added support for reading alpha channel

[wxWidgets.git] / docs / latex / wx / textfile.tex

\section{\class{wxTextFile}}\label{wxtextfile}

The wxTextFile is a simple class which allows to work with text files on line by
line basis. It also understands the differences in line termination characters
under different platforms and will not do anything bad to files with "non
native" line termination sequences - in fact, it can be also used to modify the
text files and change the line termination characters from one type (say DOS) to
another (say Unix).

One word of warning: the class is not at all optimized for big files and so it
will load the file entirely into memory when opened. Of course, you should not
work in this way with large files (as an estimation, anything over 1 Megabyte is
surely too big for this class). On the other hand, it is not a serious
limitation for the small files like configuration files or programs sources
which are well handled by wxTextFile.

The typical things you may do with wxTextFile in order are:

\begin{itemize}\itemsep=0pt
\item Create and open it: this is done with either 
\helpref{Create}{wxtextfilecreate} or \helpref{Open}{wxtextfileopen} 
function which opens the file (name may be specified either as the argument to
these functions or in the constructor), reads its contents in memory (in the
case of {\tt Open()}) and closes it.
\item Work with the lines in the file: this may be done either with "direct
access" functions like \helpref{GetLineCount}{wxtextfilegetlinecount} and 
\helpref{GetLine}{wxtextfilegetline} ({\it operator[]} does exactly the same
but looks more like array addressing) or with "sequential access" functions
which include \helpref{GetFirstLine}{wxtextfilegetfirstline}/
\helpref{GetNextLine}{wxtextfilegetnextline} and also 
\helpref{GetLastLine}{wxtextfilegetlastline}/\helpref{GetPrevLine}{wxtextfilegetprevline}.
For the sequential access functions the current line number is maintained: it is
returned by \helpref{GetCurrentLine}{wxtextfilegetcurrentline} and may be
changed with \helpref{GoToLine}{wxtextfilegotoline}.
\item Add/remove lines to the file: \helpref{AddLine}{wxtextfileaddline} and 
\helpref{InsertLine}{wxtextfileinsertline} add new lines while 
\helpref{RemoveLine}{wxtextfileremoveline} deletes the existing ones.
\item Save your changes: notice that the changes you make to the file will {\bf
not} be saved automatically; calling \helpref{Close}{wxtextfileclose} or doing
nothing discards them! To save the changes you must explicitly call 
\helpref{Write}{wxtextfilewrite} - here, you may also change the line
termination type if you wish.
\end{itemize}

\wxheading{Derived from}

No base class

\wxheading{Include files}

<wx/textfile.h>

\wxheading{Data structures}

The following constants identify the line termination type:

\begin{verbatim}
enum wxTextFileType
{
    wxTextFileType_None,  // incomplete (the last line of the file only)
    wxTextFileType_Unix,  // line is terminated with 'LF' = 0xA = 10 = '\n'
    wxTextFileType_Dos,   //                         'CR' 'LF'
    wxTextFileType_Mac    //                         'CR' = 0xD = 13 = '\r'
};
\end{verbatim}

\wxheading{See also}

\helpref{wxFile}{wxfile}

\latexignore{\rtfignore{\wxheading{Members}}}

\membersection{wxTextFile::wxTextFile}\label{wxtextfilectordef}

\constfunc{}{wxTextFile}{\void}

Default constructor, use \helpref{Create}{wxtextfilecreate} or 
\helpref{Open}{wxtextfileopen} with a file name parameter to initialize the object.

\membersection{wxTextFile::wxTextFile}\label{wxtextfilector}

\constfunc{}{wxTextFile}{\param{const wxString\& }{strFile}}

Constructor does not load the file into memory, use Open() to do it. 

\membersection{wxTextFile::\destruct{wxTextFile}}\label{wxtextfiledtor}

\constfunc{}{\destruct{wxTextFile}}{\void}

Destructor does nothing.

\membersection{wxTextFile::AddLine}\label{wxtextfileaddline}

\constfunc{void}{AddLine}{\param{const wxString\& }{str}, \param{wxTextFileType }{type = typeDefault}}

Adds a line to the end of file.

\membersection{wxTextFile::Close}\label{wxtextfileclose}

\constfunc{bool}{Close}{\void}

Closes the file and frees memory, {\bf losing all changes}. Use \helpref{Write()}{wxtextfilewrite} 
if you want to save them.

\membersection{wxTextFile::Create}\label{wxtextfilecreate}

\constfunc{bool}{Create}{\void}

\constfunc{bool}{Create}{\param{const wxString\& }{strFile}}

Creates the file with the given name or the name which was given in the
\helpref{constructor}{wxtextfilector}. The array of file lines is initially
empty.

It will fail if the file already exists, \helpref{Open}{wxtextfileopen} should
be used in this case.

\membersection{wxTextFile::Exists}\label{wxtextfileexists}

\constfunc{bool}{Exists}{\void}

Return true if file exists - the name of the file should have been specified
in the constructor before calling Exists().

\membersection{wxTextFile::IsOpened}\label{wxtextfileisopened}

\constfunc{bool}{IsOpened}{\void}

Returns true if the file is currently opened.

\membersection{wxTextFile::GetLineCount}\label{wxtextfilegetlinecount}

\constfunc{size\_t}{GetLineCount}{\void}

Get the number of lines in the file.

\membersection{wxTextFile::GetLine}\label{wxtextfilegetline}

\constfunc{wxString\&}{GetLine}{\param{size\_t }{n}}

Retrieves the line number {\it n} from the file. The returned line may be
modified but you shouldn't add line terminator at the end - this will be done
by wxTextFile.

\membersection{wxTextFile::operator[]}\label{wxtextfileoperatorarray}

\constfunc{wxString\&}{operator[]}{\param{size\_t }{n}}

The same as \helpref{GetLine}{wxtextfilegetline}.

\membersection{wxTextFile::GetCurrentLine}\label{wxtextfilegetcurrentline}

\constfunc{size\_t}{GetCurrentLine}{\void}

Returns the current line: it has meaning only when you're using
GetFirstLine()/GetNextLine() functions, it doesn't get updated when
you're using "direct access" functions like GetLine(). GetFirstLine() and
GetLastLine() also change the value of the current line, as well as
GoToLine().

\membersection{wxTextFile::GoToLine}\label{wxtextfilegotoline}

\constfunc{void}{GoToLine}{\param{size\_t }{n}}

Changes the value returned by \helpref{GetCurrentLine}{wxtextfilegetcurrentline} 
and used by \helpref{GetFirstLine()}{wxtextfilegetfirstline}/\helpref{GetNextLine()}{wxtextfilegetnextline}.

\membersection{wxTextFile::Eof}\label{wxtextfileeof}

\constfunc{bool}{Eof}{\void}

Returns true if the current line is the last one.

\membersection{wxTextFile::GetEOL}\label{wxtextfilegeteol}

\constfunc{static const char*}{GetEOL}{\param{wxTextFileType }{type = typeDefault}}

Get the line termination string corresponding to given constant. {\it typeDefault} is
the value defined during the compilation and corresponds to the native format
of the platform, i.e. it will be wxTextFileType\_Dos under Windows,
wxTextFileType\_Unix under Unix (including Mac OS X when compiling with the
Apple Developer Tools) and wxTextFileType\_Mac under Mac OS (including
Mac OS X when compiling with CodeWarrior).

\membersection{wxTextFile::GetFirstLine}\label{wxtextfilegetfirstline}

\constfunc{wxString\&}{GetFirstLine}{\void}

This method together with \helpref{GetNextLine()}{wxtextfilegetnextline} 
allows more "iterator-like" traversal of the list of lines, i.e. you may
write something like:

\begin{verbatim}
wxTextFile file;
...
for ( str = file.GetFirstLine(); !file.Eof(); str = file.GetNextLine() )
{
    // do something with the current line in str
}
// do something with the last line in str
\end{verbatim}

\membersection{wxTextFile::GetNextLine}\label{wxtextfilegetnextline}

\func{wxString\&}{GetNextLine}{\void}

Gets the next line (see \helpref{GetFirstLine}{wxtextfilegetfirstline} for 
the example).

\membersection{wxTextFile::GetPrevLine}\label{wxtextfilegetprevline}

\func{wxString\&}{GetPrevLine}{\void}

Gets the previous line in the file.

\membersection{wxTextFile::GetLastLine}\label{wxtextfilegetlastline}

\func{wxString\&}{GetLastLine}{\void}

Gets the last line of the file. Together with 
\helpref{GetPrevLine}{wxtextfilegetprevline} it allows to enumerate the lines
in the file from the end to the beginning like this:

\begin{verbatim}
wxTextFile file;
...
for ( str = file.GetLastLine();
      file.GetCurrentLine() > 0;
      str = file.GetPrevLine() )
{
    // do something with the current line in str
}
// do something with the first line in str
\end{verbatim}

\membersection{wxTextFile::GetLineType}\label{wxtextfilegetlinetype}

\constfunc{wxTextFileType}{GetLineType}{\param{size\_t }{n}}

Get the type of the line (see also \helpref{GetEOL}{wxtextfilegeteol})

\membersection{wxTextFile::GuessType}\label{wxtextfileguesstype}

\constfunc{wxTextFileType}{GuessType}{\void}

Guess the type of file (which is supposed to be opened). If sufficiently
many lines of the file are in DOS/Unix/Mac format, the corresponding value will
be returned. If the detection mechanism fails wxTextFileType\_None is returned.

\membersection{wxTextFile::GetName}\label{wxtextfilegetname}

\constfunc{const char*}{GetName}{\void}

Get the name of the file.

\membersection{wxTextFile::InsertLine}\label{wxtextfileinsertline}

\constfunc{void}{InsertLine}{\param{const wxString\& }{str}, \param{size\_t }{n}, \param{wxTextFileType }{type = typeDefault}}

Insert a line before the line number {\it n}.

\membersection{wxTextFile::Open}\label{wxtextfileopen}

\constfunc{bool}{Open}{\param{wxMBConv\&}{ conv = wxConvUTF8}}

\constfunc{bool}{Open}{\param{const wxString\& }{strFile}, \param{wxMBConv\&}{ conv = wxConvUTF8}}

Open() opens the file with the given name or the name which was given in the
\helpref{constructor}{wxtextfilector} and also loads file in memory on
success. It will fail if the file does not exist, 
\helpref{Create}{wxtextfilecreate} should be used in this case.

The {\it conv} argument is only meaningful in Unicode build of wxWindows when
it is used to convert the file to wide character representation.

\membersection{wxTextFile::RemoveLine}\label{wxtextfileremoveline}

\constfunc{void}{RemoveLine}{\param{size\_t }{n}}

Delete line number {\it n} from the file.

\membersection{wxTextFile::Write}\label{wxtextfilewrite}

\constfunc{bool}{Write}{\param{wxTextFileType }{typeNew = wxTextFileType\_None}, \param{wxMBConv\&}{ conv = wxConvUTF8}}

Change the file on disk. The {\it typeNew} parameter allows you to change the
file format (default argument means "don't change type") and may be used to
convert, for example, DOS files to Unix.

The {\it conv} argument is only meaningful in Unicode build of wxWindows when
it is used to convert all lines to multibyte representation before writing them
them to physical file.

Returns true if operation succeeded, false if it failed.