1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 // See net/disk_cache/disk_cache.h for the public interface of the cache.
6 
7 #ifndef NET_DISK_CACHE_BLOCKFILE_MAPPED_FILE_H_
8 #define NET_DISK_CACHE_BLOCKFILE_MAPPED_FILE_H_
9 
10 #include <stddef.h>
11 
12 #include "base/macros.h"
13 #include "net/base/net_export.h"
14 #include "net/disk_cache/blockfile/file.h"
15 #include "net/disk_cache/blockfile/file_block.h"
16 #include "net/net_buildflags.h"
17 
18 namespace base {
19 class FilePath;
20 }
21 
22 namespace disk_cache {
23 
24 // This class implements a memory mapped file used to access block-files. The
25 // idea is that the header and bitmap will be memory mapped all the time, and
26 // the actual data for the blocks will be access asynchronously (most of the
27 // time).
28 class NET_EXPORT_PRIVATE MappedFile : public File {
29  public:
MappedFile()30   MappedFile() : File(true), init_(false) {}
31 
32   // Performs object initialization. name is the file to use, and size is the
33   // amount of data to memory map from the file. If size is 0, the whole file
34   // will be mapped in memory.
35   void* Init(const base::FilePath& name, size_t size);
36 
buffer()37   void* buffer() const {
38     return buffer_;
39   }
40 
41   // Loads or stores a given block from the backing file (synchronously).
42   bool Load(const FileBlock* block);
43   bool Store(const FileBlock* block);
44 
45   // Flush the memory-mapped section to disk (synchronously).
46   void Flush();
47 
48   // Heats up the file system cache and make sure the file is fully
49   // readable (synchronously).
50   bool Preload();
51 
52  private:
53   ~MappedFile() override;
54 
55   bool init_;
56 #if defined(OS_WIN)
57   HANDLE section_;
58 #endif
59   void* buffer_;  // Address of the memory mapped buffer.
60   size_t view_size_;  // Size of the memory pointed by buffer_.
61 #if BUILDFLAG(POSIX_AVOID_MMAP)
62   void* snapshot_;  // Copy of the buffer taken when it was last flushed.
63 #endif
64 
65   DISALLOW_COPY_AND_ASSIGN(MappedFile);
66 };
67 
68 // Helper class for calling Flush() on exit from the current scope.
69 class ScopedFlush {
70  public:
ScopedFlush(MappedFile * file)71   explicit ScopedFlush(MappedFile* file) : file_(file) {}
~ScopedFlush()72   ~ScopedFlush() {
73     file_->Flush();
74   }
75  private:
76   MappedFile* file_;
77 };
78 
79 }  // namespace disk_cache
80 
81 #endif  // NET_DISK_CACHE_BLOCKFILE_MAPPED_FILE_H_
82