org.apache.tools.zip.Simple8BitZipEncoding Maven / Gradle / Ivy
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* 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
*
* 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:
*
*
* - Characters 0x0000 to 0x007f are encoded as the corresponding
* byte values 0x00 to 0x7f.
* - 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)
*
*
* 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.
*
* The methods of this class are reentrant.
*/
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 {
public final char unicode;
public final byte code;
Simple8BitChar(final byte code, final char unicode) {
this.code = code;
this.unicode = unicode;
}
public int compareTo(final 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(final Object o) {
if (o instanceof Simple8BitChar) {
final 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 reverseMapping;
/**
* @param highChars The characters for byte values of 128 to 255
* stored as an array of 128 chars.
*/
public Simple8BitZipEncoding(final char[] highChars) {
this.highChars = highChars.clone();
final List temp =
new ArrayList(this.highChars.length);
byte code = 127;
for (char highChar : this.highChars) {
temp.add(new Simple8BitChar(++code, highChar));
}
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(final 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(final char c) {
if (c >= 0 && c < 128) {
return true;
}
final 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(final ByteBuffer bb, final char c) {
if (c >= 0 && c < 128) {
bb.put((byte) c);
return true;
}
final 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(final char c) {
// for performance an simplicity, yet another reincarnation of
// binary search...
int i0 = 0;
int i1 = this.reverseMapping.size();
while (i1 > i0) {
final int i = i0 + (i1 - i0) / 2;
final 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;
}
final 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(final String name) {
for (int i = 0; i < name.length(); ++i) {
final 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(final String name) {
ByteBuffer out = ByteBuffer.allocate(name.length()
+ 6 + (name.length() + 1) / 2);
for (int i = 0; i < name.length(); ++i) {
final 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(final byte[] data) throws IOException {
final char[] ret = new char[data.length];
for (int i = 0; i < data.length; ++i) {
ret[i] = this.decodeByte(data[i]);
}
return new String(ret);
}
}