mirror of https://github.com/qpdf/qpdf.git
67 lines
1.5 KiB
C++
67 lines
1.5 KiB
C++
#include <qpdf/BitStream.hh>
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#include <qpdf/QIntC.hh>
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// See comments in bits_functions.hh
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#define BITS_READ 1
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#include <qpdf/bits_functions.hh>
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BitStream::BitStream(unsigned char const* p, size_t nbytes) :
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start(p),
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nbytes(nbytes)
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{
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reset();
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}
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void
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BitStream::reset()
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{
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p = start;
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bit_offset = 7;
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if (QIntC::to_uint(nbytes) > static_cast<unsigned int>(-1) / 8) {
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throw std::runtime_error("array too large for bitstream");
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}
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bits_available = 8 * nbytes;
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}
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unsigned long long
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BitStream::getBits(size_t nbits)
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{
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return read_bits(this->p, this->bit_offset, this->bits_available, nbits);
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}
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long long
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BitStream::getBitsSigned(size_t nbits)
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{
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unsigned long long bits = read_bits(this->p, this->bit_offset, this->bits_available, nbits);
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long long result = 0;
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if (static_cast<long long>(bits) > 1LL << (nbits - 1)) {
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result = static_cast<long long>(bits - (1ULL << nbits));
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} else {
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result = static_cast<long long>(bits);
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}
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return result;
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}
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int
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BitStream::getBitsInt(size_t nbits)
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{
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return static_cast<int>(
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// line-break
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QIntC::to_uint(read_bits(this->p, this->bit_offset, this->bits_available, nbits)));
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}
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void
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BitStream::skipToNextByte()
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{
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if (bit_offset != 7) {
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size_t bits_to_skip = bit_offset + 1;
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if (bits_available < bits_to_skip) {
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throw std::logic_error("INTERNAL ERROR: overflow skipping to next byte in bitstream");
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}
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bit_offset = 7;
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++p;
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bits_available -= bits_to_skip;
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}
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}
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