利用zlib库对HTTP收到的gzip数据解压

1、首先说为什么采用zlib解压，因为zlib可以解压内存数据。

2、下载zlib库后，自己在projcts目录里面根据需要编译lib库

3、静态链接只需要zlib.h ;zconf.h;zlib.lib三个文件即可(动态的不介绍了)

4、解压函数：

/* HTTP gzip decompress */
int httpgzdecompress(Byte *zdata, uLong nzdata,
Byte *data, uLong *ndata)
{
int err = 0;
z_stream d_stream = { 0 }; /* decompression stream */
static char dummy_head[2] =
{
0x8 + 0x7 * 0x10,
(((0x8 + 0x7 * 0x10) * 0x100 + 30) / 31 * 31) & 0xFF,
};
d_stream.zalloc = (alloc_func)0;
d_stream.zfree = (free_func)0;
d_stream.opaque = (voidpf)0;
d_stream.next_in = zdata;
d_stream.avail_in = 0;
d_stream.next_out = data;
//if (inflateInit2(&d_stream, -MAX_WBITS) != Z_OK) return -1;
if (inflateInit2(&d_stream, 47) != Z_OK) return -1;
while (d_stream.total_out < *ndata && d_stream.total_in < nzdata) {
d_stream.avail_in = d_stream.avail_out = 1; /* force small buffers */
if ((err = inflate(&d_stream, Z_NO_FLUSH)) == Z_STREAM_END) break;
if (err != Z_OK)
{
if (err == Z_DATA_ERROR)
{
d_stream.next_in = (Bytef*)dummy_head;
d_stream.avail_in = sizeof(dummy_head);
if ((err = inflate(&d_stream, Z_NO_FLUSH)) != Z_OK)
{
return -1;
}
}
else return -1;
}
}
if (inflateEnd(&d_stream) != Z_OK) return -1;
*ndata = d_stream.total_out;
return 0;
}

直接调用就OK了 注意传入的buffer数据和长度都要赋值

eg：

char* pDest = new char[1024 * 16];

uLong ulLength = 1024*16;

gzdecompress((Byte*)precvBuff, nCount, (Byte*)pDest, &ulLength);