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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 "base/component_export.h"
#include "base/containers/span.h"
#include "components/persistent_cache/backend_params.h"
#include "components/persistent_cache/entry_metadata.h"
namespace persistent_cache {
class Entry;
// 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;
// Initializes the cache. Must be called exactly once before any other
// method. No further method can be called if this fails.
virtual bool Initialize() = 0;
// Used to get a handle to entry associated with `key`. Returns `nullptr` if
// `key` is not found. Returned entry will remain valid and its contents will
// be accessible for its entire lifetime. Note: Backends have to outlive
// entries they vend.
//
// Thread-safe.
virtual std::unique_ptr<Entry> Find(std::string_view key) = 0;
// Used to add an entry containing `content` and associated with `key`.
// Metadata associated with the entry can be provided in `metadata` or the
// object can be default initialized to signify no metadata.
//
// This call will never report failure and `content` is expected (but not
// guaranteed) to be resident upon return.
//
// Implementations are allowed to free other unused entries on demand to make
// room or fail when full.
//
// Thread-safe.
virtual void 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;
protected:
Backend();
};
} // namespace persistent_cache
#endif // COMPONENTS_PERSISTENT_CACHE_BACKEND_H_
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