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QTextStream: optimize putString()

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Instead of filling a QString with the padding characters, use a
QVarLengthArray. Do this only in the code path where it's actually
needed, and mark that code path as unlikely.

Change-Id: I11e04ccc4a07e16e430f2ea6dbb2f0f736908f5b
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Marc Mutz 2015-10-15 03:05:26 +02:00
parent 035f5478a5
commit aa485aee2f
1 changed files with 15 additions and 10 deletions
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25
src/corelib/io/qtextstream.cpp
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@ -222,6 +222,8 @@ static const int QTEXTSTREAM_BUFFERSIZE = 16384;
#include "qbuffer.h"
#include "qfile.h"
#include "qnumeric.h"
#include "qvarlengtharray.h"
#ifndef Q_OS_WINCE
#include <locale.h>
#endif
@ -896,13 +898,15 @@ inline void QTextStreamPrivate::putChar(QChar ch)
*/
void QTextStreamPrivate::putString(const QChar *data, int len, bool number)
{
QString pad;
int padLeft = 0, padRight = 0;
// handle padding
int padSize = params.fieldWidth - len;
if (padSize > 0) {
pad = QString(padSize, params.padChar);
if (Q_UNLIKELY(padSize > 0)) {
// handle padding
static const int PreallocatedPadding = 80; // typical line length
QVarLengthArray<QChar, PreallocatedPadding> pad(padSize);
std::fill_n(pad.begin(), padSize, params.padChar);
int padLeft = 0, padRight = 0;
switch (params.fieldAlignment) {
case QTextStream::AlignLeft:
padRight = padSize;
@ -925,11 +929,12 @@ void QTextStreamPrivate::putString(const QChar *data, int len, bool number)
padRight = padSize - padSize/2;
break;
}
write(pad.constData(), padLeft);
write(data, len);
write(pad.constData(), padRight);
} else {
write(data, len);
}
write(pad.constData(), padLeft);
write(data, len);
write(pad.constData(), padRight);
}
/*!