NSData轉成16進制

//Data轉成16進制

-(NSString *)getHexCheckSum:(NSData *)_sourceData

{

    //轉 16 進制的 Check Sum 算法

    int _checkSum  = 0;

    int _dataLength = _sourceData.length;

    Byte *_bytes = (Byte *)[_sourceData bytes];

    for( int i=0; i<_dataLength; i++ )

        {

             //Force the Byte to Unsigned Byte ( to Scope in 0 ~ 255 ) and Convert to Integer type.

             _checkSum += (int)( _bytes[i]&0xff );

             //_checkSum += _bytes[i];

             }

     return [NSString stringWithFormat:@"%x", _checkSum];

}