eeb552d0d5
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@43613 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
349 lines
11 KiB
TeX
349 lines
11 KiB
TeX
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
%% Name: file.tex
|
|
%% Purpose: wxFile documentation
|
|
%% Author: Vadim Zeitlin
|
|
%% Modified by:
|
|
%% Created: 14.01.02 (extracted from file.tex)
|
|
%% RCS-ID: $Id$
|
|
%% Copyright: (c) Vadim Zeitlin
|
|
%% License: wxWindows license
|
|
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
|
|
|
\section{\class{wxFile}}\label{wxfile}
|
|
|
|
A wxFile performs raw file I/O. This is a very small class designed to
|
|
minimize the overhead of using it - in fact, there is hardly any overhead at
|
|
all, but using it brings you automatic error checking and hides differences
|
|
between platforms and compilers. wxFile also automatically closes the file in
|
|
its destructor making it unnecessary to worry about forgetting to do it.
|
|
wxFile is a wrapper around {\tt file descriptor.} - see also
|
|
\helpref{wxFFile}{wxffile} for a wrapper around {\tt FILE} structure.
|
|
|
|
{\tt wxFileOffset} is used by the wxFile functions which require offsets as
|
|
parameter or return them. If the platform supports it, wxFileOffset is a typedef
|
|
for a native 64 bit integer, otherwise a 32 bit integer is used for wxFileOffset.
|
|
|
|
\wxheading{Derived from}
|
|
|
|
None.
|
|
|
|
\wxheading{Include files}
|
|
|
|
<wx/file.h>
|
|
|
|
\wxheading{Constants}
|
|
|
|
wx/file.h defines the following constants:
|
|
|
|
\begin{verbatim}
|
|
#define wxS_IRUSR 00400
|
|
#define wxS_IWUSR 00200
|
|
#define wxS_IXUSR 00100
|
|
|
|
#define wxS_IRGRP 00040
|
|
#define wxS_IWGRP 00020
|
|
#define wxS_IXGRP 00010
|
|
|
|
#define wxS_IROTH 00004
|
|
#define wxS_IWOTH 00002
|
|
#define wxS_IXOTH 00001
|
|
|
|
// default mode for the new files: corresponds to umask 022
|
|
#define wxS_DEFAULT (wxS_IRUSR | wxS_IWUSR | wxS_IRGRP | wxS_IWGRP | wxS_IROTH | wxS_IWOTH)
|
|
\end{verbatim}
|
|
|
|
These constants define the file access rights and are used with
|
|
\helpref{wxFile::Create}{wxfilecreate} and \helpref{wxFile::Open}{wxfileopen}.
|
|
|
|
The {\it OpenMode} enumeration defines the different modes for opening a file,
|
|
it is defined inside wxFile class so its members should be specified with {\it wxFile::} scope
|
|
resolution prefix. It is also used with \helpref{wxFile::Access}{wxfileaccess} function.
|
|
|
|
\twocolwidtha{7cm}
|
|
\begin{twocollist}\itemsep=0pt%
|
|
\twocolitem{{\bf wxFile::read}}{Open file for reading or test if it can be opened for reading with Access()}
|
|
\twocolitem{{\bf wxFile::write}}{Open file for writing deleting the contents of the file if it already exists
|
|
or test if it can be opened for writing with Access()}
|
|
\twocolitem{{\bf wxFile::read\_write}}{Open file for reading and writing; can not be used with Access()}
|
|
\twocolitem{{\bf wxFile::write\_append}}{Open file for appending: the file is opened for writing, but the old
|
|
contents of the file is not erased and the file pointer is initially placed at the end of the file;
|
|
can not be used with Access(). This is the same as {\bf wxFile::write} if the
|
|
file doesn't exist.}
|
|
\twocolitem{{\bf wxFile::write\_excl}}{Open the file securely for writing (Uses O\_EXCL | O\_CREAT).
|
|
Will fail if the file already exists, else create and open it atomically. Useful for opening temporary files without being vulnerable to race exploits.}
|
|
\end{twocollist}
|
|
|
|
Other constants defined elsewhere but used by wxFile functions are wxInvalidOffset which represents an
|
|
invalid value of type {\it wxFileOffset} and is returned by functions returning {\it wxFileOffset} on error and the seek
|
|
mode constants used with \helpref{Seek()}{wxfileseek}:
|
|
|
|
\twocolwidtha{7cm}
|
|
\begin{twocollist}\itemsep=0pt%
|
|
\twocolitem{{\bf wxFromStart}}{Count offset from the start of the file}
|
|
\twocolitem{{\bf wxFromCurrent}}{Count offset from the current position of the file pointer}
|
|
\twocolitem{{\bf wxFromEnd}}{Count offset from the end of the file (backwards)}
|
|
\end{twocollist}
|
|
|
|
\latexignore{\rtfignore{\wxheading{Members}}}
|
|
|
|
|
|
\membersection{wxFile::wxFile}\label{wxfilector}
|
|
|
|
\func{}{wxFile}{\void}
|
|
|
|
Default constructor.
|
|
|
|
\func{}{wxFile}{\param{const char*}{ filename}, \param{wxFile::OpenMode}{ mode = wxFile::read}}
|
|
|
|
Opens a file with the given mode. As there is no way to return whether the
|
|
operation was successful or not from the constructor you should test the
|
|
return value of \helpref{IsOpened}{wxfileisopened} to check that it didn't
|
|
fail.
|
|
|
|
\func{}{wxFile}{\param{int}{ fd}}
|
|
|
|
Associates the file with the given file descriptor, which has already been opened.
|
|
|
|
\wxheading{Parameters}
|
|
|
|
\docparam{filename}{The filename.}
|
|
|
|
\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}.}
|
|
|
|
\docparam{fd}{An existing file descriptor (see \helpref{Attach()}{wxfileattach} for the list of predefined descriptors)}
|
|
|
|
|
|
\membersection{wxFile::\destruct{wxFile}}\label{wxfiledtor}
|
|
|
|
\func{}{\destruct{wxFile}}{\void}
|
|
|
|
Destructor will close the file.
|
|
|
|
{\bf NB:} it is not virtual so you should not use wxFile polymorphically.
|
|
|
|
|
|
\membersection{wxFile::Access}\label{wxfileaccess}
|
|
|
|
\func{static bool}{Access}{\param{const char *}{ name}, \param{OpenMode}{ mode}}
|
|
|
|
This function verifies if we may access the given file in specified mode. Only
|
|
values of wxFile::read or wxFile::write really make sense here.
|
|
|
|
|
|
\membersection{wxFile::Attach}\label{wxfileattach}
|
|
|
|
\func{void}{Attach}{\param{int}{ fd}}
|
|
|
|
Attaches an existing file descriptor to the wxFile object. Example of predefined
|
|
file descriptors are 0, 1 and 2 which correspond to stdin, stdout and stderr (and
|
|
have symbolic names of {\bf wxFile::fd\_stdin}, {\bf wxFile::fd\_stdout} and {\bf wxFile::fd\_stderr}).
|
|
|
|
The descriptor should be already opened and it will be closed by wxFile
|
|
object.
|
|
|
|
|
|
\membersection{wxFile::Close}\label{wxfileclose}
|
|
|
|
\func{void}{Close}{\void}
|
|
|
|
Closes the file.
|
|
|
|
|
|
\membersection{wxFile::Create}\label{wxfilecreate}
|
|
|
|
\func{bool}{Create}{\param{const char*}{ filename}, \param{bool}{ overwrite = false}, \param{int }{access = wxS\_DEFAULT}}
|
|
|
|
Creates a file for writing. If the file already exists, setting {\bf overwrite} to true
|
|
will ensure it is overwritten.
|
|
|
|
|
|
\membersection{wxFile::Detach}\label{wxfiledetach}
|
|
|
|
\func{void}{Detach}{\void}
|
|
|
|
Get back a file descriptor from wxFile object - the caller is responsible for closing the file if this
|
|
descriptor is opened. \helpref{IsOpened()}{wxfileisopened} will return false after call to Detach().
|
|
|
|
|
|
\membersection{wxFile::fd}\label{wxfilefd}
|
|
|
|
\constfunc{int}{fd}{\void}
|
|
|
|
Returns the file descriptor associated with the file.
|
|
|
|
|
|
\membersection{wxFile::Eof}\label{wxfileeof}
|
|
|
|
\constfunc{bool}{Eof}{\void}
|
|
|
|
Returns true if the end of the file has been reached.
|
|
|
|
Note that the behaviour of the file pointer based class
|
|
\helpref{wxFFile}{wxffile} is different as \helpref{wxFFile::Eof}{wxffileeof}
|
|
will return true here only if an attempt has been made to read
|
|
{\it past} the last byte of the file, while wxFile::Eof() will return true
|
|
even before such attempt is made if the file pointer is at the last position
|
|
in the file.
|
|
|
|
Note also that this function doesn't work on unseekable file descriptors
|
|
(examples include pipes, terminals and sockets under Unix) and an attempt to
|
|
use it will result in an error message in such case. So, to read the entire
|
|
file into memory, you should write a loop which uses
|
|
\helpref{Read}{wxfileread} repeatedly and tests its return condition instead
|
|
of using Eof() as this will not work for special files under Unix.
|
|
|
|
|
|
\membersection{wxFile::Exists}\label{wxfileexists}
|
|
|
|
\func{static bool}{Exists}{\param{const char*}{ filename}}
|
|
|
|
Returns true if the given name specifies an existing regular file (not a
|
|
directory or a link)
|
|
|
|
|
|
\membersection{wxFile::Flush}\label{wxfileflush}
|
|
|
|
\func{bool}{Flush}{\void}
|
|
|
|
Flushes the file descriptor.
|
|
|
|
Note that wxFile::Flush is not implemented on some Windows compilers
|
|
due to a missing fsync function, which reduces the usefulness of this function
|
|
(it can still be called but it will do nothing on unsupported compilers).
|
|
|
|
|
|
\membersection{wxFile::GetKind}\label{wxfilegetfilekind}
|
|
|
|
\constfunc{wxFileKind}{GetKind}{\void}
|
|
|
|
Returns the type of the file. Possible return values are:
|
|
|
|
\begin{verbatim}
|
|
enum wxFileKind
|
|
{
|
|
wxFILE_KIND_UNKNOWN,
|
|
wxFILE_KIND_DISK, // a file supporting seeking to arbitrary offsets
|
|
wxFILE_KIND_TERMINAL, // a tty
|
|
wxFILE_KIND_PIPE // a pipe
|
|
};
|
|
|
|
\end{verbatim}
|
|
|
|
|
|
\membersection{wxFile::IsOpened}\label{wxfileisopened}
|
|
|
|
\constfunc{bool}{IsOpened}{\void}
|
|
|
|
Returns true if the file has been opened.
|
|
|
|
|
|
\membersection{wxFile::Length}\label{wxfilelength}
|
|
|
|
\constfunc{wxFileOffset}{Length}{\void}
|
|
|
|
Returns the length of the file.
|
|
|
|
|
|
\membersection{wxFile::Open}\label{wxfileopen}
|
|
|
|
\func{bool}{Open}{\param{const char*}{ filename}, \param{wxFile::OpenMode}{ mode = wxFile::read}}
|
|
|
|
Opens the file, returning true if successful.
|
|
|
|
\wxheading{Parameters}
|
|
|
|
\docparam{filename}{The filename.}
|
|
|
|
\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}.}
|
|
|
|
|
|
\membersection{wxFile::Read}\label{wxfileread}
|
|
|
|
\func{size\_t}{Read}{\param{void*}{ buffer}, \param{size\_t}{ count}}
|
|
|
|
Reads the specified number of bytes into a buffer, returning the actual number read.
|
|
|
|
\wxheading{Parameters}
|
|
|
|
\docparam{buffer}{A buffer to receive the data.}
|
|
|
|
\docparam{count}{The number of bytes to read.}
|
|
|
|
\wxheading{Return value}
|
|
|
|
The number of bytes read, or the symbol {\bf wxInvalidOffset} (-1) if there was an error.
|
|
|
|
|
|
\membersection{wxFile::Seek}\label{wxfileseek}
|
|
|
|
\func{wxFileOffset}{Seek}{\param{wxFileOffset }{ofs}, \param{wxSeekMode }{mode = wxFromStart}}
|
|
|
|
Seeks to the specified position.
|
|
|
|
\wxheading{Parameters}
|
|
|
|
\docparam{ofs}{Offset to seek to.}
|
|
|
|
\docparam{mode}{One of {\bf wxFromStart}, {\bf wxFromEnd}, {\bf wxFromCurrent}.}
|
|
|
|
\wxheading{Return value}
|
|
|
|
The actual offset position achieved, or wxInvalidOffset on failure.
|
|
|
|
|
|
\membersection{wxFile::SeekEnd}\label{wxfileseekend}
|
|
|
|
\func{wxFileOffset}{SeekEnd}{\param{wxFileOffset }{ofs = 0}}
|
|
|
|
Moves the file pointer to the specified number of bytes relative to the end of
|
|
the file. For example, \texttt{SeekEnd($-5$)} would position the pointer $5$
|
|
bytes before the end.
|
|
|
|
\wxheading{Parameters}
|
|
|
|
\docparam{ofs}{Number of bytes before the end of the file.}
|
|
|
|
\wxheading{Return value}
|
|
|
|
The actual offset position achieved, or wxInvalidOffset on failure.
|
|
|
|
|
|
\membersection{wxFile::Tell}\label{wxfiletell}
|
|
|
|
\constfunc{wxFileOffset}{Tell}{\void}
|
|
|
|
Returns the current position or wxInvalidOffset if file is not opened or if another
|
|
error occurred.
|
|
|
|
|
|
\membersection{wxFile::Write}\label{wxfilewrite}
|
|
|
|
\func{size\_t}{Write}{\param{const void*}{ buffer}, \param{size\_t}{ count}}
|
|
|
|
Writes the specified number of bytes from a buffer.
|
|
|
|
\wxheading{Parameters}
|
|
|
|
\docparam{buffer}{A buffer containing the data.}
|
|
|
|
\docparam{count}{The number of bytes to write.}
|
|
|
|
\wxheading{Return value}
|
|
|
|
the number of bytes actually written
|
|
|
|
|
|
\membersection{wxFile::Write}\label{wxfilewrites}
|
|
|
|
\func{bool}{Write}{\param{const wxString\& }{s}, \param{wxMBConv\&}{ conv = wxConvUTF8}}
|
|
|
|
Writes the contents of the string to the file, returns true on success.
|
|
|
|
The second argument is only meaningful in Unicode build of wxWidgets when
|
|
{\it conv} is used to convert {\it s} to multibyte representation.
|
|
|
|
Note that this method only works with {\tt NUL}-terminated strings, if you want
|
|
to write data with embedded {\tt NUL}s to the file you should use the other
|
|
\helpref{Write() overload}{wxfilewrite}.
|
|
|