JarResources.java

/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

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.google.security.zynamics.zylib.plugins;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipInputStream;

/**
 * JarResources: JarResources maps all resources included in a Zip or Jar file. Additionaly, it
 * provides a method to extract one as a blob.
 */
public final class JarResources {
  // jar resource mapping tables
  private final Hashtable<String, Integer> htSizes = new Hashtable<String, Integer>();

  private final Hashtable<String, byte[]> htJarContents = new Hashtable<String, byte[]>();
  // a jar file
  private final String jarFileName;

  // external debug flag
  public boolean debugOn = false;

  /**
   * creates a JarResources. It extracts all resources from a Jar into an internal hashtable, keyed
   * by resource names.
   * 
   * @param jarFileName a jar or zip file
   */
  public JarResources(final String jarFileName) {
    this.jarFileName = jarFileName;
    init();
  }

  /**
   * Dumps a zip entry into a string.
   * 
   * @param ze a ZipEntry
   */
  private String dumpZipEntry(final ZipEntry ze) {
    final StringBuffer sb = new StringBuffer();
    if (ze.isDirectory()) {
      sb.append("d ");
    } else {
      sb.append("f ");
    }

    if (ze.getMethod() == ZipEntry.STORED) {
      sb.append("stored   ");
    } else {
      sb.append("defalted ");
    }

    sb.append(ze.getName());
    sb.append("\t");
    sb.append("" + ze.getSize());
    if (ze.getMethod() == ZipEntry.DEFLATED) {
      sb.append("/" + ze.getCompressedSize());
    }

    return sb.toString();
  }

  /** initializes internal hash tables with Jar file resources. */
  private void init() {
    try {
      // extracts just sizes only.
      final ZipFile zf = new ZipFile(jarFileName);
      final Enumeration<? extends ZipEntry> e = zf.entries();
      while (e.hasMoreElements()) {
        final ZipEntry ze = e.nextElement();

        if (debugOn) {
          System.out.println(dumpZipEntry(ze));
        }

        htSizes.put(ze.getName(), (int) ze.getSize());
      }
      zf.close();

      // extract resources and put them into the hashtable.
      final FileInputStream fis = new FileInputStream(jarFileName);
      final BufferedInputStream bis = new BufferedInputStream(fis);
      final ZipInputStream zis = new ZipInputStream(bis);
      ZipEntry ze = null;
      while ((ze = zis.getNextEntry()) != null) {
        if (ze.isDirectory()) {
          continue;
        }

        if (debugOn) {
          System.out.println("ze.getName()=" + ze.getName() + "," + "getSize()=" + ze.getSize());
        }

        int size = (int) ze.getSize();
        // -1 means unknown size.
        if (size == -1) {
          size = htSizes.get(ze.getName()).intValue();
        }

        final byte[] b = new byte[size];
        int rb = 0;
        int chunk = 0;
        while ((size - rb) > 0) {
          chunk = zis.read(b, rb, size - rb);
          if (chunk == -1) {
            break;
          }
          rb += chunk;
        }

        // add to internal resource hashtable
        htJarContents.put(ze.getName(), b);

        if (debugOn) {
          System.out.println(ze.getName() + "  rb=" + rb + ",size=" + size + ",csize="
              + ze.getCompressedSize());
        }
      }
      zis.close();
    } catch (final NullPointerException e) {
      System.out.println("done.");
    } catch (IOException e) {
      e.printStackTrace();
    } 
  }

  /**
   * Extracts a jar resource as a blob.
   * 
   * @param name a resource name.
   */
  public byte[] getResource(final String name) {
    return htJarContents.get(name);
  }

} // End of JarResources class.