net.freeutils.charset.ByteLookupCharset Maven / Gradle / Ivy
/*
* Copyright © 2005-2015 Amichai Rothman
*
* This file is part of JCharset - the Java Charset package.
*
* JCharset is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* JCharset is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with JCharset. If not, see A charset C is said to contain a charset D if,
* and only if, every character representable in D is also
* representable in C. If this relationship holds then it is
* guaranteed that every string that can be encoded in D can also be
* encoded in C without performing any replacements.
*
*
That C contains D does not imply that each character
* representable in C by a particular byte sequence is represented
* in D by the same byte sequence, although sometimes this is the
* case.
*
*
Every charset contains itself.
*
*
This method computes an approximation of the containment relation:
* If it returns true then the given charset is known to be
* contained by this charset; if it returns false, however, then
* it is not necessarily the case that the given charset is not contained
* in this charset.
*
* @return true if, and only if, the given charset
* is contained in this charset
*/
public boolean contains(Charset cs) {
return this.getClass().isInstance(cs);
}
/**
* Constructs a new decoder for this charset.
*
* @return a new decoder for this charset
*/
public CharsetDecoder newDecoder() {
return new Decoder(this);
}
/**
* Constructs a new encoder for this charset.
*
* @return a new encoder for this charset
*
* @throws UnsupportedOperationException
* if this charset does not support encoding
*/
public CharsetEncoder newEncoder() {
return new Encoder(this);
}
/**
* The Encoder inner class handles the encoding of the
* charset using the lookup table.
*/
protected class Encoder extends CharsetEncoder {
/**
* Constructs an Encoder.
*
* @param cs the charset to which this encoder belongs
*/
protected Encoder(Charset cs) {
super(cs, 1f, 1f);
}
/**
* Encodes one or more characters into one or more bytes.
*
* @param in the input character buffer
* @param out the output byte buffer
* @return a coder-result object describing the reason for termination
*/
protected CoderResult encodeLoop(CharBuffer in, ByteBuffer out) {
int b, c;
int[][] lookup = CHAR_TO_BYTE; // getfield bytecode optimization
int[] table;
int remaining = in.remaining();
while (remaining-- > 0) {
if (out.remaining() < 1)
return CoderResult.OVERFLOW; // we need exactly one byte per char
c = in.get();
table = lookup[c >>> 8];
b = table == null ? -1 : table[c & 0xFF];
if (b == -1) {
in.position(in.position() - 1);
return CoderResult.unmappableForLength(1);
}
out.put((byte)(b & 0xFF));
}
return CoderResult.UNDERFLOW;
}
}
/**
* The Decoder inner class handles the decoding of the
* charset using the inverse lookup table.
*/
protected class Decoder extends CharsetDecoder {
/**
* Constructs a Decoder.
*
* @param cs the charset to which this decoder belongs
*/
protected Decoder(Charset cs) {
super(cs, 1f, 1f);
}
/**
* Decodes one or more bytes into one or more characters.
*
* @param in the input byte buffer
* @param out the output character buffer
* @return a coder-result object describing the reason for termination
*/
protected CoderResult decodeLoop(ByteBuffer in, CharBuffer out) {
int c;
int[] lookup = BYTE_TO_CHAR; // getfield bytecode optimization
int remaining = in.remaining();
while (remaining-- > 0) {
if (out.remaining() < 1)
return CoderResult.OVERFLOW; // we need exactly one char per byte
c = lookup[in.get() & 0xFF];
if (c == -1) {
in.position(in.position() - 1);
return CoderResult.malformedForLength(1);
}
out.put((char)c);
}
return CoderResult.UNDERFLOW;
}
}
}