org.ros.internal.message.Md5Generator.java Source code

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Here is the source code for org.ros.internal.message.Md5Generator.java

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/*
 * Copyright (C) 2011 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package org.ros.internal.message;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;

import org.apache.commons.codec.digest.DigestUtils;
import org.ros.internal.message.definition.MessageDefinitionParser;
import org.ros.internal.message.definition.MessageDefinitionParser.MessageDefinitionVisitor;
import org.ros.internal.message.definition.MessageDefinitionTupleParser;
import org.ros.internal.message.field.PrimitiveFieldType;
import org.ros.message.MessageDefinitionProvider;

import java.util.List;

/**
 * @author damonkohler@google.com (Damon Kohler)
 */
public class Md5Generator {

    /**
     * Used to build output as Hex
     */
    private static final char[] DIGITS_LOWER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c',
            'd', 'e', 'f' };

    private final MessageDefinitionProvider messageDefinitionProvider;

    public Md5Generator(MessageDefinitionProvider messageDefinitionProvider) {
        this.messageDefinitionProvider = messageDefinitionProvider;
    }

    public String generate(String messageType) {
        String messageDefinition = messageDefinitionProvider.get(messageType);
        Preconditions.checkNotNull(messageDefinition, "No definition for message type: " + messageType);
        List<String> parts = MessageDefinitionTupleParser.parse(messageDefinition, -1);
        StringBuilder text = new StringBuilder();
        for (String part : parts) {
            text.append(generateText(messageType, part));
        }
        byte[] md5 = DigestUtils.md5(text.toString());
        return new String(encodeHex(md5, DIGITS_LOWER));
    }

    private static char[] encodeHex(byte[] data, char[] toDigits) {
        int l = data.length;
        char[] out = new char[l << 1];
        // two characters form the hex value.
        for (int i = 0, j = 0; i < l; i++) {
            out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
            out[j++] = toDigits[0x0F & data[i]];
        }
        return out;
    }

    private String generateText(String messageType, String messageDefinition) {
        final List<String> constants = Lists.newArrayList();
        final List<String> variables = Lists.newArrayList();
        MessageDefinitionVisitor visitor = new MessageDefinitionVisitor() {
            @Override
            public void variableValue(String type, String name) {
                if (!PrimitiveFieldType.existsFor(type)) {
                    type = generate(type);
                }
                variables.add(String.format("%s %s\n", type, name));
            }

            @Override
            public void variableList(String type, int size, String name) {
                if (!PrimitiveFieldType.existsFor(type)) {
                    String md5Checksum = generate(type);
                    variables.add(String.format("%s %s\n", md5Checksum, name));
                } else {
                    if (size != -1) {
                        variables.add(String.format("%s[%d] %s\n", type, size, name));
                    } else {
                        variables.add(String.format("%s[] %s\n", type, name));
                    }
                }
            }

            @Override
            public void constantValue(String type, String name, String value) {
                constants.add(String.format("%s %s=%s\n", type, name, value));
            }
        };
        MessageDefinitionParser messageDefinitionParser = new MessageDefinitionParser(visitor);
        messageDefinitionParser.parse(messageType, messageDefinition);
        String text = "";
        for (String constant : constants) {
            text += constant;
        }
        for (String variable : variables) {
            text += variable;
        }
        return text.trim();
    }
}