在sqlite目标C中解压缩保存为blob的文件

Question

我无法解压缩保存在Sqlite As Blob中的zip文件，在我查询db之后它返回给我一个NSData。我尝试了inflate方法，但它返回此错误“数据解压缩失败，代码为-3”。任何意见??

谢谢！

这是代码

    NSData *content = [[NSData alloc] initWithBytes:sqlite3_column_blob(statement, 3) length:sqlite3_column_bytes(statement, 3)];
   content = [NSData gzipInflate:content];

/// Ns数据类别

@implementation NSData (Unzip)


+ (NSData *)gzipInflate:(NSData*)data
{
    if ([data length] == 0) return data;

    unsigned full_length = [data length];
    unsigned 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 = [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 = [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;
}
@end