MemoryChunk.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.general.memmanager;

import com.google.common.base.Preconditions;

/**
 * Used to store a contiguous chunk of memory.
 * 
 */
public class MemoryChunk implements Comparable<MemoryChunk> {
  /**
   * The address of the memory chunk.
   */
  private final long m_address;

  /**
   * The data inside the chunk.
   */
  private byte[] m_data;

  /**
   * Creates a new memory chunk object with the given byte data.
   * 
   * @param address The start address of the chunk.
   * @param data The initial data of the memory chunk.
   * 
   * @throws IllegalArgumentException Thrown if the address is less than 0.
   * @throws NullPointerException Thrown if the initial data is null.
   */
  public MemoryChunk(final long address, final byte[] data) {
    Preconditions.checkArgument(address >= 0, "Chunk addresses can't be less than 0");
    Preconditions.checkNotNull(data, "Initial data can't be null");
    Preconditions.checkArgument(data.length != 0, "Initial data can't be empty");

    m_address = address;
    m_data = data;
  }

  /**
   * Creates a new memory chunk object that is initialized with bytes of value 0.
   *
   * @param address The start address of the chunk.
   * @param size The size of the chunk.
   */
  public MemoryChunk(final long address, final int size) {
    this(address, new byte[size]);
  }

  /**
   * Used to order chunks according to their address.
   */
  @Override
  public int compareTo(final MemoryChunk chunk) {
    return Long.compare(m_address, chunk.m_address);
  }

  /**
   * Adds a number of 0-bytes at the end of the memory chunk.
   *
   * @param size The number of 0-bytes to add.
   *
   * @throws IllegalArgumentException Thrown if the number of bytes to add is not positive.
   */
  public void extend(final int size) {
    Preconditions.checkArgument(size > 0, "The number of bytes to add must be positive");

    final byte[] data = new byte[m_data.length + size];

    System.arraycopy(m_data, 0, data, 0, m_data.length);

    m_data = data;
  }

  /**
   * Returns the start address of the memory chunk.
   *
   * @return The start address of the memory chunk.
   */
  public long getAddress() {
    return m_address;
  }

  /**
   * Returns the data of the memory chunk.
   *
   * @return The data of the memory chunk.
   */
  public byte[] getBytes() {
    return m_data;
  }

  /**
   * Returns the length of the memory chunk.
   *
   * @return The length of the memory chunk.
   */
  public int getLength() {
    return m_data.length;
  }

  /**
   * Loads a single byte from the given address.
   *
   * @param address The address where the byte is stored.
   *
   * @return The value of the byte at the given address.
   *
   * @throws IndexOutOfBoundsException Thrown if the address is not part of the memory chunk.
   */
  public byte loadByte(final long address) {
    return m_data[(int) (address - m_address)];
  }

  /**
   * Prints the content of the memory chunk to stdout.
   */
  public void print() {
    System.out.printf("%08X: ", m_address);

    for (final byte element : m_data) {
      System.out.printf("%02X ", element);
    }

    System.out.println();
  }

  /**
   * Stores a range of bytes in the memory chunk.
   *
   * @param address The start address of the new data.
   * @param data The new data.
   *
   * @throws IndexOutOfBoundsException Thrown if the memory chunk is not large enough to hold the
   *         data.
   * @throws NullPointerException Thrown if the passed data is null.
   */
  public void store(final long address, final byte[] data) {
    System.arraycopy(data, 0, m_data, (int) (address - m_address), data.length);
  }

  /**
   * Stores a single byte at the given address.
   *
   * @param address The address where the byte is stored.
   * @param b The value of the byte.
   *
   * @throws IndexOutOfBoundsException Thrown if the address is not part of the memory chunk.
   */
  public void storeByte(final long address, final byte b) {
    m_data[(int) (address - m_address)] = b;
  }
}