com.perforce.p4java.impl.mapbased.rpc.packet
Class RpcPacketPreamble

java.lang.Object
  com.perforce.p4java.impl.mapbased.rpc.packet.RpcPacketPreamble

public class RpcPacketPreamble
extends Object

The five byte preamble appended to every text packet payload.

The format (as divined from the C++ API) is designed to provide a very simple sanity check checksum and encode the length in bytes of the accompanying RPC payload:

      byte[1] = ( payload_length / 0x1 ) % 0x100;
      byte[2] = ( payload_length / 0x100 ) % 0x100;
      byte[3] = ( payload_length / 0x10000 ) % 0x100;
      byte[4] = ( payload_length / 0x1000000 ) % 0x100;
      byte[0] = byte[1] ^ byte[2] ^ byte[3] ^ byte[4];
 

This can generally only be calculated after the other packet elements have been serialized, which is irritating but not too annoying.

Field Summary

static int	RPC_PREAMBLE_CHKSUM_SIZE Size in bytes of the preamble checksum.
static int	RPC_PREAMBLE_SIZE The size in bytes of the standard text packet RPC packet preamble.

Method Summary

static RpcPacketPreamble	constructPreamble(ByteBuffer payload) Calculate and construct a suitable preamble for the passed-in payload buffer.
static RpcPacketPreamble	constructPreamble(int payloadLength) Calculate and construct a suitable preamble for the passed-in payload buffer length.
int	getPayloadSize() Return the payload size (in bytes) specified by this preamble.
boolean	isValidChecksum() Return true iff the simple checksum checks out.
ByteBuffer	marshal() Return a ByteBuffer representing the marshaled version of this preamble.
byte[]	marshalAsBytes()
static RpcPacketPreamble	retrievePreamble(byte[] bytes) Retrieve the preamble from raw bytes.
static RpcPacketPreamble	retrievePreamble(ByteBuffer payload) Retrieve a preamble from the passed-in payload byte buffer.

Methods inherited from class java.lang.Object

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

Field Detail

RPC_PREAMBLE_CHKSUM_SIZE

public static final int RPC_PREAMBLE_CHKSUM_SIZE

Size in bytes of the preamble checksum. This is a very fundamental value; changing it will probably cause total destruction within P4Java...

See Also:

Constant Field Values

RPC_PREAMBLE_SIZE

public static final int RPC_PREAMBLE_SIZE

The size in bytes of the standard text packet RPC packet preamble.

See Also:

Constant Field Values

Method Detail

constructPreamble

public static RpcPacketPreamble constructPreamble(ByteBuffer payload)

Calculate and construct a suitable preamble for the passed-in payload buffer. Does not affect the incoming buffer at all (i.e. marks and limits, etc. are unaffected). Assumes the payload starts at buffer byte position zero and uses the buffer's limit as the length.

Parameters:

payload - non-null byte buffer representing the payload

Returns:

new RpcPacketPreamble for the payload

constructPreamble

public static RpcPacketPreamble constructPreamble(int payloadLength)

Calculate and construct a suitable preamble for the passed-in payload buffer length.

retrievePreamble

public static RpcPacketPreamble retrievePreamble(ByteBuffer payload)

Retrieve a preamble from the passed-in payload byte buffer. Will move the byte buffer pointer accordingly.

Parameters:

payload - non-null payload

Returns:

new RpcPacketPreamble as retrieved from the payload buffer.

retrievePreamble

public static RpcPacketPreamble retrievePreamble(byte[] bytes)

Retrieve the preamble from raw bytes. Most sanity checking is done in the RpcPacketPreamble constructor.

getPayloadSize

public int getPayloadSize()

Return the payload size (in bytes) specified by this preamble.

Returns:

the associated payload size in bytes.

isValidChecksum

public boolean isValidChecksum()

Return true iff the simple checksum checks out.

marshal

public ByteBuffer marshal()

Return a ByteBuffer representing the marshaled version of this preamble. Buffer will need to be flipped before sending...

Returns:

non-null ByteBuffer ready for sending

marshalAsBytes

public byte[] marshalAsBytes()