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1 % automatically generated by HelpGen from tempfile.tex at 10/Jan/99 19:24:44
2 \section{\class{wxTempFile}}\label{wxtempfile}
3
4 wxTempFile provides a relatively safe way to replace the contents of the
5 existing file. The name is explained by the fact that it may be also used as
6 just a temporary file if you don't replace the old file contents.
7
8 Usually, when a program replaces the contents of some file it first opens it for
9 writing, thus losing all of the old data and then starts recreating it. This
10 approach is not very safe because during the regeneration of the file bad things
11 may happen: the program may find that there is an internal error preventing it
12 from completing file generation, the user may interrupt it (especially if file
13 generation takes long time) and, finally, any other external interrupts (power
14 supply failure or a disk error) will leave you without either the original file
15 or the new one.
16
17 wxTempFile addresses this problem by creating a temporary file which is meant to
18 replace the original file - but only after it is fully written. So, if the user
19 interrupts the program during the file generation, the old file won't be lost.
20 Also, if the program discovers itself that it doesn't want to replace the old
21 file there is no problem - in fact, wxTempFile will {\bf not} replace the old
22 file by default, you should explicitly call \helpref{Commit}{wxtempfilecommit}
23 to do it. Calling \helpref{Discard}{wxtempfilediscard} explicitly discards any
24 modifications: it closes and deletes the temporary file and leaves the original
25 file unchanged. If you don't call neither of Commit() and Discard(), the
26 destructor will call Discard() automatically.
27
28 To summarize: if you want to replace another file, create an instance of
29 wxTempFile passing the name of the file to be replaced to the constructor (you
30 may also use default constructor and pass the file name to
31 \helpref{Open}{wxtempfileopen}). Then you can \helpref{write}{wxtempfilewrite}
32 to wxTempFile using \helpref{wxFile}{wxfile}-like functions and later call
33 Commit() to replace the old file (and close this one) or call Discard() to cancel
34 the modifications.
35
36 \wxheading{Derived from}
37
38 No base class
39
40 \wxheading{Include files}
41
42 <wx/file.h>
43
44 \wxheading{Library}
45
46 \helpref{wxBase}{librarieslist}
47
48 \wxheading{See also:}
49
50 \helpref{wxFile}{wxfile}\\
51 \helpref{wxTempFileOutputStream}{wxtempfileoutputstream}
52
53 \latexignore{\rtfignore{\wxheading{Members}}}
54
55 \membersection{wxTempFile::wxTempFile}\label{wxtempfilewxtempfilector}
56
57 \func{}{wxTempFile}{\void}
58
59 Default constructor - \helpref{Open}{wxtempfileopen} must be used to open the
60 file.
61
62 \membersection{wxTempFile::wxTempFile}\label{wxtempfilewxtempfile}
63
64 \func{}{wxTempFile}{\param{const wxString\& }{strName}}
65
66 Associates wxTempFile with the file to be replaced and opens it. You should use
67 \helpref{IsOpened}{wxtempfileisopened} to verify if the constructor succeeded.
68
69 \membersection{wxTempFile::Open}\label{wxtempfileopen}
70
71 \func{bool}{Open}{\param{const wxString\& }{strName}}
72
73 Open the temporary file, returns {\tt true} on success, {\tt false} if an error
74 occurred.
75
76 {\it strName} is the name of file to be replaced. The temporary file is always
77 created in the directory where {\it strName} is. In particular, if
78 {\it strName} doesn't include the path, it is created in the current directory
79 and the program should have write access to it for the function to succeed.
80
81 \membersection{wxTempFile::IsOpened}\label{wxtempfileisopened}
82
83 \constfunc{bool}{IsOpened}{\void}
84
85 Returns {\tt true} if the file was successfully opened.
86
87 \membersection{wxTempFile::Length}\label{wxtempfilelength}
88
89 \constfunc{wxFileOffset}{Length}{\void}
90
91 Returns the length of the file.
92
93 \membersection{wxTempFile::Seek}\label{wxtempfileseek}
94
95 \func{wxFileOffset}{Seek}{\param{wxFileOffset }{ofs}, \param{wxSeekMode }{mode = wxFromStart}}
96
97 Seeks to the specified position.
98
99 \membersection{wxTempFile::Tell}\label{wxtempfiletell}
100
101 \constfunc{wxFileOffset}{Tell}{\void}
102
103 Returns the current position or wxInvalidOffset if file is not opened or if another
104 error occurred.
105
106 \membersection{wxTempFile::Write}\label{wxtempfilewrite}
107
108 \func{bool}{Write}{\param{const void }{*p}, \param{size\_t }{n}}
109
110 Write to the file, return {\tt true} on success, {\tt false} on failure.
111
112 \membersection{wxTempFile::Write}\label{wxtempfilewrites}
113
114 \func{bool}{Write}{\param{const wxString\& }{str}, \param{const wxMBConv\&}{ conv = wxConvUTF8}}
115
116 Write to the file, return {\tt true} on success, {\tt false} on failure.
117
118 The second argument is only meaningful in Unicode build of wxWidgets when
119 {\it conv} is used to convert {\it str} to multibyte representation.
120
121 \membersection{wxTempFile::Commit}\label{wxtempfilecommit}
122
123 \func{bool}{Commit}{\void}
124
125 Validate changes: deletes the old file of name m\_strName and renames the new
126 file to the old name. Returns {\tt true} if both actions succeeded. If {\tt false} is
127 returned it may unfortunately mean two quite different things: either that
128 either the old file couldn't be deleted or that the new file couldn't be renamed
129 to the old name.
130
131 \membersection{wxTempFile::Discard}\label{wxtempfilediscard}
132
133 \func{void}{Discard}{\void}
134
135 Discard changes: the old file contents is not changed, temporary file is
136 deleted.
137
138 \membersection{wxTempFile::\destruct{wxTempFile}}\label{wxtempfiledtor}
139
140 \func{}{\destruct{wxTempFile}}{\void}
141
142 Destructor calls \helpref{Discard()}{wxtempfilediscard} if temporary file
143 is still opened.
144