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      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_MAPPED_FILE_H_
      8 #define NET_DISK_CACHE_MAPPED_FILE_H_
      9 
     10 #include "net/base/net_export.h"
     11 #include "net/disk_cache/file.h"
     12 #include "net/disk_cache/file_block.h"
     13 
     14 namespace base {
     15 class FilePath;
     16 }
     17 
     18 namespace disk_cache {
     19 
     20 // This class implements a memory mapped file used to access block-files. The
     21 // idea is that the header and bitmap will be memory mapped all the time, and
     22 // the actual data for the blocks will be access asynchronously (most of the
     23 // time).
     24 class NET_EXPORT_PRIVATE MappedFile : public File {
     25  public:
     26   MappedFile() : File(true), init_(false) {}
     27 
     28   // Performs object initialization. name is the file to use, and size is the
     29   // amount of data to memory map from the file. If size is 0, the whole file
     30   // will be mapped in memory.
     31   void* Init(const base::FilePath& name, size_t size);
     32 
     33   void* buffer() const {
     34     return buffer_;
     35   }
     36 
     37   // Loads or stores a given block from the backing file (synchronously).
     38   bool Load(const FileBlock* block);
     39   bool Store(const FileBlock* block);
     40 
     41   // Asynchronous versions of Load/Store, following the semantics of File::Read
     42   // and File::Write.
     43   bool Load(const FileBlock* block, FileIOCallback* callback, bool* completed);
     44   bool Store(const FileBlock* block, FileIOCallback* callback, bool* completed);
     45 
     46   // Flush the memory-mapped section to disk (synchronously).
     47   void Flush();
     48 
     49  private:
     50   virtual ~MappedFile();
     51 
     52   bool init_;
     53 #if defined(OS_WIN)
     54   HANDLE section_;
     55 #endif
     56   void* buffer_;  // Address of the memory mapped buffer.
     57   size_t view_size_;  // Size of the memory pointed by buffer_.
     58 #if defined(POSIX_AVOID_MMAP)
     59   void* snapshot_;  // Copy of the buffer taken when it was last flushed.
     60 #endif
     61 
     62   DISALLOW_COPY_AND_ASSIGN(MappedFile);
     63 };
     64 
     65 // Helper class for calling Flush() on exit from the current scope.
     66 class ScopedFlush {
     67  public:
     68   explicit ScopedFlush(MappedFile* file) : file_(file) {}
     69   ~ScopedFlush() {
     70     file_->Flush();
     71   }
     72  private:
     73   MappedFile* file_;
     74 };
     75 
     76 }  // namespace disk_cache
     77 
     78 #endif  // NET_DISK_CACHE_MAPPED_FILE_H_
     79