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1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
2 %% Name: file.tex
3 %% Purpose: wxFile documentation
4 %% Author: Vadim Zeitlin
5 %% Modified by:
6 %% Created: 14.01.02 (extracted from file.tex)
7 %% RCS-ID: $Id$
8 %% Copyright: (c) Vadim Zeitlin
9 %% License: wxWidgets license
10 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
11
12 \section{\class{wxFile}}\label{wxfile}
13
14 A wxFile performs raw file I/O. This is a very small class designed to
15 minimize the overhead of using it - in fact, there is hardly any overhead at
16 all, but using it brings you automatic error checking and hides differences
17 between platforms and compilers. wxFile also automatically closes the file in
18 its destructor making it unnecessary to worry about forgetting to do it.
19 wxFile is a wrapper around {\tt file descriptor.} - see also
20 \helpref{wxFFile}{wxffile} for a wrapper around {\tt FILE} structure.
21
22 \wxheading{Derived from}
23
24 None.
25
26 \wxheading{Include files}
27
28 <wx/file.h>
29
30 \wxheading{Constants}
31
32 wx/file.h defines the following constants:
33
34 \begin{verbatim}
35 #define wxS_IRUSR 00400
36 #define wxS_IWUSR 00200
37 #define wxS_IXUSR 00100
38
39 #define wxS_IRGRP 00040
40 #define wxS_IWGRP 00020
41 #define wxS_IXGRP 00010
42
43 #define wxS_IROTH 00004
44 #define wxS_IWOTH 00002
45 #define wxS_IXOTH 00001
46
47 // default mode for the new files: corresponds to umask 022
48 #define wxS_DEFAULT (wxS_IRUSR | wxS_IWUSR | wxS_IRGRP | wxS_IWGRP | wxS_IROTH | wxS_IWOTH)
49 \end{verbatim}
50
51 These constants define the file access rights and are used with
52 \helpref{wxFile::Create}{wxfilecreate} and \helpref{wxFile::Open}{wxfileopen}.
53
54 The {\it OpenMode} enumeration defines the different modes for opening a file,
55 it is defined inside wxFile class so its members should be specified with {\it wxFile::} scope
56 resolution prefix. It is also used with \helpref{wxFile::Access}{wxfileaccess} function.
57
58 \twocolwidtha{7cm}
59 \begin{twocollist}\itemsep=0pt%
60 \twocolitem{{\bf wxFile::read}}{Open file for reading or test if it can be opened for reading with Access()}
61 \twocolitem{{\bf wxFile::write}}{Open file for writing deleting the contents of the file if it already exists
62 or test if it can be opened for writing with Access()}
63 \twocolitem{{\bf wxFile::read\_write}}{Open file for reading and writing; can not be used with Access()}
64 \twocolitem{{\bf wxFile::write\_append}}{Open file for appending: the file is opened for writing, but the old
65 contents of the file is not erased and the file pointer is initially placed at the end of the file;
66 can not be used with Access(). This is the same as {\bf wxFile::write} if the
67 file doesn't exist.}
68 \twocolitem{{\bf wxFile::write\_excl}}{Open the file securely for writing (Uses O\_EXCL | O\_CREAT).
69 Will fail if the file already exists, else create and open it atomically. Useful for opening temporary files without being vulnerable to race exploits.}
70 \end{twocollist}
71
72 Other constants defined elsewhere but used by wxFile functions are wxInvalidOffset which represents an
73 invalid value of type {\it off\_t} and is returned by functions returning {\it off\_t} on error and the seek
74 mode constants used with \helpref{Seek()}{wxfileseek}:
75
76 \twocolwidtha{7cm}
77 \begin{twocollist}\itemsep=0pt%
78 \twocolitem{{\bf wxFromStart}}{Count offset from the start of the file}
79 \twocolitem{{\bf wxFromCurrent}}{Count offset from the current position of the file pointer}
80 \twocolitem{{\bf wxFromEnd}}{Count offset from the end of the file (backwards)}
81 \end{twocollist}
82
83 \latexignore{\rtfignore{\wxheading{Members}}}
84
85 \membersection{wxFile::wxFile}\label{wxfileconstr}
86
87 \func{}{wxFile}{\void}
88
89 Default constructor.
90
91 \func{}{wxFile}{\param{const char*}{ filename}, \param{wxFile::OpenMode}{ mode = wxFile::read}}
92
93 Opens a file with the given mode. As there is no way to return whether the
94 operation was successful or not from the constructor you should test the
95 return value of \helpref{IsOpened}{wxfileisopened} to check that it didn't
96 fail.
97
98 \func{}{wxFile}{\param{int}{ fd}}
99
100 Associates the file with the given file descriptor, which has already been opened.
101
102 \wxheading{Parameters}
103
104 \docparam{filename}{The filename.}
105
106 \docparam{mode}{The mode in which to open the file. May be one of {\bf wxFile::read}, {\bf wxFile::write} and {\bf wxFile::read\_write}.}
107
108 \docparam{fd}{An existing file descriptor (see \helpref{Attach()}{wxfileattach} for the list of predefined descriptors)}
109
110 \membersection{wxFile::\destruct{wxFile}}
111
112 \func{}{\destruct{wxFile}}{\void}
113
114 Destructor will close the file.
115
116 {\bf NB:} it is not virtual so you should not use wxFile polymorphically.
117
118 \membersection{wxFile::Access}\label{wxfileaccess}
119
120 \func{static bool}{Access}{\param{const char *}{ name}, \param{OpenMode}{ mode}}
121
122 This function verifies if we may access the given file in specified mode. Only
123 values of wxFile::read or wxFile::write really make sense here.
124
125 \membersection{wxFile::Attach}\label{wxfileattach}
126
127 \func{void}{Attach}{\param{int}{ fd}}
128
129 Attaches an existing file descriptor to the wxFile object. Example of predefined
130 file descriptors are 0, 1 and 2 which correspond to stdin, stdout and stderr (and
131 have symbolic names of {\bf wxFile::fd\_stdin}, {\bf wxFile::fd\_stdout} and {\bf wxFile::fd\_stderr}).
132
133 The descriptor should be already opened and it will be closed by wxFile
134 object.
135
136 \membersection{wxFile::Close}\label{wxfileclose}
137
138 \func{void}{Close}{\void}
139
140 Closes the file.
141
142 \membersection{wxFile::Create}\label{wxfilecreate}
143
144 \func{bool}{Create}{\param{const char*}{ filename}, \param{bool}{ overwrite = false}, \param{int }{access = wxS\_DEFAULT}}
145
146 Creates a file for writing. If the file already exists, setting {\bf overwrite} to true
147 will ensure it is overwritten.
148
149 \membersection{wxFile::Detach}\label{wxfiledetach}
150
151 \func{void}{Detach}{\void}
152
153 Get back a file descriptor from wxFile object - the caller is responsible for closing the file if this
154 descriptor is opened. \helpref{IsOpened()}{wxfileisopened} will return false after call to Detach().
155
156 \membersection{wxFile::fd}\label{wxfilefd}
157
158 \constfunc{int}{fd}{\void}
159
160 Returns the file descriptor associated with the file.
161
162 \membersection{wxFile::Eof}\label{wxfileeof}
163
164 \constfunc{bool}{Eof}{\void}
165
166 Returns true if the end of the file has been reached.
167
168 Note that the behaviour of the file pointer based class
169 \helpref{wxFFile}{wxffile} is different as \helpref{wxFFile::Eof}{wxffileeof}
170 will return true here only if an attempt has been made to read
171 {\it past} the last byte of the file, while wxFile::Eof() will return true
172 even before such attempt is made if the file pointer is at the last position
173 in the file.
174
175 Note also that this function doesn't work on unseekable file descriptors
176 (examples include pipes, terminals and sockets under Unix) and an attempt to
177 use it will result in an error message in such case. So, to read the entire
178 file into memory, you should write a loop which uses
179 \helpref{Read}{wxfileread} repeatedly and tests its return condition instead
180 of using Eof() as this will not work for special files under Unix.
181
182 \membersection{wxFile::Exists}\label{wxfileexists}
183
184 \func{static bool}{Exists}{\param{const char*}{ filename}}
185
186 Returns true if the given name specifies an existing regular file (not a
187 directory or a link)
188
189 \membersection{wxFile::Flush}\label{wxfileflush}
190
191 \func{bool}{Flush}{\void}
192
193 Flushes the file descriptor.
194
195 Note that wxFile::Flush is not implemented on some Windows compilers
196 due to a missing fsync function, which reduces the usefulness of this function
197 (it can still be called but it will do nothing on unsupported compilers).
198
199 \membersection{wxFile::IsOpened}\label{wxfileisopened}
200
201 \constfunc{bool}{IsOpened}{\void}
202
203 Returns true if the file has been opened.
204
205 \membersection{wxFile::Length}\label{wxfilelength}
206
207 \constfunc{off\_t}{Length}{\void}
208
209 Returns the length of the file.
210
211 \membersection{wxFile::Open}\label{wxfileopen}
212
213 \func{bool}{Open}{\param{const char*}{ filename}, \param{wxFile::OpenMode}{ mode = wxFile::read}}
214
215 Opens the file, returning true if successful.
216
217 \wxheading{Parameters}
218
219 \docparam{filename}{The filename.}
220
221 \docparam{mode}{The mode in which to open the file. May be one of {\bf wxFile::read}, {\bf wxFile::write} and {\bf wxFile::read\_write}.}
222
223 \membersection{wxFile::Read}\label{wxfileread}
224
225 \func{off\_t}{Read}{\param{void*}{ buffer}, \param{off\_t}{ count}}
226
227 Reads the specified number of bytes into a buffer, returning the actual number read.
228
229 \wxheading{Parameters}
230
231 \docparam{buffer}{A buffer to receive the data.}
232
233 \docparam{count}{The number of bytes to read.}
234
235 \wxheading{Return value}
236
237 The number of bytes read, or the symbol {\bf wxInvalidOffset} (-1) if there was an error.
238
239 \membersection{wxFile::Seek}\label{wxfileseek}
240
241 \func{off\_t}{Seek}{\param{off\_t }{ofs}, \param{wxSeekMode }{mode = wxFromStart}}
242
243 Seeks to the specified position.
244
245 \wxheading{Parameters}
246
247 \docparam{ofs}{Offset to seek to.}
248
249 \docparam{mode}{One of {\bf wxFromStart}, {\bf wxFromEnd}, {\bf wxFromCurrent}.}
250
251 \wxheading{Return value}
252
253 The actual offset position achieved, or wxInvalidOffset on failure.
254
255 \membersection{wxFile::SeekEnd}\label{wxfileseekend}
256
257 \func{off\_t}{SeekEnd}{\param{off\_t }{ofs = 0}}
258
259 Moves the file pointer to the specified number of bytes before the end of the file.
260
261 \wxheading{Parameters}
262
263 \docparam{ofs}{Number of bytes before the end of the file.}
264
265 \wxheading{Return value}
266
267 The actual offset position achieved, or wxInvalidOffset on failure.
268
269 \membersection{wxFile::Tell}\label{wxfiletell}
270
271 \constfunc{off\_t}{Tell}{\void}
272
273 Returns the current position or wxInvalidOffset if file is not opened or if another
274 error occurred.
275
276 \membersection{wxFile::Write}\label{wxfilewrite}
277
278 \func{size\_t}{Write}{\param{const void*}{ buffer}, \param{off\_t}{ count}}
279
280 Writes the specified number of bytes from a buffer.
281
282 \wxheading{Parameters}
283
284 \docparam{buffer}{A buffer containing the data.}
285
286 \docparam{count}{The number of bytes to write.}
287
288 \wxheading{Return value}
289
290 the number of bytes actually written
291
292 \membersection{wxFile::Write}\label{wxfilewrites}
293
294 \func{bool}{Write}{\param{const wxString\& }{s}, \param{wxMBConv\&}{ conv = wxConvUTF8}}
295
296 Writes the contents of the string to the file, returns true on success.
297
298 The second argument is only meaningful in Unicode build of wxWidgets when
299 {\it conv} is used to convert {\it s} to multibyte representation.
300
301 Note that this method only works with {\tt NUL}-terminated strings, if you want
302 to write data with embedded {\tt NUL}s to the file you should use the other
303 \helpref{Write() overload}{wxfilewrite}.
304