iOS蓝牙通信 - 数据转换

大端小端

• 测试

  int32_t a = 0x1122;
  int32_t big = CFSwapInt32HostToBig(a);
  NSData *data = [NSData dataWithBytes:&a length:sizeof(a)];
  NSData *datab = [NSData dataWithBytes:&big length:sizeof(big)];
  
  小端序 data: 0x22 0x11 0x00 0x00 
  大端序 datab: 0x00 0x00 0x11 0x22 
  

• 是否是小端模式

  - (int) isLittleEndian
  {
      int i = 0x12345678;
      char *c = &i;
      return ((c[0] == 0x78) && (c[1] == 0x56) && (c[2] == 0x34) && (c[3] == 0x12));
  }
  

数据转换

• int 转 NSData

  int value  = 1;
  NSData *data = [NSData dataWithBytes:&value length:1];    
  

• NSData 转 int

  int value = 0;
  [data getBytes:&value range:NSMakeRange(0, 2)];
  

• 数组 转 NSData

  • 写法1

  NSMutableData *data = [NSMutableData data];
  Byte value = 0x01;
  [data appendBytes:&value length:sizeof(value)];
  

  • 写法2

  NSMutableData *data = [NSMutableData data];
  Byte value[6] = {0x06,0x00,0x00,0x03,0x04,0x04};
  [data appendBytes:value length:sizeof(value)];
  

  • 写法3

  Byte value[6] = {0};
  value[0]=0x06;
  value[1]=0x00;
  value[2]=0x00;
  value[3]=0x03;
  value[4]=0x04;
  value[5]=0x04;
  NSData * data = [NSData dataWithBytes:value length:sizeof(value)];
  

• Byte 转 NSData

  Byte byte  = 0x55;
  NSData *data = [NSData dataWithBytes:&byte lenght:7];
  

• NSData 转 Byte

  NSString *str = @"123";　　
  NSData *data = [str dataUsingEncoding: NSUTF8StringEncoding];　　
  Byte *byte = (Byte *)[data bytes];