用NSData直接操作binary data

//下列這五個是你會用到的NSData方法

//將另一個NSData加到原來的NSData後面

-(void)appendData:(NSData*)otherData

//將bytes直接加入NSData,參數為1.bytes的起始位置(要加&),2.bytes的長度
-(void)appendBytes:(const void*)bytes length:(NSUInteger)length

//截取其中某一段NSData
-(NSData*)subdataWithRange:(NSRange)range

//從你的NSData中copy某段bytes出來，存到你新建的buffer（要加&）中（存數值資料，而非NSData）
-(void)getBytes:(void*)buffer range:(NSRange)range

//從你的NSData中從頭copy某段指定長度的bytes出來，存到你新建的buffer（要加&）中（存數值資料，而非NSData）
-(void)getBytes:(void*)buffer length:(NSUInteger)length

//底下是一些範例
//直接取得binary檔案
NSURL *imgPath = [[NSBundle mainBundle] URLForResource:@"yourBinary" withExtension:@"bin"];
        NSString *stringPath = [imgPath absoluteString];

        NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:stringPath]];

//要把NSData轉回NSNumber時(這裡是以short為範例)
  short s;
  [yourData getBytes:&s range:range];
  NSNumber* stepCount = [NSNumber numberWithUnsignedShort:s];


// low level read method - read data while there is data and space available in the input buffer

- (void)_readData

{

    uint8_t buf[EAD_INPUT_BUFFER_SIZE];

    while ([[_session inputStream] hasBytesAvailable])

    {

        NSInteger bytesRead = [[_session inputStream] read:buf maxLength:EAD_INPUT_BUFFER_SIZE];

        if (_readData == nil)

        {

            _readData = [[NSMutableData alloc] init];

        }

        [_readData appendBytes:(void *)buf length:bytesRead];

        //NSLog(@"read %d bytes from input stream", bytesRead);

    }

    

    [[NSNotificationCenter defaultCenter] postNotificationName:EADSessionDataReceivedNotification object:self userInfo:nil];

    //清空_readData

    if( _readData )

    {

        [_readData setLength:0];

    }

}

// high level read method

// 這裡輸入的參數為你想要切的長度。

- (NSData *)readData:(NSUInteger)bytesToRead

{

    NSData *data = nil;

    if ([_readData length] >= bytesToRead)

    {

        NSRange range = NSMakeRange(0, bytesToRead);

        data = [_readData subdataWithRange:range];

        [_readData replaceBytesInRange:range withBytes:NULL length:0];

    }

    return data;

}

// get number of bytes read into local buffer

-(NSUInteger)readBytesAvailable

{

    return [_readData length];

}

//自己寫的切封包
+ (NSArray*)splitDataIntoChunks:(NSData*)data size:(NSUInteger)bytesPerChunk{

    

    if(!data) return nil;

    

    NSMutableArray* array = [[NSMutableArray alloc]init];
    NSUInteger dataLength = [data length];
    NSUInteger chunkCount = 0;
    while (chunkCount < dataLength)
    {
        NSRange range = NSMakeRange(chunkCount, bytesPerChunk);
        NSData* chunk = [data subdataWithRange:range];
        [array addObject:chunk];
        chunkCount += 2;
    }

    return array;

}