android-calculatorpp/android-app/src/main/java/org/solovyev/android/calculator/plot/GraphData.java

package org.solovyev.android.calculator.plot;

import javax.annotation.Nonnull;

class GraphData {

	private int size = 0;

	private int allocatedSize = 4;
	private float[] xs = new float[allocatedSize];
	private float[] ys = new float[allocatedSize];

	private GraphData() {
	}

	@Nonnull
	static GraphData newEmptyInstance() {
		return new GraphData();
	}

	void swap(@Nonnull GraphData that) {
		float savedXs[] = that.xs;
		float savedYs[] = that.ys;
		int savedSize = that.size;
		int savedAllocatedSize = that.allocatedSize;

		that.xs = this.xs;
		that.ys = this.ys;
		that.size = this.size;
		that.allocatedSize = this.allocatedSize;

		this.xs = savedXs;
		this.ys = savedYs;
		this.size = savedSize;
		this.allocatedSize = savedAllocatedSize;
	}

	void push(float x, float y) {
		if (size >= allocatedSize) {
			makeSpaceAtTheEnd(size + 1);
		}

		xs[size] = x;
		ys[size] = y;
		++size;
	}

	private void makeSpaceAtTheEnd(int newSize) {
		int oldAllocatedSize = allocatedSize;
		while (newSize > allocatedSize) {
			allocatedSize += allocatedSize;
		}

		if (oldAllocatedSize != allocatedSize) {
			float[] a = new float[allocatedSize];
			System.arraycopy(xs, 0, a, 0, this.size);
			xs = a;
			a = new float[allocatedSize];
			System.arraycopy(ys, 0, a, 0, this.size);
			ys = a;
		}
	}


	float getLastX() {
		return xs[size - 1];
	}

	float getLastY() {
		return ys[size - 1];
	}

	float getFirstX() {
		return xs[0];
	}

	float getFirstY() {
		return ys[0];
	}

	void pop() {
		--size;
	}

	boolean empty() {
		return size == 0;
	}

	void clear() {
		size = 0;
	}

	void eraseBefore(float x) {
		int i = 0;
		while (i < size && xs[i] < x) {
			++i;
		}
		// step back as xs[i] >= x and xs[i-1] < x
		--i;

		if (i > 0) {
			size -= i;
			System.arraycopy(xs, i, xs, 0, size);
			System.arraycopy(ys, i, ys, 0, size);
		}
	}

	void eraseAfter(float x) {
		int i = size - 1;
		while (i >= 0 && x < xs[i]) {
			--i;
		}

		// step next as xs[i] > x and xs[i+1] <= x
		++i;

		if (i < size - 1) {
			size = i + 1;
		}
	}

	int findPositionAfter(float x, float y) {
		int i = 0;
		while (i < size && xs[i] <= x) {
			++i;
		}

		if (Float.isNaN(y)) {
			while (i < size && Float.isNaN(ys[i])) {
				++i;
			}
		}

		return i;
	}

	void append(GraphData that) {
		makeSpaceAtTheEnd(size + that.size);
		int position = that.findPositionAfter(xs[size - 1], ys[size - 1]);
		System.arraycopy(that.xs, position, xs, size, that.size - position);
		System.arraycopy(that.ys, position, ys, size, that.size - position);
		size += that.size - position;
	}

	public String toString() {
		StringBuilder b = new StringBuilder();
		b.append(size).append(": ");
		for (int i = 0; i < size; ++i) {
			b.append(xs[i]).append(", ");
		}
		return b.toString();
	}

	public float[] getXs() {
		return xs;
	}

	public float[] getYs() {
		return ys;
	}

	public int getSize() {
		return size;
	}
}