I'm using Qt to make some audio output. There is an example audioouput, where pure virtual function qint64 QIODevice::readData ( char * data, qint64 maxSize ) is reimplemented like this(this is not actual code from example).
qint64 Generator::readData(char *data, qint64 len)
{
memcpy(data, m_buffer.data(), len);
return len;
}
So, we get pointer to data, copy memory from our buffer to this data. I'm wondering whether I can just assign pointer data to new location, like this:
qint64 Generator::readData(char *data, qint64 len)
{
data = m_buffer.data();
return len;
}
Because, memcpy is slow and C. So can I? Thank you!
OK, just not to receive comments "what is slow": first - memcpy slower than pointer assignment second - yes, I have latency in sound playing, I want to make program optimal at every point.
P.S. I'm trying to do it, and I have no sound, so maybe answer is no. Then why?
The signature of this method only lets you return the data by copying them. Assigning the pointer is pointless because this parameter is passed as a copy, so the assigned value won't be visible outside your method.
memcpy is not at all slow for realtime audio output (unless you are doing it on an 8-bit processor).
Too slow audio code can cause gaps in the sound but not latency. Latency is a result of a too big audio buffer.