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1 // Copyright (c) 2011, Google Inc.
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are
6 // met:
7 //
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9 // notice, this list of conditions and the following disclaimer.
10 //     * Redistributions in binary form must reproduce the above
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12 // in the documentation and/or other materials provided with the
13 // distribution.
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16 // this software without specific prior written permission.
17 //
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 
30 // memory_mapped_file.h: Define the google_breakpad::MemoryMappedFile
31 // class, which maps a file into memory for read-only access.
32 
33 #ifndef COMMON_LINUX_MEMORY_MAPPED_FILE_H_
34 #define COMMON_LINUX_MEMORY_MAPPED_FILE_H_
35 
36 #include <stddef.h>
37 #include "common/basictypes.h"
38 #include "common/memory_range.h"
39 
40 namespace google_breakpad {
41 
42 // A utility class for mapping a file into memory for read-only access of
43 // the file content. Its implementation avoids calling into libc functions
44 // by directly making system calls for open, close, mmap, and munmap.
45 class MemoryMappedFile {
46  public:
47   MemoryMappedFile();
48 
49   // Constructor that calls Map() to map a file at |path| into memory.
50   // If Map() fails, the object behaves as if it is default constructed.
51   MemoryMappedFile(const char* path, size_t offset);
52 
53   ~MemoryMappedFile();
54 
55   // Maps a file at |path| into memory, which can then be accessed via
56   // content() as a MemoryRange object or via data(), and returns true on
57   // success. Mapping an empty file will succeed but with data() and size()
58   // returning NULL and 0, respectively. An existing mapping is unmapped
59   // before a new mapping is created.
60   bool Map(const char* path, size_t offset);
61 
62   // Unmaps the memory for the mapped file. It's a no-op if no file is
63   // mapped.
64   void Unmap();
65 
66   // Returns a MemoryRange object that covers the memory for the mapped
67   // file. The MemoryRange object is empty if no file is mapped.
content()68   const MemoryRange& content() const { return content_; }
69 
70   // Returns a pointer to the beginning of the memory for the mapped file.
71   // or NULL if no file is mapped or the mapped file is empty.
data()72   const void* data() const { return content_.data(); }
73 
74   // Returns the size in bytes of the mapped file, or zero if no file
75   // is mapped.
size()76   size_t size() const { return content_.length(); }
77 
78  private:
79   // Mapped file content as a MemoryRange object.
80   MemoryRange content_;
81 
82   DISALLOW_COPY_AND_ASSIGN(MemoryMappedFile);
83 };
84 
85 }  // namespace google_breakpad
86 
87 #endif  // COMMON_LINUX_MEMORY_MAPPED_FILE_H_
88