IOS压缩解压缩

压缩

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-(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];            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

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-(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;         }    }