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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_PERSISTENT_CACHE_BACKEND_H_
#define COMPONENTS_PERSISTENT_CACHE_BACKEND_H_
#include <stdint.h>
#include <optional>
#include <string_view>
#include "base/component_export.h"
#include "base/containers/span.h"
#include "base/types/expected.h"
#include "components/persistent_cache/buffer_provider.h"
#include "components/persistent_cache/entry_metadata.h"
#include "components/persistent_cache/lock_state.h"
#include "components/persistent_cache/transaction_error.h"
namespace persistent_cache {
enum class BackendType;
// The persistence mechanism backing up the cache.
class COMPONENT_EXPORT(PERSISTENT_CACHE) Backend {
public:
virtual ~Backend();
// Not copyable or moveable.
Backend(const Backend&) = delete;
Backend(Backend&&) = delete;
Backend& operator=(const Backend&) = delete;
Backend& operator=(Backend&&) = delete;
// See `PersistentCache::Find()`.
// Note: Backends have to outlive entries they vend.
//
// Thread-safe.
virtual base::expected<std::optional<EntryMetadata>, TransactionError> Find(
std::string_view key,
BufferProvider buffer_provider) = 0;
// See `PersistentCache::Insert()`.
// Thread-safe.
virtual base::expected<void, TransactionError> Insert(
std::string_view key,
base::span<const uint8_t> content,
EntryMetadata metadata) = 0;
// Used to get type of instance. Intended for things like metrics recording.
// Externally behavior of all backend types should be equivalent and control
// flow should not be tailored to the type.
virtual BackendType GetType() const = 0;
// Used to understand if the instance has read only access. Intended for
// things like metrics recording. Externally behavior of all backend types
// should be equivalent for reads. Writes should probably not be attempted if
// not permitted.
virtual bool IsReadOnly() const = 0;
// See `PersistentCache::Abandon()` documentation.
virtual LockState Abandon() = 0;
protected:
Backend();
};
} // namespace persistent_cache
#endif // COMPONENTS_PERSISTENT_CACHE_BACKEND_H_
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