Package com.trilead.ssh2.channel

Class FifoBuffer

  • class FifoBuffer
extends java.lang.Object
    FIFO buffer for a reader thread and a writer thread to collaborate. Unlike a ring buffer, which uses a fixed memory regardless of the number of bytes currently in the buffer, this implementation uses a single linked list to reduce the memory footprint when the reader closely follows the writer, regardless of the capacity limit set in the constructor. In trilead, the writer puts the data we receive from the network, and the user code acts as a reader. A user code normally drains the buffer more quickly than what the network delivers, so this implementation saves memory while simultaneously allowing us to advertise a bigger window size for a large latency network.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      (package private) static class  FifoBuffer.Page
      Unit of buffer, singly linked and lazy created as needed.
      (package private) class  FifoBuffer.Pointer
      Points to a specific byte in a FifoBuffer.Page.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private boolean closed
      Set to true when the writer closes the write end.
      private int limit
      Cap to the # of bytes that we can hold.
      private java.lang.Object lock  
      private int pageSize  
      private FifoBuffer.Pointer r
      The position at which the next read/write will happen.
      private int sz
      Number of bytes currently in this ring buffer
      private FifoBuffer.Pointer w
      The position at which the next read/write will happen.

    • Constructor Summary

      Constructors 
      Constructor Description
      FifoBuffer​(int pageSize, int limit)  
      FifoBuffer​(java.lang.Object lock, int pageSize, int limit)  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void close()  
      private FifoBuffer.Page newPage()  
      int read​(byte[] buf, int start, int len)  
      (package private) int readable()
      Number of bytes readable
      private void releaseRing()
      If the ring is no longer needed, release the buffer.
      void setLimit​(int newLimit)  
      (package private) int writable()
      Number of bytes writable
      void write​(byte[] buf, int start, int len)  
      int writeTo​(java.io.OutputStream out)
      Write whatever readable to the specified OutputStream, then return.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • lock

        private final java.lang.Object lock

      • sz

        private int sz
        Number of bytes currently in this ring buffer

      • limit

        private int limit
        Cap to the # of bytes that we can hold.

      • pageSize

        private final int pageSize

      • closed

        private boolean closed
        Set to true when the writer closes the write end.

    • Constructor Detail

      • FifoBuffer

        FifoBuffer​(int pageSize,
           int limit)

      • FifoBuffer

        FifoBuffer​(java.lang.Object lock,
           int pageSize,
           int limit)

    • Method Detail

      • setLimit

        public void setLimit​(int newLimit)

      • readable

        int readable()
        Number of bytes readable

      • writable

        int writable()
        Number of bytes writable

      • write

        public void write​(byte[] buf,
                  int start,
                  int len)
           throws java.lang.InterruptedException
        Throws:
        java.lang.InterruptedException

      • close

        public void close()

      • releaseRing

        private void releaseRing()
        If the ring is no longer needed, release the buffer.

      • read

        public int read​(byte[] buf,
                int start,
                int len)
         throws java.lang.InterruptedException
        Throws:
        java.lang.InterruptedException
        See Also:
        InputStream.read(byte[],int,int)

      • writeTo

        public int writeTo​(java.io.OutputStream out)
            throws java.io.IOException
        Write whatever readable to the specified OutputStream, then return.
        Throws:
        java.io.IOException