dispatch_data_t和NSData的相互转换

/// NSData 转 dispatch_data_t
/// @param nsdata NSData
- (dispatch_data_t)dispatchDataFromNsdata:(NSData *)nsdata {
    if (nsdata == nil) {
        return nil;
    }
    Byte byte[nsdata.length];
    [nsdata getBytes:byte length:nsdata.length];
    dispatch_data_t data = dispatch_data_create(byte, nsdata.length, nil, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
    return data;
}

/// dispatch_data_t 转 NSData
/// @param dispatchData dispatch_data_t
- (NSData *)nsdataFromDispatchData:(dispatch_data_t)dispatchData {
    if (dispatchData == nil) {
        return nil;
    }
    const void *buffer = NULL;
    size_t size = 0;
    dispatch_data_t new_data_file = dispatch_data_create_map(dispatchData, &buffer, &size);
    if(new_data_file) {/* to avoid warning really - since dispatch_data_create_map demands we care about the return arg */}
    NSData *nsdata = [[NSData alloc] initWithBytes:buffer length:size];
    return nsdata;
}