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/*
* Copyright (c) 2022, Lucas Chollet <lucas.chollet@free.fr>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/ByteBuffer.h>
#include <AK/Error.h>
#include <AK/Noncopyable.h>
#include <AK/Vector.h>
namespace AK {
class CircularBuffer {
AK_MAKE_NONCOPYABLE(CircularBuffer);
public:
static ErrorOr<CircularBuffer> create_empty(size_t size);
static ErrorOr<CircularBuffer> create_initialized(ByteBuffer);
CircularBuffer(CircularBuffer&& other) = default;
CircularBuffer& operator=(CircularBuffer&& other) = default;
~CircularBuffer() = default;
size_t write(ReadonlyBytes bytes);
Bytes read(Bytes bytes);
ErrorOr<void> discard(size_t discarded_bytes);
ErrorOr<size_t> fill_from_stream(Stream&);
ErrorOr<size_t> flush_to_stream(Stream&);
/// Compared to `read()`, this starts reading from an offset that is `distance` bytes
/// before the current write pointer and allows for reading already-read data.
ErrorOr<Bytes> read_with_seekback(Bytes bytes, size_t distance);
ErrorOr<size_t> copy_from_seekback(size_t distance, size_t length);
struct Match {
size_t distance;
size_t length;
};
/// This searches the seekback buffer (between read head and limit) for occurrences where it matches the next `length` bytes from the read buffer.
/// Supplying any hints will only consider those distances, in case existing offsets need to be validated.
/// Note that, since we only start searching at the read head, the length between read head and write head is excluded from the distance.
ErrorOr<Vector<Match>> find_copy_in_seekback(size_t maximum_length, size_t minimum_length = 2, Optional<Vector<size_t> const&> distance_hints = {}) const;
[[nodiscard]] size_t empty_space() const;
[[nodiscard]] size_t used_space() const;
[[nodiscard]] size_t capacity() const;
[[nodiscard]] size_t seekback_limit() const;
Optional<size_t> offset_of(StringView needle, Optional<size_t> from = {}, Optional<size_t> until = {}) const;
void clear();
private:
CircularBuffer(ByteBuffer);
[[nodiscard]] bool is_wrapping_around() const;
[[nodiscard]] Bytes next_write_span();
[[nodiscard]] ReadonlyBytes next_read_span() const;
[[nodiscard]] ReadonlyBytes next_read_span_with_seekback(size_t distance) const;
ByteBuffer m_buffer {};
size_t m_reading_head {};
size_t m_used_space {};
size_t m_seekback_limit {};
};
}
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