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/*

* Reference arithmetic coding

*

* Copyright (c) Project Nayuki

* MIT License. See readme file.

* https://www.nayuki.io/page/reference-arithmetic-coding

*/

#pragma once

#include <istream>

#include <ostream>

/*

* 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.

*/

class BitInputStream final {

/*---- Fields ----*/

// The underlying byte stream to read from.

private: std::istream &input;

// Either in the range [0x00, 0xFF] if bits are available, or EOF if end of stream is reached.

private: int currentByte;

// Number of remaining bits in the current byte, always between 0 and 7 (inclusive).

private: int numBitsRemaining;

/*---- Constructor ----*/

// Constructs a bit input stream based on the given byte input stream.

public: explicit BitInputStream(std::istream &in);

/*---- Methods ----*/

// Reads a bit from this 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();

// Reads a bit from this stream. Returns 0 or 1 if a bit is available, or throws an exception

// if the end of stream is reached. The end of stream always occurs on a byte boundary.

public: int readNoEof();

};

/*

* A stream where bits can be written to. Because they are written to an underlying

* byte stream, the end of the stream is padded with 0's up to a multiple of 8 bits.

* The bits are written in big endian.

*/

class BitOutputStream final {

/*---- Fields ----*/

// The underlying byte stream to write to.

private: std::ostream &output;

// The accumulated bits for the current byte, always in the range [0x00, 0xFF].

private: int currentByte;

// Number of accumulated bits in the current byte, always between 0 and 7 (inclusive).

private: int numBitsFilled;

/*---- Constructor ----*/

// Constructs a bit output stream based on the given byte output stream.

public: explicit BitOutputStream(std::ostream &out);

/*---- Methods ----*/

// Writes a bit to the stream. The given bit must be 0 or 1.

public: void write(int b);

// Writes the minimum number of "0" bits (between 0 and 7 of them) as padding to

// reach the next byte boundary. Most applications will require the bits in the last

// partial byte to be written before the underlying stream is closed. Note that this

// method merely writes data to the underlying output stream but does not close it.

public: void finish();

};