网上有很多针对zlib的总结，但是很零散，自己经过总结，实现了用zlib压缩一个文件为gzip格式，似的可以直接使用winr工具解压。
具体方法是使用zlib的deflate系列函数，将buffer压缩为gzip格式，deflateInit2的参数注意使用MAX_WBITS+16，这样压缩后可以带gzip的头、尾信息。
然后将压缩后的内容直接写入到目标文件，保存为.gz， 使用WinR就可以直接解压了。
demo程序如下(deflate_gzip.c)：
#include <stdio.h>
#include <stdlib.h>
#include <zlib.h> /*******************************************************************************
* Compress gzip data
* @parm[data] data buffer to be compressed
* @parm[dlen] data buffer length
* @parm[zdata] data buffer to save the compressed datas
* @parm[zdlen] compressed data buffer length
* return: 0 - OK; -1 - FAIL
*******************************************************************************/
int gzcompress(Bytef *data, uLong dlen, Bytef *zdata, uLong *zdlen)
{
int err = ;
z_stream c_stream; printf("%s: data=%p, dlen=%lu, zdata=%p, *zdlen=%lu\n",
__func__, data, dlen, zdata, *zdlen); if(data && dlen > )
{
c_stream.zalloc = NULL;
c_stream.zfree = NULL;
c_stream.opaque = NULL;
//use parm 'MAX_WBITS+16' so that gzip headers are contained
if(deflateInit2(&c_stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
MAX_WBITS + , , Z_DEFAULT_STRATEGY) != Z_OK)
{
printf("%s: deflateinit2 failed!\n",__func__);
return -;
}
c_stream.next_in = data;
c_stream.avail_in = dlen;
c_stream.next_out = zdata;
c_stream.avail_out = *zdlen;
while(c_stream.avail_in != && c_stream.total_out < *zdlen)
{
if(deflate(&c_stream, Z_NO_FLUSH) != Z_OK) {
printf("%s: deflate failed!\n",__func__);
return -;
}
}
if(c_stream.avail_in != ) {
printf("%s: avail_in not zero!\n",__func__);
return c_stream.avail_in;
}
for(;;)
{
if((err = deflate(&c_stream, Z_FINISH)) == Z_STREAM_END)
break;
if(err != Z_OK) {
printf("%s: deflate finish fail: %d\n",__func__, err);
return -;
}
}
if(deflateEnd(&c_stream) != Z_OK) {
printf("%s: deflate end failed!\n",__func__);
return -;
}
*zdlen = c_stream.total_out;
return ;
}
return -;
} /*******************************************************************************
* Compress a file into a gzip file
* @parm[input_name] the file path to be compressed
* @parm[output_name] output path of compressed gzip file
* return: 0 - OK; -1 - FAIL
*******************************************************************************/
int compress_file_to_gzip(char * input_name, char * output_name)
{
FILE *fp = NULL;
uLong flen, clen;
unsigned char * fbuf = NULL;
unsigned char * cbuf = NULL;
char def_output_name[PATH_MAX] = {}; if((fp = fopen(input_name, "rb")) == NULL)
{
printf("%s: can not open %s!\n", __func__, input_name);
return -;
} /*load file content to buffer*/
fseek(fp, 0L, SEEK_END);
flen = ftell(fp);
fseek(fp, 0L, SEEK_SET);
fbuf = (unsigned char *)malloc(flen * sizeof(unsigned char));
if(NULL == fbuf){
printf("%s: no enough memory!\n", __func__);
goto __error;
}
fread(fbuf, sizeof(unsigned char), flen, fp);
fclose(fp);
fp = NULL; /*compute compressBound*/
clen = compressBound(flen);
cbuf = (unsigned char *)malloc(clen * sizeof(unsigned char));
if(NULL == cbuf) {
printf("%s: no enough memory!\n", __func__);
goto __error;
} if(gzcompress(fbuf, flen, cbuf, &clen))
{
printf("%s: compress %s failed!\n", __func__, input_name);
goto __error;
} if(NULL == output_name) {
snprintf(def_output_name, sizeof(def_output_name),
"%s.gz", input_name);
output_name = def_output_name;
}
if((fp = fopen(output_name, "wb")) == NULL)
{
printf("%s: can not open %s!\n", __func__, output_name);
goto __error;
}
fwrite(cbuf, sizeof(unsigned char), clen, fp); fclose(fp);
free(fbuf);
free(cbuf);
return ; __error:
if(fp) fclose(fp);
if(fbuf) free(fbuf);
if(cbuf) free(cbuf);
return -;
} int main(int argc, char * argv[])
{
if(argc < ) {
printf("too few args!\n");
return ;
} if(argc < ) {
return compress_file_to_gzip(argv[],NULL);
} return compress_file_to_gzip(argv[], argv[]);
}
编译命令：
gcc -o zlibtest deflate_gzip.c.c -lz
如果编译连接的时候示找不到deflate等函数，则需要安装zlib库，ubuntu下：
sudo apt-get install zlib1g zlib1g-dev zlibc
参考内容链接：