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AK: Add OutputBitStream class

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This will be used in the deflate compressor.
This commit is contained in:
Idan Horowitz 2021-03-01 17:43:54 +02:00 committed by Andreas Kling
parent 5a0ebdb109
commit 0ddc0e45ae
Notes: sideshowbarker 2024-07-18 21:24:40 +09:00 
Author: https://github.com/IdanHo
Commit: https://github.com/SerenityOS/serenity/commit/0ddc0e45aec
Pull-request: https://github.com/SerenityOS/serenity/pull/5750
Issue: https://github.com/SerenityOS/serenity/issues/3989
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/bcoles
2 changed files with 82 additions and 0 deletions
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80
AK/BitStream.h
View file

@ -1,5 +1,6 @@
/*
* Copyright (c) 2020, the SerenityOS developers.
* Copyright (c) 2021, Idan Horowitz <idan.horowitz@gmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -121,6 +122,85 @@ private:
InputStream& m_stream;
};
class OutputBitStream final : public OutputStream {
public:
explicit OutputBitStream(OutputStream& stream)
: m_stream(stream)
{
}
// WARNING: write aligns to the next byte boundary before writing, if unaligned writes are needed this should be rewritten
size_t write(ReadonlyBytes bytes) override
{
if (has_any_error())
return 0;
align_to_byte_boundary();
if (has_fatal_error()) // if align_to_byte_boundary failed
return 0;
return m_stream.write(bytes);
}
bool write_or_error(ReadonlyBytes bytes) override
{
if (write(bytes) < bytes.size()) {
set_fatal_error();
return false;
}
return true;
}
void write_bits(u32 bits, size_t count)
{
VERIFY(count <= 32);
size_t n_written = 0;
while (n_written < count) {
if (m_stream.has_any_error()) {
set_fatal_error();
return;
}
if (m_next_byte.has_value()) {
m_next_byte.value() |= ((bits >> n_written) & 1) << m_bit_offset;
++n_written;
if (m_bit_offset++ == 7) {
m_stream << m_next_byte.value();
m_next_byte.clear();
}
} else {
m_bit_offset = 0;
m_next_byte = 0;
}
}
}
void write_bit(bool bit)
{
write_bits(bit, 1);
}
void align_to_byte_boundary()
{
if (m_next_byte.has_value()) {
if (!m_stream.write_or_error(ReadonlyBytes { &m_next_byte.value(), 1 })) {
set_fatal_error();
}
m_next_byte.clear();
}
}
size_t bit_offset() const
{
return m_bit_offset;
}
private:
Optional<u8> m_next_byte;
size_t m_bit_offset { 0 };
OutputStream& m_stream;
};
}
using AK::InputBitStream;
using AK::OutputBitStream;

2
AK/Forward.h
View file

@ -51,6 +51,7 @@ class InputMemoryStream;
class DuplexMemoryStream;
class OutputStream;
class InputBitStream;
class OutputBitStream;
class OutputMemoryStream;
template<size_t Capacity>
@ -160,6 +161,7 @@ using AK::NonnullOwnPtrVector;
using AK::NonnullRefPtr;
using AK::NonnullRefPtrVector;
using AK::Optional;
using AK::OutputBitStream;
using AK::OutputMemoryStream;
using AK::OutputStream;
using AK::OwnPtr;