截取掉NSData末尾0x00

截取字符串末尾结束符。和硬件通讯时，往往接收到的数据带有字符串结束符0x00，如果不截取掉，JSON解析不了。下面提供截取的方法，将NSData的byte取出，循环查找末尾是否是0x00，是则截取掉

+ (NSData *)trimData:(NSData *)data {
    NSMutableData *msgData = data.mutableCopy;
    if (msgData.length >= 1) {
        BOOL index = YES;
        while (index) {
            NSData *trimData = [msgData subdataWithRange:NSMakeRange(msgData.length-1, 1)];
            Byte lastByte[1];
            [trimData getBytes:lastByte range:NSMakeRange(0, 1)];
            if (lastByte[0] == 0x00) {
                [msgData replaceBytesInRange:NSMakeRange(msgData.length-1, 1) withBytes:NULL length:0];
                index = YES;
            } else {
                index = NO;
            }
        }
    }
    return msgData;
}