ManifestEntry.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * 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 com.motorolamobility.studio.android.certmanager.packaging.sign;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Iterator;
import java.util.jar.Attributes;

import org.bouncycastle.util.encoders.Base64Encoder;

import com.motorola.studio.android.common.log.StudioLogger;

/**
 * A Class representing a Manifest Entry.
 */
public class ManifestEntry
{
    /**
     * New line string according Jar specification
     */
    public static final String MANIFEST_NEW_LINE = "\r\n";

    public static final String ENTRY_NAME_ATTRIBUTE = "Name: ";

    public static final String UTF8_CHARSET = "UTF-8";

    /**
     * Safe line size limit according Jar Specification
     */
    public static final int SAFE_LIMIT = 72;

    private final String name;

    private final Attributes attributes;

    /**
     * Create a new ManifestEntry with the desired name and attributes
     * @param name
     * @param attr
     */
    public ManifestEntry(String name, Attributes attr)
    {
        this.name = name;
        this.attributes = attr;
    }

    /**
     * Get the manifest as it will be written in the Manifest file
     * @return a byte array representing the manifest entry
     */
    public byte[] toManifestEntryBytes()
    {
        byte[] result = null;
        DataOutputStream dataOut = null;
        ByteArrayOutputStream stream = null;
        try
        {
            stream = new ByteArrayOutputStream();
            dataOut = new DataOutputStream(stream);
            String nameField = wrap72bytes(ENTRY_NAME_ATTRIBUTE + name);
            dataOut.writeBytes(nameField);
            dataOut.writeBytes(MANIFEST_NEW_LINE);
            dataOut.writeBytes(getAttributesString());
            dataOut.writeBytes(MANIFEST_NEW_LINE);
            dataOut.writeBytes(MANIFEST_NEW_LINE);
            result = stream.toString().getBytes(UTF8_CHARSET);

        }
        catch (IOException e)
        {
            StudioLogger.error(ManifestEntry.class, "Error getting manifest like bytes");
        }
        finally
        {
            try
            {
                if (dataOut != null)
                {
                    dataOut.close();
                }
                if (stream != null)
                {
                    stream.close();
                }
            }
            catch (IOException e)
            {
                StudioLogger
                        .error("Could not close stream while writing manifest" + e.getMessage());
            }
        }

        return result;
    }

    /**
     * Digest the entire entry
     * @return a byte array with the SHA-1 sum of this entry
     */
    public byte[] digest()
    {
        byte[] digested = null;
        try
        {
            MessageDigest digester = MessageDigest.getInstance("SHA-1");
            digester.reset();
            digester.update(toManifestEntryBytes());
            digested = digester.digest();
        }
        catch (NoSuchAlgorithmException e)
        {
            StudioLogger.error(ManifestEntry.class, "Error digesting manifest bytes");
        }
        return digested;
    }

    /**
     * Get this Entry attributes as it will be written in the Manifest file
     * @return
     */
    private String getAttributesString()
    {
        StringBuilder builder = new StringBuilder();
        Iterator<Object> it = attributes.keySet().iterator();
        while (it.hasNext())
        {
            Object next = it.next();
            String line = wrap72bytes(next + ": " + attributes.get(next));
            if (it.hasNext())
            {
                line += MANIFEST_NEW_LINE;
            }
            builder.append(line);
        }
        return builder.toString();
    }

    /**
     * Wrap a string into another string with at most 72 bytes per line
     * According Jar spec, each line must have at most 72 bytes
     * @param line
     * @return the wrapped string
     */
    public static String wrap72bytes(String line)
    {
        String returnString = line;

        if (line.length() > SAFE_LIMIT)
        {
            int maximumLength = SAFE_LIMIT - MANIFEST_NEW_LINE.length();
            StringBuilder wrapped = new StringBuilder();
            int index = maximumLength;
            String first = line.substring(0, index); //get first SAFE_LIMIT - MANIFEST_NEW_LINE.length() bytes
            first += MANIFEST_NEW_LINE;
            wrapped.append(first);
            while (index < line.length())
            {
                String medium = " ";
                if ((index + maximumLength) < line.length())
                {
                    medium += line.substring(index, index + maximumLength); //get the maximum length minus the blank space size
                }
                else
                {
                    medium += line.substring(index);
                }
                wrapped.append(medium);
                index += maximumLength;
            }
            returnString = wrapped.toString();
        }

        return returnString;
    }

    /**
     * Get this entry name
     * @return this entry name
     */
    public String getName()
    {
        return name;
    }

    /**
     * Get this entry ready to be written in the Signature File
     * @return this entry ready to be written in the Signature File
     * @throws IOException if some error occurs during encoding
     */
    public String toDigestedManifestEntry() throws IOException
    {
        Base64Encoder encoder = new Base64Encoder();
        StringBuilder builder = new StringBuilder();
        ByteArrayOutputStream output = null;

        try
        {
            output = new ByteArrayOutputStream();

            builder.append(wrap72bytes(ENTRY_NAME_ATTRIBUTE + name));
            builder.append(MANIFEST_NEW_LINE);
            builder.append(ISignConstants.SHA1_DIGEST + ": ");

            byte[] digest = digest();
            encoder.encode(digest, 0, digest.length, output);

            builder.append(output.toString());
            builder.append(MANIFEST_NEW_LINE);
        }
        finally
        {
            if (output != null)
            {
                try
                {
                    output.close();
                }
                catch (IOException e)
                {
                    StudioLogger.error("Could not close stream: " + e.getMessage());
                }
            }
        }
        return builder.toString();
    }
}