com.itextpdf.io.codec.BitFile Maven / Gradle / Ivy
/*
This file is part of the iText (R) project.
Copyright (c) 1998-2022 iText Group NV
Authors: Bruno Lowagie, Paulo Soares, et al.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License version 3
as published by the Free Software Foundation with the addition of the
following permission added to Section 15 as permitted in Section 7(a):
FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
OF THIRD PARTY RIGHTS
This program 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program; if not, see http://www.gnu.org/licenses or write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA, 02110-1301 USA, or download the license from the following URL:
http://itextpdf.com/terms-of-use/
The interactive user interfaces in modified source and object code versions
of this program must display Appropriate Legal Notices, as required under
Section 5 of the GNU Affero General Public License.
In accordance with Section 7(b) of the GNU Affero General Public License,
a covered work must retain the producer line in every PDF that is created
or manipulated using iText.
You can be released from the requirements of the license by purchasing
a commercial license. Buying such a license is mandatory as soon as you
develop commercial activities involving the iText software without
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These activities include: offering paid services to customers as an ASP,
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For more information, please contact iText Software Corp. at this
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*/
package com.itextpdf.io.codec;
import java.io.IOException;
import java.io.OutputStream;
/**
* Came from GIFEncoder initially.
* Modified - to allow for output compressed data without the block counts
* which breakup the compressed data stream for GIF.
*/
class BitFile {
OutputStream output;
byte buffer[];
int index;
// bits left at current index that are avail.
int bitsLeft;
/**
* note this also indicates gif format BITFile.
**/
boolean blocks = false;
/**
* @param output destination for output data
* @param blocks GIF LZW requires block counts for output data
**/
public BitFile(OutputStream output, boolean blocks) {
this.output = output;
this.blocks = blocks;
buffer = new byte[256];
index = 0;
bitsLeft = 8;
}
public void flush() throws IOException {
int numBytes = index + (bitsLeft == 8 ? 0 : 1);
if (numBytes > 0) {
if (blocks)
output.write(numBytes);
output.write(buffer, 0, numBytes);
buffer[0] = 0;
index = 0;
bitsLeft = 8;
}
}
public void writeBits(int bits, int numbits) throws IOException {
int bitsWritten = 0;
// gif block count
int numBytes = 255;
do {
// This handles the GIF block count stuff
if ((index == 254 && bitsLeft == 0) || index > 254) {
if (blocks)
output.write(numBytes);
output.write(buffer, 0, numBytes);
buffer[0] = 0;
index = 0;
bitsLeft = 8;
}
// bits contents fit in current index byte
if (numbits <= bitsLeft)
{
// GIF
if (blocks)
{
buffer[index] |= (byte) ((bits & ((1 << numbits) - 1)) << (8 - bitsLeft));
bitsWritten += numbits;
bitsLeft -= numbits;
numbits = 0;
} else {
buffer[index] |= (byte) ((bits & ((1 << numbits) - 1)) << (bitsLeft - numbits));
bitsWritten += numbits;
bitsLeft -= numbits;
numbits = 0;
}
} else {
// bits overflow from current byte to next.
// GIF
if (blocks)
{
// if bits > space left in current byte then the lowest order bits
// of code are taken and put in current byte and rest put in next.
buffer[index] |= (byte) ((bits & ((1 << bitsLeft) - 1)) << (8 - bitsLeft));
bitsWritten += bitsLeft;
bits >>= bitsLeft;
numbits -= bitsLeft;
buffer[++index] = 0;
bitsLeft = 8;
} else {
// if bits > space left in current byte then the highest order bits
// of code are taken and put in current byte and rest put in next.
// at highest order bit location !!
int topbits = (bits >>> (numbits - bitsLeft)) & ((1 << bitsLeft) - 1);
buffer[index] |= (byte) topbits;
// ok this many bits gone off the top
numbits -= bitsLeft;
bitsWritten += bitsLeft;
// next index
buffer[++index] = 0;
bitsLeft = 8;
}
}
} while (numbits != 0);
}
}