Disk cache: Reference CL for the implementation of file format version 3.

net/disk_cache/v3/sparse_control_v3.h

+// 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.
+
+#ifndef NET_DISK_CACHE_V3_SPARSE_CONTROL_V3_H_
+#define NET_DISK_CACHE_V3_SPARSE_CONTROL_V3_H_
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "net/base/completion_callback.h"
+#include "net/disk_cache/bitmap.h"
+#include "net/disk_cache/disk_format_base.h"
+
+namespace net {
+class IOBuffer;
+class DrainableIOBuffer;
+}
+
+namespace disk_cache {
+
+class Entry;
+class EntryImplV3;
+
+// This class provides support for the sparse capabilities of the disk cache.
+// Basically, sparse IO is directed from EntryImpl to this class, and we split
+// the operation into multiple small pieces, sending each one to the
+// appropriate entry. An instance of this class is asociated with each entry
+// used directly for sparse operations (the entry passed in to the constructor).
+class SparseControlV3 {
+ public:
+  typedef net::CompletionCallback CompletionCallback;
+
+  // The operation to perform.
+  enum SparseOperation {
+    kNoOperation,
+    kReadOperation,
+    kWriteOperation,
+    kGetRangeOperation
+  };
+
+  explicit SparseControlV3(EntryImplV3* entry);
+  ~SparseControlV3();
+
+  void Close();
+
+  // Performs a quick test to see if the entry is sparse or not, without
+  // generating disk IO (so the answer provided is only a best effort).
+  bool CouldBeSparse() const;
+
+  // Performs an actual sparse read or write operation for this entry. |op| is
+  // the operation to perform, |offset| is the desired sparse offset, |buf| and
+  // |buf_len| specify the actual data to use and |callback| is the callback
+  // to use for asynchronous operations. See the description of the Read /
+  // WriteSparseData for details about the arguments. The return value is the
+  // number of bytes read or written, or a net error code.
+  int StartIO(SparseOperation op, int64 offset, net::IOBuffer* buf,
+              int buf_len, const CompletionCallback& callback);
+
+  // Implements Entry::GetAvailableRange().
+  int GetAvailableRange(int64 offset, int len, int64* start,
+                        const CompletionCallback& callback);
+
+  // Cancels the current sparse operation (if any).
+  void CancelIO();
+
+  // Returns OK if the entry can be used for new IO or ERR_IO_PENDING if we are
+  // busy. If the entry is busy, we'll invoke the callback when we are ready
+  // again. See disk_cache::Entry::ReadyToUse() for more info.
+  int ReadyToUse(const CompletionCallback& completion_callback);
+
+  // Deletes the children entries of |entry|.
+  static void DeleteChildren(EntryImplV3* entry);
+
+ private:
+  enum State {
+    STATE_NONE,
+    STATE_INIT,
+    STATE_CREATE_SPARSE_ENTRY,
+    STATE_CREATE_SPARSE_ENTRY_COMPLETE,
+    STATE_OPEN_SPARSE_ENTRY,
+    STATE_OPEN_SPARSE_ENTRY_COMPLETE,
+    STATE_READ_BITMAP_COMPLETE,
+    STATE_GET_CHILD_KEY,
+    STATE_OPEN_CHILD,
+    STATE_OPEN_CHILD_COMPLETE,
+    STATE_READ_SIGNATURE_COMPLETE,
+    STATE_CLOSE_CHILD,
+    STATE_CLOSE_CHILD_COMPLETE,
+    STATE_CREATE_CHILD,
+    STATE_CREATE_CHILD_COMPLETE,
+    STATE_WRITE_BITMAP,
+    STATE_WRITE_BITMAP_COMPLETE,
+    STATE_DO_CHILD_IO,
+    STATE_DO_CHILD_IO_COMPLETE,
+    STATE_CLOSE    
+  };
+
+  int DoLoop(int result);
+  int DoInit();
+  int DoCreateSparseEntry();
+  int DoCreateSparseEntryComplete(int result);
+  int DoOpenSparseEntry(int data_len);
+  int DoOpenSparseEntryComplete(int result);
+  int DoReadBitmapComplete(int result);
+  int DoGetChildKey();
+  int DoOpenChild();
+  int DoOpenChildComplete(int result);
+  int DoReadSignatureComplete(int result);
+  int DoCloseChild();
+  int DoCloseChildComplete(int result);
+  int DoCreateChild();
+  int DoCreateChildComplete(int result);
+  int DoWriteBitmap();
+  int DoWriteBitmapComplete(int result);
+  int DoChildIO();
+  int DoChildIOComplete(int result);
+  int DoClose();
+
+  std::string GenerateChildKey();
+
+  // Deletes the current child and continues the current operation (open).
+  int KillChildAndContinue();
+
+  // Returns true if the required child is tracked by the parent entry, i.e. it
+  // was already created.
+  bool ChildPresent();
+
+  // Sets the bit for the current child to the provided |value|. In other words,
+  // starts or stops tracking this child.
+  void SetChildBit(bool value);
+
+  // Verify that the range to be accessed for the current child is appropriate.
+  // Returns false if an error is detected or there is no need to perform the
+  // current IO operation (for instance if the required range is not stored by
+  // the child).
+  bool VerifyRange();
+
+  // Updates the contents bitmap for the current range, based on the result of
+  // the current operation.
+  void UpdateRange(int result);
+
+  // Returns the number of bytes stored at |block_index|, if its allocation-bit
+  // is off (because it is not completely filled).
+  int PartialBlockLength(int block_index) const;
+
+  // Initializes the sparse info for the current child.
+  void InitChildData();
+
+  // Performs the required work for GetAvailableRange for one child.
+  int GetAvailableRangeImpl();
+
+  void LogChildOperationStart();
+  void LogChildOperationEnd(int result);
+  int LogCompletion(int result);
+
+  // Reports to the user that we are done.
+  void HandleResult(int result);
+  void HanldeAbortCallbacks();
+
+  // Invoked by the callback of asynchronous operations.
+  void OnIOComplete(int result);
+
+  EntryImplV3* entry_;  // The sparse entry.
+  Entry* child_;  // The current child entry.
+  SparseOperation operation_;
+  State next_state_;
+  bool init_;
+  bool range_found_;  // True if GetAvailableRange found something.
+  bool abort_;  // True if we should abort the current operation ASAP.
+  bool valid_;
+  bool closing_;
+
+  SparseHeader sparse_header_;  // Data about the children of entry_.
+  Bitmap children_map_;  // The actual bitmap of children.
+  SparseData child_data_;  // Parent and allocation map of child_.
+  Bitmap child_map_;  // The allocation map as a bitmap.
+
+  CompletionCallback user_callback_;
+  CompletionCallback callback_;
+  std::vector<CompletionCallback> abort_callbacks_;
+  int64 offset_;  // Current sparse offset.
+  scoped_refptr<net::DrainableIOBuffer> user_buf_;
+  scoped_refptr<net::IOBuffer> buf_;
+  std::string key_;
+  int buf_len_;  // Bytes to read or write.
+  int child_offset_;  // Offset to use for the current child.
+  int child_len_;  // Bytes to read or write for this child.
+  int result_;
+  int64* range_start_;
+
+  DISALLOW_COPY_AND_ASSIGN(SparseControlV3);
+};
+
+}  // namespace disk_cache
+
+#endif  // NET_DISK_CACHE_V3_SPARSE_CONTROL_V3_H_