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Initial fixed huffman coding for png.

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This commit is contained in:
James Grogan 2022-11-28 10:16:04 +00:00
parent e4f9393ee7
commit 7f5009fb5e
39 changed files with 1294 additions and 440 deletions
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55
src/core/streams/BitStream.cpp
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@ -24,6 +24,7 @@ void BitStream::write(uint32_t data)
unsigned num_bytes = sizeof(uint32_t);
for(unsigned idx=0; idx<num_bytes;idx++)
{
std::cout << "Writing byte " << idx << " for multibyte" << std::endl;
writeByte(ByteUtils::getByteN(data, idx));
}
}
@ -46,18 +47,70 @@ unsigned BitStream::getCurrentBitOffset() const
return mBitOffset;
}
std::string BitStream::logLocation()
{
std::stringstream sstr;
sstr << "Byte offset " << mByteOffset<< " | Bit offset " << mBitOffset;
sstr << " | Working byte " << ByteUtils::toString(getCurrentByte()) << '\n';
return sstr.str();
}
std::string BitStream::logNextNBytes(unsigned n) const
{
std::stringstream sstr;
unsigned count{0};
for(auto byte : peekNextNBytes(n))
{
sstr << count << " | " << ByteUtils::toString(byte) + '\n';
sstr << mByteOffset + count << " | " << ByteUtils::toString(byte) + '\n';
count++;
}
return sstr.str();
}
void BitStream::writeNBits(uint32_t data, unsigned length)
{
const auto num_left = 8 - mBitOffset;
const int overshoot = length - num_left;
if (overshoot > 0)
{
unsigned char lower_bits = ByteUtils::getLowerNBits(data, num_left);
mCurrentByte |= lower_bits << mBitOffset;
writeByte(mCurrentByte, false);
auto num_bytes = overshoot / 8;
for (unsigned idx=0; idx< num_bytes; idx++)
{
mCurrentByte = ByteUtils::getMBitsAtN(data, overshoot, idx*8 + num_left);
writeByte(mCurrentByte, false);
}
if (const auto remainder = overshoot % 8; remainder > 0)
{
mCurrentByte = ByteUtils::getMBitsAtN(data, remainder, num_bytes*8 + num_left);
mBitOffset = remainder;
}
else
{
mCurrentByte = 0;
mBitOffset = 0;
}
}
else
{
mCurrentByte |= (static_cast<unsigned char>(data) << mBitOffset);
mBitOffset += length;
if (mBitOffset == 8)
{
writeByte(mCurrentByte, false);
mCurrentByte = 0;
mBitOffset = 0;
}
}
}
bool BitStream::readNextNBits(unsigned n, unsigned char& buffer)
{
if (mByteOffset < 0)