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113 lines
3.9 KiB
C++
113 lines
3.9 KiB
C++
/*
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* Copyright (c) 2021, kleines Filmröllchen <filmroellchen@serenityos.org>.
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* Copyright (c) 2023, Sam Atkins <atkinssj@serenityos.org>.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Error.h>
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#include <AK/OwnPtr.h>
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#include <AK/Stream.h>
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#include <AK/Vector.h>
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namespace AK {
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/// A stream class that allows for reading/writing on a preallocated memory area
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/// using a single read/write head.
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class FixedMemoryStream : public SeekableStream {
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public:
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explicit FixedMemoryStream(Bytes bytes, bool writing_enabled = true);
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explicit FixedMemoryStream(ReadonlyBytes bytes);
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virtual bool is_eof() const override;
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virtual bool is_open() const override;
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virtual void close() override;
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virtual ErrorOr<void> truncate(size_t) override;
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virtual ErrorOr<Bytes> read_some(Bytes bytes) override;
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virtual ErrorOr<void> read_until_filled(Bytes bytes) override;
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virtual ErrorOr<size_t> seek(i64 offset, SeekMode seek_mode = SeekMode::SetPosition) override;
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virtual ErrorOr<size_t> write_some(ReadonlyBytes bytes) override;
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virtual ErrorOr<void> write_until_depleted(ReadonlyBytes bytes) override;
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size_t offset() const;
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size_t remaining() const;
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/// Read a value, but referring to the stream's underlying data instead of copying it.
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/// Of course, only use this if you know the lifetime of the data will exceed the value's.
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// FIXME: Would be nicer to be able to return T& but Variant (and thus ErrorOr) can't hold references.
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template<typename T>
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requires(Traits<T>::is_trivially_serializable())
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ErrorOr<T*> read_in_place()
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{
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if constexpr (!IsConst<T>) {
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if (!m_writing_enabled)
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return Error::from_string_view_or_print_error_and_return_errno("Tried to obtain a non-const reference from a read-only FixedMemoryStream"sv, EINVAL);
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}
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T* value = reinterpret_cast<T*>(m_bytes.offset_pointer(m_offset));
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TRY(discard(sizeof(T)));
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return value;
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}
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/// Read a span of values, referring to the stream's underlying data instead of copying it.
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/// Of course, only use this if you know the lifetime of the data will exceed the span's.
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template<typename T>
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requires(Traits<T>::is_trivially_serializable())
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ErrorOr<Span<T>> read_in_place(size_t count)
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{
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if constexpr (!IsConst<T>) {
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if (!m_writing_enabled)
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return Error::from_string_view_or_print_error_and_return_errno("Tried to obtain a non-const span from a read-only FixedMemoryStream"sv, EINVAL);
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}
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Span<T> span { reinterpret_cast<T*>(m_bytes.offset_pointer(m_offset)), count };
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TRY(discard(sizeof(T) * count));
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return span;
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}
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private:
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Bytes m_bytes;
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size_t m_offset { 0 };
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bool m_writing_enabled { true };
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};
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/// A stream class that allows for writing to an automatically allocating memory area
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/// and reading back the written data afterwards.
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class AllocatingMemoryStream final : public Stream {
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public:
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static constexpr size_t CHUNK_SIZE = 4096;
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virtual ErrorOr<Bytes> read_some(Bytes) override;
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virtual ErrorOr<size_t> write_some(ReadonlyBytes) override;
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virtual ErrorOr<void> discard(size_t) override;
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virtual bool is_eof() const override;
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virtual bool is_open() const override;
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virtual void close() override;
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size_t used_buffer_size() const;
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ErrorOr<Optional<size_t>> offset_of(ReadonlyBytes needle) const;
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private:
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// Note: We set the inline buffer capacity to zero to make moving chunks as efficient as possible.
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using Chunk = AK::Detail::ByteBuffer<0>;
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ErrorOr<ReadonlyBytes> next_read_range();
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ErrorOr<Bytes> next_write_range();
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void cleanup_unused_chunks();
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Vector<Chunk> m_chunks;
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size_t m_read_offset = 0;
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size_t m_write_offset = 0;
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};
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}
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#if USING_AK_GLOBALLY
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using AK::AllocatingMemoryStream;
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using AK::FixedMemoryStream;
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#endif
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