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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);
}
}
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