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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 free software: you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 *
 * This file is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Lesser Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this file. If not, see <http://www.gnu.org/licenses/>.
 * ************************************************************************* */
#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);
	}
}