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Improve QBitArray's construction performance a little

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Ask for an uninitialized byte array, since we're about to memset(3) it
anyway. And don't overwrite the initial byte either.

Change-Id: I2caa2ef395ad5684416e6cd336c0444de7787b5d
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
This commit is contained in:
Thiago Macieira 2013-08-28 18:37:00 -07:00 committed by The Qt Project
parent e13e90fb55
commit 260a983052
1 changed files with 4 additions and 5 deletions
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9
src/corelib/tools/qbitarray.cpp
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@ -136,15 +136,14 @@ QT_BEGIN_NAMESPACE
initialized with \a value, which defaults to false (0).
*/
QBitArray::QBitArray(int size, bool value)
: d(size <= 0 ? 0 : 1 + (size + 7)/8, Qt::Uninitialized)
{
Q_ASSERT_X(size >= 0, "QBitArray::QBitArray", "Size must be greater than or equal to 0.");
if (size <= 0) {
d.resize(0);
if (size <= 0)
return;
}
d.resize(1 + (size+7)/8);
uchar* c = reinterpret_cast<uchar*>(d.data());
memset(c, value ? 0xff : 0, d.size());
memset(c + 1, value ? 0xff : 0, d.size() - 1);
*c = d.size()*8 - size;
if (value && size && size % 8)
*(c+1+size/8) &= (1 << (size%8)) - 1;