Class OutputBitStream

  • All Implemented Interfaces:
    Closeable, Flushable, AutoCloseable
    Direct Known Subclasses:
    DebugOutputBitStream

    public class OutputBitStream
    extends Object
    implements Flushable, Closeable
    Bit-level output stream.

    This class wraps any OutputStream so that you can treat it as bit stream. Constructors and methods closely resemble those of 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 wrap a byte array; this is much more lightweight than wrapping a FastByteArrayOutputStream wrapping the array, but overflowing the array will cause an 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 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 java.io, this class provides a 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 RepositionableStream and to fetch by reflection the FileChannel underlying the given output stream, in this order. If either reference can be successfully fetched, you can use directly the position() method with argument pos with the same semantics of a 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 suitable constructor.

    This class is not synchronised. If multiple threads access an instance of this class concurrently, they must be synchronised externally.

    Since:
    0.1
    Author:
    Sebastiano Vigna
    See Also:
    OutputStream, InputBitStream
    • Method Summary

      Modifier and Type Method Description
      int align()
      Aligns the stream.
      void close()
      Closes the bit stream.
      void copyFrom​(InputBitStream ibs, long length)
      Copies a given number of bits from a given input bit stream into this output bit stream.
      void flush()
      Flushes the bit stream.
      void position​(long position)
      Sets this stream bit position, if it is based on a RepositionableStream or on a FileChannel.
      long write​(byte[] bits, long len)
      Writes a sequence of bits.
      long write​(byte[] bits, long offset, long len)
      Writes a sequence of bits, starting from a given offset.
      int write​(BooleanIterator i)
      Writes a sequence of bits emitted by a boolean iterator.
      int writeBit​(boolean bit)
      Writes a bit.
      int writeBit​(int bit)
      Writes a bit.
      protected long writeByteOffset​(byte[] bits, int offset, long len)
      Writes a sequence of bits, starting from a given byte offset.
      int writeDelta​(int x)
      Writes a natural number in δ coding.
      long writeDeltas​(int[] a, int count)
      Writes a given amount of natural numbers in δ coding.
      int writeGamma​(int x)
      Writes a natural number in γ coding.
      long writeGammas​(int[] a, int count)
      Writes a given amount of natural numbers in γ coding.
      int writeGolomb​(int x, int b)
      Writes a natural number in Golomb coding.
      int writeGolomb​(int x, int b, int log2b)
      Writes a natural number in Golomb coding.
      int writeInt​(int x, int len)
      Writes a fixed number of bits from an integer.
      int writeLong​(long x, int len)
      Writes a fixed number of bits from a long.
      int writeLongDelta​(long x)
      Writes a long natural number in δ coding.
      int writeLongGamma​(long x)
      Writes a long natural number in γ coding.
      long writeLongGolomb​(long x, long b)
      Writes a long natural number in Golomb coding.
      long writeLongGolomb​(long x, long b, int log2b)
      Writes a long natural number in Golomb coding.
      int writeLongMinimalBinary​(long x, long b)
      Writes a long natural number in a limited range using a minimal binary coding.
      int writeLongMinimalBinary​(long x, long b, int log2b)
      Writes a long natural number in a limited range using a minimal binary coding.
      int writeLongNibble​(long x)
      Writes a long natural number in variable-length nibble coding.
      int writeLongShiftedGamma​(long x)
      Writes a long natural number in shifted γ coding.
      long writeLongSkewedGolomb​(long x, long b)
      Writes a long natural number in skewed Golomb coding.
      long writeLongUnary​(long x)
      Writes a long natural number in unary coding.
      int writeLongZeta​(long x, int k)
      Writes a long natural number in ζ coding.
      int writeMinimalBinary​(int x, int b)
      Writes a natural number in a limited range using a minimal binary coding.
      int writeMinimalBinary​(int x, int b, int log2b)
      Writes a natural number in a limited range using a minimal binary coding.
      int writeNibble​(int x)
      Writes a natural number in variable-length nibble coding.
      int writeShiftedGamma​(int x)
      Writes a natural number in shifted γ coding.
      long writeShiftedGammas​(int[] a, int count)
      Writes a given amount of natural numbers in shifted γ coding.
      int writeSkewedGolomb​(int x, int b)
      Writes a natural number in skewed Golomb coding.
      int writeUnary​(int x)
      Writes a natural number in unary coding.
      int writeZeta​(int x, int k)
      Writes a natural number in ζ coding.
      long writtenBits()
      Returns the number of bits written to this bit stream.
      void writtenBits​(long writtenBits)
      Sets the number of bits written to this bit stream.
    • Field Detail

      • GAMMA

        public static final int[] GAMMA
      • DELTA

        public static final int[] DELTA
      • ZETA_3

        public static final int[] ZETA_3
      • SHIFTED_GAMMA

        public static final int[] SHIFTED_GAMMA
      • DEFAULT_BUFFER_SIZE

        public static final int DEFAULT_BUFFER_SIZE
        The default size of the byte buffer in bytes (16Ki).
        See Also:
        Constant Field Values
      • buffer

        protected byte[] buffer
        The stream buffer.
      • free

        protected int free
        Current number of free bits in the bit buffer (the bits in the buffer are stored high).
      • pos

        protected int pos
        Current position in the byte buffer.
      • position

        protected long position
        Current position of the underlying output stream.
      • avail

        protected int avail
        Current number of bytes available in the byte buffer.
      • fileChannel

        protected final FileChannel fileChannel
        The cached file channel underlying os.
      • repositionableStream

        protected final RepositionableStream repositionableStream
        os cast to a positionable stream.
      • wrapping

        protected final boolean wrapping
        True if we are wrapping an array.
    • Constructor Detail

      • OutputBitStream

        protected OutputBitStream()
        This (non-public) constructor exists just to provide fake initialisation for classes such as DebugOutputBitStream.
      • OutputBitStream

        public OutputBitStream​(OutputStream os)
        Creates a new output bit stream wrapping a given output stream using a buffer of size DEFAULT_BUFFER_SIZE.

        This constructor performs the reflective tests that are necessary to support position(long).

        Parameters:
        os - the output stream to wrap.
      • OutputBitStream

        public OutputBitStream​(OutputStream os,
                               boolean testForPosition)
        Creates a new output bit stream wrapping a given output stream using a buffer of size DEFAULT_BUFFER_SIZE.
        Parameters:
        os - the output stream to wrap.
        testForPosition - if false, the reflective test that is necessary to support position(long) in case os does not support RepositionableStream will not be performed.
      • OutputBitStream

        public OutputBitStream​(OutputStream os,
                               int bufSize)
        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 position(long).

        Parameters:
        os - the output stream to wrap.
        bufSize - the size in byte of the buffer; it may be 0, denoting no buffering.
      • OutputBitStream

        public OutputBitStream​(OutputStream os,
                               int bufSize,
                               boolean testForPosition)
        Creates a new output bit stream wrapping a given output stream with a specified buffer size.
        Parameters:
        os - the output stream to wrap.
        bufSize - the size in byte of the buffer; it may be 0, denoting no buffering.
        testForPosition - if false, the reflective test that is necessary to support position(long) in case os does not support RepositionableStream will not be performed.
      • OutputBitStream

        public OutputBitStream​(FileOutputStream os,
                               int bufSize)
        Creates a new output bit stream wrapping a given file output stream with a specified buffer size.

        This constructor invokes directly FileOutputStream.getChannel() to support position(long).

        Parameters:
        os - the output stream to wrap.
        bufSize - the size in byte of the buffer; it may be 0, denoting no buffering.
      • OutputBitStream

        public OutputBitStream​(byte[] a)
        Creates a new output bit stream wrapping a given byte array.
        Parameters:
        a - the byte array to wrap.
      • OutputBitStream

        public OutputBitStream​(String name,
                               int bufSize)
                        throws FileNotFoundException
        Creates a new output bit stream writing to file.
        Parameters:
        name - the name of the file.
        bufSize - the size in byte of the buffer; it may be 0, denoting no buffering.
        Throws:
        FileNotFoundException
      • OutputBitStream

        public OutputBitStream​(File file,
                               int bufSize)
                        throws FileNotFoundException
        Creates a new output bit stream writing to file.
        Parameters:
        file - the file.
        bufSize - the size in byte of the buffer; it may be 0, denoting no buffering.
        Throws:
        FileNotFoundException
    • Method Detail

      • flush

        public void flush()
                   throws IOException
        Flushes the bit stream.

        This method will align the stream, write the bit buffer, empty the byte buffer and delegate to the 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 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.

        Specified by:
        flush in interface Flushable
        Throws:
        IOException
      • writtenBits

        public long writtenBits()
        Returns the number of bits written to this bit stream.
        Returns:
        the number of bits written so far.
      • writtenBits

        public void writtenBits​(long 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 flush().

        Parameters:
        writtenBits - the new value for the number of bits written so far.
      • align

        public int align()
                  throws IOException
        Aligns the stream. After a call to this method, the stream is byte aligned. Zeroes are used to pad it if necessary.
        Returns:
        the number of padding bits.
        Throws:
        IOException
      • write

        public long write​(byte[] bits,
                          long len)
                   throws IOException
        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.
        Parameters:
        bits - a vector containing the bits to be written.
        len - a bit length.
        Returns:
        the number of bits written (len).
        Throws:
        IOException
      • write

        public long write​(byte[] bits,
                          long offset,
                          long len)
                   throws IOException
        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.
        Parameters:
        bits - a vector containing the bits to be written.
        offset - a bit offset from which to start to write.
        len - a bit length.
        Returns:
        the number of bits written (len).
        Throws:
        IOException
      • writeByteOffset

        protected long writeByteOffset​(byte[] bits,
                                       int offset,
                                       long len)
                                throws IOException
        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 write(byte[], long, long).

        Parameters:
        bits - a vector containing the bits to be written.
        offset - an offset, expressed in bytes.
        len - a bit length.
        Returns:
        the number of bits written (len).
        Throws:
        IOException
      • writeBit

        public int writeBit​(boolean bit)
                     throws IOException
        Writes a bit.
        Parameters:
        bit - a bit.
        Returns:
        the number of bits written.
        Throws:
        IOException
      • writeBit

        public int writeBit​(int bit)
                     throws IOException
        Writes a bit.
        Parameters:
        bit - a bit.
        Returns:
        the number of bits written.
        Throws:
        IOException
      • write

        public int write​(BooleanIterator i)
                  throws IOException
        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.

        Parameters:
        i - a boolean iterator.
        Returns:
        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.
        Throws:
        IOException
      • writeInt

        public int writeInt​(int x,
                            int len)
                     throws IOException
        Writes a fixed number of bits from an integer.
        Parameters:
        x - an integer.
        len - a bit length; this many lower bits of the first argument will be written (the most significant bit first).
        Returns:
        the number of bits written (len).
        Throws:
        IOException
      • writeLong

        public int writeLong​(long x,
                             int len)
                      throws IOException
        Writes a fixed number of bits from a long.
        Parameters:
        x - a long.
        len - a bit length; this many lower bits of the first argument will be written (the most significant bit first).
        Returns:
        the number of bits written (len).
        Throws:
        IOException
      • writeUnary

        public int writeUnary​(int x)
                       throws IOException
        Writes a natural number in unary coding.

        The unary coding of a natural number n is given by 0n1.

        Parameters:
        x - a natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
      • writeLongUnary

        public long writeLongUnary​(long x)
                            throws IOException
        Writes a long natural number in unary coding.
        Parameters:
        x - a long natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
        See Also:
        writeUnary(int)
      • writeGamma

        public int writeGamma​(int x)
                       throws IOException
        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.

        Parameters:
        x - a natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
      • writeGammas

        public long writeGammas​(int[] a,
                                int count)
                         throws IOException
        Writes a given amount of natural numbers in γ coding.
        Parameters:
        a - an array at least count natural numbers.
        count - the number of elements of a to be written.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
        See Also:
        writeGamma(int)
      • writeLongGamma

        public int writeLongGamma​(long x)
                           throws IOException
        Writes a long natural number in γ coding.
        Parameters:
        x - a long natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
        See Also:
        writeGamma(int)
      • writeShiftedGamma

        public int writeShiftedGamma​(int x)
                              throws IOException
        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).
        Parameters:
        x - a natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
      • writeShiftedGammas

        public long writeShiftedGammas​(int[] a,
                                       int count)
                                throws IOException
        Writes a given amount of natural numbers in shifted γ coding.
        Parameters:
        a - an array at least count natural numbers.
        count - the number of elements of a to be written.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
        See Also:
        writeShiftedGamma(int)
      • writeDelta

        public int writeDelta​(int x)
                       throws IOException
        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.
        Parameters:
        x - a natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
      • writeLongDelta

        public int writeLongDelta​(long x)
                           throws IOException
        Writes a long natural number in δ coding.
        Parameters:
        x - a long natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
        See Also:
        writeDelta(int)
      • writeDeltas

        public long writeDeltas​(int[] a,
                                int count)
                         throws IOException
        Writes a given amount of natural numbers in δ coding.
        Parameters:
        a - an array at least count natural numbers.
        count - the number of elements of a to be written.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
        See Also:
        writeDelta(int)
      • writeMinimalBinary

        public int writeMinimalBinary​(int x,
                                      int b)
                               throws IOException
        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.

        Parameters:
        x - a natural number.
        b - a strict upper bound for x.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a nonpositive base.
        IOException
      • writeMinimalBinary

        public int writeMinimalBinary​(int x,
                                      int b,
                                      int log2b)
                               throws IOException
        Writes a natural number in a limited range using a minimal binary coding. This method is faster than writeMinimalBinary(int,int) because it does not have to compute log2b.
        Parameters:
        x - a natural number.
        b - a strict upper bound for x.
        log2b - the floor of the base-2 logarithm of the bound.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a nonpositive base.
        IOException
        See Also:
        writeMinimalBinary(int, int)
      • writeLongMinimalBinary

        public int writeLongMinimalBinary​(long x,
                                          long b)
                                   throws IOException
        Writes a long natural number in a limited range using a minimal binary coding.
        Parameters:
        x - a natural number.
        b - a strict upper bound for x.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a nonpositive base.
        IOException
        See Also:
        writeMinimalBinary(int, int)
      • writeLongMinimalBinary

        public int writeLongMinimalBinary​(long x,
                                          long b,
                                          int log2b)
                                   throws IOException
        Writes a long natural number in a limited range using a minimal binary coding. This method is faster than writeLongMinimalBinary(long,long) because it does not have to compute log2b.
        Parameters:
        x - a long natural number.
        b - a strict upper bound for x.
        log2b - the floor of the base-2 logarithm of the bound.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a nonpositive base.
        IOException
        See Also:
        writeMinimalBinary(int, int)
      • writeGolomb

        public int writeGolomb​(int x,
                               int b)
                        throws IOException
        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 unary, followed by the remainder in 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.

        Parameters:
        x - a natural number.
        b - the modulus for the coding.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a negative modulus.
        IOException
      • writeGolomb

        public int writeGolomb​(int x,
                               int b,
                               int log2b)
                        throws IOException
        Writes a natural number in Golomb coding. This method is faster than writeGolomb(int,int) because it does not have to compute log2b.
        Parameters:
        x - a natural number.
        b - the modulus for the coding.
        log2b - the floor of the base-2 logarithm of the coding modulus (it is irrelevant when b is zero).
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a negative modulus.
        IOException
        See Also:
        writeGolomb(int, int)
      • writeLongGolomb

        public long writeLongGolomb​(long x,
                                    long b)
                             throws IOException
        Writes a long natural number in Golomb coding.
        Parameters:
        x - a long natural number.
        b - the modulus for the coding.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a negative modulus.
        IOException
        See Also:
        writeGolomb(int, int)
      • writeLongGolomb

        public long writeLongGolomb​(long x,
                                    long b,
                                    int log2b)
                             throws IOException
        Writes a long natural number in Golomb coding. This method is faster than writeLongGolomb(long,long) because it does not have to compute log2b.
        Parameters:
        x - a long natural number.
        b - the modulus for the coding.
        log2b - the floor of the base-2 logarithm of the coding modulus (it is irrelevant when b is zero).
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a negative modulus.
        IOException
        See Also:
        writeGolomb(int, int)
      • writeSkewedGolomb

        public int writeSkewedGolomb​(int x,
                                     int b)
                              throws IOException
        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.

        Parameters:
        x - a natural number.
        b - the modulus for the coding.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a negative modulus.
        IOException
      • writeLongSkewedGolomb

        public long writeLongSkewedGolomb​(long x,
                                          long b)
                                   throws IOException
        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.

        Parameters:
        x - a long natural number.
        b - the modulus for the coding.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a negative modulus.
        IOException
        See Also:
        writeSkewedGolomb(int, int)
      • writeZeta

        public int writeZeta​(int x,
                             int k)
                      throws IOException
        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.

        Parameters:
        x - a natural number.
        k - the shrinking factor.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a nonpositive shrinking factor.
        IOException
      • writeLongZeta

        public int writeLongZeta​(long x,
                                 int k)
                          throws IOException
        Writes a long natural number in ζ coding.
        Parameters:
        x - a long natural number.
        k - the shrinking factor.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number or use a nonpositive shrinking factor.
        IOException
        See Also:
        writeZeta(int, int)
      • writeNibble

        public int writeNibble​(int x)
                        throws IOException
        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.

        Parameters:
        x - a natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
      • writeLongNibble

        public int writeLongNibble​(long x)
                            throws IOException
        Writes a long natural number in variable-length nibble coding.
        Parameters:
        x - a long natural number.
        Returns:
        the number of bits written.
        Throws:
        IllegalArgumentException - if you try to write a negative number.
        IOException
        See Also:
        writeNibble(int)
      • copyFrom

        public void copyFrom​(InputBitStream ibs,
                             long length)
                      throws IOException
        Copies a given number of bits from a given input bit stream into this output bit stream.
        Parameters:
        ibs - an input bit stream.
        length - the number of bits to copy.
        Throws:
        EOFException - if there are not enough bits to copy.
        IOException