org.apache.coyote.ajp

## Class AjpMessage

- java.lang.Object
- - org.apache.coyote.ajp.AjpMessage

-     public class AjpMessage
      extends Object

  A single packet for communication between the web server and the container. Designed to be reused many times with no creation of garbage. Understands the format of data types for these packets. Can be used (somewhat confusingly) for both incoming and outgoing packets.
  Author:
    Henri Gomez, Dan Milstein, Keith Wannamaker, Kevin Seguin, Costin Manolache

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected byte[]` | `buf` Fixed size buffer.
    `protected int` | `len` This actually means different things depending on whether the packet is read or write.
    `protected int` | `pos` The current read or write position in the buffer.
    `protected static StringManager` | `sm` The string manager for this package.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `AjpMessage(int packetSize)`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `appendByte(int val)` Append a byte (1 byte) to the message.
    `void` | `appendByteChunk(ByteChunk bc)` Write a ByteChunk out at the current write position.
    `void` | `appendBytes(byte[] b, int off, int numBytes)` Copy a chunk of bytes into the packet, starting at the current write position.
    `void` | `appendBytes(ByteBuffer b)` Copy a chunk of bytes into the packet, starting at the current write position.
    `void` | `appendBytes(MessageBytes mb)` Write a MessageBytes out at the current write position.
    `void` | `appendInt(int val)` Add a short integer (2 bytes) to the message.
    `void` | `end()` For a packet to be sent to the web server, finish the process of accumulating data and write the length of the data payload into the header.
    `void` | `getBodyBytes(MessageBytes mb)`
    `byte[]` | `getBuffer()` Return the underlying byte buffer.
    `byte` | `getByte()`
    `void` | `getBytes(MessageBytes mb)`
    `int` | `getInt()` Read an integer from packet, and advance the read position past it.
    `int` | `getLen()` Return the current message length.
    `int` | `getLongInt()` Read a 32 bits integer from packet, and advance the read position past it.
    `protected static String` | `hex(int x)`
    `protected static String` | `hexLine(byte[] buf, int start, int len)`
    `int` | `peekInt()`
    `int` | `processHeader(boolean toContainer)`
    `void` | `reset()` Prepare this packet for accumulating a message from the container to the web server.

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### sm

          protected static final StringManager sm

      The string manager for this package.

    - #### buf

          protected final byte[] buf

      Fixed size buffer.

    - #### pos

          protected int pos

      The current read or write position in the buffer.

    - #### len

          protected int len

      This actually means different things depending on whether the packet is read or write. For read, it's the length of the payload (excluding the header). For write, it's the length of the packet as a whole (counting the header). Oh, well.

  - ### Constructor Detail

    - #### AjpMessage

          public AjpMessage(int packetSize)

  - ### Method Detail

    - #### reset

          public void reset()

      Prepare this packet for accumulating a message from the container to the web server. Set the write position to just after the header (but leave the length unwritten, because it is as yet unknown).

    - #### end

          public void end()

      For a packet to be sent to the web server, finish the process of accumulating data and write the length of the data payload into the header.

    - #### getBuffer

          public byte[] getBuffer()

      Return the underlying byte buffer.
      Returns:
        The buffer

    - #### getLen

          public int getLen()

      Return the current message length.
      Returns:
        For read, it's the length of the payload (excluding the header). For write, it's the length of the packet as a whole (counting the header).

    - #### appendInt

          public void appendInt(int val)

      Add a short integer (2 bytes) to the message.
      Parameters:
        `val` - The integer to append

    - #### appendByte

          public void appendByte(int val)

      Append a byte (1 byte) to the message.
      Parameters:
        `val` - The byte value to append

    - #### appendBytes

          public void appendBytes(MessageBytes mb)

      Write a MessageBytes out at the current write position. A null MessageBytes is encoded as a string with length 0.
      Parameters:
        `mb` - The data to write

    - #### appendByteChunk

          public void appendByteChunk(ByteChunk bc)

      Write a ByteChunk out at the current write position. A null ByteChunk is encoded as a string with length 0.
      Parameters:
        `bc` - The data to write

    - #### appendBytes

          public void appendBytes(byte[] b,
                         int off,
                         int numBytes)

      Copy a chunk of bytes into the packet, starting at the current write position. The chunk of bytes is encoded with the length in two bytes first, then the data itself, and finally a terminating \0 (which is not included in the encoded length).
      Parameters:
        `b` - The array from which to copy bytes.
        `off` - The offset into the array at which to start copying
        `numBytes` - The number of bytes to copy.

    - #### appendBytes

          public void appendBytes(ByteBuffer b)

      Copy a chunk of bytes into the packet, starting at the current write position. The chunk of bytes is encoded with the length in two bytes first, then the data itself, and finally a terminating \0 (which is not included in the encoded length).
      Parameters:
        `b` - The ByteBuffer from which to copy bytes.

    - #### getInt

          public int getInt()

      Read an integer from packet, and advance the read position past it. Integers are encoded as two unsigned bytes with the high-order byte first, and, as far as I can tell, in little-endian order within each byte.
      Returns:
        The integer value read from the message

    - #### peekInt

          public int peekInt()

    - #### getByte

          public byte getByte()

    - #### getBytes

          public void getBytes(MessageBytes mb)

    - #### getBodyBytes

          public void getBodyBytes(MessageBytes mb)

    - #### getLongInt

          public int getLongInt()

      Read a 32 bits integer from packet, and advance the read position past it. Integers are encoded as four unsigned bytes with the high-order byte first, and, as far as I can tell, in little-endian order within each byte.
      Returns:
        The long value read from the message

    - #### processHeader

          public int processHeader(boolean toContainer)

    - #### hexLine

          protected static String hexLine(byte[] buf,
                       int start,
                       int len)

    - #### hex

          protected static String hex(int x)

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