IOS压缩解压缩

#import <zlib.h>

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];

    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 *)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;
    }
}