Add QTextStream::readLine() overload

The most common use case for QTextStream::readLine() is reading
a file line by line in a loop. The existing readLine() method
allocates new memory for each line, that results in a loss of
speed. The introduced overload can use already allocated memory.

Besides it allows you to not think about filesystem specifics.
The current QFile documentation suggests a separate way to read
files from /proc filesystem. With this overload it's possible
to use the same idiom in all cases:

    QTextStream in(&file);
    QString line;
    while (in.readLine(&line)) {
        process_line(line);
    }

The idea was inspired by the blog post of Ivan Čukić:
http://ivan.fomentgroup.org/blog/2014/10/03/api-design-and-impact-on-the-performance-qt-vs-stl-example/

Change-Id: I0c62b4a52681870589bc099905e83ed69e03dd40
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/corelib/io/qtextstream.h b/src/corelib/io/qtextstream.h
index b15e7772e2..6f5e2473e4 100644
--- a/src/corelib/io/qtextstream.h
+++ b/src/corelib/io/qtextstream.h
@@ -124,6 +124,7 @@ public:
     void skipWhiteSpace();
 
     QString readLine(qint64 maxlen = 0);
+    bool readLine(QString *line, qint64 maxlen = 0);
     QString readAll();
     QString read(qint64 maxlen);