Appending text to a file

[janus]

Hi,

I would like to crate a ics (iCalendar) file. The file content is something like this.

BEGIN:VCALENDAR
VERSION:2.0
PRODID:http://www.example.com/calendarapplication/
METHOD:PUBLISH
BEGIN:VEVENT
UID:461092315540@example.com
ORGANIZER;CN="Alice Balder, Example Inc.":MAILTO:alice@example.com
SUMMARY:Eine Kurzinfo
DESCRIPTION:Beschreibung des Termines
CLASS:PUBLIC
DTSTART:20060910T220000Z
DTEND:20060919T215900Z
DTSTAMP:20060812T125900Z
END:VEVENT
END:VCALENDAR

BEGIN:VCALENDAR
VERSION:2.0
PRODID:http://www.example.com/calendarapplication/
METHOD:PUBLISH
BEGIN:VEVENT
UID:461092315540@example.com
ORGANIZER;CN="Alice Balder, Example Inc.":MAILTO:alice@example.com
SUMMARY:Eine Kurzinfo
DESCRIPTION:Beschreibung des Termines
CLASS:PUBLIC
DTSTART:20060910T220000Z
DTEND:20060919T215900Z
DTSTAMP:20060812T125900Z
END:VEVENT
END:VCALENDAR

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What is the best way to add an VEVENT in between BEGIN:VCALENDAR and END:VCALENDAR?

Do I need to read the whole file, remove END:VCALENDAR, append the new VEVENT + END:VCALENDAR and then write the whole thing again? When the calendar grows from week to week this might not be the best way.

[seneca]

You can open the file for read/write, find END:VCALENDAR by seeking from the end and then just write over it.

[janus]

Hi,

thx, I tried this:

QFile file("inout.txt");
    if (file.open(QIODevice::ReadWrite | QIODevice::Text)) {
 
		 QTextStream in(&file);
 
		 while (!in.atEnd()) {
 
			 if (in.readLine() == "END:VCALENDAR") {
				 //here I need to overwrite - how?
				 in << "TEST\nEND:VCALENDAR\n";
				 break;
			 }
		 }
     }

QFile file("inout.txt");
    if (file.open(QIODevice::ReadWrite | QIODevice::Text)) {

		 QTextStream in(&file);

		 while (!in.atEnd()) {

			 if (in.readLine() == "END:VCALENDAR") {
				 //here I need to overwrite - how?
				 in << "TEST\nEND:VCALENDAR\n";
				 break;
			 }
		 }
     }

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the end of the file looks like this:

END:VCALENDARTEST
END:VCALENDAR

END:VCALENDARTEST
END:VCALENDAR

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How can move "backwards" to overwrite the line? Start reading the file from the end does not work, I guess ...

[janus]

Seems to work like this:

QFile file("inout.txt");
    if (file.open(QIODevice::ReadWrite | QIODevice::Text)) {
 
		 QTextStream in(&file);
 
		 while (!in.atEnd()) {
			 qint64 last = in.pos();
			 if (in.readLine() == "END:VCALENDAR") {
				 in.seek(last);
				 in << "TEST\nEND:VCALENDAR\n";
				 break;
			 }
		 }
     }

QFile file("inout.txt");
    if (file.open(QIODevice::ReadWrite | QIODevice::Text)) {

		 QTextStream in(&file);

		 while (!in.atEnd()) {
			 qint64 last = in.pos();
			 if (in.readLine() == "END:VCALENDAR") {
				 in.seek(last);
				 in << "TEST\nEND:VCALENDAR\n";
				 break;
			 }
		 }
     }

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is this the best way to achieve that?

[jpn]

You are still reading the whole file line by line. You should seek at QFile::size() minus something at start writing from there.

[wysota]

Or there is libical...

[janus]

Finally ... not perfect i guess

int strSize = QString("END:VCALENDAR").size();
    	qint64 fileSize = file.size();
 
	QTextStream in(&file);
 
	in.seek(fileSize - strSize);
 
	if (in.readLine() == "END:VCALENDAR") {
		in.seek(fileSize - strSize);
		in << "TEST\nEND:VCALENDAR";
        }

int strSize = QString("END:VCALENDAR").size();
    	qint64 fileSize = file.size();

	QTextStream in(&file);

	in.seek(fileSize - strSize);

	if (in.readLine() == "END:VCALENDAR") {
		in.seek(fileSize - strSize);
		in << "TEST\nEND:VCALENDAR";
        }

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[janus]

Searching the right position seems to work, but when appending event text i get "strange" symbols () in the text file:

file

BEGIN:VCALENDAR
PRODID:ID
VERSION:2.0
BEGIN:VEVENT //in this line i try to start writing the event text

BEGIN:VCALENDAR
PRODID:ID
VERSION:2.0
BEGIN:VEVENT //in this line i try to start writing the event text

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code

QString event;
	event.append("BEGIN:VEVENT");
	event.append("\n");
	event.append("UID:").append(DTSTAMP).append("-@cutefarm.de");
	event.append("\n");
	event.append("DTSTAMP:").append(DTSTAMP);
	event.append("\n");
	event.append("DTSTART:").append(DTSTAMP);
	event.append("\n");
	event.append("DTEND:").append(DTSTAMP);
	event.append("\n");
	event.append("SUMMARY:").append(SUMMARY);
	event.append("\n");
	event.append("DESCRIPTION:").append(DESCRIPTION);
	event.append("\n");
	event.append("CLASS:PRIVATE");
	event.append("\n");
	event.append("CATEGORIES:BUSINESS,HUMAN RESOURCES");
	event.append("\n");
	event.append("END:VEVENT");
	event.append("\n");
	event.append("END:VCALENDAR");
 
....
 
		if (in.readLine() == "END:VCALENDAR") {
			in.seek(in.pos()  - QString("END:VCALENDAR").size());
			in << event;
		}
	}

QString event;
	event.append("BEGIN:VEVENT");
	event.append("\n");
	event.append("UID:").append(DTSTAMP).append("-@cutefarm.de");
	event.append("\n");
	event.append("DTSTAMP:").append(DTSTAMP);
	event.append("\n");
	event.append("DTSTART:").append(DTSTAMP);
	event.append("\n");
	event.append("DTEND:").append(DTSTAMP);
	event.append("\n");
	event.append("SUMMARY:").append(SUMMARY);
	event.append("\n");
	event.append("DESCRIPTION:").append(DESCRIPTION);
	event.append("\n");
	event.append("CLASS:PRIVATE");
	event.append("\n");
	event.append("CATEGORIES:BUSINESS,HUMAN RESOURCES");
	event.append("\n");
	event.append("END:VEVENT");
	event.append("\n");
	event.append("END:VCALENDAR");

....

		if (in.readLine() == "END:VCALENDAR") {
			in.seek(in.pos()  - QString("END:VCALENDAR").size());
			in << event;
		}
	}

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How can I avoid these characters?

[janus]

google is my friend :-)

in.setGenerateByteOrderMark(false) did it.