1 /* setmat.c 4.1 83/03/09 */ 2 /* 3 * setmat: set the value in m[r, c] to nval. 4 */ 5 6 #include "bit.h" 7 8 setmat(m, rows, cols, r, c, nval) 9 bitmat m; 10 int rows, cols, r, c, nval; 11 { 12 register int offset, thisbit; 13 14 if (r<0 || c<0 || r>=rows || c>=cols) { 15 #ifdef TRACE 16 if (trace) 17 fprintf(trace, "setmat range error: (%d, %d) <- %d in a (%d, %d) matrix %x\n", r, c, nval, rows, cols, m); 18 #endif 19 20 return; 21 } 22 offset = r*((cols+7)>>3) + (c>>3); 23 thisbit = 0x80 >> (c&7); 24 if (nval) 25 m[offset] |= thisbit; 26 else 27 m[offset] &= ~thisbit; 28 } 29