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66 lines
1.3 KiB
C++
66 lines
1.3 KiB
C++
#include <qpdf/BitStream.hh>
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// See comments in bits.cc
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#define BITS_READ 1
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#include "bits.icc"
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BitStream::BitStream(unsigned char const* p, int 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 (static_cast<unsigned int>(nbytes) > static_cast<unsigned int>(-1) / 8)
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{
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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(int nbits)
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{
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return read_bits(this->p, this->bit_offset,
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this->bits_available, nbits);
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}
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long long
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BitStream::getBitsSigned(int nbits)
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{
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unsigned long long bits = read_bits(this->p, this->bit_offset,
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this->bits_available, nbits);
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long long result = 0;
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if (static_cast<long long>(bits) > 1 << (nbits - 1))
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{
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result = static_cast<long long>(bits - (1 << nbits));
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}
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else
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{
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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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void
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BitStream::skipToNextByte()
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{
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if (bit_offset != 7)
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{
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unsigned int bits_to_skip = bit_offset + 1;
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if (bits_available < bits_to_skip)
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{
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throw std::logic_error(
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"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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