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#ident "$Id: run_tbl.c,v 4.1 1997/01/12 14:54:22 gert Exp $ Copyright (c) 1994 Gert Doering"
/* run_tbl.c
*
* this file is part of the mgetty+sendfax distribution
*
* compute a set of arrays that will speed up finding the run length
* of black or white bits in a byte enourmously
* (I do not include the array as it is larger than the source and
* computation is fast enough - 0.005 secs on my machine...)
*/
#include "ugly.h"
static unsigned char tab[9] = { 0x00,
0x01, 0x03, 0x07, 0x0f,
0x1f, 0x3f, 0x7f, 0xff };
char w_rtab[8][256];
char b_rtab[8][256];
void make_run_tables _P0( void )
{
int i, j, k, m; /* byte = kkkjjjmm, "j" starts at bit "i" */
int mask; /* black mask (all ones), start bit i, j bits wide */
for ( i=0; i<8; i++ ) /* for (all starting bits) */
{
for ( j=i+1; j>=0; j-- ) /* for (all possible run lengths) */
{
mask = tab[j] << ((i-j)+1);
if ( i == 7 ) /* no fill bits to the left */
{
if ( j == i+1 ) /* no fill bits to the right */
{
w_rtab[i][0 ] = j;
b_rtab[i][mask] = j;
}
else /* fill bits to the right */
for ( m = ( 1 << (i-j) ) -1 ; m >= 0; m-- )
{
w_rtab[i][0 + (1<<(i-j)) + m ] = j;
b_rtab[i][mask+ 0 + m ] = j;
}
}
else /* i != 7 -> fill higher bits */
for ( k = (0x80>>i) -1; k>= 0; k-- )
{
if ( j == i+1 ) /* no noise to the right */
{
w_rtab[i][ (k << (i+1)) + 0 ] = j;
b_rtab[i][ (k << (i+1)) + mask ] = j;
}
else /* fill bits to left + right */
for ( m = ( 1 << (i-j) ) -1; m >= 0; m-- )
{
w_rtab[i][ (k << (i+1)) + 0 + (1<<(i-j)) + m ] = j;
b_rtab[i][ (k << (i+1)) + mask + 0 + m ] = j;
}
} /* end for (k) [noise left of top bit] */
} /* end for (j) [span] */
} /* end for (i) [top bit] */
}
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