Index: net/disk_cache/disk_cache.h |
diff --git a/net/disk_cache/disk_cache.h b/net/disk_cache/disk_cache.h |
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-// Copyright (c) 2012 The Chromium Authors. All rights reserved. |
-// Use of this source code is governed by a BSD-style license that can be |
-// found in the LICENSE file. |
- |
-// Defines the public interface of the disk cache. For more details see |
-// http://dev.chromium.org/developers/design-documents/network-stack/disk-cache |
- |
-#ifndef NET_DISK_CACHE_DISK_CACHE_H_ |
-#define NET_DISK_CACHE_DISK_CACHE_H_ |
- |
-#include <string> |
-#include <vector> |
- |
-#include "base/basictypes.h" |
-#include "base/memory/ref_counted.h" |
-#include "base/memory/scoped_ptr.h" |
-#include "base/time/time.h" |
-#include "net/base/cache_type.h" |
-#include "net/base/completion_callback.h" |
-#include "net/base/net_export.h" |
- |
-namespace base { |
-class FilePath; |
-class SingleThreadTaskRunner; |
-} |
- |
-namespace net { |
-class IOBuffer; |
-class NetLog; |
-} |
- |
-namespace disk_cache { |
- |
-class Entry; |
-class Backend; |
- |
-// Returns an instance of a Backend of the given |type|. |path| points to a |
-// folder where the cached data will be stored (if appropriate). This cache |
-// instance must be the only object that will be reading or writing files to |
-// that folder. The returned object should be deleted when not needed anymore. |
-// If |force| is true, and there is a problem with the cache initialization, the |
-// files will be deleted and a new set will be created. |max_bytes| is the |
-// maximum size the cache can grow to. If zero is passed in as |max_bytes|, the |
-// cache will determine the value to use. |thread| can be used to perform IO |
-// operations if a dedicated thread is required; a valid value is expected for |
-// any backend that performs operations on a disk. The returned pointer can be |
-// NULL if a fatal error is found. The actual return value of the function is a |
-// net error code. If this function returns ERR_IO_PENDING, the |callback| will |
-// be invoked when a backend is available or a fatal error condition is reached. |
-// The pointer to receive the |backend| must remain valid until the operation |
-// completes (the callback is notified). |
-NET_EXPORT int CreateCacheBackend( |
- net::CacheType type, |
- net::BackendType backend_type, |
- const base::FilePath& path, |
- int max_bytes, |
- bool force, |
- const scoped_refptr<base::SingleThreadTaskRunner>& thread, |
- net::NetLog* net_log, |
- scoped_ptr<Backend>* backend, |
- const net::CompletionCallback& callback); |
- |
-// The root interface for a disk cache instance. |
-class NET_EXPORT Backend { |
- public: |
- typedef net::CompletionCallback CompletionCallback; |
- |
- class Iterator { |
- public: |
- virtual ~Iterator() {} |
- |
- // OpenNextEntry returns |net::OK| and provides |next_entry| if there is an |
- // entry to enumerate. It returns |net::ERR_FAILED| at the end of |
- // enumeration. If the function returns |net::ERR_IO_PENDING|, then the |
- // final result will be passed to the provided |callback|, otherwise |
- // |callback| will not be called. If any entry in the cache is modified |
- // during iteration, the result of this function is thereafter undefined. |
- // |
- // Calling OpenNextEntry after the backend which created it is destroyed |
- // may fail with |net::ERR_FAILED|; however it should not crash. |
- // |
- // Some cache backends make stronger guarantees about mutation during |
- // iteration, see top comment in simple_backend_impl.h for details. |
- virtual int OpenNextEntry(Entry** next_entry, |
- const CompletionCallback& callback) = 0; |
- }; |
- |
- // If the backend is destroyed when there are operations in progress (any |
- // callback that has not been invoked yet), this method cancels said |
- // operations so the callbacks are not invoked, possibly leaving the work |
- // half way (for instance, dooming just a few entries). Note that pending IO |
- // for a given Entry (as opposed to the Backend) will still generate a |
- // callback from within this method. |
- virtual ~Backend() {} |
- |
- // Returns the type of this cache. |
- virtual net::CacheType GetCacheType() const = 0; |
- |
- // Returns the number of entries in the cache. |
- virtual int32 GetEntryCount() const = 0; |
- |
- // Opens an existing entry. Upon success, |entry| holds a pointer to an Entry |
- // object representing the specified disk cache entry. When the entry pointer |
- // is no longer needed, its Close method should be called. The return value is |
- // a net error code. If this method returns ERR_IO_PENDING, the |callback| |
- // will be invoked when the entry is available. The pointer to receive the |
- // |entry| must remain valid until the operation completes. |
- virtual int OpenEntry(const std::string& key, Entry** entry, |
- const CompletionCallback& callback) = 0; |
- |
- // Creates a new entry. Upon success, the out param holds a pointer to an |
- // Entry object representing the newly created disk cache entry. When the |
- // entry pointer is no longer needed, its Close method should be called. The |
- // return value is a net error code. If this method returns ERR_IO_PENDING, |
- // the |callback| will be invoked when the entry is available. The pointer to |
- // receive the |entry| must remain valid until the operation completes. |
- virtual int CreateEntry(const std::string& key, Entry** entry, |
- const CompletionCallback& callback) = 0; |
- |
- // Marks the entry, specified by the given key, for deletion. The return value |
- // is a net error code. If this method returns ERR_IO_PENDING, the |callback| |
- // will be invoked after the entry is doomed. |
- virtual int DoomEntry(const std::string& key, |
- const CompletionCallback& callback) = 0; |
- |
- // Marks all entries for deletion. The return value is a net error code. If |
- // this method returns ERR_IO_PENDING, the |callback| will be invoked when the |
- // operation completes. |
- virtual int DoomAllEntries(const CompletionCallback& callback) = 0; |
- |
- // Marks a range of entries for deletion. This supports unbounded deletes in |
- // either direction by using null Time values for either argument. The return |
- // value is a net error code. If this method returns ERR_IO_PENDING, the |
- // |callback| will be invoked when the operation completes. |
- // Entries with |initial_time| <= access time < |end_time| are deleted. |
- virtual int DoomEntriesBetween(base::Time initial_time, |
- base::Time end_time, |
- const CompletionCallback& callback) = 0; |
- |
- // Marks all entries accessed since |initial_time| for deletion. The return |
- // value is a net error code. If this method returns ERR_IO_PENDING, the |
- // |callback| will be invoked when the operation completes. |
- // Entries with |initial_time| <= access time are deleted. |
- virtual int DoomEntriesSince(base::Time initial_time, |
- const CompletionCallback& callback) = 0; |
- |
- // Returns an iterator which will enumerate all entries of the cache in an |
- // undefined order. |
- virtual scoped_ptr<Iterator> CreateIterator() = 0; |
- |
- // Return a list of cache statistics. |
- virtual void GetStats( |
- std::vector<std::pair<std::string, std::string> >* stats) = 0; |
- |
- // Called whenever an external cache in the system reuses the resource |
- // referred to by |key|. |
- virtual void OnExternalCacheHit(const std::string& key) = 0; |
-}; |
- |
-// This interface represents an entry in the disk cache. |
-class NET_EXPORT Entry { |
- public: |
- typedef net::CompletionCallback CompletionCallback; |
- typedef net::IOBuffer IOBuffer; |
- |
- // Marks this cache entry for deletion. |
- virtual void Doom() = 0; |
- |
- // Releases this entry. Calling this method does not cancel pending IO |
- // operations on this entry. Even after the last reference to this object has |
- // been released, pending completion callbacks may be invoked. |
- virtual void Close() = 0; |
- |
- // Returns the key associated with this cache entry. |
- virtual std::string GetKey() const = 0; |
- |
- // Returns the time when this cache entry was last used. |
- virtual base::Time GetLastUsed() const = 0; |
- |
- // Returns the time when this cache entry was last modified. |
- virtual base::Time GetLastModified() const = 0; |
- |
- // Returns the size of the cache data with the given index. |
- virtual int32 GetDataSize(int index) const = 0; |
- |
- // Copies cached data into the given buffer of length |buf_len|. Returns the |
- // number of bytes read or a network error code. If this function returns |
- // ERR_IO_PENDING, the completion callback will be called on the current |
- // thread when the operation completes, and a reference to |buf| will be |
- // retained until the callback is called. Note that as long as the function |
- // does not complete immediately, the callback will always be invoked, even |
- // after Close has been called; in other words, the caller may close this |
- // entry without having to wait for all the callbacks, and still rely on the |
- // cleanup performed from the callback code. |
- virtual int ReadData(int index, int offset, IOBuffer* buf, int buf_len, |
- const CompletionCallback& callback) = 0; |
- |
- // Copies data from the given buffer of length |buf_len| into the cache. |
- // Returns the number of bytes written or a network error code. If this |
- // function returns ERR_IO_PENDING, the completion callback will be called |
- // on the current thread when the operation completes, and a reference to |
- // |buf| will be retained until the callback is called. Note that as long as |
- // the function does not complete immediately, the callback will always be |
- // invoked, even after Close has been called; in other words, the caller may |
- // close this entry without having to wait for all the callbacks, and still |
- // rely on the cleanup performed from the callback code. |
- // If truncate is true, this call will truncate the stored data at the end of |
- // what we are writing here. |
- virtual int WriteData(int index, int offset, IOBuffer* buf, int buf_len, |
- const CompletionCallback& callback, |
- bool truncate) = 0; |
- |
- // Sparse entries support: |
- // |
- // A Backend implementation can support sparse entries, so the cache keeps |
- // track of which parts of the entry have been written before. The backend |
- // will never return data that was not written previously, so reading from |
- // such region will return 0 bytes read (or actually the number of bytes read |
- // before reaching that region). |
- // |
- // There are only two streams for sparse entries: a regular control stream |
- // (index 0) that must be accessed through the regular API (ReadData and |
- // WriteData), and one sparse stream that must me accessed through the sparse- |
- // aware API that follows. Calling a non-sparse aware method with an index |
- // argument other than 0 is a mistake that results in implementation specific |
- // behavior. Using a sparse-aware method with an entry that was not stored |
- // using the same API, or with a backend that doesn't support sparse entries |
- // will return ERR_CACHE_OPERATION_NOT_SUPPORTED. |
- // |
- // The storage granularity of the implementation should be at least 1 KB. In |
- // other words, storing less than 1 KB may result in an implementation |
- // dropping the data completely, and writing at offsets not aligned with 1 KB, |
- // or with lengths not a multiple of 1 KB may result in the first or last part |
- // of the data being discarded. However, two consecutive writes should not |
- // result in a hole in between the two parts as long as they are sequential |
- // (the second one starts where the first one ended), and there is no other |
- // write between them. |
- // |
- // The Backend implementation is free to evict any range from the cache at any |
- // moment, so in practice, the previously stated granularity of 1 KB is not |
- // as bad as it sounds. |
- // |
- // The sparse methods don't support multiple simultaneous IO operations to the |
- // same physical entry, so in practice a single object should be instantiated |
- // for a given key at any given time. Once an operation has been issued, the |
- // caller should wait until it completes before starting another one. This |
- // requirement includes the case when an entry is closed while some operation |
- // is in progress and another object is instantiated; any IO operation will |
- // fail while the previous operation is still in-flight. In order to deal with |
- // this requirement, the caller could either wait until the operation |
- // completes before closing the entry, or call CancelSparseIO() before closing |
- // the entry, and call ReadyForSparseIO() on the new entry and wait for the |
- // callback before issuing new operations. |
- |
- // Behaves like ReadData() except that this method is used to access sparse |
- // entries. |
- virtual int ReadSparseData(int64 offset, IOBuffer* buf, int buf_len, |
- const CompletionCallback& callback) = 0; |
- |
- // Behaves like WriteData() except that this method is used to access sparse |
- // entries. |truncate| is not part of this interface because a sparse entry |
- // is not expected to be reused with new data. To delete the old data and |
- // start again, or to reduce the total size of the stream data (which implies |
- // that the content has changed), the whole entry should be doomed and |
- // re-created. |
- virtual int WriteSparseData(int64 offset, IOBuffer* buf, int buf_len, |
- const CompletionCallback& callback) = 0; |
- |
- // Returns information about the currently stored portion of a sparse entry. |
- // |offset| and |len| describe a particular range that should be scanned to |
- // find out if it is stored or not. |start| will contain the offset of the |
- // first byte that is stored within this range, and the return value is the |
- // minimum number of consecutive stored bytes. Note that it is possible that |
- // this entry has stored more than the returned value. This method returns a |
- // net error code whenever the request cannot be completed successfully. If |
- // this method returns ERR_IO_PENDING, the |callback| will be invoked when the |
- // operation completes, and |start| must remain valid until that point. |
- virtual int GetAvailableRange(int64 offset, int len, int64* start, |
- const CompletionCallback& callback) = 0; |
- |
- // Returns true if this entry could be a sparse entry or false otherwise. This |
- // is a quick test that may return true even if the entry is not really |
- // sparse. This method doesn't modify the state of this entry (it will not |
- // create sparse tracking data). GetAvailableRange or ReadSparseData can be |
- // used to perform a definitive test of whether an existing entry is sparse or |
- // not, but that method may modify the current state of the entry (making it |
- // sparse, for instance). The purpose of this method is to test an existing |
- // entry, but without generating actual IO to perform a thorough check. |
- virtual bool CouldBeSparse() const = 0; |
- |
- // Cancels any pending sparse IO operation (if any). The completion callback |
- // of the operation in question will still be called when the operation |
- // finishes, but the operation will finish sooner when this method is used. |
- virtual void CancelSparseIO() = 0; |
- |
- // Returns OK if this entry can be used immediately. If that is not the |
- // case, returns ERR_IO_PENDING and invokes the provided callback when this |
- // entry is ready to use. This method always returns OK for non-sparse |
- // entries, and returns ERR_IO_PENDING when a previous operation was cancelled |
- // (by calling CancelSparseIO), but the cache is still busy with it. If there |
- // is a pending operation that has not been cancelled, this method will return |
- // OK although another IO operation cannot be issued at this time; in this |
- // case the caller should just wait for the regular callback to be invoked |
- // instead of using this method to provide another callback. |
- // |
- // Note that CancelSparseIO may have been called on another instance of this |
- // object that refers to the same physical disk entry. |
- // Note: This method is deprecated. |
- virtual int ReadyForSparseIO(const CompletionCallback& callback) = 0; |
- |
- protected: |
- virtual ~Entry() {} |
-}; |
- |
-struct EntryDeleter { |
- void operator()(Entry* entry) { |
- // Note that |entry| is ref-counted. |
- entry->Close(); |
- } |
-}; |
- |
-// Automatically closes an entry when it goes out of scope. |
-typedef scoped_ptr<Entry, EntryDeleter> ScopedEntryPtr; |
- |
-} // namespace disk_cache |
- |
-#endif // NET_DISK_CACHE_DISK_CACHE_H_ |