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The RabbitMQ Java client library allows Java applications to interface with RabbitMQ.
// Copyright (c) 2007-Present Pivotal Software, Inc. All rights reserved.
//
// This software, the RabbitMQ Java client library, is triple-licensed under the
// Mozilla Public License 1.1 ("MPL"), the GNU General Public License version 2
// ("GPL") and the Apache License version 2 ("ASL"). For the MPL, please see
// LICENSE-MPL-RabbitMQ. For the GPL, please see LICENSE-GPL2. For the ASL,
// please see LICENSE-APACHE2.
//
// This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND,
// either express or implied. See the LICENSE file for specific language governing
// rights and limitations of this software.
//
// If you have any questions regarding licensing, please contact us at
// [email protected].
package com.rabbitmq.client.impl.nio;
import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.MalformedFrameException;
import com.rabbitmq.client.impl.Frame;
import java.io.DataInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;
/**
* Class to create AMQP frames from a {@link ReadableByteChannel}.
* Supports partial frames: a frame can be read in several attempts
* from the {@link NioLoop}. This can happen when the channel won't
* read any more bytes in the middle of a frame building. The state
* of the outstanding frame is saved up, and the builder will
* start where it left off when the {@link NioLoop} comes back to
* this connection.
* This class is not thread safe.
*
* @since 4.4.0
*/
public class FrameBuilder {
private static final int PAYLOAD_OFFSET = 1 /* type */ + 2 /* channel */ + 4 /* payload size */;
protected final ReadableByteChannel channel;
protected final ByteBuffer applicationBuffer;
// to store the bytes of the outstanding data
// 3 byte-long because the longest we read is an unsigned int
// (not need to store the latest byte)
private final int[] frameBuffer = new int[3];
private int frameType;
private int frameChannel;
private byte[] framePayload;
private int bytesRead = 0;
public FrameBuilder(ReadableByteChannel channel, ByteBuffer buffer) {
this.channel = channel;
this.applicationBuffer = buffer;
}
/**
* Read a frame from the network.
* This method returns null f a frame could not have been fully built from
* the network. The client must then retry later (typically
* when the channel notifies it has something to read).
*
* @return a complete frame or null if a frame couldn't have been fully built
* @throws IOException
* @see Frame#readFrom(DataInputStream)
*/
public Frame readFrame() throws IOException {
while (somethingToRead()) {
if (bytesRead == 0) {
// type
frameType = readFromBuffer();
if (frameType == 'A') {
handleProtocolVersionMismatch();
}
} else if (bytesRead == 1) {
// channel 1/2
frameBuffer[0] = readFromBuffer();
} else if (bytesRead == 2) {
// channel 2/2
frameChannel = (frameBuffer[0] << 8) + (readFromBuffer() << 0);
} else if (bytesRead == 3) {
// payload size 1/4
frameBuffer[0] = readFromBuffer();
} else if (bytesRead == 4) {
// payload size 2/4
frameBuffer[1] = readFromBuffer();
} else if (bytesRead == 5) {
// payload size 3/4
frameBuffer[2] = readFromBuffer();
} else if (bytesRead == 6) {
// payload size 4/4
int framePayloadSize = ((frameBuffer[0] << 24) + (frameBuffer[1] << 16) + (frameBuffer[2] << 8) + (readFromBuffer() << 0));
framePayload = new byte[framePayloadSize];
} else if (bytesRead >= PAYLOAD_OFFSET && bytesRead < framePayload.length + PAYLOAD_OFFSET) {
framePayload[bytesRead - PAYLOAD_OFFSET] = (byte) readFromBuffer();
} else if (bytesRead == framePayload.length + PAYLOAD_OFFSET) {
int frameEndMarker = readFromBuffer();
if (frameEndMarker != AMQP.FRAME_END) {
throw new MalformedFrameException("Bad frame end marker: " + frameEndMarker);
}
bytesRead = 0;
return new Frame(frameType, frameChannel, framePayload);
} else {
throw new IllegalStateException("Number of read bytes incorrect: " + bytesRead);
}
bytesRead++;
}
return null;
}
/**
* Tells whether there's something to read in the application buffer or not.
* Tries to read from the network if necessary.
*
* @return true if there's something to read in the application buffer
* @throws IOException
*/
protected boolean somethingToRead() throws IOException {
if (!applicationBuffer.hasRemaining()) {
applicationBuffer.clear();
int read = NioHelper.read(channel, applicationBuffer);
applicationBuffer.flip();
if (read > 0) {
return true;
} else {
return false;
}
} else {
return true;
}
}
private int readFromBuffer() {
return applicationBuffer.get() & 0xff;
}
/**
* Handle a protocol version mismatch.
* @return
* @throws IOException
* @see Frame#protocolVersionMismatch(DataInputStream)
*/
private void handleProtocolVersionMismatch() throws IOException {
// Probably an AMQP.... header indicating a version mismatch
// Otherwise meaningless, so try to read the version,
// and throw an exception, whether we read the version
// okay or not.
// Try to read everything from the network, this header
// is small and should never require several network reads.
byte[] expectedBytes = new byte[] { 'M', 'Q', 'P' };
int expectedBytesCount = 0;
while (somethingToRead() && expectedBytesCount < 3) {
// We expect the letters M, Q, P in that order: generate an informative error if they're not found
int nextByte = readFromBuffer();
if (nextByte != expectedBytes[expectedBytesCount]) {
throw new MalformedFrameException("Invalid AMQP protocol header from server: expected character " +
expectedBytes[expectedBytesCount] + ", got " + nextByte);
}
expectedBytesCount++;
}
if (expectedBytesCount != 3) {
throw new MalformedFrameException("Invalid AMQP protocol header from server: read only "
+ (expectedBytesCount + 1) + " byte(s) instead of 4");
}
int[] signature = new int[4];
for (int i = 0; i < 4; i++) {
if (somethingToRead()) {
signature[i] = readFromBuffer();
} else {
throw new MalformedFrameException("Invalid AMQP protocol header from server");
}
}
MalformedFrameException x;
if (signature[0] == 1 &&
signature[1] == 1 &&
signature[2] == 8 &&
signature[3] == 0) {
x = new MalformedFrameException("AMQP protocol version mismatch; we are version " +
AMQP.PROTOCOL.MAJOR + "-" + AMQP.PROTOCOL.MINOR + "-" + AMQP.PROTOCOL.REVISION +
", server is 0-8");
} else {
String sig = "";
for (int i = 0; i < 4; i++) {
if (i != 0)
sig += ",";
sig += signature[i];
}
x = new MalformedFrameException("AMQP protocol version mismatch; we are version " +
AMQP.PROTOCOL.MAJOR + "-" + AMQP.PROTOCOL.MINOR + "-" + AMQP.PROTOCOL.REVISION +
", server sent signature " + sig);
}
throw x;
}
}