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 <stddef.h> 9 #include <stdint.h> 10 11 #include "base/base_export.h" 12 #include "base/files/file.h" 13 #include "base/macros.h" 14 #include "build/build_config.h" 15 16 #if defined(OS_WIN) 17 #include <windows.h> 18 #endif 19 20 namespace base { 21 22 class FilePath; 23 24 class BASE_EXPORT MemoryMappedFile { 25 public: 26 // The default constructor sets all members to invalid/null values. 27 MemoryMappedFile(); 28 ~MemoryMappedFile(); 29 30 // Used to hold information about a region [offset + size] of a file. 31 struct BASE_EXPORT Region { 32 static const Region kWholeFile; 33 34 bool operator==(const Region& other) const; 35 bool operator!=(const Region& other) const; 36 37 // Start of the region (measured in bytes from the beginning of the file). 38 int64_t offset; 39 40 // Length of the region in bytes. 41 int64_t size; 42 }; 43 44 // Opens an existing file and maps it into memory. Access is restricted to 45 // read only. If this object already points to a valid memory mapped file 46 // then this method will fail and return false. If it cannot open the file, 47 // the file does not exist, or the memory mapping fails, it will return false. 48 // Later we may want to allow the user to specify access. 49 bool Initialize(const FilePath& file_name); 50 51 // As above, but works with an already-opened file. MemoryMappedFile takes 52 // ownership of |file| and closes it when done. 53 bool Initialize(File file); 54 55 // As above, but works with a region of an already-opened file. 56 bool Initialize(File file, const Region& region); 57 58 #if defined(OS_WIN) 59 // Opens an existing file and maps it as an image section. Please refer to 60 // the Initialize function above for additional information. 61 bool InitializeAsImageSection(const FilePath& file_name); 62 #endif // OS_WIN 63 data()64 const uint8_t* data() const { return data_; } length()65 size_t length() const { return length_; } 66 67 // Is file_ a valid file handle that points to an open, memory mapped file? 68 bool IsValid() const; 69 70 private: 71 // Given the arbitrarily aligned memory region [start, size], returns the 72 // boundaries of the region aligned to the granularity specified by the OS, 73 // (a page on Linux, ~32k on Windows) as follows: 74 // - |aligned_start| is page aligned and <= |start|. 75 // - |aligned_size| is a multiple of the VM granularity and >= |size|. 76 // - |offset| is the displacement of |start| w.r.t |aligned_start|. 77 static void CalculateVMAlignedBoundaries(int64_t start, 78 int64_t size, 79 int64_t* aligned_start, 80 int64_t* aligned_size, 81 int32_t* offset); 82 83 // Map the file to memory, set data_ to that memory address. Return true on 84 // success, false on any kind of failure. This is a helper for Initialize(). 85 bool MapFileRegionToMemory(const Region& region); 86 87 // Closes all open handles. 88 void CloseHandles(); 89 90 File file_; 91 uint8_t* data_; 92 size_t length_; 93 94 #if defined(OS_WIN) 95 win::ScopedHandle file_mapping_; 96 bool image_; // Map as an image. 97 #endif 98 99 DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile); 100 }; 101 102 } // namespace base 103 104 #endif // BASE_FILES_MEMORY_MAPPED_FILE_H_ 105