* compression stream */
    int err;
    int len = strlen(hello)+1;

    c_stream.zalloc = (alloc_func)0;
    c_stream.zfree = (free_func)0;
    c_stream.opaque = (voidpf)0;

    err = deflateInit(&c_stream, Z_DEFAULT_COMPRESSION);
    CHECK_ERR(err, "deflateInit");

    c_stream.next_in  = (Bytef*)hello;
    c_stream.next_out = compr;

    while (c_stream.total_in != (uLong)len && c_stream.total_out < comprLen) {
        c_stream.avail_in = c_stream.avail_out = 1; /* force small buffers */
        err = deflate(&c_stream, Z_NO_FLUSH);
        CHECK_ERR(err, "deflate");
    }
    /* Finish the stream, still forcing small buffers: */
    for (;;) {
        c_stream.avail_out = 1;
        err = deflate(&c_stream, Z_FINISH);
        if (err == Z_STREAM_END) break;
        CHECK_ERR(err, "deflate");
    }

    err = deflateEnd(&c_stream);
    CHECK_ERR(err, "deflateEnd");
}

/* ===========================================================================
 * Test inflate() with small buffers
 */
void test_inflate(compr, comprLen, uncompr, uncomprLen)
    Byte *compr, *uncompr;
    uLong comprLen, uncomprLen;
{
    int err;
    z_stream d_stream; /* decompression stream */

    strcpy((char*)uncompr, "garbage");

    d_stream.zalloc = (alloc_func)0;
    d_stream.zfree = (free_func)0;
    d_stream.opaque = (voidpf)0;

    d_stream.next_in  = compr;
    d_stream.avail_in = 0;
    d_stream.next_out = uncompr;

    err = inflateInit(&d_stream);
    CHECK_ERR(err, "inflateInit");

    while (d_stream.total_out < uncomprLen && d_stream.total_in < comprLen) {
        d_stream.avail_in = d_stream.avail_out = 1; /* force small buffers */
        err = inflate(&d_stream, Z_NO_FLUSH);
        if (err == Z_STREAM_END) break;
        CHECK_ERR(err, "inflate");
    }

    err = inflateEnd(&d_stream);
    CHECK_ERR(err, "inflateEnd");

    if (strcmp((char*)uncompr, hello)) {
        fprintf(stderr, "bad inflate\n");
	exit(1);
    } else {
        printf("inflate(): %s\n", (char *)uncompr);
    }
}

/* ===========================================================================
 * Test deflate() with large buffers and dynamic change of compression level
 */
void test_large_deflate(compr, comprLen, uncompr, uncomprLen)
    Byte *compr, *uncompr;
    uLong comprLen, uncomprLen;
{
    z_stream c_stream; /* compression stream */
    int err;

    c_stream.zalloc = (alloc_func)0;
    c_stream.zfree = (free_func)0;
    c_stream.opaque = (voidpf)0;

    err = deflateInit(&c_stream, Z_BEST_SPEED);
    CHECK_ERR(err, "deflateInit");

    c_stream.next_out = compr;
    c_stream.avail_out = (uInt)comprLen;

    /* At this point, uncompr is still mostly zeroes, so it should compress
     * very well:
     */
    c_stream.next_in = uncompr;
    c_stream.avail_in = (uInt)uncomprLen;
    err = deflate(&c_stream, Z_NO_FLUSH);
    CHECK_ERR(err, "deflate");
    if (c_stream.avail_in != 0) {
        fprintf(stderr, "deflate not greedy\n");
	exit(1);
    }

    /* Feed in already compressed data and switch to no compression: */
    deflateParams(&c_stream, Z_NO_COMPRESSION, Z_DEFAULT_STRATEGY);
    c_stream.next_in = compr;
    c_stream.avail_in = (uInt)comprLen/2;
    err = deflate(&c_stream, Z_NO_FLUSH);
    CHECK_ERR(err, "deflate");

    /* Switch back to compressing mode: */