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/*
* Copyright (c) 2022, Lucas Chollet <lucas.chollet@free.fr>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/CircularBuffer.h>
#include <AK/MemMem.h>
namespace AK {
CircularBuffer::CircularBuffer(ByteBuffer buffer)
: m_buffer(move(buffer))
{
}
ErrorOr<CircularBuffer> CircularBuffer::create_empty(size_t size)
{
auto temporary_buffer = TRY(ByteBuffer::create_uninitialized(size));
CircularBuffer circular_buffer { move(temporary_buffer) };
return circular_buffer;
}
ErrorOr<CircularBuffer> CircularBuffer::create_initialized(ByteBuffer buffer)
{
CircularBuffer circular_buffer { move(buffer) };
circular_buffer.m_used_space = circular_buffer.m_buffer.size();
return circular_buffer;
}
size_t CircularBuffer::empty_space() const
{
return capacity() - m_used_space;
}
size_t CircularBuffer::used_space() const
{
return m_used_space;
}
size_t CircularBuffer::capacity() const
{
return m_buffer.size();
}
size_t CircularBuffer::seekback_limit() const
{
return m_seekback_limit;
}
bool CircularBuffer::is_wrapping_around() const
{
return capacity() <= m_reading_head + m_used_space;
}
Optional<size_t> CircularBuffer::offset_of(StringView needle, Optional<size_t> from, Optional<size_t> until) const
{
auto const read_from = from.value_or(0);
auto const read_until = until.value_or(m_used_space);
VERIFY(read_from <= read_until);
Array<ReadonlyBytes, 2> spans {};
spans[0] = next_read_span();
auto const original_span_0_size = spans[0].size();
if (read_from > 0)
spans[0] = spans[0].slice(min(spans[0].size(), read_from));
if (spans[0].size() + read_from > read_until)
spans[0] = spans[0].trim(read_until - read_from);
else if (is_wrapping_around())
spans[1] = m_buffer.span().slice(max(original_span_0_size, read_from) - original_span_0_size, min(read_until, m_used_space) - original_span_0_size);
auto maybe_found = AK::memmem(spans.begin(), spans.end(), needle.bytes());
if (maybe_found.has_value())
*maybe_found += read_from;
return maybe_found;
}
void CircularBuffer::clear()
{
m_reading_head = 0;
m_used_space = 0;
m_seekback_limit = 0;
}
Bytes CircularBuffer::next_write_span()
{
if (is_wrapping_around())
return m_buffer.span().slice(m_reading_head + m_used_space - capacity(), capacity() - m_used_space);
return m_buffer.span().slice(m_reading_head + m_used_space, capacity() - (m_reading_head + m_used_space));
}
ReadonlyBytes CircularBuffer::next_read_span() const
{
return m_buffer.span().slice(m_reading_head, min(capacity() - m_reading_head, m_used_space));
}
ReadonlyBytes CircularBuffer::next_read_span_with_seekback(size_t distance) const
{
VERIFY(m_seekback_limit <= capacity());
VERIFY(distance <= m_seekback_limit);
// Note: We are adding the capacity once here to ensure that we can wrap around the negative space by using modulo.
auto read_offset = (capacity() + m_reading_head + m_used_space - distance) % capacity();
return m_buffer.span().slice(read_offset, min(capacity() - read_offset, m_seekback_limit));
}
size_t CircularBuffer::write(ReadonlyBytes bytes)
{
auto remaining = bytes.size();
while (remaining > 0) {
auto const next_span = next_write_span();
if (next_span.size() == 0)
break;
auto const written_bytes = bytes.slice(bytes.size() - remaining).copy_trimmed_to(next_span);
m_used_space += written_bytes;
m_seekback_limit += written_bytes;
if (m_seekback_limit > capacity())
m_seekback_limit = capacity();
remaining -= written_bytes;
}
return bytes.size() - remaining;
}
Bytes CircularBuffer::read(Bytes bytes)
{
auto remaining = bytes.size();
while (remaining > 0) {
auto const next_span = next_read_span();
if (next_span.size() == 0)
break;
auto written_bytes = next_span.copy_trimmed_to(bytes.slice(bytes.size() - remaining));
m_used_space -= written_bytes;
m_reading_head += written_bytes;
if (m_reading_head >= capacity())
m_reading_head -= capacity();
remaining -= written_bytes;
}
return bytes.trim(bytes.size() - remaining);
}
ErrorOr<Bytes> CircularBuffer::read_with_seekback(Bytes bytes, size_t distance)
{
if (distance > m_seekback_limit)
return Error::from_string_literal("Tried a seekback read beyond the seekback limit");
auto remaining = bytes.size();
while (remaining > 0) {
auto const next_span = next_read_span_with_seekback(distance);
if (next_span.size() == 0)
break;
auto written_bytes = next_span.copy_trimmed_to(bytes.slice(bytes.size() - remaining));
distance -= written_bytes;
remaining -= written_bytes;
}
return bytes.trim(bytes.size() - remaining);
}
ErrorOr<void> CircularBuffer::discard(size_t discarding_size)
{
if (m_used_space < discarding_size)
return Error::from_string_literal("Can not discard more data than what the buffer contains");
m_used_space -= discarding_size;
m_reading_head = (m_reading_head + discarding_size) % capacity();
return {};
}
}
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