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/*
* Copyright (c) 2020, the SerenityOS developers.
* Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Optional.h>
#include <AK/Stream.h>
namespace AK {
class InputBitStream final : public InputStream {
public:
explicit InputBitStream(InputStream& stream)
: m_stream(stream)
{
}
size_t read(Bytes bytes) override
{
if (has_any_error())
return 0;
size_t nread = 0;
if (bytes.size() >= 1) {
if (m_next_byte.has_value()) {
bytes[0] = m_next_byte.value();
m_next_byte.clear();
++nread;
}
}
return nread + m_stream.read(bytes.slice(nread));
}
bool read_or_error(Bytes bytes) override
{
if (read(bytes) != bytes.size()) {
set_fatal_error();
return false;
}
return true;
}
bool unreliable_eof() const override { return !m_next_byte.has_value() && m_stream.unreliable_eof(); }
bool discard_or_error(size_t count) override
{
if (count >= 1) {
if (m_next_byte.has_value()) {
m_next_byte.clear();
--count;
}
}
return m_stream.discard_or_error(count);
}
u64 read_bits(size_t count)
{
u64 result = 0;
size_t nread = 0;
while (nread < count) {
if (m_stream.has_any_error()) {
set_fatal_error();
return 0;
}
if (m_next_byte.has_value()) {
const auto bit = (m_next_byte.value() >> m_bit_offset) & 1;
result |= bit << nread;
++nread;
if (m_bit_offset++ == 7)
m_next_byte.clear();
} else {
m_stream >> m_next_byte;
m_bit_offset = 0;
}
}
return result;
}
u64 read_bits_big_endian(size_t count)
{
u64 result = 0;
size_t nread = 0;
while (nread < count) {
if (m_stream.has_any_error()) {
set_fatal_error();
return 0;
}
if (m_next_byte.has_value()) {
// read an entire byte
if (((count - nread) >= 8) && m_bit_offset == 0) {
// shift existing bytes over
result <<= 8;
result |= m_next_byte.value();
nread += 8;
m_next_byte.clear();
} else {
const auto bit = (m_next_byte.value() >> (7 - m_bit_offset)) & 1;
result <<= 1;
result |= bit;
++nread;
if (m_bit_offset++ == 7)
m_next_byte.clear();
}
} else {
m_stream >> m_next_byte;
m_bit_offset = 0;
}
}
return result;
}
bool read_bit() { return static_cast<bool>(read_bits(1)); }
bool read_bit_big_endian() { return static_cast<bool>(read_bits_big_endian(1)); }
void align_to_byte_boundary()
{
if (m_next_byte.has_value())
m_next_byte.clear();
}
bool handle_any_error() override
{
bool handled_errors = m_stream.handle_any_error();
return Stream::handle_any_error() || handled_errors;
}
private:
Optional<u8> m_next_byte;
size_t m_bit_offset { 0 };
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);
if (count == 32 && !m_next_byte.has_value()) { // fast path for aligned 32 bit writes
m_stream << bits;
return;
}
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 if (count - n_written >= 16) { // fast path for aligned 16 bit writes
m_stream << (u16)((bits >> n_written) & 0xFFFF);
n_written += 16;
} else if (count - n_written >= 8) { // fast path for aligned 8 bit writes
m_stream << (u8)((bits >> n_written) & 0xFF);
n_written += 8;
} 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;
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