我使用以下两种方法。

压缩：

+(NSData*) compressData:(NSData*) uncompressedData {
if ([uncompressedData length] == 0) return uncompressedData;

z_stream strm;

strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
strm.total_out = 0;
strm.next_in=(Bytef *)[uncompressedData bytes];
strm.avail_in = (unsigned int)[uncompressedData length];

// Compresssion Levels:
//   Z_NO_COMPRESSION
//   Z_BEST_SPEED
//   Z_BEST_COMPRESSION
//   Z_DEFAULT_COMPRESSION

if (deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, (15+16), 8, Z_DEFAULT_STRATEGY) != Z_OK) return nil;

NSMutableData *compressed = [NSMutableData dataWithLength:16384];  // 16K chunks for expansion

do {

    if (strm.total_out >= [compressed length])
        [compressed increaseLengthBy: 16384];

    strm.next_out = [compressed mutableBytes] + strm.total_out;
    strm.avail_out = (unsigned int)([compressed length] - strm.total_out);

    deflate(&strm, Z_FINISH);  

} while (strm.avail_out == 0);

deflateEnd(&strm);

[compressed setLength: strm.total_out];
return [NSData dataWithData:compressed];
}

解压缩：

+(NSData*) uncompressGZip(NSData*) compressedData {
if ([compressedData length] == 0) return compressedData;

NSUInteger full_length = [compressedData length];
NSUInteger 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 = (unsigned int)[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 = (unsigned int)([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;
}
}