circularbuffer.cpp
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#include "circularbuffer.h"
#include <math.h>
CircularBuffer::CircularBuffer(double interval, size_t numPoints):
d_y(NULL),
d_referenceTime(0.0),
d_startIndex(0),
d_offset(0.0)
{
fill(interval, numPoints);
}
void CircularBuffer::fill(double interval, size_t numPoints)
{
if ( interval <= 0.0 || numPoints < 2 )
return;
d_values.resize(numPoints);
d_values.fill(0.0);
if ( d_y )
{
d_step = interval / (numPoints - 2);
for ( size_t i = 0; i < numPoints; i++ )
d_values[i] = d_y(i * d_step);
}
d_interval = interval;
}
void CircularBuffer::setFunction(double(*y)(double))
{
d_y = y;
}
void CircularBuffer::setReferenceTime(double timeStamp)
{
d_referenceTime = timeStamp;
const double startTime = ::fmod(d_referenceTime, d_values.size() * d_step);
d_startIndex = int(startTime / d_step); // floor
d_offset = ::fmod(startTime, d_step);
}
double CircularBuffer::referenceTime() const
{
return d_referenceTime;
}
size_t CircularBuffer::size() const
{
return d_values.size();
}
QPointF CircularBuffer::sample(size_t i) const
{
const int size = d_values.size();
int index = d_startIndex + i;
if ( index >= size )
index -= size;
const double x = i * d_step - d_offset - d_interval;
const double y = d_values.data()[index];
return QPointF(x, y);
}
QRectF CircularBuffer::boundingRect() const
{
return QRectF(-1.0, -d_interval, 2.0, d_interval);
}