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/* ****************************************************************************
 * horizontal_scroll.c -- Scroll the screen horizontally.
 * Copyright (C)      2011 Pierre Le Gall <legallpierre89@gmail.com>
 * Copyright (C) 2016-2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
 *
 * This file is part of the 'casiowin/monochromelib' module in libcarrot, an
 * experimental modular libc project.
 *
 * This file is governed by the CeCILL-C license under French law and abiding
 * by the rules of distribution of free software. You can use, modify and or
 * redistribute it under the terms of the CeCILL-C license as circulated by
 * CEA, CNRS and INRIA at the following URL: http://www.cecill.info
 *
 * As a counterpart to the access to the source code and rights to copy, modify
 * and redistribute granted by the license, users are provided only with a
 * limited warranty and the software's author, the holder of the economic
 * rights, and the successive licensors have only limited liability.
 *
 * In this respect, the user's attention is drawn to the risks associated with
 * loading, using, modifying and/or developing and reproducing the software by
 * the user in light of its specific status of free software, that may mean
 * that it is complicated to manipulate, and that also therefore means that it
 * is reserved for developers and experienced professionals having in-depth
 * computer knowledge. Users are therefore encouraged to load and test the
 * software's suitability as regards their requirements in conditions enabling
 * the security of their systems and/or data to be ensured and, more generally,
 * to use and operate it in the same conditions as regards security.
 *
 * The fact that you are presently reading this means you have had knowledge of
 * the CeCILL-C license and that you accept its terms.
 * ************************************************************************* */
#include <monochrome.h>

void ML_horizontal_scroll(int scroll)
{
	int i, j;
	char line[16], shift, *vram;
	unsigned char next;
	unsigned short word;
	vram = ML_vram_adress();
	scroll %= 128;
	shift = 8-(scroll&7);
	for(i=0 ; i<64 ; i++)
	{
		for(j=0 ; j<16 ; j++) line[j] = vram[(i<<4)+((j-(scroll>>3)+15)&15)];
		next = line[15];
		vram[(i<<4)+15] = 0;
		for(j=15 ; j>0 ; j--)
		{
			word = next << shift;
			next = line[j-1];
			vram[(i<<4)+j] |= *((char*)&word+1);
			vram[(i<<4)+j-1] = *((char*)&word);
		}
		word = next << shift;
		vram[(i<<4)] |= *((char*)&word+1);
		vram[(i<<4)+15] |= *((char*)&word);
	}
}