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/*

* Reference arithmetic coding

* Copyright (c) Project Nayuki

*

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

* https://github.com/nayuki/Reference-arithmetic-coding

*/

#include <limits>

#include <stdexcept>

#include "BitIoStream.hpp"

BitInputStream::BitInputStream(std::istream &in) :

input(in),

currentByte(0),

numBitsRemaining(0) {}

int BitInputStream::read() {

if (currentByte == -1)

return -1;

if (numBitsRemaining == 0) {

currentByte = input.get(); // Note: istream.get() returns int, not char

if (currentByte == EOF)

return -1;

if (currentByte < 0 || currentByte > 255)

throw std::logic_error("Assertion error");

numBitsRemaining = 8;

}

if (numBitsRemaining <= 0)

throw std::logic_error("Assertion error");

numBitsRemaining--;

return (currentByte >> numBitsRemaining) & 1;

}

int BitInputStream::readNoEof() {

int result = read();

if (result != -1)

return result;

else

throw std::runtime_error("End of stream");

}

BitOutputStream::BitOutputStream(std::ostream &out) :

output(out),

currentByte(0),

numBitsFilled(0) {}

void BitOutputStream::write(int b) {

if (b != 0 && b != 1)

throw std::domain_error("Argument must be 0 or 1");

currentByte = (currentByte << 1) | b;

numBitsFilled++;

if (numBitsFilled == 8) {

// Note: ostream.put() takes char, which may be signed/unsigned

if (std::numeric_limits<char>::is_signed)

currentByte -= (currentByte >> 7) << 8;

output.put(static_cast<char>(currentByte));

currentByte = 0;

numBitsFilled = 0;

}

}

void BitOutputStream::finish() {

while (numBitsFilled != 0)

write(0);

}