先上代码再说o(* ̄︶ ̄*)o
写命令的时候拼接用mutabledata拼接,不要用byte拼,这样处理会更简单一些
#pragma mark - check字段校验和 - (NSData *)checkFieldCheckout:(NSData *)originalData { // data 转 16进制 NSString *originalStr = [requestTool hexStringFromData:originalData]; // 数组 每个字节分装 NSMutableArray *originalArr = [self getArrWithString:originalStr]; // 定义一个最后的需要的字段 uint8_t checkNum = 0x00; // 每个字节转化成 Uint8_t 然后相加 最后得出一个需要的字节 for (NSInteger i = 0; i < originalArr.count; i++) { NSString *str = [NSString stringWithFormat:@"0x%@",originalArr[i]]; const char *temChar = [str UTF8String]; int temW; sscanf(temChar, "0x%2x",&temW); checkNum += temW; } NSLog(@"%x", checkNum); // 赋值到 自定义的 struct 这里可以不用 struct horse_check check; check.CHECK = checkNum; // 转化成data输出 NSData *checkNumData = [NSData dataWithBytes:&check length:1]; return checkNumData; }
//这里用到的自定义的东西
struct horse_check { uint8_t CHECK; };
- (NSMutableArray *)getArrWithString:(NSString *)keysource { NSMutableArray *keysourceArr = [NSMutableArray array]; for (NSInteger i = 0; i < keysource.length/2; i++) { NSString *str = [keysource substringWithRange:NSMakeRange(2*i, 2)]; str = [NSString stringWithFormat:@"%@",str]; [keysourceArr addObject:str]; } return keysourceArr; }
/** * data 转 16进制 */ + (NSString *)hexStringFromData:(NSData *)data { NSAssert(data.length > 0, @"data.length <= 0"); NSMutableString *hexString = [[NSMutableString alloc] init]; const Byte *bytes = data.bytes; for (NSUInteger i=0; i<data.length; i++) { Byte value = bytes[i]; Byte high = (value & 0xf0) >> 4; Byte low = value & 0xf; [hexString appendFormat:@"%x%x", high, low]; } return hexString; }