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// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 3. Neither the name of the copyright holders nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.

package org.objectweb.asm.commons;

import java.util.ArrayList;
import java.util.List;

import org.objectweb.asm.Attribute;
import org.objectweb.asm.ByteVector;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Label;

/**
 * ModuleHashes attribute. This attribute is specific to the OpenJDK and may change in the future.
 *
 * @author Remi Forax
 */
public final class ModuleHashesAttribute extends Attribute {
  public String algorithm;
  public List modules;
  public List hashes;

  /**
   * Constructs an attribute with a hashing algorithm, a list of module names, and a list of the same
   * length of hashes.
   *
   * @param algorithm the hashing algorithm name.
   * @param modules a list of module name
   * @param hashes a list of hash, one for each module name.
   */
  public ModuleHashesAttribute(
      final String algorithm, final List modules, final List hashes) {
    super("ModuleHashes");
    this.algorithm = algorithm;
    this.modules = modules;
    this.hashes = hashes;
  }

  /**
   * Constructs an empty attribute that can be used as prototype to be passed as argument of the method
   * {@link ClassReader#accept(org.objectweb.asm.ClassVisitor, Attribute[], int)}.
   */
  public ModuleHashesAttribute() {
    this(null, null, null);
  }

  @Override
  protected Attribute read(
      ClassReader cr, int off, int len, char[] buf, int codeOff, Label[] labels) {
    String hashAlgorithm = cr.readUTF8(off, buf);

    int count = cr.readUnsignedShort(off + 2);
    ArrayList modules = new ArrayList(count);
    ArrayList hashes = new ArrayList(count);
    off += 4;

    for (int i = 0; i < count; i++) {
      String module = cr.readModule(off, buf);
      int hashLength = cr.readUnsignedShort(off + 2);
      off += 4;

      byte[] hash = new byte[hashLength];
      for (int j = 0; j < hashLength; j++) {
        hash[j] = (byte) (cr.readByte(off + j) & 0xff);
      }
      off += hashLength;

      modules.add(module);
      hashes.add(hash);
    }
    return new ModuleHashesAttribute(hashAlgorithm, modules, hashes);
  }

  @Override
  protected ByteVector write(ClassWriter cw, byte[] code, int len, int maxStack, int maxLocals) {
    ByteVector v = new ByteVector();
    int index = cw.newUTF8(algorithm);
    v.putShort(index);

    int count = (modules == null) ? 0 : modules.size();
    v.putShort(count);

    for (int i = 0; i < count; i++) {
      String module = modules.get(i);
      v.putShort(cw.newModule(module));

      byte[] hash = hashes.get(i);
      v.putShort(hash.length);
      for (byte b : hash) {
        v.putByte(b);
      }
    }
    return v;
  }
}