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.
+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.
\wxheading{Derived from}
wx/file.h defines the following constants:
-{\small
\begin{verbatim}
#define wxS_IRUSR 00400
#define wxS_IWUSR 00200
// 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's defined inside wxFile class so its members should be specified with {\it wxFile::} scope
+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}
\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()}
+can not be used with Access(). This is the same as {\bf wxFile::write} if the
+file doesn't exist.}
\end{twocollist}
Other constants defined elsewhere but used by wxFile functions are wxInvalidOffset which represents an
\func{}{wxFile}{\param{int}{ fd}}
-Opens a file with the given file descriptor, which has already been opened.
+Associates the file with the given file descriptor, which has already been opened.
\wxheading{Parameters}
Destructor will close the file.
-NB: it is not virtual so you should {\it not} derive from wxFile!
+NB: it is not virtual so you should use wxFile polymorphically.
\membersection{wxFile::Access}\label{wxfileaccess}
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 wxFile::fd\_stdin, wxFile::fd\_stdout and wxFile::fd\_stderr).
+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.
\constfunc{bool}{Eof}{\void}
-Returns TRUE if the end of the file has been reached (the last byte has been read).
+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.
+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.
+Returns TRUE if the given name specifies an existing regular file (not a
+directory or a link)
\membersection{wxFile::Flush}\label{wxfileflush}
\constfunc{off\_t}{Tell}{\void}
Returns the current position or wxInvalidOffset if file is not opened or if another
-error occured.
+error occurred.
\membersection{wxFile::Write}\label{wxfilewrite}
-\func{bool}{Write}{\param{const void*}{ buffer}, \param{off\_t}{ count}}
+\func{size\_t}{Write}{\param{const void*}{ buffer}, \param{off\_t}{ count}}
Writes the specified number of bytes from a buffer.
\wxheading{Return value}
-TRUE if the operation was successful.
+the number of bytes actually written
\membersection{wxFile::Write}\label{wxfilewrites}
\section{\class{wxFFile}}\label{wxffile}
-A wxFFile performs raw file I/O. This is a very small class designed to
+wxFFile implements buffered 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.
+between platforms and compilers. It wraps inside it a {\tt FILE *} handle used
+by standard C IO library (also known as {\tt stdio}).
\wxheading{Derived from}
\docparam{filename}{The filename.}
-\docparam{mode}{The mode in which to open the file using standard C strings.}
+\docparam{mode}{The mode in which to open the file using standard C strings.
+Note that you should use {\tt "b"} flag if you use binary files under Windows
+or the results might be unexpected due to automatic newline conversion done
+for the text files.}
\docparam{fp}{An existing file descriptor, such as stderr.}
\membersection{wxFFile::Write}\label{wxffilewrite}
-\func{size_t}{Write}{\param{const void*}{ buffer}, \param{size\_t}{ count}}
+\func{size\_t}{Write}{\param{const void*}{ buffer}, \param{size\_t}{ count}}
Writes the specified number of bytes from a buffer.
projects / wxWidgets.git / blobdiff