OpenShot Library | libopenshot-audio 0.2.0
juce_MemoryMappedFile.h
1
2/** @weakgroup juce_core-files
3 * @{
4 */
5/*
6 ==============================================================================
7
8 This file is part of the JUCE library.
9 Copyright (c) 2017 - ROLI Ltd.
10
11 JUCE is an open source library subject to commercial or open-source
12 licensing.
13
14 The code included in this file is provided under the terms of the ISC license
15 http://www.isc.org/downloads/software-support-policy/isc-license. Permission
16 To use, copy, modify, and/or distribute this software for any purpose with or
17 without fee is hereby granted provided that the above copyright notice and
18 this permission notice appear in all copies.
19
20 JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
21 EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
22 DISCLAIMED.
23
24 ==============================================================================
25*/
26
27namespace juce
28{
29
30//==============================================================================
31/**
32 Maps a file into virtual memory for easy reading and/or writing.
33
34 @tags{Core}
35*/
37{
38public:
39 /** The read/write flags used when opening a memory mapped file. */
41 {
42 readOnly, /**< Indicates that the memory can only be read. */
43 readWrite /**< Indicates that the memory can be read and written to - changes that are
44 made will be flushed back to disk at the whim of the OS. */
45 };
46
47 /** Opens a file and maps it to an area of virtual memory.
48
49 The file should already exist, and should already be the size that you want to work with
50 when you call this. If the file is resized after being opened, the behaviour is undefined.
51
52 If the file exists and the operation succeeds, the getData() and getSize() methods will
53 return the location and size of the data that can be read or written. Note that the entire
54 file is not read into memory immediately - the OS simply creates a virtual mapping, which
55 will lazily pull the data into memory when blocks are accessed.
56
57 If the file can't be opened for some reason, the getData() method will return a null pointer.
58
59 If exclusive is false then other apps can also open the same memory mapped file and use this
60 mapping as an effective way of communicating. If exclusive is true then the mapped file will
61 be opened exclusively - preventing other apps to access the file which may improve the
62 performance of accessing the file.
63 */
64 MemoryMappedFile (const File& file, AccessMode mode, bool exclusive = false);
65
66 /** Opens a section of a file and maps it to an area of virtual memory.
67
68 The file should already exist, and should already be the size that you want to work with
69 when you call this. If the file is resized after being opened, the behaviour is undefined.
70
71 If the file exists and the operation succeeds, the getData() and getSize() methods will
72 return the location and size of the data that can be read or written. Note that the entire
73 file is not read into memory immediately - the OS simply creates a virtual mapping, which
74 will lazily pull the data into memory when blocks are accessed.
75
76 If the file can't be opened for some reason, the getData() method will return a null pointer.
77
78 NOTE: The start of the actual range used may be rounded-down to a multiple of the OS's page-size,
79 so do not assume that the mapped memory will begin at exactly the position you requested - always
80 use getRange() to check the actual range that is being used.
81 */
82 MemoryMappedFile (const File& file,
84 AccessMode mode,
85 bool exclusive = false);
86
87 /** Destructor. */
89
90 /** Returns the address at which this file has been mapped, or a null pointer if
91 the file couldn't be successfully mapped.
92 */
93 void* getData() const noexcept { return address; }
94
95 /** Returns the number of bytes of data that are available for reading or writing.
96 This will normally be the size of the file.
97 */
98 size_t getSize() const noexcept { return (size_t) range.getLength(); }
99
100 /** Returns the section of the file at which the mapped memory represents. */
102
103private:
104 //==============================================================================
105 void* address = nullptr;
106 Range<int64> range;
107
108 #if JUCE_WINDOWS
109 void* fileHandle = nullptr;
110 #else
111 int fileHandle = 0;
112 #endif
113
114 void openInternal (const File&, AccessMode, bool);
115
116 JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (MemoryMappedFile)
117};
118
119} // namespace juce
120
121/** @}*/
Holds a resizable array of primitive or copy-by-value objects.
Definition juce_Array.h:60
Represents a local file or directory.
Definition juce_File.h:45
Maps a file into virtual memory for easy reading and/or writing.
Range< int64 > getRange() const noexcept
Returns the section of the file at which the mapped memory represents.
~MemoryMappedFile()
Destructor.
void * getData() const noexcept
Returns the address at which this file has been mapped, or a null pointer if the file couldn't be suc...
size_t getSize() const noexcept
Returns the number of bytes of data that are available for reading or writing.
AccessMode
The read/write flags used when opening a memory mapped file.
@ readOnly
Indicates that the memory can only be read.
#define JUCE_API
This macro is added to all JUCE public class declarations.