convert NSMutableData to NSData

-(NSData*)FunTest

NSMutableData *theData = [NSMutableData data];

char bytesToAppend[5] = 0x01, 0xf0, 0x64, 0x0, 0x6a;

[theData appendBytes:bytesToAppend length:sizeof(bytesToAppend)];

[theData appendBytes:bytesToAppend length:sizeof(bytesToAppend)];

NSData *immutableData = [NSData dataWithData:theData];

return immutableData;

convert NSMutableData to NSData