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comparison: xpcom/glue/FileUtils.h

xpcom/glue/FileUtils.h

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1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
2 * This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5
6 #ifndef mozilla_FileUtils_h
7 #define mozilla_FileUtils_h
8
9 #include "nscore.h" // nullptr
10
11 #if defined(XP_UNIX)
12 # include <unistd.h>
13 #elif defined(XP_WIN)
14 # include <io.h>
15 #endif
16 #include "prio.h"
17
18 #include "mozilla/Scoped.h"
19 #include "nsIFile.h"
20 #include <errno.h>
21 #include <limits.h>
22
23 namespace mozilla {
24
25 #if defined(XP_WIN)
26 typedef void* filedesc_t;
27 typedef const wchar_t* pathstr_t;
28 #else
29 typedef int filedesc_t;
30 typedef const char* pathstr_t;
31 #endif
32
33 /**
34 * ScopedCloseFD is a RAII wrapper for POSIX file descriptors
35 *
36 * Instances |close()| their fds when they go out of scope.
37 */
38 struct ScopedCloseFDTraits
39 {
40 typedef int type;
41 static type empty() { return -1; }
42 static void release(type fd) {
43 if (fd != -1) {
44 while ((close(fd) == -1) && (errno == EINTR)) {
45 ;
46 }
47 }
48 }
49 };
50 typedef Scoped<ScopedCloseFDTraits> ScopedClose;
51
52 #if !defined(XPCOM_GLUE)
53
54 /**
55 * AutoFDClose is a RAII wrapper for PRFileDesc.
56 *
57 * Instances |PR_Close| their fds when they go out of scope.
58 **/
59 struct ScopedClosePRFDTraits
60 {
61 typedef PRFileDesc* type;
62 static type empty() { return nullptr; }
63 static void release(type fd) {
64 if (fd != nullptr) {
65 PR_Close(fd);
66 }
67 }
68 };
69 typedef Scoped<ScopedClosePRFDTraits> AutoFDClose;
70
71 /* RAII wrapper for FILE descriptors */
72 struct ScopedCloseFileTraits
73 {
74 typedef FILE *type;
75 static type empty() { return nullptr; }
76 static void release(type f) {
77 if (f) {
78 fclose(f);
79 }
80 }
81 };
82 typedef Scoped<ScopedCloseFileTraits> ScopedCloseFile;
83
84 /**
85 * Fallocate efficiently and continuously allocates files via fallocate-type APIs.
86 * This is useful for avoiding fragmentation.
87 * On sucess the file be padded with zeros to grow to aLength.
88 *
89 * @param aFD file descriptor.
90 * @param aLength length of file to grow to.
91 * @return true on success.
92 */
93 NS_COM_GLUE bool fallocate(PRFileDesc *aFD, int64_t aLength);
94
95 /**
96 * Use readahead to preload shared libraries into the file cache before loading.
97 * WARNING: This function should not be used without a telemetry field trial
98 * demonstrating a clear performance improvement!
99 *
100 * @param aFile nsIFile representing path to shared library
101 */
102 NS_COM_GLUE void ReadAheadLib(nsIFile* aFile);
103
104 /**
105 * Use readahead to preload a file into the file cache before reading.
106 * WARNING: This function should not be used without a telemetry field trial
107 * demonstrating a clear performance improvement!
108 *
109 * @param aFile nsIFile representing path to shared library
110 * @param aOffset Offset into the file to begin preloading
111 * @param aCount Number of bytes to preload (SIZE_MAX implies file size)
112 * @param aOutFd Pointer to file descriptor. If specified, ReadAheadFile will
113 * return its internal, opened file descriptor instead of closing it.
114 */
115 NS_COM_GLUE void ReadAheadFile(nsIFile* aFile, const size_t aOffset = 0,
116 const size_t aCount = SIZE_MAX,
117 filedesc_t* aOutFd = nullptr);
118
119 #endif // !defined(XPCOM_GLUE)
120
121 /**
122 * Use readahead to preload shared libraries into the file cache before loading.
123 * WARNING: This function should not be used without a telemetry field trial
124 * demonstrating a clear performance improvement!
125 *
126 * @param aFilePath path to shared library
127 */
128 NS_COM_GLUE void ReadAheadLib(pathstr_t aFilePath);
129
130 /**
131 * Use readahead to preload a file into the file cache before loading.
132 * WARNING: This function should not be used without a telemetry field trial
133 * demonstrating a clear performance improvement!
134 *
135 * @param aFilePath path to shared library
136 * @param aOffset Offset into the file to begin preloading
137 * @param aCount Number of bytes to preload (SIZE_MAX implies file size)
138 * @param aOutFd Pointer to file descriptor. If specified, ReadAheadFile will
139 * return its internal, opened file descriptor instead of closing it.
140 */
141 NS_COM_GLUE void ReadAheadFile(pathstr_t aFilePath, const size_t aOffset = 0,
142 const size_t aCount = SIZE_MAX,
143 filedesc_t* aOutFd = nullptr);
144
145 /**
146 * Use readahead to preload a file into the file cache before reading.
147 * When this function exits, the file pointer is guaranteed to be in the same
148 * position it was in before this function was called.
149 * WARNING: This function should not be used without a telemetry field trial
150 * demonstrating a clear performance improvement!
151 *
152 * @param aFd file descriptor opened for read access
153 * (on Windows, file must be opened with FILE_FLAG_SEQUENTIAL_SCAN)
154 * @param aOffset Offset into the file to begin preloading
155 * @param aCount Number of bytes to preload (SIZE_MAX implies file size)
156 */
157 NS_COM_GLUE void ReadAhead(filedesc_t aFd, const size_t aOffset = 0,
158 const size_t aCount = SIZE_MAX);
159
160
161 /* Define ReadSysFile() only on GONK to avoid unnecessary lubxul bloat.
162 Also define it in debug builds, so that unit tests for it can be written
163 and run in non-GONK builds. */
164 #if (defined(MOZ_WIDGET_GONK) || defined(DEBUG)) && defined(XP_UNIX)
165
166 #ifndef ReadSysFile_PRESENT
167 #define ReadSysFile_PRESENT
168 #endif /* ReadSysFile_PRESENT */
169
170 #define MOZ_TEMP_FAILURE_RETRY(exp) (__extension__({ \
171 typeof (exp) _rc; \
172 do { \
173 _rc = (exp); \
174 } while (_rc == -1 && errno == EINTR); \
175 _rc; \
176 }))
177
178 /**
179 * Read the contents of a file.
180 * This function is intended for reading a single-lined text files from
181 * /sys/. If the file ends with a newline ('\n') then it will be discarded.
182 * The output buffer will always be '\0'-terminated on successful completion.
183 * If aBufSize == 0, then this function will return true if the file exists
184 * and is readable (it will not attempt to read anything from it).
185 * On failure the contents of aBuf after this call will be undefined and the
186 * value of the global variable errno will be set accordingly.
187 * @return true on success, notice that less than requested bytes could have
188 * been read if the file was smaller
189 */
190 bool
191 ReadSysFile(
192 const char* aFilename,
193 char* aBuf,
194 size_t aBufSize);
195
196 /**
197 * Parse the contents of a file, assuming it contains a decimal integer.
198 * @return true on success
199 */
200 bool
201 ReadSysFile(
202 const char* aFilename,
203 int* aVal);
204
205 /**
206 * Parse the contents of a file, assuming it contains a boolean value
207 * (either 0 or 1).
208 * @return true on success
209 */
210 bool
211 ReadSysFile(
212 const char* aFilename,
213 bool* aVal);
214
215 #endif /* (MOZ_WIDGET_GONK || DEBUG) && XP_UNIX */
216
217 } // namespace mozilla
218 #endif

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