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package it.unimi.dsi.io;
/*
* DSI utilities
*
* Copyright (C) 2002-2019 Sebastiano Vigna
*
* 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 3 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 program; if not, see This class wraps any {@link OutputStream} so that you can treat it as
* bit stream. Constructors and methods closely resemble those of
* {@link OutputStream}. Data can be added to such a stream in several ways:
* writing an integer or long in fixed-width, unary, γ, δ, ζ and Golomb
* coding, or providing a vector of bytes.
*
*
This class can also {@linkplain #OutputBitStream(byte[]) wrap a byte
* array}; this is much more lightweight than wrapping a {@link
* it.unimi.dsi.fastutil.io.FastByteArrayOutputStream} wrapping the array, but overflowing the array
* will cause an {@link java.io.IOException}.
*
*
Note that when writing using a vector of bytes bits are written in the natural
* way: the first bit is bit 7 of the first byte, the eighth bit is bit 0 of
* the first byte, the ninth bit is bit 7 of the second byte and so on. When
* writing integers using some coding, instead, the lower bits are considered
* for coding (in the fixed-width case, the given number of bits, otherwise
* the lower bits starting from the most significant one).
*
*
The bit stream format
*
* The bit streams written by this class are big endian. That is,
* the first bit of the stream is bit 7 of the first byte, the eightth bit
* is bit 0 of the first byte, the ninth bit is bit 7 of the second byte and so on.
*
*
Blocks of bits (such as coded integers) are written starting from the
* most significant bit. In other words, if you take the first bytes of a stream
* and print them in binary you will see exactly the sequence of bits you have
* written. In particular, if you write 32-bit integers you will get a stream
* which is identical to the one produced by a {@link java.io.DataOutput}.
*
*
Additional features:
*
*
*
* - This class provides an internal buffer. By setting a buffer of
* length 0 at creation time, you can actually bypass the buffering system:
* Note, however, that several classes providing buffering have synchronised
* methods, so using a wrapper instead of the internal buffer is likely to lead
* to a performance drop.
*
*
- To work around the schizophrenic relationship between streams and random
* access files in {@link java.io}, this class provides a {@link #flush()}
* method that byte-aligns the streams, flushes to the underlying byte stream
* all data and resets the internal state. At this point, you can safely reposition
* the underlying stream and write again afterwards. For instance, this is safe
* and will perform as expected:
*
* FileOutputStream fos = new FileOutputStream(...);
* OutputBitStream obs = new OutputBitStream(fos);
* ... write operations on obs ...
* obs.flush();
* fos.getChannel().position(...);
* ... other write operations on obs ...
*
*
* As a commodity, an instance of this class will try to cast the underlying
* byte stream to a {@link RepositionableStream} and to fetch by reflection the
* {@link java.nio.channels.FileChannel} underlying the given output stream, in
* this order. If either reference can be successfully fetched, you can use
* directly the {@link #position(long) position()} method with argument
* pos with the same semantics of a {@link #flush()}, followed by
* a call to position(pos / 8) (where the latter method belongs
* either to the underlying stream or to its underlying file channel). The
* specified position must be byte aligned, as there is no clean way of reading
* a fraction of a byte with the current APIs. However, since the reflective checks are quite
* heavy they can be disabled using a {@linkplain OutputBitStream#OutputBitStream(OutputStream, boolean) suitable constructor}.
*
*
*
* This class is not synchronised. If multiple threads
* access an instance of this class concurrently, they must be synchronised externally.
*
* @see java.io.OutputStream
* @see it.unimi.dsi.io.InputBitStream
* @author Sebastiano Vigna
* @since 0.1
*/
public class OutputBitStream implements Flushable, Closeable {
public static final int MAX_PRECOMPUTED = 4096;
private final static boolean DEBUG = false;
/* Precomputed tables: the lower 24 bits contain the (right-aligned) code,
* the upper 8 bits contain the code length. */
public static final int[] GAMMA = new int[MAX_PRECOMPUTED], DELTA = new int[MAX_PRECOMPUTED], ZETA_3 = new int[MAX_PRECOMPUTED],
SHIFTED_GAMMA = new int[MAX_PRECOMPUTED];
static {
/* We load all precomputed arrays from resource files,
* to work around the limit on static initialiser code. */
try {
InputBitStream.fillArrayFromResource("gamma.out.12", GAMMA);
InputBitStream.fillArrayFromResource("delta.out.12", DELTA);
InputBitStream.fillArrayFromResource("zeta3.out.12", ZETA_3);
InputBitStream.fillArrayFromResource("shiftedgamma.out.12", SHIFTED_GAMMA);
}
catch (IOException e) {
throw new RuntimeException(e);
}
}
/** The default size of the byte buffer in bytes (16Ki). */
public final static int DEFAULT_BUFFER_SIZE = 16 * 1024;
/** The underlying {@link OutputStream}. */
protected final OutputStream os;
/** The number of bits written to this bit stream. */
private long writtenBits;
/** Current bit buffer. */
private int current;
/** The stream buffer. */
protected byte[] buffer;
/** Current number of free bits in the bit buffer (the bits in the buffer are stored high). */
protected int free;
/** Current position in the byte buffer. */
protected int pos;
/** Current position of the underlying output stream. */
protected long position;
/** Current number of bytes available in the byte buffer. */
protected int avail;
/** Size of the small buffer for temporary usage. */
final static int TEMP_BUFFER_SIZE = 128;
/** The cached file channel underlying {@link #os}. */
protected final FileChannel fileChannel;
/** {@link #os} cast to a positionable stream. */
protected final RepositionableStream repositionableStream;
/** True if we are wrapping an array. */
protected final boolean wrapping;
/** This (non-public) constructor exists just to provide fake initialisation for classes such as {@link DebugOutputBitStream}.
*/
protected OutputBitStream() {
os = null;
fileChannel = null;
repositionableStream = null;
wrapping = false;
}
/** Creates a new output bit stream wrapping a given output stream using a buffer of size {@link #DEFAULT_BUFFER_SIZE}.
*
*
This constructor performs the reflective tests that are necessary to support {@link #position(long)}.
*
* @param os the output stream to wrap.
*/
public OutputBitStream(final OutputStream os) {
this(os, true);
}
/** Creates a new output bit stream wrapping a given output stream using a buffer of size {@link #DEFAULT_BUFFER_SIZE}.
*
* @param os the output stream to wrap.
* @param testForPosition if false, the reflective test that is necessary to support {@link #position(long)}
* in case os does not support {@link RepositionableStream} will not be performed.
*/
public OutputBitStream(final OutputStream os, final boolean testForPosition) {
this(os, DEFAULT_BUFFER_SIZE);
}
/** Creates a new output bit stream wrapping a given output stream with a specified buffer size.
*
*
This constructor performs the reflective tests that are necessary to support {@link #position(long)}.
*
* @param os the output stream to wrap.
* @param bufSize the size in byte of the buffer; it may be 0, denoting no buffering.
*/
public OutputBitStream(final OutputStream os, final int bufSize) {
this(os, bufSize, true);
}
/** Creates a new output bit stream wrapping a given output stream with a specified buffer size.
*
* @param os the output stream to wrap.
* @param bufSize the size in byte of the buffer; it may be 0, denoting no buffering.
* @param testForPosition if false, the reflective test that is necessary to support {@link #position(long)}
* in case os does not support {@link RepositionableStream} will not be performed.
*/
public OutputBitStream(final OutputStream os, final int bufSize, final boolean testForPosition) {
this.os = os;
wrapping = false;
if (bufSize != 0) {
this.buffer = new byte[bufSize];
avail = bufSize;
}
free = 8;
if (os instanceof RepositionableStream) {
repositionableStream = (RepositionableStream)os;
fileChannel = null;
}
else if (testForPosition) {
FileChannel fc = null;
try {
fc = (FileChannel)(os.getClass().getMethod("getChannel")).invoke(os, new Object[] {});
}
catch(IllegalAccessException e) {}
catch(IllegalArgumentException e) {}
catch(NoSuchMethodException e) {}
catch(InvocationTargetException e) {}
catch(ClassCastException e) {}
fileChannel = fc;
repositionableStream = null;
}
else {
repositionableStream = null;
fileChannel = null;
}
}
/** Creates a new output bit stream wrapping a given file output stream using a buffer of size {@link #DEFAULT_BUFFER_SIZE}.
*
*
This constructor invokes directly {@link FileOutputStream#getChannel()} to support {@link #position(long)}.
*
* @param os the output stream to wrap.
*/
public OutputBitStream(final FileOutputStream os) {
this(os, DEFAULT_BUFFER_SIZE);
}
/** Creates a new output bit stream wrapping a given file output stream with a specified buffer size.
*
*
This constructor invokes directly {@link FileOutputStream#getChannel()} to support {@link #position(long)}.
*
* @param os the output stream to wrap.
* @param bufSize the size in byte of the buffer; it may be 0, denoting no buffering.
*/
public OutputBitStream(final FileOutputStream os, final int bufSize) {
this.os = os;
wrapping = false;
if (bufSize != 0) {
this.buffer = new byte[bufSize];
avail = bufSize;
}
free = 8;
repositionableStream = null;
fileChannel = os.getChannel();
}
/** Creates a new output bit stream wrapping a given byte array.
*
* @param a the byte array to wrap.
*/
public OutputBitStream(final byte[] a) {
os = null;
free = 8;
buffer = a;
avail = a.length;
wrapping = true;
fileChannel = null;
repositionableStream = null;
}
/** Creates a new output bit stream writing to file.
*
* @param name the name of the file.
* @param bufSize the size in byte of the buffer; it may be 0, denoting no buffering.
*/
public OutputBitStream(final String name, final int bufSize) throws FileNotFoundException {
this(new FileOutputStream(name), bufSize);
}
/** Creates a new output bit stream writing to a file.
*
* @param name the name of the file.
*/
public OutputBitStream(final String name) throws FileNotFoundException {
this(new FileOutputStream(name), DEFAULT_BUFFER_SIZE);
}
/** Creates a new output bit stream writing to file.
*
* @param file the file.
* @param bufSize the size in byte of the buffer; it may be 0, denoting no buffering.
*/
public OutputBitStream(final File file, final int bufSize) throws FileNotFoundException {
this(new FileOutputStream(file), bufSize);
}
/** Creates a new output bit stream writing to a file.
*
* @param file the file.
*/
public OutputBitStream(final File file) throws FileNotFoundException {
this(new FileOutputStream(file), DEFAULT_BUFFER_SIZE);
}
/** Flushes the bit stream.
*
*
This method will align the stream, write the bit buffer, empty the
* byte buffer and delegate to the {@link OutputStream#flush()} method of
* the underlying output stream.
*
*
This method is provided so that users of this class can easily wrap
* repositionable streams (for instance, file-based streams, which can be
* repositioned using the underlying {@link
* java.nio.channels.FileChannel}).
It is guaranteed that after calling
* this method the underlying stream can be repositioned, and that the next
* write to the underlying output stream will start with the content of the
* first write method called afterwards.
*/
@Override
public void flush() throws IOException {
align();
if (os != null) {
if (buffer != null) {
os.write(buffer, 0, pos);
position += pos;
pos = 0;
avail = buffer.length;
}
os.flush();
}
}
/** Closes the bit stream. All resources associated with the stream are released.
*/
@Override
public void close() throws IOException {
flush();
if (os != null && os != System.out && os != System.err) os.close();
buffer = null;
}
/** Returns the number of bits written to this bit stream.
*
* @return the number of bits written so far.
*/
public long writtenBits() {
return writtenBits;
}
/** Sets the number of bits written to this bit stream.
*
*
This method is provided so that, for instance, the
* user can reset via writtenBits(0) the written-bits count
* after a {@link #flush()}.
*
* @param writtenBits the new value for the number of bits written so far.
*/
public void writtenBits(final long writtenBits) {
this.writtenBits = writtenBits;
}
/** Writes a byte to the stream.
*
*
This method takes care of managing the buffering logic transparently.
*
*
However, this method does not update {@link #writtenBits}.
* The caller should increment {@link #writtenBits} by 8 at each call.
*/
private void write(final int b) throws IOException {
if (avail-- == 0) {
if (os == null) {
avail = 0;
throw new IOException("Array full");
}
if (buffer == null) {
os.write(b);
position++;
avail = 0;
return;
}
os.write(buffer);
position += buffer.length;
avail = buffer.length - 1;
pos = 0;
}
buffer[pos++] = (byte)b;
}
/** Writes bits in the bit buffer, possibly flushing it.
*
* You cannot write more than {@link #free} bits with this method. However,
* after having written {@link #free} bits the bit buffer will be empty. In
* particular, there should never be 0 free bits in the buffer.
*
* @param b the bits to write in the lower positions; the remaining positions must be zero.
* @param len the number of bits to write (0 is safe and causes no action).
* @return the number of bits written.
* @throws IllegalArgumentException if one tries to write more bits than available in the buffer and debug is enabled.
*/
private int writeInCurrent(final int b, final int len) throws IOException {
//System.err.println("Writing " + len + " bits out of " + Fast.binary(b));
if (DEBUG) if (len > free) throw new IllegalArgumentException(Integer.toString(len) + " bit(s) to write, " + free + " available.");
current |= (b & ((1 << len) - 1)) << (free -= len);
if (free == 0) {
write(current);
free = 8;
current = 0;
}
writtenBits += len;
return len;
}
/** Aligns the stream.
*
* After a call to this method, the stream is byte aligned. Zeroes
* are used to pad it if necessary.
*
* @return the number of padding bits.
*/
public int align() throws IOException {
if (free != 8) return writeInCurrent(0, free);
else return 0;
}
/** Sets this stream bit position, if it is based on a {@link RepositionableStream} or on a {@link java.nio.channels.FileChannel}.
*
*
Given an underlying stream that implements {@link
* RepositionableStream} or that can provide a {@link
* java.nio.channels.FileChannel} via the getChannel() method,
* a call to this method has the same semantics of a {@link #flush()},
* followed by a call to {@link
* java.nio.channels.FileChannel#position(long) position(position / 8)} on
* the byte stream. Currently there is no clean, working way of supporting
* out-of-byte-boundary positioning.
*
* @param position the new position expressed as a bit offset; it must be byte-aligned.
* @throws IllegalArgumentException when trying to position outside of byte boundaries.
* @throws UnsupportedOperationException if the underlying byte stream does not implement
* {@link RepositionableStream} and if the channel it returns is not a {@link java.nio.channels.FileChannel}.
* @see FileChannel#position(long)
*/
public void position(final long position) throws IOException {
if (position < 0) throw new IllegalArgumentException("Illegal position: " + position);
if ((position & 7) != 0) throw new IllegalArgumentException("Not a byte-aligned position: " + position);
if (wrapping) {
if ((position >>> 3) > buffer.length) throw new IllegalArgumentException("Illegal position: " + position);
flush();
free = 8;
pos = (int)(position >>> 3);
avail = buffer.length - pos;
}
else if (repositionableStream != null) {
flush();
if (position >>> 3 != this.position) repositionableStream.position(this.position = position >>> 3);
}
else if (fileChannel != null) {
flush();
if (position >>> 3 != this.position) fileChannel.position(this.position = position >>> 3);
}
else throw new UnsupportedOperationException("position() can only be called if the underlying byte stream implements the RepositionableStream interface or if the getChannel() method of the underlying byte stream exists and returns a FileChannel");
}
/** Writes a sequence of bits.
*
* Bits will be written in the natural way: the first bit is bit 7 of the
* first byte, the eightth bit is bit 0 of the first byte, the ninth bit is
* bit 7 of the second byte and so on.
*
* @param bits a vector containing the bits to be written.
* @param len a bit length.
* @return the number of bits written (len).
*/
public long write(final byte[] bits, final long len) throws IOException {
return writeByteOffset(bits, 0, len);
}
/** Writes a sequence of bits, starting from a given offset.
*
* Bits will be written in the natural way: the first bit is bit 7 of the
* first byte, the eightth bit is bit 0 of the first byte, the ninth bit is
* bit 7 of the second byte and so on.
*
* @param bits a vector containing the bits to be written.
* @param offset a bit offset from which to start to write.
* @param len a bit length.
* @return the number of bits written (len).
*/
public long write(final byte[] bits, final long offset, final long len) throws IOException {
final int initial = (int)(8 - (offset & 0x7));
if (initial == 8) return writeByteOffset(bits, (int)offset / 8, len);
if (len <= initial) return writeInt((0xFF & bits[(int)(offset / 8)]) >>> (initial - len), (int)len);
return writeInt(bits[(int)(offset / 8)], initial) + writeByteOffset(bits, (int)(offset / 8 + 1), len - initial);
}
/** Writes a sequence of bits, starting from a given byte offset.
*
* Bits will be written in the natural way: the first bit is bit 7 of the
* first byte, the eightth bit is bit 0 of the first byte, the ninth bit is
* bit 7 of the second byte and so on.
*
*
This method is used to support methods such as {@link #write(byte[], long, long)}.
*
* @param bits a vector containing the bits to be written.
* @param offset an offset, expressed in bytes.
* @param len a bit length.
* @return the number of bits written (len).
*/
protected long writeByteOffset(final byte[] bits, final int offset, long len) throws IOException {
if (len == 0) return 0;
if (len <= free) {
return writeInCurrent(bits[offset] >>> 8 - len, (int)len);
}
else {
final int shift = free;
int i, j;
writeInCurrent(bits[offset] >>> 8 - shift, shift);
len -= shift;
j = offset;
i = (int)(len >> 3);
while(i-- != 0) {
write(bits[j] << shift | (bits[j + 1] & 0xFF) >>> 8 - shift);
writtenBits += 8;
j++;
}
final int queue = (int)(len & 7);
if (queue != 0) {
if (queue <= 8 - shift) {
writeInCurrent(bits[j] >>> 8 - shift - queue, queue);
}
else {
writeInCurrent(bits[j], 8 - shift);
writeInCurrent(bits[j + 1] >>> 16 - queue - shift, queue + shift - 8);
}
}
return len + shift;
}
}
/** Writes a bit.
*
* @param bit a bit.
* @return the number of bits written.
*/
public int writeBit(final boolean bit) throws IOException {
return writeInCurrent(bit ? 1 : 0, 1);
}
/** Writes a bit.
*
* @param bit a bit.
* @return the number of bits written.
*/
public int writeBit(final int bit) throws IOException {
if (bit < 0 || bit > 1) throw new IllegalArgumentException("The argument " + bit + " is not a bit.");
return writeInCurrent(bit, 1);
}
/** Writes a sequence of bits emitted by a boolean iterator.
*
*
If the iterator throws an exception, it is catched,
* and the return value is given by the number of bits written
* increased by one and with the sign changed.
*
* @param i a boolean iterator.
* @return if i did not throw a runtime exception,
* the number of bits written; otherwise, the number of bits written,
* plus one, with the sign changed.
*/
public int write(final BooleanIterator i) throws IOException {
int count = 0;
boolean bit;
while(i.hasNext()) {
try {
bit = i.nextBoolean();
}
catch(RuntimeException hide) {
return -count - 1;
}
writeBit(bit);
count++;
}
return count;
}
/** Writes a fixed number of bits from an integer.
*
* @param x an integer.
* @param len a bit length; this many lower bits of the first argument will be written
* (the most significant bit first).
* @return the number of bits written (len).
*/
public int writeInt(int x, final int len) throws IOException {
if (len < 0 || len > 32) throw new IllegalArgumentException("You cannot write " + len + " bits to an integer.");
if (len <= free) return writeInCurrent(x, len);
int i = len - free;
final int queue = i & 7;
if (free != 0) writeInCurrent(x >>> i, free);
// Dirty trick: since queue < 8, we pre-write the last bits in the bit buffer.
if (queue != 0) {
i -= queue;
writeInCurrent(x, queue);
x >>>= queue;
}
if (i == 32) write(x >>> 24);
if (i > 23) write(x >>> 16);
if (i > 15) write(x >>> 8);
if (i > 7) write(x);
writtenBits += i;
return len;
}
/** Writes a fixed number of bits from a long.
*
* @param x a long.
* @param len a bit length; this many lower bits of the first argument will be written
* (the most significant bit first).
* @return the number of bits written (len).
*/
public int writeLong(long x, final int len) throws IOException {
if (len < 0 || len > 64) throw new IllegalArgumentException("You cannot write " + len + " bits to a long.");
if (len <= free) return writeInCurrent((int)x, len);
int i = len - free;
final int queue = i & 7;
if (free != 0) writeInCurrent((int)(x >>> i), free);
// Dirty trick: since queue < 8, we pre-write the last bits in the bit buffer.
if (queue != 0) {
i -= queue;
writeInCurrent((int)x, queue);
x >>>= queue;
}
if (i == 64) write((int)(x >>> 56));
if (i > 55) write((int)(x >>> 48));
if (i > 47) write((int)(x >>> 40));
if (i > 39) write((int)(x >>> 32));
if (i > 31) write((int)x >>> 24);
if (i > 23) write((int)x >>> 16);
if (i > 15) write((int)x >>> 8);
if (i > 7) write((int)x);
writtenBits += i;
return len;
}
/** Writes a natural number in unary coding.
*
*
The unary coding of a natural number n is given
* by 0n1.
*
* @param x a natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
*/
public int writeUnary(int x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x < free) return writeInCurrent(1, x + 1);
final int shift = free;
x -= shift;
writtenBits += shift;
write(current);
free = 8;
current = 0;
int i = x >> 3;
writtenBits += (x & 0x7FFFFFF8);
while(i-- != 0) write(0);
writeInCurrent(1, (x & 7) + 1);
return x + shift + 1;
}
/** Writes a long natural number in unary coding.
*
* @param x a long natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
* @see #writeUnary(int)
*/
public long writeLongUnary(long x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x < free) return writeInCurrent(1, (int)x + 1);
final int shift = free;
x -= shift;
writtenBits += shift;
write(current);
free = 8;
current = 0;
long i = x >> 3;
writtenBits += (x & 0x7FFFFFFFFFFFFFF8L);
while(i-- != 0) write(0);
writeInCurrent(1, (int)(x & 7) + 1);
return x + shift + 1;
}
/** Writes a natural number in γ coding.
*
*
The γ coding of a positive number of k bits is
* obtained writing k-1 in unary, followed by the lower
* k-1 bits of the number. The coding of a natural number is
* obtained by adding one and coding.
*
* @param x a natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
*/
public int writeGamma(int x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x < MAX_PRECOMPUTED) return writeInt(GAMMA[x], GAMMA[x] >>> 26);
final int msb = Fast.mostSignificantBit(++x);
return writeUnary(msb) + writeInt(x, msb);
}
/** Writes a given amount of natural numbers in γ coding.
*
* @param a an array at least count natural numbers.
* @param count the number of elements of a to be written.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
* @see #writeGamma(int)
*/
public long writeGammas(final int[] a, final int count) throws IOException {
long l = 0;
for(int i = 0; i < count; i++) {
int x = a[i];
if (x < MAX_PRECOMPUTED) {
l += writeInt(GAMMA[x], GAMMA[x] >>> 26);
continue;
}
final int msb = Fast.mostSignificantBit(++x);
l += writeUnary(msb) + writeInt(x, msb);
}
return l;
}
/** Writes a long natural number in γ coding.
*
* @param x a long natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
* @see #writeGamma(int)
*/
public int writeLongGamma(long x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x < MAX_PRECOMPUTED) return writeInt(GAMMA[(int)x], GAMMA[(int)x] >>> 26);
final int msb = Fast.mostSignificantBit(++x);
return writeUnary(msb) + writeLong(x, msb);
}
/** Writes a natural number in shifted γ coding.
*
* The shifted γ coding of 0 is 1. The coding of a positive number
* of k bits is
* obtained writing k in unary, followed by the lower
* k-1 bits of the number (equivalently, by writing
* k zeroes followed by the number).
*
* @param x a natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
*/
public int writeShiftedGamma(int x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x < MAX_PRECOMPUTED) return writeInt(SHIFTED_GAMMA[x], SHIFTED_GAMMA[x] >>> 26);
final int msb = Fast.mostSignificantBit(x);
return writeUnary(msb + 1) + (msb > 0 ? writeInt(x, msb) : 0);
}
/** Writes a long natural number in shifted γ coding.
*
* @param x a natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
* @see #writeShiftedGamma(int)
*/
public int writeLongShiftedGamma(long x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x < MAX_PRECOMPUTED) return writeInt(SHIFTED_GAMMA[(int)x], SHIFTED_GAMMA[(int)x] >>> 26);
final int msb = Fast.mostSignificantBit(x);
return writeUnary(msb + 1) + (msb > 0 ? writeLong(x, msb) : 0);
}
/** Writes a given amount of natural numbers in shifted γ coding.
*
* @param a an array at least count natural numbers.
* @param count the number of elements of a to be written.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
* @see #writeShiftedGamma(int)
*/
public long writeShiftedGammas(final int[] a, final int count) throws IOException {
long l = 0;
for(int i = 0; i < count; i++) {
int x = a[i];
if (x < MAX_PRECOMPUTED) {
l += writeInt(SHIFTED_GAMMA[x], SHIFTED_GAMMA[x] >>> 26);
continue;
}
final int msb = Fast.mostSignificantBit(x);
l += writeUnary(msb + 1) + (msb > 0 ? writeInt(x, msb) : 0);
}
return l;
}
/** Writes a natural number in δ coding.
*
* The δ coding of a positive number of k bits is
* obtained writing k-1 in γ coding, followed by the
* lower k-1 bits of the number. The coding of a natural
* number is obtained by adding one and coding.
*
* @param x a natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
*/
public int writeDelta(int x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x < MAX_PRECOMPUTED) return writeInt(DELTA[x], DELTA[x] >>> 26);
final int msb = Fast.mostSignificantBit(++x);
return writeGamma(msb) + writeInt(x, msb);
}
/** Writes a long natural number in δ coding.
*
* @param x a long natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
* @see #writeDelta(int)
*/
public int writeLongDelta(long x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x < MAX_PRECOMPUTED) return writeInt(DELTA[(int)x], DELTA[(int)x] >>> 26);
final int msb = Fast.mostSignificantBit(++x);
return writeGamma(msb) + writeLong(x, msb);
}
/** Writes a given amount of natural numbers in δ coding.
*
* @param a an array at least count natural numbers.
* @param count the number of elements of a to be written.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
* @see #writeDelta(int)
*/
public long writeDeltas(final int[] a, final int count) throws IOException {
long l = 0;
for(int i = 0; i < count; i++) {
int x = a[i];
if (x < MAX_PRECOMPUTED) {
l += writeInt(DELTA[x], DELTA[x] >>> 26);
continue;
}
final int msb = Fast.mostSignificantBit(++x);
l += writeGamma(msb) + writeInt(x, msb);
}
return l;
}
/** Writes a natural number in a limited range using a minimal binary coding.
*
*
A minimal binary code is an optimal code for the uniform distribution.
* This method uses an optimal code in which shorter words are assigned to
* smaller integers.
*
* @param x a natural number.
* @param b a strict upper bound for x.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a nonpositive base.
*/
public int writeMinimalBinary(final int x, final int b) throws IOException {
if (b < 1) throw new IllegalArgumentException("The bound " + b + " is not positive");
return writeMinimalBinary(x, b, Fast.mostSignificantBit(b));
}
/** Writes a natural number in a limited range using a minimal binary coding.
*
* This method is faster than {@link #writeMinimalBinary(int,int)} because it does not
* have to compute log2b.
*
* @param x a natural number.
* @param b a strict upper bound for x.
* @param log2b the floor of the base-2 logarithm of the bound.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a nonpositive base.
* @see #writeMinimalBinary(int, int)
*/
public int writeMinimalBinary(final int x, final int b, final int log2b) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (b < 1) throw new IllegalArgumentException("The bound " + b + " is not positive");
if (x >= b) throw new IllegalArgumentException("The argument " + x + " exceeds the bound " + b);
// Numbers smaller than m are encoded in log2b bits.
final int m = (1 << log2b + 1) - b;
if (x < m) return writeInt(x, log2b);
else return writeInt(m + x, log2b + 1);
}
/** Writes a long natural number in a limited range using a minimal binary coding.
*
* @param x a natural number.
* @param b a strict upper bound for x.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a nonpositive base.
* @see #writeMinimalBinary(int, int)
*/
public int writeLongMinimalBinary(final long x, final long b) throws IOException {
if (b < 1) throw new IllegalArgumentException("The bound " + b + " is not positive");
return writeLongMinimalBinary(x, b, Fast.mostSignificantBit(b));
}
/** Writes a long natural number in a limited range using a minimal binary coding.
*
* This method is faster than {@link #writeLongMinimalBinary(long,long)} because it does not
* have to compute log2b.
*
* @param x a long natural number.
* @param b a strict upper bound for x.
* @param log2b the floor of the base-2 logarithm of the bound.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a nonpositive base.
* @see #writeMinimalBinary(int, int)
*/
public int writeLongMinimalBinary(final long x, final long b, final int log2b) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (b < 1) throw new IllegalArgumentException("The bound " + b + " is not positive");
if (x >= b) throw new IllegalArgumentException("The argument " + x + " exceeds the bound " + b);
// Numbers smaller than m are encoded in log2b bits.
final long m = (1L << log2b + 1) - b;
if (x < m) return writeLong(x, log2b);
else return writeLong(m + x, log2b + 1);
}
/** Writes a natural number in Golomb coding.
*
*
Golomb coding with modulo b writes a natural number x as the quotient of
* the division of x and b in {@linkplain #writeUnary(int) unary},
* followed by the remainder in {@linkplain #writeMinimalBinary(int, int) minimal binary code}.
*
*
This method implements also the case in which b is 0: in this case,
* the argument x may only be zero, and nothing will be written.
*
* @param x a natural number.
* @param b the modulus for the coding.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a negative modulus.
*/
public int writeGolomb(final int x, final int b) throws IOException {
return writeGolomb(x, b, Fast.mostSignificantBit(b));
}
/** Writes a natural number in Golomb coding.
*
* This method is faster than {@link #writeGolomb(int,int)} because it does not
* have to compute log2b.
*
* @param x a natural number.
* @param b the modulus for the coding.
* @param log2b the floor of the base-2 logarithm of the coding modulus (it is irrelevant when b is zero).
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a negative modulus.
* @see #writeGolomb(int, int)
*/
public int writeGolomb(final int x, final int b, final int log2b) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (b < 0) throw new IllegalArgumentException("The modulus " + b + " is negative");
if (b == 0) {
if (x != 0) throw new IllegalArgumentException("The modulus is 0, but the argument is " + x);
return 0;
}
final int l = writeUnary(x / b);
// The remainder to be encoded.
return l + writeMinimalBinary(x % b, b, log2b);
}
/** Writes a long natural number in Golomb coding.
*
* @param x a long natural number.
* @param b the modulus for the coding.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a negative modulus.
* @see #writeGolomb(int, int)
*/
public long writeLongGolomb(final long x, final long b) throws IOException {
return writeLongGolomb(x, b, Fast.mostSignificantBit(b));
}
/** Writes a long natural number in Golomb coding.
*
* This method is faster than {@link #writeLongGolomb(long,long)} because it does not
* have to compute log2b.
*
* @param x a long natural number.
* @param b the modulus for the coding.
* @param log2b the floor of the base-2 logarithm of the coding modulus (it is irrelevant when b is zero).
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a negative modulus.
* @see #writeGolomb(int, int)
*/
public long writeLongGolomb(final long x, final long b, final int log2b) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (b < 0) throw new IllegalArgumentException("The modulus " + b + " is negative");
if (b == 0) {
if (x != 0) throw new IllegalArgumentException("The modulus is 0, but the argument is " + x);
return 0;
}
final long l = writeLongUnary(x / b);
// The remainder to be encoded.
return l + writeLongMinimalBinary(x % b, b, log2b);
}
/** Writes a natural number in skewed Golomb coding.
*
*
This method implements also the case in which b is 0: in this case,
* the argument x may only be zero, and nothing will be written.
*
* @param x a natural number.
* @param b the modulus for the coding.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a negative modulus.
*/
public int writeSkewedGolomb(final int x, final int b) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (b < 0) throw new IllegalArgumentException("The modulus " + b + " is negative");
if (b == 0) {
if (x != 0) throw new IllegalArgumentException("The modulus is 0, but the argument is " + x);
return 0;
}
final int i = Fast.mostSignificantBit(x / b + 1);
final int l = writeUnary(i);
final int M = ((1 << i + 1) - 1) * b;
final int m = (M / (2 * b)) * b;
return l + writeMinimalBinary(x - m, M - m);
}
/** Writes a long natural number in skewed Golomb coding.
*
*
This method implements also the case in which b is 0: in this case,
* the argument x may only be zero, and nothing will be written.
*
* @param x a long natural number.
* @param b the modulus for the coding.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a negative modulus.
* @see #writeSkewedGolomb(int, int)
*/
public long writeLongSkewedGolomb(final long x, final long b) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (b < 0) throw new IllegalArgumentException("The modulus " + b + " is negative");
if (b == 0) {
if (x != 0) throw new IllegalArgumentException("The modulus is 0, but the argument is " + x);
return 0;
}
final long i = Fast.mostSignificantBit(x / b + 1);
final long l = writeLongUnary(i);
final long M = ((1L << i + 1) - 1) * b;
final long m = (M / (2 * b)) * b;
return l + writeLongMinimalBinary(x - m, M - m);
}
/** Writes a natural number in ζ coding.
*
*
ζ coding (with modulo k) records positive numbers in
* the intervals
* [1,2k-1],[2k,2k+1-1],…,[2hk,2(h+1)k-1]
* by coding h in unary, followed by a minimal binary coding of
* the offset in the interval. The coding of a natural number is obtained
* by adding one and coding.
*
*
ζ codes were defined by
* Paolo Boldi and Sebastiano Vigna in
* “Codes for the World−Wide Web”,
* Internet Math., 2(4):405-427, 2005. The paper contains also a detailed analysis.
*
* @param x a natural number.
* @param k the shrinking factor.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a nonpositive shrinking factor.
*/
public int writeZeta(int x, final int k) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (k < 1) throw new IllegalArgumentException("The shrinking factor " + k + " is not positive");
if (k == 3 && x < MAX_PRECOMPUTED) return writeInt(ZETA_3[x], ZETA_3[x] >>> 26);
final int msb = Fast.mostSignificantBit(++x);
final int h = msb / k;
final int l = writeUnary(h);
final int left = 1 << h * k;
return l + (x - left < left
? writeInt(x - left, h * k + k - 1)
: writeInt(x, h * k + k));
}
/** Writes a long natural number in ζ coding.
*
* @param x a long natural number.
* @param k the shrinking factor.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number or use a nonpositive shrinking factor.
* @see #writeZeta(int, int)
*/
public int writeLongZeta(long x, final int k) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (k < 1) throw new IllegalArgumentException("The shrinking factor " + k + " is not positive");
if (k == 3 && x < MAX_PRECOMPUTED) return writeInt(ZETA_3[(int)x], ZETA_3[(int)x] >>> 26);
final int msb = Fast.mostSignificantBit(++x);
final int h = msb / k;
final int l = writeUnary(h);
final long left = 1L << h * k;
return l + (x - left < left
? writeLong(x - left, h * k + k - 1)
: writeLong(x, h * k + k));
}
/** Writes a natural number in variable-length nibble coding.
*
*
Variable-length nibble coding records a natural number by padding its binary
* representation to the left using zeroes, until its length is a multiple of three.
* Then, the resulting string is
* broken in blocks of 3 bits, and each block is prefixed with a bit, which is
* zero for all blocks except for the last one.
* @param x a natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
*/
public int writeNibble(final int x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x == 0) return writeInt(8, 4);
final int msb = Fast.mostSignificantBit(x);
int h = msb / 3;
do {
writeBit(h == 0);
writeInt(x >> h * 3 , 3);
} while(h-- != 0);
return ((msb / 3) + 1) << 2;
}
/** Writes a long natural number in variable-length nibble coding.
*
* @param x a long natural number.
* @return the number of bits written.
* @throws IllegalArgumentException if you try to write a negative number.
* @see #writeNibble(int)
*/
public int writeLongNibble(final long x) throws IOException {
if (x < 0) throw new IllegalArgumentException("The argument " + x + " is negative");
if (x == 0) return writeInt(8, 4);
final int msb = Fast.mostSignificantBit(x);
int h = msb / 3;
do {
writeBit(h == 0);
writeInt((int)(x >> h * 3) , 3);
} while(h-- != 0);
return ((msb / 3) + 1) << 2;
}
/** Copies a given number of bits from a given input bit stream into this output bit stream.
*
* @param ibs an input bit stream.
* @param length the number of bits to copy.
* @throws EOFException if there are not enough bits to copy.
*/
public void copyFrom(final InputBitStream ibs, long length) throws IOException {
final byte[] buffer = new byte[64 * 1024];
while(length > 0) {
final int toRead = (int)Math.min(length, buffer.length * Byte.SIZE);
ibs.read(buffer, toRead);
write(buffer, 0, toRead);
length -= toRead;
}
}
}