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The RabbitMQ Java client library allows Java applications to interface with RabbitMQ.

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// 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;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.UnexpectedFrameError;

/**
 * Class responsible for piecing together a command from a series of {@link Frame}s.
 * 

Concurrency
* This class is thread-safe, since all methods are synchronised. Callers should not * synchronise on objects of this class unless they are sole owners. * @see AMQCommand */ final class CommandAssembler { private static final byte[] EMPTY_BYTE_ARRAY = new byte[0]; /** Current state, used to decide how to handle each incoming frame. */ private enum CAState { EXPECTING_METHOD, EXPECTING_CONTENT_HEADER, EXPECTING_CONTENT_BODY, COMPLETE } private CAState state; /** The method for this command */ private Method method; /** The content header for this command */ private AMQContentHeader contentHeader; /** The fragments of this command's content body - a list of byte[] */ private final List bodyN; /** sum of the lengths of all fragments */ private int bodyLength; /** No bytes of content body not yet accumulated */ private long remainingBodyBytes; public CommandAssembler(Method method, AMQContentHeader contentHeader, byte[] body) { this.method = method; this.contentHeader = contentHeader; this.bodyN = new ArrayList(2); this.bodyLength = 0; this.remainingBodyBytes = 0; appendBodyFragment(body); if (method == null) { this.state = CAState.EXPECTING_METHOD; } else if (contentHeader == null) { this.state = method.hasContent() ? CAState.EXPECTING_CONTENT_HEADER : CAState.COMPLETE; } else { this.remainingBodyBytes = contentHeader.getBodySize() - this.bodyLength; updateContentBodyState(); } } public synchronized Method getMethod() { return this.method; } public synchronized AMQContentHeader getContentHeader() { return this.contentHeader; } /** @return true if the command is complete */ public synchronized boolean isComplete() { return (this.state == CAState.COMPLETE); } /** Decides whether more body frames are expected */ private void updateContentBodyState() { this.state = (this.remainingBodyBytes > 0) ? CAState.EXPECTING_CONTENT_BODY : CAState.COMPLETE; } private void consumeMethodFrame(Frame f) throws IOException { if (f.type == AMQP.FRAME_METHOD) { this.method = AMQImpl.readMethodFrom(f.getInputStream()); this.state = this.method.hasContent() ? CAState.EXPECTING_CONTENT_HEADER : CAState.COMPLETE; } else { throw new UnexpectedFrameError(f, AMQP.FRAME_METHOD); } } private void consumeHeaderFrame(Frame f) throws IOException { if (f.type == AMQP.FRAME_HEADER) { this.contentHeader = AMQImpl.readContentHeaderFrom(f.getInputStream()); this.remainingBodyBytes = this.contentHeader.getBodySize(); updateContentBodyState(); } else { throw new UnexpectedFrameError(f, AMQP.FRAME_HEADER); } } private void consumeBodyFrame(Frame f) { if (f.type == AMQP.FRAME_BODY) { byte[] fragment = f.getPayload(); this.remainingBodyBytes -= fragment.length; updateContentBodyState(); if (this.remainingBodyBytes < 0) { throw new UnsupportedOperationException("%%%%%% FIXME unimplemented"); } appendBodyFragment(fragment); } else { throw new UnexpectedFrameError(f, AMQP.FRAME_BODY); } } /** Stitches together a fragmented content body into a single byte array */ private byte[] coalesceContentBody() { if (this.bodyLength == 0) return EMPTY_BYTE_ARRAY; if (this.bodyN.size() == 1) return this.bodyN.get(0); byte[] body = new byte[bodyLength]; int offset = 0; for (byte[] fragment : this.bodyN) { System.arraycopy(fragment, 0, body, offset, fragment.length); offset += fragment.length; } this.bodyN.clear(); this.bodyN.add(body); return body; } public synchronized byte[] getContentBody() { return coalesceContentBody(); } private void appendBodyFragment(byte[] fragment) { if (fragment == null || fragment.length == 0) return; bodyN.add(fragment); bodyLength += fragment.length; } /** * @param f frame to be incorporated * @return true if command becomes complete * @throws IOException if error reading frame */ public synchronized boolean handleFrame(Frame f) throws IOException { switch (this.state) { case EXPECTING_METHOD: consumeMethodFrame(f); break; case EXPECTING_CONTENT_HEADER: consumeHeaderFrame(f); break; case EXPECTING_CONTENT_BODY: consumeBodyFrame(f); break; default: throw new IllegalStateException("Bad Command State " + this.state); } return isComplete(); } }





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