JAVA NIO Scatter/Gather(矢量IO)
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矢量IO=Scatter/Gather:
在多个缓冲区上实现一个简单的IO操作。减少或避免了缓冲区拷贝和系统调用(IO)
write:Gather
数据从几个缓冲区顺序抽取并沿着通道发送,就好比全部缓冲区全部连接起来放入一个大的缓冲区进行发送,缓冲区本身不具备gather能力。
read:Scatter
从通道读取的数据会按顺序散布到多个缓冲区,直到缓冲区被填满或者通道数据读完。
Gather:
Scatter:
示例代码:
/** * channel Gather/Scatter */ public static void channelGatherScatter(){ ByteBuffer head = ByteBuffer.allocate(4); ByteBuffer body = ByteBuffer.allocate(100); RandomAccessFile afile = null; RandomAccessFile bfile = null; ReadWriteLock readWriteLock = new ReentrantReadWriteLock(); try { afile = new RandomAccessFile("hello.txt", "r"); bfile = new RandomAccessFile("hehe.txt", "rw"); readWriteLock.readLock().lock(); FileChannel fileChannel = afile.getChannel(); ByteBuffer[] buffers = {head, body}; while (fileChannel.read(buffers) != -1){ } head.flip(); body.flip(); System.out.println(new String(head.array())); System.out.println(new String(body.array())); readWriteLock.readLock().unlock(); fileChannel.close(); afile.close(); readWriteLock.writeLock().lock(); FileChannel bfileChannel = bfile.getChannel(); while (bfileChannel.write(buffers) > 0){ } readWriteLock.writeLock().unlock(); bfileChannel.close(); bfile.close(); }catch (Exception e){ e.printStackTrace(); } }
带offset、length参数重载read write方法,指明从那个buffer开始,共使用多少个buffer。
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