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#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;
}
}
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