/*
* $Id: ASCIIHexDecode.java,v 1.2 2007-12-20 18:33:32 rbair Exp $
*
* Copyright 2004 Sun Microsystems, Inc., 4150 Network Circle,
* Santa Clara, California 95054, U.S.A. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package com.sun.pdfview.decode;
import java.io.ByteArrayOutputStream;
import java.nio.ByteBuffer;
import com.sun.pdfview.PDFObject;
import com.sun.pdfview.PDFParseException;
import com.sun.pdfview.PDFFile;
/**
* decode an array of hex nybbles into a byte array
*
* @author Mike Wessler
*/
public class ASCIIHexDecode {
private ByteBuffer buf;
/**
* initialize the decoder with an array of bytes in ASCIIHex format
*/
private ASCIIHexDecode(ByteBuffer buf) {
this.buf = buf;
}
/**
* get the next character from the input
* @return a number from 0-15, or -1 for the end character
*/
private int readHexDigit() throws PDFParseException {
// read until we hit a non-whitespace character or the
// end of the stream
while (buf.remaining() > 0) {
int c = (int) buf.get();
// see if we found a useful character
if (!PDFFile.isWhiteSpace((char) c)) {
if (c >= '0' && c <= '9') {
c -= '0';
} else if (c >= 'a' && c <= 'f') {
c -= 'a' - 10;
} else if (c >= 'A' && c <= 'F') {
c -= 'A' - 10;
} else if (c == '>') {
c = -1;
} else {
// unknown character
throw new PDFParseException("Bad character " + c +
"in ASCIIHex decode");
}
// return the useful character
return c;
}
}
// end of stream reached
throw new PDFParseException("Short stream in ASCIIHex decode");
}
/**
* decode the array
* @return the decoded bytes
*/
private ByteBuffer decode() throws PDFParseException {
// start at the beginning of the buffer
buf.rewind();
// allocate the output buffer
ByteArrayOutputStream baos = new ByteArrayOutputStream();
while (true) {
int first = readHexDigit();
int second = readHexDigit();
if (first == -1) {
break;
} else if (second == -1) {
baos.write((byte) (first << 4));
break;
} else {
baos.write((byte) ((first << 4) + second));
}
}
return ByteBuffer.wrap(baos.toByteArray());
}
/**
* decode an array of bytes in ASCIIHex format.
* <p>
* ASCIIHex format consists of a sequence of Hexidecimal
* digits, with possible whitespace, ending with the
* '>' character.
*
* @param buf the encoded ASCII85 characters in a byte
* buffer
* @param params parameters to the decoder (ignored)
* @return the decoded bytes
*/
public static ByteBuffer decode(ByteBuffer buf, PDFObject params)
throws PDFParseException
{
ASCIIHexDecode me = new ASCIIHexDecode(buf);
return me.decode();
}
}