qfile.3qt

Trolltech公司发布的基于C++图形开发环境

'\" t
.TH QFile 3qt "24 January 2005" "Trolltech AS" \" -*- nroff -*-
.\" Copyright 1992-2001 Trolltech AS.  All rights reserved.  See the
.\" license file included in the distribution for a complete license
.\" statement.
.\"
.ad l
.nh
.SH NAME
QFile \- I/O device that operates on files
.br
.PP
\fC#include <qfile.h>\fR
.PP
Inherits QIODevice.
.PP
.SS "Public Members"
.in +1c
.ti -1c
.BI "\fBQFile\fR () "
.br
.ti -1c
.BI "\fBQFile\fR ( const QString & name ) "
.br
.ti -1c
.BI "\fB~QFile\fR () "
.br
.ti -1c
.BI "QString \fBname\fR () const"
.br
.ti -1c
.BI "void \fBsetName\fR ( const QString & name ) "
.br
.ti -1c
.BI "typedef \fBQCString\fR ( * EncoderFn )( const QString & " "fileName" ") "
.br
.ti -1c
.BI "typedef \fBQString\fR ( * DecoderFn )( const QCString & " "localfileName" ") "
.br
.ti -1c
.BI "bool \fBexists\fR () const"
.br
.ti -1c
.BI "bool \fBremove\fR () "
.br
.ti -1c
.BI "virtual bool \fBopen\fR ( int ) "
.br
.ti -1c
.BI "bool \fBopen\fR ( int, FILE * ) "
.br
.ti -1c
.BI "bool \fBopen\fR ( int, int ) "
.br
.ti -1c
.BI "virtual void \fBclose\fR () "
.br
.ti -1c
.BI "virtual void \fBflush\fR () "
.br
.ti -1c
.BI "virtual uint \fBsize\fR () const"
.br
.ti -1c
.BI "virtual int \fBat\fR () const"
.br
.ti -1c
.BI "virtual bool \fBat\fR ( int ) "
.br
.ti -1c
.BI "virtual bool \fBatEnd\fR () const"
.br
.ti -1c
.BI "virtual int \fBreadBlock\fR ( char * " "data" ", uint len ) "
.br
.ti -1c
.BI "virtual int \fBreadLine\fR ( char * " "data" ", uint maxlen ) "
.br
.ti -1c
.BI "int \fBreadLine\fR ( QString &, uint maxlen ) "
.br
.ti -1c
.BI "virtual int \fBgetch\fR () "
.br
.ti -1c
.BI "virtual int \fBputch\fR ( int ) "
.br
.ti -1c
.BI "virtual int \fBungetch\fR ( int ) "
.br
.ti -1c
.BI "int \fBhandle\fR () const"
.br
.in -1c
.SS "Static Public Members"
.in +1c
.ti -1c
.BI "QCString \fBencodeName\fR ( const QString & fileName ) "
.br
.ti -1c
.BI "QString \fBdecodeName\fR ( const QCString & localFileName ) "
.br
.ti -1c
.BI "void \fBsetEncodingFunction\fR ( EncoderFn ) "
.br
.ti -1c
.BI "void \fBsetDecodingFunction\fR ( DecoderFn ) "
.br
.ti -1c
.BI "bool \fBexists\fR ( const QString & fileName ) "
.br
.ti -1c
.BI "bool \fBremove\fR ( const QString & fileName ) "
.br
.in -1c
.SH DESCRIPTION
The QFile class is an I/O device that operates on files.
.PP
QFile is an I/O device for reading and writing binary and text files. A QFile may be used by itself (readBlock and writeBlock) or by more conveniently using QDataStream or QTextStream.
.PP
Here is a code fragment that uses QTextStream to read a text file line by line. It prints each line with a line number.
.PP
.nf
.br
    QFile f("file.txt");
.br
    if ( f.open(IO_ReadOnly) ) {    // file opened successfully
.br
        QTextStream t( &f );        // use a text stream
.br
        QString s;
.br
        int n = 1;
.br
        while ( !t.eof() ) {        // until end of file...
.br
            s = t.readLine();       // line of text excluding '\\n'
.br
            printf( "%3d: %s\\n", n++, (const char *)s );
.br
        }
.br
        f.close();
.br
    }
.fi
.PP
The QFileInfo class holds detailed information about a file, such as access permissions, file dates and file types.
.PP
The QDir class manages directories and lists of file names.
.PP
See also QDataStream and QTextStream.
.PP
Examples:
.(l
xml/tagreader/tagreader.cpp xml/tagreader
.)l-with-features/tagreader.cpp
.SH MEMBER FUNCTION DOCUMENTATION
.SH "QFile::QFile ()"
Constructs a QFile with no name.
.SH "QFile::QFile ( const QString & name )"
Constructs a QFile with a file name \fIname.\fR
.PP
See also setName().
.SH "QFile::~QFile ()"
Destructs a QFile. Calls close().
.SH "bool QFile::at ( int pos ) \fC[virtual]\fR"
Sets the file index to \fIpos.\fR Returns TRUE if successful, otherwise FALSE.
.PP
Example:
.PP
.nf
.br
    QFile f( "data.bin" );
.br
    f.open( IO_ReadOnly );                      // index set to 0
.br
    f.at( 100 );                                // set index to 100
.br
    f.at( f.at()+50 );                          // set index to 150
.br
    f.at( f.size()-80 );                        // set index to 80 before EOF
.br
    f.close();
.fi
.PP
\fBWarning:\fR The result is undefined if the file was opened using the \fCIO_Append\fR specifier.
.PP
See also size() and open().
.PP
Reimplemented from QIODevice.
.SH "int QFile::at () const \fC[virtual]\fR"
Returns the file index.
.PP
See also size().
.PP
Reimplemented from QIODevice.
.SH "bool QFile::atEnd () const \fC[virtual]\fR"
Returns TRUE if the end of file has been reached, otherwise FALSE.
.PP
See also size().
.PP
Reimplemented from QIODevice.
.SH "void QFile::close () \fC[virtual]\fR"
Closes an open file.
.PP
The file is not closed if it was opened with an existing file handle. If the existing file handle is a \fCFILE*,\fR the file is flushed. If the existing file handle is an \fCint\fR file descriptor, nothing is done to the file.
.PP
Some "write-behind" filesystems may report an unspecified error on closing the file. These errors only indicate that something may have gone wrong since the previous open(). In such a case status() reports IO_UnspecifiedError after close(), otherwise IO_Ok.
.PP
See also open() and flush().
.PP
Reimplemented from QIODevice.
.SH "QString QFile::decodeName ( const QCString & localFileName ) \fC[static]\fR"
This does the reverse of QFile::encodeName().
.PP
See also setDecodingFunction().
.SH "QCString QFile::encodeName ( const QString & fileName ) \fC[static]\fR"
When you use QFile, QFileInfo, and QDir to access the filesystem with Qt, you can use Unicode filenames. On Unix, these filenames are converted to an 8-bit encoding. If you want to do your own file I/O on Unix, you should convert the filename using this function. On Windows NT, Unicode filenames are supported directly in the filesystem and this function should be avoided. On Windows 95, non-Latin1 locales are not supported at this time.
.PP
By default, this function converts to the local 8-bit encoding determined by the user's locale. This is sufficient for filenames that the user chooses. Filenames hard-coded into the application should only use 7-bit ASCII filename characters.
.PP
The conversion scheme can be changed using setEncodingFunction(). This might be useful if you wish to give the user an option to store in filenames in UTF-8, etc., but beware that such filenames would probably then be unrecognizable when seen by other programs.
.PP
See also decodeName().
.SH "bool QFile::exists () const"
Returns TRUE if this file exists, otherwise FALSE.
.PP
See also name().
.SH "bool QFile::exists ( const QString & fileName ) \fC[static]\fR"
Returns TRUE if the file given by \fIfileName\fR exists, otherwise FALSE.
.SH "void QFile::flush () \fC[virtual]\fR"
Flushes the file buffer to the disk.