X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/a660d684eda27638bca0384b2058911a31c8e845..2245b2b2c3339ecf023e5880caa803610a5d1907:/docs/latex/wx/file.tex diff --git a/docs/latex/wx/file.tex b/docs/latex/wx/file.tex index fec5c31d87..4b2160def6 100644 --- a/docs/latex/wx/file.tex +++ b/docs/latex/wx/file.tex @@ -1,12 +1,85 @@ +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%% 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. Note that wxFile::Flush is not implemented on some Windows compilers -due to a missing fsync function, which reduces the usefulness of this class. +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. \wxheading{Derived from} None. +\wxheading{Include files} + + + +\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 off\_t} and is returned by functions returning {\it off\_t} 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{wxfileconstr} @@ -17,11 +90,14 @@ Default constructor. \func{}{wxFile}{\param{const char*}{ filename}, \param{wxFile::OpenMode}{ mode = wxFile::read}} -Opens a file with the given mode. +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}} -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} @@ -29,19 +105,33 @@ Opens a file with the given file descriptor, which has already been opened. \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.} +\docparam{fd}{An existing file descriptor (see \helpref{Attach()}{wxfileattach} for the list of predefined descriptors)} \membersection{wxFile::\destruct{wxFile}} \func{}{\destruct{wxFile}}{\void} -Destructor. This is not virtual, for efficiency. +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. +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} @@ -51,28 +141,60 @@ Closes the file. \membersection{wxFile::Create}\label{wxfilecreate} -\func{bool}{Create}{\param{const char*}{ filename}, \param{bool}{ overwrite = FALSE}} +\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 file exists. +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. Not implemented for some Windows compilers. +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::IsOpened}\label{wxfileisopened} @@ -112,11 +234,11 @@ Reads the specified number of bytes into a buffer, returning the actual number r \wxheading{Return value} -The number of bytes read, or the symbol {\bf ofsInvalid} (-1) if there was an error. +The number of bytes read, or the symbol {\bf wxInvalidOffset} (-1) if there was an error. \membersection{wxFile::Seek}\label{wxfileseek} -\func{off\_t}{Seek}{\param{off\_t }{ofs}, \param{wxFile::SeekMode }{mode = wxFile::FromStart}} +\func{off\_t}{Seek}{\param{off\_t }{ofs}, \param{wxSeekMode }{mode = wxFromStart}} Seeks to the specified position. @@ -124,11 +246,11 @@ Seeks to the specified position. \docparam{ofs}{Offset to seek to.} -\docparam{mode}{One of {\bf wxFile::FromStart}, {\bf wxFile::FromEnd}, {\bf wxFile::FromCurrent}.} +\docparam{mode}{One of {\bf wxFromStart}, {\bf wxFromEnd}, {\bf wxFromCurrent}.} \wxheading{Return value} -The actual offset position achieved, or ofsInvalid on failure. +The actual offset position achieved, or wxInvalidOffset on failure. \membersection{wxFile::SeekEnd}\label{wxfileseekend} @@ -142,17 +264,18 @@ Moves the file pointer to the specified number of bytes before the end of the fi \wxheading{Return value} -The actual offset position achieved, or ofsInvalid on failure. +The actual offset position achieved, or wxInvalidOffset on failure. \membersection{wxFile::Tell}\label{wxfiletell} \constfunc{off\_t}{Tell}{\void} -Returns the current position. +Returns the current position or wxInvalidOffset if file is not opened or if another +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. @@ -164,6 +287,14 @@ 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} + +\func{bool}{Write}{\param{const wxString\& }{s}, \param{wxMBConv&}{ conv = wxConvLibc}} + +Writes the contents of the string to the file, returns TRUE on success. +The second argument is only meaningful in Unicode build of wxWindows when +{\it conv} is used to convert {\it s} to multibyte representation.