test_gzip.cpp

#include <stdio.h>
#include<stdlib.h>
#include <string.h>
#include <zlib.h>

// gzCompress: do the compressing
int gzCompress(const char *src, int srcLen, char *dest, int destLen)
{
	z_stream c_stream;
	int err = 0;
	int windowBits = 15;
	int GZIP_ENCODING = 16;

	if(src && srcLen > 0)
	{
		c_stream.zalloc = (alloc_func)0;
		c_stream.zfree = (free_func)0;
		c_stream.opaque = (voidpf)0;
		if(deflateInit2(&c_stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED, 
                    windowBits | GZIP_ENCODING, 8, Z_DEFAULT_STRATEGY) != Z_OK) return -1;
		c_stream.next_in  = (Bytef *)src;
		c_stream.avail_in  = srcLen;
		c_stream.next_out = (Bytef *)dest;
		c_stream.avail_out  = destLen;
		while (c_stream.avail_in != 0 && c_stream.total_out < destLen) 
		{
			if(deflate(&c_stream, Z_NO_FLUSH) != Z_OK) return -1;
		}
        	if(c_stream.avail_in != 0) return c_stream.avail_in;
		for (;;) {
			if((err = deflate(&c_stream, Z_FINISH)) == Z_STREAM_END) break;
			if(err != Z_OK) return -1;
		}
		if(deflateEnd(&c_stream) != Z_OK) return -1;
		return c_stream.total_out;
	}
	return -1;
}

// gzDecompress: do the decompressing
int gzDecompress(const char *src, int srcLen, const char *dst, int dstLen){
	z_stream strm;
	strm.zalloc=NULL;
	strm.zfree=NULL;
	strm.opaque=NULL;
	 
	strm.avail_in = srcLen;
	strm.avail_out = dstLen;
	strm.next_in = (Bytef *)src;
	strm.next_out = (Bytef *)dst;
	 
	int err=-1, ret=-1;
	err = inflateInit2(&strm, MAX_WBITS+16);
	if (err == Z_OK){
	    err = inflate(&strm, Z_FINISH);
	    if (err == Z_STREAM_END){
	        ret = strm.total_out;
	    }
	    else{
	        inflateEnd(&strm);
	        return err;
	    }
	}
	else{
	    inflateEnd(&strm);
	    return err;
	}
	inflateEnd(&strm);
	return err;
}

int main()
{
	char* src = (char*)"just for test, dd, dd, dd";
	int size_src = strlen(src);
	char* compressed = (char*)malloc(size_src*2);
	memset(compressed, 0, size_src*2);
	printf("to compress src: %s\n", src);
	printf("to compress src size: %d\n", size_src);

	int gzSize = gzCompress(src, size_src, compressed, size_src*2);
	if (gzSize <= 0)
	{
		printf("compress error.\n");
		return -1;
	}
	printf("compressed: ");
	int i = 0;
	for (; i<gzSize; ++i)
	{
		printf("%02x ", compressed[i]);
	}
	printf("\ncompressed size: %d\n", gzSize);

	char* uncompressed = (char*)malloc(size_src*2);
	memset(uncompressed, 0, size_src*2);
	int ret = gzDecompress(compressed, gzSize, uncompressed, size_src*2);
	printf("uncompressed: %s\n", uncompressed);
	printf("uncompressed size: %d\n", strlen(uncompressed));

	free(compressed);
	free(uncompressed);
	return 0;
}