在實際開發中，我們經常要對比較大的資料進行壓縮後再上傳伺服器，下面是我在專案中壓縮資料時所使用的壓縮方法：

對資料進行壓縮：

 zipAndUnzip *zipAnd = [[zipAndUnzip alloc] init];
    
    NSString *str = @"六六六六了還是德國大使館和低俗化工及第三方換個撒點恢復健康的十分好的設計哈佛的號發的撒開了鳳凰健康的十分健康的沙發";
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    NSData *dataDeflate = [zipAnd gzipDeflate:data];

對資料進行解壓：

NSData *dataInflate =  [zipAnd gzipInflate:dataDeflate];
    NSString *aString = [[NSString alloc] initWithData:dataInflate encoding:NSUTF8StringEncoding];

壓縮的方法是：

//壓縮
- (NSData *)gzipDeflate:(NSData*)data
{
    if ([data length] == 0) return data;
    
    z_stream strm;
    
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    strm.total_out = 0;
    strm.next_in=(Bytef *)[data bytes];
    strm.avail_in = (uInt)[data 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 = (uInt)([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];
}
 

解壓縮的方法是：

//解壓縮
- (NSData *)gzipInflate:(NSData*)data
{
    if ([data length] == 0) return data;
    
    unsigned long full_length = [data length];
    unsigned long  half_length = [data length] / 2;
    
    NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length];
    BOOL done = NO;
    int status;
    
    z_stream strm;
    strm.next_in = (Bytef *)[data bytes];
    strm.avail_in = (uInt)[data 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 = (uInt)([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;
}