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Add signed support to BitStream and BitWriter
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@ -30,6 +30,23 @@ BitStream::getBits(int nbits)
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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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@ -17,6 +17,21 @@ BitWriter::writeBits(unsigned long long val, unsigned int bits)
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write_bits(this->ch, this->bit_offset, val, bits, this->pl);
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}
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void
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BitWriter::writeBitsSigned(long long val, unsigned int bits)
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{
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unsigned long long uval = 0;
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if (val < 0)
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{
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uval = static_cast<unsigned long long>((1 << bits) + val);
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}
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else
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{
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uval = static_cast<unsigned long long>(val);
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}
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writeBits(uval, bits);
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}
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void
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BitWriter::flush()
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{
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@ -15,6 +15,8 @@ class BitStream
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QPDF_DLL
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unsigned long long getBits(int nbits);
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QPDF_DLL
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long long getBitsSigned(int nbits);
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QPDF_DLL
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void skipToNextByte();
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private:
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@ -16,6 +16,8 @@ class BitWriter
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BitWriter(Pipeline* pl);
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QPDF_DLL
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void writeBits(unsigned long long val, unsigned int bits);
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QPDF_DLL
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void writeBitsSigned(long long val, unsigned int bits);
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// Force any partial byte to be written to the pipeline.
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QPDF_DLL
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void flush();
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@ -124,6 +124,13 @@ test()
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b.skipToNextByte();
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std::cout << b.getBits(8) << std::endl;
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std::cout << std::endl;
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b.reset();
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std::cout << b.getBitsSigned(3) << std::endl;
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std::cout << b.getBitsSigned(6) << std::endl;
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std::cout << b.getBitsSigned(5) << std::endl;
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std::cout << b.getBitsSigned(1) << std::endl;
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std::cout << b.getBitsSigned(17) << std::endl;
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std::cout << std::endl;
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// Write tests
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@ -159,6 +166,13 @@ test()
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bw.writeBits(0xABUL, 8);
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bw.flush();
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print_buffer(bp);
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bw.writeBitsSigned(-1, 3); // 111
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bw.writeBitsSigned(-12, 6); // 110100
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bw.writeBitsSigned(4, 3); // 100
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bw.writeBitsSigned(-4, 3); // 100
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bw.writeBitsSigned(-1, 1); // 1
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bw.flush();
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print_buffer(bp);
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delete bp;
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}
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@ -36,6 +36,12 @@ byte offset = 8, bit offset = 7, bits available = 0
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21
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101
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-1
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-22
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5
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0
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-39559
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ch = f0, bit_offset = 2
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ch = 00, bit_offset = 6
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ch = 14, bit_offset = 0
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@ -56,4 +62,6 @@ f5 15 65 79 12 89 75 4b
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f0 ab
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fa 49
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done
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