Iphone 上使用libz库解压zip，gzip文件

转自：http://blog.csdn.net/sjzsp/article/details/6315114

服务器上返回的数据是个压缩包，这个文件折腾了我1天多的时间，今天看到这个帖子才算折腾完毕。xml数据终于解压成功。

最近做的一个东西中，需要从网络获取xml文件，但是该文件用了gzip压缩的。搜索一 下有人说gzip压缩的用urlrequest可以自己解压，但是这必须从服务器返回的header中有accept－Encoding说明是gzip 的。也就是用这句就可以实现自解压：

[urlRequest addValue:@"gzip" forHTTPHeaderField:@"Accept-Encoding"];

这个在我的项目中没有作用，因为服务器返回的header中没有Accept－Encoding的说明。这就需要手动解压了！解压需要导入libz.1.2.3.dylib库，导入#import "zlib.h"

下面是解压的代码：

 

-(NSData *)uncompressZippedData:(NSData *)compressedData  

{  

 

    if ([compressedData length] == 0) return compressedData;  

 

    unsigned full_length = [compressedData length];  

 

    unsigned half_length = [compressedData length] / 2;  

    NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length];  

    BOOL done = NO;  

    int status;  

    z_stream strm;  

    strm.next_in = (Bytef *)[compressedData bytes];  

    strm.avail_in = [compressedData length];  

    strm.total_out = 0;  

    strm.zalloc = Z_NULL;  

    strm.zfree = Z_NULL;  

    if (inflateInit2(&strm, (15+32)) != Z_OK) return nil;  

    while (!done) {  

        // Make sure we have enough room and reset the lengths.  

        if (strm.total_out >= [decompressed length]) {  

            [decompressed increaseLengthBy: half_length];  

        }  

        strm.next_out = [decompressed mutableBytes] + strm.total_out;  

        strm.avail_out = [decompressed length] - strm.total_out;  

        // Inflate another chunk.  

        status = inflate (&strm, Z_SYNC_FLUSH);  

        if (status == Z_STREAM_END) {  

            done = YES;  

        } else if (status != Z_OK) {  

            break;  

        }  

 

    }  

    if (inflateEnd (&strm) != Z_OK) return nil;  

    // Set real length.  

    if (done) {  

        [decompressed setLength: strm.total_out];  

        return [NSData dataWithData: decompressed];  

    } else {  

        return nil;  

    }  

}