Android Open Source - JiangHomeStyle_Android_Phone Simple8 Bit Zip Encoding

• Back to App/phone  ↑

From Project

Back to project page JiangHomeStyle_Android_Phone.

License

The source code is released under:

Apache License

Java Source Code

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 */*w  w w. j ava  2  s . c  o m*/
 * 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.apache.tools.zip;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * This ZipEncoding implementation implements a simple 8bit character set, which
 * mets the following restrictions:
 * 
 * <ul>
 * <li>Characters 0x0000 to 0x007f are encoded as the corresponding byte values
 * 0x00 to 0x7f.</li>
 * <li>All byte codes from 0x80 to 0xff are mapped to a unique unicode character
 * in the range 0x0080 to 0x7fff. (No support for UTF-16 surrogates)
 * </ul>
 * 
 * <p>
 * These restrictions most notably apply to the most prominent omissions of
 * java-1.4's {@link java.nio.charset.Charset Charset} implementation, Cp437 and
 * Cp850.
 * </p>
 * 
 * <p>
 * The methods of this class are reentrant.
 * </p>
 */
class Simple8BitZipEncoding implements ZipEncoding
{

  /**
   * A character entity, which is put to the reverse mapping table of a simple
   * encoding.
   */
  private static final class Simple8BitChar implements Comparable<Simple8BitChar>
  {
    public final char unicode;
    public final byte code;

    Simple8BitChar(byte code, char unicode)
    {
      this.code = code;
      this.unicode = unicode;
    }

    public int compareTo(Simple8BitChar a)
    {
      return this.unicode - a.unicode;
    }

    @Override
    public String toString()
    {
      return "0x" + Integer.toHexString(0xffff & unicode) + "->0x" + Integer.toHexString(0xff & code);
    }

    @Override
    public boolean equals(Object o)
    {
      if (o instanceof Simple8BitChar)
      {
        Simple8BitChar other = (Simple8BitChar) o;
        return unicode == other.unicode && code == other.code;
      }
      return false;
    }

    @Override
    public int hashCode()
    {
      return unicode;
    }
  }

  /**
   * The characters for byte values of 128 to 255 stored as an array of 128
   * chars.
   */
  private final char[] highChars;

  /**
   * A list of {@link Simple8BitChar} objects sorted by the unicode field.
   * This list is used to binary search reverse mapping of unicode characters
   * with a character code greater than 127.
   */
  private final List<Simple8BitChar> reverseMapping;

  /**
   * @param highChars
   *            The characters for byte values of 128 to 255 stored as an
   *            array of 128 chars.
   */
  public Simple8BitZipEncoding(char[] highChars)
  {
    this.highChars = highChars.clone();
    List<Simple8BitChar> temp = new ArrayList<Simple8BitChar>(this.highChars.length);

    byte code = 127;

    for (int i = 0; i < this.highChars.length; ++i)
    {
      temp.add(new Simple8BitChar(++code, this.highChars[i]));
    }

    Collections.sort(temp);
    this.reverseMapping = Collections.unmodifiableList(temp);
  }

  /**
   * Return the character code for a given encoded byte.
   * 
   * @param b
   *            The byte to decode.
   * @return The associated character value.
   */
  public char decodeByte(byte b)
  {
    // code 0-127
    if (b >= 0)
    {
      return (char) b;
    }

    // byte is signed, so 128 == -128 and 255 == -1
    return this.highChars[128 + b];
  }

  /**
   * @param c
   *            The character to encode.
   * @return Whether the given unicode character is covered by this encoding.
   */
  public boolean canEncodeChar(char c)
  {

    if (c >= 0 && c < 128)
    {
      return true;
    }

    Simple8BitChar r = this.encodeHighChar(c);
    return r != null;
  }

  /**
   * Pushes the encoded form of the given character to the given byte buffer.
   * 
   * @param bb
   *            The byte buffer to write to.
   * @param c
   *            The character to encode.
   * @return Whether the given unicode character is covered by this encoding.
   *         If {@code false} is returned, nothing is pushed to the byte
   *         buffer.
   */
  public boolean pushEncodedChar(ByteBuffer bb, char c)
  {

    if (c >= 0 && c < 128)
    {
      bb.put((byte) c);
      return true;
    }

    Simple8BitChar r = this.encodeHighChar(c);
    if (r == null)
    {
      return false;
    }
    bb.put(r.code);
    return true;
  }

  /**
   * @param c
   *            A unicode character in the range from 0x0080 to 0x7f00
   * @return A Simple8BitChar, if this character is covered by this encoding.
   *         A {@code null} value is returned, if this character is not
   *         covered by this encoding.
   */
  private Simple8BitChar encodeHighChar(char c)
  {
    // for performance an simplicity, yet another reincarnation of
    // binary search...
    int i0 = 0;
    int i1 = this.reverseMapping.size();

    while (i1 > i0)
    {

      int i = i0 + (i1 - i0) / 2;

      Simple8BitChar m = this.reverseMapping.get(i);

      if (m.unicode == c)
      {
        return m;
      }

      if (m.unicode < c)
      {
        i0 = i + 1;
      }
      else
      {
        i1 = i;
      }
    }

    if (i0 >= this.reverseMapping.size())
    {
      return null;
    }

    Simple8BitChar r = this.reverseMapping.get(i0);

    if (r.unicode != c)
    {
      return null;
    }

    return r;
  }

  /**
   * @see org.apache.tools.zip.ZipEncoding#canEncode(java.lang.String)
   */
  public boolean canEncode(String name)
  {

    for (int i = 0; i < name.length(); ++i)
    {

      char c = name.charAt(i);

      if (!this.canEncodeChar(c))
      {
        return false;
      }
    }

    return true;
  }

  /**
   * @see org.apache.tools.zip.ZipEncoding#encode(java.lang.String)
   */
  public ByteBuffer encode(String name)
  {
    ByteBuffer out = ByteBuffer.allocate(name.length() + 6 + (name.length() + 1) / 2);

    for (int i = 0; i < name.length(); ++i)
    {

      char c = name.charAt(i);

      if (out.remaining() < 6)
      {
        out = ZipEncodingHelper.growBuffer(out, out.position() + 6);
      }

      if (!this.pushEncodedChar(out, c))
      {

        ZipEncodingHelper.appendSurrogate(out, c);
      }
    }

    out.limit(out.position());
    out.rewind();
    return out;
  }

  /**
   * @see org.apache.tools.zip.ZipEncoding#decode(byte[])
   */
  public String decode(byte[] data) throws IOException
  {
    char[] ret = new char[data.length];

    for (int i = 0; i < data.length; ++i)
    {
      ret[i] = this.decodeByte(data[i]);
    }

    return new String(ret);
  }

}

Java Source Code List

• Back to App/phone  ↑