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// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef ZIRCON_SYSTEM_ULIB_BLOBFS_CACHE_NODE_H_
#define ZIRCON_SYSTEM_ULIB_BLOBFS_CACHE_NODE_H_
#ifndef __Fuchsia__
#error Fuchsia-only Header
#endif
#include <digest/digest.h>
#include <fbl/function.h>
#include <fbl/intrusive_wavl_tree.h>
#include <fbl/mutex.h>
#include <fbl/ref_ptr.h>
#include <fs/vnode.h>
namespace blobfs {
using digest::Digest;
// Forward declared because CacheNode needs a mechanism for accessing the class
// when it runs out of strong references.
class BlobCache;
// An abstract blob-backed Vnode, which is managed by the BlobCache.
class CacheNode : public fs::Vnode, fbl::Recyclable<CacheNode> {
public:
// Intrusive methods and structures.
using WAVLTreeNodeState = fbl::WAVLTreeNodeState<CacheNode*>;
struct TypeWavlTraits {
static WAVLTreeNodeState& node_state(CacheNode& b) { return b.type_wavl_state_; }
};
bool InContainer() const { return type_wavl_state_.InContainer(); }
explicit CacheNode(const Digest& digest);
virtual ~CacheNode();
// Invoked by fbl::RefPtr when all strong references to RefPtr<CacheNode> go out of scope.
//
// If a derived class wishes to participate in the Cache's lifetime management,
// they must implement the following:
//
// void fbl_recycle() final {
// CacheNode::fbl_recycle();
// }
void fbl_recycle() override;
// Returns a reference to the BlobCache.
//
// The BlobCache must outlive all CacheNodes; this method is invoked from the recycler
// of a CacheNode.
//
// The implementation of this method must not invoke any other CacheNode methods.
// The implementation of this method must not attempt to acquire a reference to |this|.
virtual BlobCache& Cache() = 0;
// Identifies if the node should be recycled when it is terminated,
// keeping it cached (although possibly in a reduced state).
//
// This should be true as long as the blob exists on persistent storage, and
// would be visible again on reboot.
//
// The implementation of this method must not invoke any other CacheNode methods.
// The implementation of this method must not attempt to acquire a reference to |this|.
virtual bool ShouldCache() const = 0;
// Places the Vnode into a low-memory state. This function may be invoked when
// migrating the node from a "live cache" to a "closed cache".
//
// The implementation of this method must not invoke any other CacheNode methods.
// The implementation of this method must not attempt to acquire a reference to |this|.
virtual void ActivateLowMemory() = 0;
// Returns the node's digest.
const uint8_t* GetKey() const { return &digest_[0]; }
private:
friend struct TypeWavlTraits;
WAVLTreeNodeState type_wavl_state_ = {};
uint8_t digest_[digest::kSha256Length] = {};
};
} // namespace blobfs
#endif // ZIRCON_SYSTEM_ULIB_BLOBFS_CACHE_NODE_H_