119 lines
4.4 KiB
C#
119 lines
4.4 KiB
C#
/*
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* Reference arithmetic coding
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* Copyright (c) Project Nayuki
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*
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* https://www.nayuki.io/page/reference-arithmetic-coding
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* https://github.com/nayuki/Reference-arithmetic-coding
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*/
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using System;
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/// <summary>
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/// Encodes symbols and writes to an arithmetic-coded bit stream. Not thread-safe. </summary>
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/// <seealso cref= ArithmeticDecoder </seealso>
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public sealed class ArithmeticEncoder : ArithmeticCoderBase
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{
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/*---- Fields ----*/
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// The underlying bit output stream (not null).
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private BitOutputStream output;
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// Number of saved underflow bits. This value can grow without bound,
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// so a truly correct implementation would use a BigInteger.
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private int numUnderflow;
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/*---- Constructor ----*/
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/// <summary>
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/// Constructs an arithmetic coding encoder based on the specified bit output stream. </summary>
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/// <param name="numBits"> the number of bits for the arithmetic coding range </param>
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/// <param name="out"> the bit output stream to write to </param>
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/// <exception cref="NullPointerException"> if the output stream is {@code null} </exception>
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/// <exception cref="IllegalArgumentException"> if stateSize is outside the range [1, 62] </exception>
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public ArithmeticEncoder(int numBits, BitOutputStream @out) : base(numBits)
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{
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output = @out; //Objects.requireNonNull(@out);
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numUnderflow = 0;
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}
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/*---- Methods ----*/
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/// <summary>
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/// Encodes the specified symbol based on the specified frequency table.
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/// This updates this arithmetic coder's state and may write out some bits. </summary>
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/// <param name="freqs"> the frequency table to use </param>
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/// <param name="symbol"> the symbol to encode </param>
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/// <exception cref="NullPointerException"> if the frequency table is {@code null} </exception>
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/// <exception cref="IllegalArgumentException"> if the symbol has zero frequency
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/// or the frequency table's total is too large </exception>
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/// <exception cref="IOException"> if an I/O exception occurred </exception>
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//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
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//ORIGINAL LINE: public void write(FrequencyTable freqs, int symbol) throws java.io.IOException
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public void write(FrequencyTable freqs, int symbol)
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{
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write(new CheckedFrequencyTable(freqs), symbol);
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}
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/// <summary>
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/// Encodes the specified symbol based on the specified frequency table.
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/// Also updates this arithmetic coder's state and may write out some bits. </summary>
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/// <param name="freqs"> the frequency table to use </param>
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/// <param name="symbol"> the symbol to encode </param>
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/// <exception cref="NullPointerException"> if the frequency table is {@code null} </exception>
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/// <exception cref="IllegalArgumentException"> if the symbol has zero frequency
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/// or the frequency table's total is too large </exception>
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/// <exception cref="IOException"> if an I/O exception occurred </exception>
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//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
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//ORIGINAL LINE: public void write(CheckedFrequencyTable freqs, int symbol) throws java.io.IOException
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public void write(CheckedFrequencyTable freqs, int symbol)
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{
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update(freqs, symbol);
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}
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/// <summary>
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/// Terminates the arithmetic coding by flushing any buffered bits, so that the output can be decoded properly.
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/// It is important that this method must be called at the end of the each encoding process.
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/// <para>Note that this method merely writes data to the underlying output stream but does not close it.</para> </summary>
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/// <exception cref="IOException"> if an I/O exception occurred </exception>
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//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
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//ORIGINAL LINE: public void finish() throws java.io.IOException
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public void finish()
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{
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output.write(1);
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}
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//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in C#:
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//ORIGINAL LINE: protected void shift() throws java.io.IOException
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protected internal override void shift()
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{
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int bit = (int)((long)((ulong)low >> (numStateBits - 1)));
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output.write(bit);
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// Write out the saved underflow bits
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for (; numUnderflow > 0; numUnderflow--)
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{
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output.write(bit ^ 1);
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}
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}
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protected internal override void underflow()
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{
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if (numUnderflow == int.MaxValue)
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{
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throw new ArgumentException("Maximum underflow reached");
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}
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numUnderflow++;
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}
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}
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