e126517457
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@32796 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
141 lines
5.3 KiB
TeX
141 lines
5.3 KiB
TeX
% automatically generated by HelpGen from tempfile.tex at 10/Jan/99 19:24:44
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\section{\class{wxTempFile}}\label{wxtempfile}
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wxTempFile provides a relatively safe way to replace the contents of the
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existing file. The name is explained by the fact that it may be also used as
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just a temporary file if you don't replace the old file contents.
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Usually, when a program replaces the contents of some file it first opens it for
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writing, thus losing all of the old data and then starts recreating it. This
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approach is not very safe because during the regeneration of the file bad things
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may happen: the program may find that there is an internal error preventing it
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from completing file generation, the user may interrupt it (especially if file
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generation takes long time) and, finally, any other external interrupts (power
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supply failure or a disk error) will leave you without either the original file
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or the new one.
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wxTempFile addresses this problem by creating a temporary file which is meant to
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replace the original file - but only after it is fully written. So, if the user
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interrupts the program during the file generation, the old file won't be lost.
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Also, if the program discovers itself that it doesn't want to replace the old
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file there is no problem - in fact, wxTempFile will {\bf not} replace the old
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file by default, you should explicitly call \helpref{Commit}{wxtempfilecommit}
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to do it. Calling \helpref{Discard}{wxtempfilediscard} explicitly discards any
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modifications: it closes and deletes the temporary file and leaves the original
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file unchanged. If you don't call neither of Commit() and Discard(), the
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destructor will call Discard() automatically.
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To summarize: if you want to replace another file, create an instance of
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wxTempFile passing the name of the file to be replaced to the constructor (you
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may also use default constructor and pass the file name to
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\helpref{Open}{wxtempfileopen}). Then you can \helpref{write}{wxtempfilewrite}
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to wxTempFile using \helpref{wxFile}{wxfile}-like functions and later call
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Commit() to replace the old file (and close this one) or call Discard() to cancel
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the modifications.
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\wxheading{Derived from}
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No base class
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\wxheading{Include files}
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<wx/file.h>
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\wxheading{See also:}
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\helpref{wxFile}{wxfile}\\
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\helpref{wxTempFileOutputStream}{wxtempfileoutputstream}
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\latexignore{\rtfignore{\wxheading{Members}}}
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\membersection{wxTempFile::wxTempFile}\label{wxtempfilewxtempfilector}
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\func{}{wxTempFile}{\void}
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Default constructor - \helpref{Open}{wxtempfileopen} must be used to open the
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file.
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\membersection{wxTempFile::wxTempFile}\label{wxtempfilewxtempfile}
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\func{}{wxTempFile}{\param{const wxString\& }{strName}}
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Associates wxTempFile with the file to be replaced and opens it. You should use
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\helpref{IsOpened}{wxtempfileisopened} to verify if the constructor succeeded.
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\membersection{wxTempFile::Open}\label{wxtempfileopen}
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\func{bool}{Open}{\param{const wxString\& }{strName}}
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Open the temporary file, returns {\tt true} on success, {\tt false} if an error
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occurred.
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{\it strName} is the name of file to be replaced. The temporary file is always
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created in the directory where {\it strName} is. In particular, if
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{\it strName} doesn't include the path, it is created in the current directory
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and the program should have write access to it for the function to succeed.
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\membersection{wxTempFile::IsOpened}\label{wxtempfileisopened}
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\constfunc{bool}{IsOpened}{\void}
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Returns {\tt true} if the file was successfully opened.
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\membersection{wxTempFile::Length}\label{wxtempfilelength}
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\constfunc{wxFileOffset}{Length}{\void}
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Returns the length of the file.
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\membersection{wxTempFile::Seek}\label{wxtempfileseek}
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\func{wxFileOffset}{Seek}{\param{wxFileOffset }{ofs}, \param{wxSeekMode }{mode = wxFromStart}}
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Seeks to the specified position.
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\membersection{wxTempFile::Tell}\label{wxtempfiletell}
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\constfunc{wxFileOffset}{Tell}{\void}
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Returns the current position or wxInvalidOffset if file is not opened or if another
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error occurred.
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\membersection{wxTempFile::Write}\label{wxtempfilewrite}
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\func{bool}{Write}{\param{const void }{*p}, \param{size\_t }{n}}
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Write to the file, return {\tt true} on success, {\tt false} on failure.
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\membersection{wxTempFile::Write}\label{wxtempfilewrites}
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\func{bool}{Write}{\param{const wxString\& }{str}, \param{wxMBConv\&}{ conv = wxConvLibc}}
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Write to the file, return {\tt true} on success, {\tt false} on failure.
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The second argument is only meaningful in Unicode build of wxWidgets when
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{\it conv} is used to convert {\it str} to multibyte representation.
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\membersection{wxTempFile::Commit}\label{wxtempfilecommit}
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\func{bool}{Commit}{\void}
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Validate changes: deletes the old file of name m\_strName and renames the new
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file to the old name. Returns {\tt true} if both actions succeeded. If {\tt false} is
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returned it may unfortunately mean two quite different things: either that
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either the old file couldn't be deleted or that the new file couldn't be renamed
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to the old name.
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\membersection{wxTempFile::Discard}\label{wxtempfilediscard}
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\func{void}{Discard}{\void}
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Discard changes: the old file contents is not changed, temporary file is
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deleted.
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\membersection{wxTempFile::\destruct{wxTempFile}}\label{wxtempfiledtor}
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\func{}{\destruct{wxTempFile}}{\void}
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Destructor calls \helpref{Discard()}{wxtempfilediscard} if temporary file
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is still opened.
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