/*
 * Copyright (c) 2002-2004 LWJGL Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of 'LWJGL' nor the names of
 *   its contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.lwjgl.opengl;


/**
 * $Id$ A class to
 * check buffer boundaries in GL methods. Many GL methods read data from the GL
 * into a native Buffer at its current position. If there is unsufficient space
 * in the buffer when the call is made then a buffer overflow would otherwise
 * occur and cause unexpected behaviour, a crash, or worse, a security risk.
 * Therefore in those methods where GL reads data back into a buffer, we will
 * call a bounds check method from this class to ensure that there is
 * sufficient space in the buffer.
 *
 * Thrown by the debug build library of the LWJGL if any OpenGL operation
 * causes an error.
 *
 * @author cix_foo <cix_foo@users.sourceforge.net>
 * @version $Revision$
 */
class GLBufferChecks {
	/** Static methods only! */
	private GLBufferChecks() {
	}

	/**
	 * Helper method to ensure that vertex buffer objects are disabled. If they
	 * are enabled, we'll throw an OpenGLException
	 */
	static void ensureArrayVBOdisabled() {
		if (VBOTracker.getVBOArrayStack().getState() != 0) {
			throw new OpenGLException("Cannot use Buffers when VBO is enabled");
		}
	}
	/**
	 * Helper method to ensure that vertex buffer objects are enabled. If they
	 * are disabled, we'll throw an OpenGLException
	 */
	static void ensureArrayVBOenabled() {
		if (VBOTracker.getVBOArrayStack().getState() == 0) {
			throw new OpenGLException("Cannot use offsets when VBO is disabled");
		}
	}
	/**
	 * Helper method to ensure that vertex buffer objects are disabled. If they
	 * are enabled, we'll throw an OpenGLException
	 */
	static void ensureElementVBOdisabled() {
		if (VBOTracker.getVBOElementStack().getState() != 0) {
			throw new OpenGLException("Cannot use Buffers when VBO is enabled");
		}
	}
	/**
	 * Helper method to ensure that vertex buffer objects are enabled. If they
	 * are disabled, we'll throw an OpenGLException
	 */
	static void ensureElementVBOenabled() {
		if (VBOTracker.getVBOElementStack().getState() == 0) {
			throw new OpenGLException("Cannot use offsets when VBO is disabled");
		}
	}
	/**
	 * Calculate the storage required for an image.
	 *
	 * @param format
	 *            The format of the image (example: GL_RGBA)
	 * @param type
	 *            The type of the image elements (example: GL_UNSIGNED_BYTE)
	 * @param width
	 *            The width of the image
	 * @param height
	 *            The height of the image (1 for 1D images)
	 * @param depth
	 *            The depth of the image (1 for 2D images)
	 * @return the size, in bytes, of the image
	 */
	static int calculateImageStorage(int format, int type, int width, int height, int depth) {
		int bpe;
		switch (type) {
			case GL11.GL_UNSIGNED_BYTE :
			case GL11.GL_BYTE :
				bpe = 1;
				break;
			case GL11.GL_UNSIGNED_SHORT :
			case GL11.GL_SHORT :
				bpe = 2;
				break;
			case GL11.GL_UNSIGNED_INT :
			case GL11.GL_INT :
			case GL11.GL_FLOAT :
				bpe = 4;
				break;
			default :
				// TODO: Add more types (like the GL12 types GL_UNSIGNED_INT_8_8_8_8
				return 0;
		//		throw new IllegalArgumentException("Unknown type " + type);
		}
		int epp;
		switch (format) {
			case GL11.GL_LUMINANCE:
			case GL11.GL_ALPHA:
				epp = 1;
				break;

			case GL11.GL_LUMINANCE_ALPHA:
				epp = 2;
				break;
			case GL11.GL_RGB :
			case EXTBgra.GL_BGR_EXT :
				epp = 3;
				break;
			case GL11.GL_RGBA :
			case EXTAbgr.GL_ABGR_EXT :
			case EXTBgra.GL_BGRA_EXT :
				epp = 4;
				break;
			default :
				// TODO: Add more formats. Assuming 4 is too wasteful on buffer sizes where e.g. 1 is enough (like GL_DEPTH_COMPONENT)
				return 0;
/*				// Assume 4 elements per pixel
				epp = 4;*/
		}
		return epp * bpe * width * height * depth;
	}
}