snuvi-engine/src/me/hammerle/snuviengine/api/Timer.java

package me.hammerle.snuviengine.api;

import java.nio.FloatBuffer;
import org.lwjgl.BufferUtils;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL15.*;
import static org.lwjgl.opengl.GL20.*;
import static org.lwjgl.opengl.GL30.*;

public class Timer
{
    private static final int SIZE = 128;
    
    private int index = -1;
    private final long[] times = new long[SIZE];
    private long sum = 0;
    private double callsPerSecond = 0;
    private long lastTime = System.nanoTime();
    
    private final int vao;
    private final int vbo;
    
    private final FloatBuffer buffer = BufferUtils.createFloatBuffer(18);
    
    private boolean active = false;
    
    private float expectedValue;
    
    protected Timer(float expectedValue)
    {
        this.expectedValue = expectedValue;

        vao = glGenVertexArrays();
        vbo = glGenBuffers();

        GLHelper.glBindVertexArray(vao);
        GLHelper.glBindBuffer(vbo);

        glEnableVertexAttribArray(0);
        glEnableVertexAttribArray(2);

        glVertexAttribPointer(0, 2, GL_FLOAT, false, 12, 0);
        glVertexAttribPointer(2, 4, GL_UNSIGNED_BYTE, true, 12, 8);

        glBufferData(GL_ARRAY_BUFFER, SIZE * buffer.limit() * 4, GL_STATIC_DRAW);
    }
    
    protected void setActive(boolean active)
    {
        this.active = active;
    }
    
    protected void update()
    {
        index = (index + 1) & (SIZE - 1);
        
        long time = System.nanoTime();
        sum -= times[index];
        times[index] = time - lastTime;
        sum += times[index];
        lastTime = time;
        callsPerSecond = (1_000_000_000.0 * SIZE) / sum;
        
        if(active)
        {
            float minX = index * 3;
            float minY = 0.0f;
            float maxX = minX + 2;
            float maxY = 1_000_000_000.0f / times[index];

            float diff = (maxY - expectedValue) / expectedValue;
            int r = Math.min((int) (128 * (1 - Math.min(diff, 0.0f) * 16)), 255);
            int g = Math.min((int) (128 * (1 + Math.max(diff, 0.0f) * 16)), 255);
            int b = (int) (128 * (1 - Math.abs(diff)));
            float color = Float.intBitsToFloat(r | (g << 8) | (b << 16) | 0xFF000000);

            buffer.put(minX);
            buffer.put(maxY);   
            buffer.put(color);

            buffer.put(minX);
            buffer.put(minY);   
            buffer.put(color);

            buffer.put(maxX);
            buffer.put(maxY);  
            buffer.put(color);

            buffer.put(minX);
            buffer.put(minY);   
            buffer.put(color);

            buffer.put(maxX);
            buffer.put(maxY);  
            buffer.put(color);

            buffer.put(maxX);
            buffer.put(minY);  
            buffer.put(color);

            buffer.flip();

            GLHelper.glBindBuffer(vbo);
            glBufferSubData(GL_ARRAY_BUFFER, index * buffer.limit() * 4, buffer);
        }
    }
    
    protected void setExpectedValue(float value)
    {
        expectedValue = value;
    }
    
    protected long getAverageTime()
    {
        return sum / SIZE;
    }
    
    protected long getCurrentTime()
    {
        return System.nanoTime() - lastTime;
    }
    
    protected long getTime()
    {
        return times[index];
    }
    
    protected double getCallsPerSecond()
    {
        return callsPerSecond;
    }
    
    protected void draw(Renderer r)
    {
        if(active)
        {
            r.setTextureEnabled(false);
            r.setColorEnabled(true);

            GLHelper.glBindBuffer(vbo);
            GLHelper.glBindVertexArray(vao);
            glDrawArrays(GL_TRIANGLES, 0, SIZE * 6);
        }
    }
}