nayuki.huffmancoding.BitInputStream Maven / Gradle / Ivy
/**
*
* Copyright © 2013 Nayuki Minase
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* * The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* * The Software is provided "as is", without warranty of any kind, express or
* implied, including but not limited to the warranties of merchantability,
* fitness for a particular purpose and noninfringement. In no event shall the
* authors or copyright holders be liable for any claim, damages or other
* liability, whether in an action of contract, tort or otherwise, arising from,
* out of or in connection with the Software or the use or other dealings in the
* Software.
*/
package nayuki.huffmancoding;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
/**
* A stream of bits that can be read. Because they come from an underlying byte stream, the total number of bits is always a multiple of 8. The bits are read in big endian.
*/
public final class BitInputStream {
// Underlying byte stream to read from.
private InputStream input;
// Either in the range 0x00 to 0xFF if bits are available, or is -1 if the end of stream is reached.
private int nextBits;
// Always between 0 and 7, inclusive.
private int numBitsRemaining;
private boolean isEndOfStream;
// Creates a bit input stream based on the given byte input stream.
public BitInputStream(InputStream in) {
if (in == null)
throw new NullPointerException("Argument is null");
input = in;
numBitsRemaining = 0;
isEndOfStream = false;
}
// Reads a bit from the stream. Returns 0 or 1 if a bit is available, or -1 if the end of stream is reached. The end of stream always occurs on a byte boundary.
public int read() throws IOException {
if (isEndOfStream)
return -1;
if (numBitsRemaining == 0) {
nextBits = input.read();
if (nextBits == -1) {
isEndOfStream = true;
return -1;
}
numBitsRemaining = 8;
}
numBitsRemaining--;
return (nextBits >>> numBitsRemaining) & 1;
}
// Reads a bit from the stream. Returns 0 or 1 if a bit is available, or throws an EOFException if the end of stream is reached.
public int readNoEof() throws IOException {
int result = read();
if (result != -1)
return result;
else
throw new EOFException("End of stream reached");
}
// Closes this stream and the underlying InputStream.
public void close() throws IOException {
input.close();
}
}
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