1 // Copyright 2013 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 #ifndef BASE_FILES_MEMORY_MAPPED_FILE_H_ 6 #define BASE_FILES_MEMORY_MAPPED_FILE_H_ 7 8 #include "base/base_export.h" 9 #include "base/basictypes.h" 10 #include "base/files/file.h" 11 #include "build/build_config.h" 12 13 #if defined(OS_WIN) 14 #include <windows.h> 15 #endif 16 17 namespace base { 18 19 class FilePath; 20 21 class BASE_EXPORT MemoryMappedFile { 22 public: 23 // The default constructor sets all members to invalid/null values. 24 MemoryMappedFile(); 25 ~MemoryMappedFile(); 26 27 // Used to hold information about a region [offset + size] of a file. 28 struct BASE_EXPORT Region { 29 static const Region kWholeFile; 30 31 Region(int64 offset, int64 size); 32 33 bool operator==(const Region& other) const; 34 35 // Start of the region (measured in bytes from the beginning of the file). 36 int64 offset; 37 38 // Length of the region in bytes. 39 int64 size; 40 41 private: 42 // This ctor is used only by kWholeFile, to construct a zero-sized Region 43 // (which is forbidden by the public ctor) and uniquely identify kWholeFile. 44 Region(base::LinkerInitialized); 45 }; 46 47 // Opens an existing file and maps it into memory. Access is restricted to 48 // read only. If this object already points to a valid memory mapped file 49 // then this method will fail and return false. If it cannot open the file, 50 // the file does not exist, or the memory mapping fails, it will return false. 51 // Later we may want to allow the user to specify access. 52 bool Initialize(const FilePath& file_name); 53 54 // As above, but works with an already-opened file. MemoryMappedFile takes 55 // ownership of |file| and closes it when done. 56 bool Initialize(File file); 57 58 // As above, but works with a region of an already-opened file. 59 bool Initialize(File file, const Region& region); 60 61 #if defined(OS_WIN) 62 // Opens an existing file and maps it as an image section. Please refer to 63 // the Initialize function above for additional information. 64 bool InitializeAsImageSection(const FilePath& file_name); 65 #endif // OS_WIN 66 data()67 const uint8* data() const { return data_; } length()68 size_t length() const { return length_; } 69 70 // Is file_ a valid file handle that points to an open, memory mapped file? 71 bool IsValid() const; 72 73 private: 74 // Given the arbitrarily aligned memory region [start, size], returns the 75 // boundaries of the region aligned to the granularity specified by the OS, 76 // (a page on Linux, ~32k on Windows) as follows: 77 // - |aligned_start| is page aligned and <= |start|. 78 // - |aligned_size| is a multiple of the VM granularity and >= |size|. 79 // - |offset| is the displacement of |start| w.r.t |aligned_start|. 80 static void CalculateVMAlignedBoundaries(int64 start, 81 int64 size, 82 int64* aligned_start, 83 int64* aligned_size, 84 int32* offset); 85 86 // Map the file to memory, set data_ to that memory address. Return true on 87 // success, false on any kind of failure. This is a helper for Initialize(). 88 bool MapFileRegionToMemory(const Region& region); 89 90 // Closes all open handles. 91 void CloseHandles(); 92 93 File file_; 94 uint8* data_; 95 size_t length_; 96 97 #if defined(OS_WIN) 98 win::ScopedHandle file_mapping_; 99 bool image_; // Map as an image. 100 #endif 101 102 DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile); 103 }; 104 105 } // namespace base 106 107 #endif // BASE_FILES_MEMORY_MAPPED_FILE_H_ 108