qbuffer.3qt

linux下GUI编程工具qt的在线连接帮助手册

'\" t
.TH QBuffer 3qt "11 October 2001" "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
QBuffer \- I/O device that operates on a QByteArray
.PP
\fC#include <qbuffer.h>\fR
.PP
Inherits QIODevice.
.PP
.SS "Public Members"
.in +1c
.ti -1c
.BI "\fBQBuffer\fR ()"
.br
.ti -1c
.BI "\fBQBuffer\fR ( QByteArray buf )"
.br
.ti -1c
.BI "\fB~QBuffer\fR ()"
.br
.ti -1c
.BI "QByteArray \fBbuffer\fR () const"
.br
.ti -1c
.BI "bool \fBsetBuffer\fR ( QByteArray buf )"
.br
.ti -1c
.BI "virtual Q_LONG \fBwriteBlock\fR ( const char * p, Q_ULONG len )"
.br
.ti -1c
.BI "Q_LONG \fBwriteBlock\fR ( const QByteArray & data )"
.br
.in -1c
.SH DESCRIPTION
The QBuffer class is an I/O device that operates on a QByteArray.
.PP
QBuffer is used to read and write to a memory buffer. It is normally used with a QTextStream or a QDataStream. QBuffer has an associated QByteArray which holds the buffer data. The size() of the buffer is automatically adjusted as data is written.
.PP
The constructor \fCQBuffer(QByteArray)\fR creates a QBuffer with an existing byte array. The byte array can also be set with setBuffer(). Writing to the QBuffer will modify the original byte array because QByteArray is explicitly shared.
.PP
Use open() to open the buffer before use and to set the mode (read-only, write-only, etc.). close() closes the buffer. The buffer must be closed before reopening or calling setBuffer().
.PP
A common way to use QBuffer is through QDataStream or QTextStream, which have constructors that take a QBuffer parameter. For convenience, there are also QDataStream and QTextStream constructors that take a QByteArray parameter. These constructors create and open an internal QBuffer.
.PP
Note that QTextStream can also operate on a QString (a Unicode string); a QBuffer cannot.
.PP
You can also use QBuffer directly through the standard QIODevice functions readBlock(), writeBlock() readLine(), at(), getch(), putch() and ungetch().
.PP
See also QFile, QDataStream, QTextStream, QByteArray, Shared Classes, Collection Classes and Input/Output and Networking.
.SH MEMBER FUNCTION DOCUMENTATION
.SH "QBuffer::QBuffer ()"
Constructs an empty buffer.
.SH "QBuffer::QBuffer ( QByteArray buf )"
Constructs a buffer that operates on \fIbuf\fR. If you open the buffer in write mode (<a href="qfile.html#open">IO_WriteOnly</a> or IO_ReadWrite) and write something into the buffer, \fIbuf\fR will be modified.
.PP
Example:
.PP
.nf
.br
    QCString str = "abc";
.br
    QBuffer b( str );
.br
    b.open( IO_WriteOnly );
.br
    b.at( 3 ); // position at the 4th character (the terminating \\0)
.br
    b.writeBlock( "def", 4 ); // write "def" including the terminating \\0
.br
    b.close();
.br
    // Now, str == "abcdef" with a terminating \\0
.br
.fi
.PP
See also setBuffer().
.SH "QBuffer::~QBuffer ()"
Destroys the buffer.
.SH "QByteArray QBuffer::buffer () const"
Returns this buffer's byte array.
.PP
See also setBuffer().
.SH "bool QBuffer::setBuffer ( QByteArray buf )"
Replaces the buffer's contents with \fIbuf\fR.
.PP
This may not be done when isOpen() is TRUE.
.PP
Note that if you open the buffer in write mode (<a href="qfile.html#open">IO_WriteOnly</a> or IO_ReadWrite) and write something into the buffer, \fIbuf\fR is also modified because QByteArray is an explicitly shared class.
.PP
See also buffer(), open() and close().
.SH "Q_LONG QBuffer::writeBlock ( const char * p, Q_ULONG len )\fC [virtual]\fR"
Writes \fIlen\fR bytes from \fIp\fR into the buffer at the current index, overwriting any characters there and extending the buffer if necessary. Returns the number of bytes actually written.
.PP
Returns -1 if an error occurred.
.PP
See also readBlock().
.PP
Reimplemented from QIODevice.
.SH "Q_LONG QBuffer::writeBlock ( const QByteArray & data )"
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
.PP
This convenience function takes \fIdata\fR and is the same as calling \fCwriteBlock( data.data(), data.size() )\fR.
.PP

.SH "SEE ALSO"
.BR http://doc.trolltech.com/qbuffer.html
.BR http://www.trolltech.com/faq/tech.html
.SH COPYRIGHT
Copyright 1992-2001 Trolltech AS, http://www.trolltech.com.  See the
license file included in the distribution for a complete license
statement.
.SH AUTHOR
Generated automatically from the source code.
.SH BUGS
If you find a bug in Qt, please report it as described in
.BR http://doc.trolltech.com/bughowto.html .
Good bug reports help us to help you. Thank you.
.P
The definitive Qt documentation is provided in HTML format; it is
located at $QTDIR/doc/html and can be read using Qt Assistant or with
a web browser. This man page is provided as a convenience for those
users who prefer man pages, although this format is not officially
supported by Trolltech. 
.P
If you find errors in this manual page, please report them to
.BR [e-mail] .
Please include the name of the manual page (qbuffer.3qt) and the Qt
version (3.0.0).