#include <qpdf/BitStream.hh>

#include <qpdf/QIntC.hh>

#include <qpdf/Util.hh>

// See comments in bits_functions.hh

#define BITS_READ 1

#include <qpdf/bits_functions.hh>

using namespace qpdf;

BitStream::BitStream(unsigned char const* p, size_t nbytes) :

    start(p),

    nbytes(nbytes)

{

    reset();

}

void

BitStream::reset()

{

    p = start;

    bit_offset = 7;

    if (QIntC::to_uint(nbytes) > static_cast<unsigned int>(-1) / 8) {

        throw std::runtime_error("array too large for bitstream");

    }

    bits_available = 8 * nbytes;

}

unsigned long long

BitStream::getBits(size_t nbits)

{

    return read_bits(this->p, this->bit_offset, this->bits_available, nbits);

}

long long

BitStream::getBitsSigned(size_t nbits)

{

    unsigned long long bits = read_bits(this->p, this->bit_offset, this->bits_available, nbits);

    long long result = 0;

    if (static_cast<long long>(bits) > 1LL << (nbits - 1)) {

        result = static_cast<long long>(bits - (1ULL << nbits));

    } else {

        result = static_cast<long long>(bits);

    }

    return result;

}

int

BitStream::getBitsInt(size_t nbits)

{

    return static_cast<int>(

        // line-break

        QIntC::to_uint(read_bits(this->p, this->bit_offset, this->bits_available, nbits)));

}

void

BitStream::skipToNextByte()

{

    if (bit_offset != 7) {

        size_t bits_to_skip = bit_offset + 1;

        util::internal_error_if(

            bits_available < bits_to_skip, "overflow skipping to next byte in bitstream");

        bit_offset = 7;

        ++p;

        bits_available -= bits_to_skip;

    }

}