Module Name: src
Committed By: rillig
Date: Sat May 28 18:55:16 UTC 2022
Modified Files:
src/games/gomoku: bdinit.c
Log Message:
gomoku: clean up local variable names in init_overlap
By clearly associating each variable to either frame A or frame B,
suddenly the code becomes understandable. For the benefit of future
readers, explain the naming scheme.
No functional change.
To generate a diff of this commit:
cvs rdiff -u -r1.25 -r1.26 src/games/gomoku/bdinit.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/games/gomoku/bdinit.c
diff -u src/games/gomoku/bdinit.c:1.25 src/games/gomoku/bdinit.c:1.26
--- src/games/gomoku/bdinit.c:1.25 Sat May 28 17:51:27 2022
+++ src/games/gomoku/bdinit.c Sat May 28 18:55:16 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: bdinit.c,v 1.25 2022/05/28 17:51:27 rillig Exp $ */
+/* $NetBSD: bdinit.c,v 1.26 2022/05/28 18:55:16 rillig Exp $ */
/*
* Copyright (c) 1994
@@ -34,7 +34,7 @@
#include <sys/cdefs.h>
/* from: @(#)bdinit.c 8.2 (Berkeley) 5/3/95 */
-__RCSID("$NetBSD: bdinit.c,v 1.25 2022/05/28 17:51:27 rillig Exp $");
+__RCSID("$NetBSD: bdinit.c,v 1.26 2022/05/28 18:55:16 rillig Exp $");
#include <string.h>
#include "gomoku.h"
@@ -160,6 +160,52 @@ init_board(void)
init_overlap();
}
+/*-
+ * ra direction of frame A
+ * ia index of the spot in frame A (0 to 5)
+ * rb direction of frame B
+ * ib index of the spot in frame B (0 to 5)
+ */
+static u_char
+adjust_overlap(u_char ov, int ra, int ia, int rb, int ib, int mask)
+{
+ ov |= (ib == 5) ? mask & 0xA : mask;
+ if (rb != ra)
+ return ov;
+
+ /* compute the multiple spot overlap values */
+ switch (ia) {
+ case 0:
+ if (ib == 4)
+ ov |= 0xA0;
+ else if (ib != 5)
+ ov |= 0xF0;
+ break;
+ case 1:
+ if (ib == 5)
+ ov |= 0xA0;
+ else
+ ov |= 0xF0;
+ break;
+ case 4:
+ if (ib == 0)
+ ov |= 0xC0;
+ else
+ ov |= 0xF0;
+ break;
+ case 5:
+ if (ib == 1)
+ ov |= 0xC0;
+ else if (ib != 0)
+ ov |= 0xF0;
+ break;
+ default:
+ ov |= 0xF0;
+ }
+
+ return ov;
+}
+
/*
* Initialize the overlap array.
* Each entry in the array is a bit mask with eight bits corresponding
@@ -183,69 +229,49 @@ init_overlap(void)
memset(overlap, 0, sizeof(overlap));
memset(intersect, 0, sizeof(intersect));
- u_char *op = &overlap[FAREA * FAREA];
- short *ip = &intersect[FAREA * FAREA];
- for (unsigned fi = FAREA; fi-- > 0; ) { /* each frame */
- struct combostr *cbp = &frames[fi];
- op -= FAREA;
- ip -= FAREA;
- int vertex = cbp->c_vertex;
- struct spotstr *sp1 = &board[vertex];
- int d1 = dd[cbp->c_dir];
+ /*-
+ * Variables for frames A and B:
+ *
+ * fi index of the frame in the global 'frames'
+ * r direction: 0 = right, 1 = down right, 2 = down, 3 = down left
+ * d direction delta, difference between adjacent spot indexes
+ * si index of the spot in the frame, 0 to 5
+ * sp data of the spot at index i
+ */
+
+ for (unsigned fia = FAREA; fia-- > 0; ) {
+ struct combostr *fa = &frames[fia];
+ int vertex = fa->c_vertex;
+ struct spotstr *spa = &board[vertex];
+ u_char ra = fa->c_dir;
+ int da = dd[ra];
+
/*
- * s = 5 if closed, 6 if open.
- * At this point black & white are the same.
+ * len = 5 if closed, 6 if open.
+ * At this point, Black and White have the same values.
*/
- int s = 5 + sp1->s_fval[BLACK][cbp->c_dir].cv_win;
- /* for each spot in frame A */
- for (int i = 0; i < s; i++, sp1 += d1, vertex += d1) {
+ int len = 5 + spa->s_fval[BLACK][ra].cv_win;
+
+ for (int sia = 0; sia < len; sia++, spa += da, vertex += da) {
/* the sixth spot in frame A only overlaps if it is open */
- int mask = (i == 5) ? 0xC : 0xF;
- /* for each direction */
- for (int r = 4; --r >= 0; ) {
- struct spotstr *sp2 = sp1;
- int d2 = dd[r];
- /* for each frame that intersects at spot sp1 */
- for (int f = 0; f < 6; f++, sp2 -= d2) {
- if (sp2->s_occ == BORDER)
+ int mask = (sia == 5) ? 0xC : 0xF;
+
+ for (int rb = 4; --rb >= 0; ) {
+ struct spotstr *spb = spa;
+ int db = dd[rb];
+
+ /* for each frame that intersects at spot spa */
+ for (int sib = 0; sib < 6; sib++, spb -= db) {
+ if (spb->s_occ == BORDER)
break;
- if ((sp2->s_flags & BFLAG << r) != 0)
+ if ((spb->s_flags & BFLAG << rb) != 0)
continue;
- int n = (int)(sp2->s_frame[r] - frames);
- ip[n] = (short)vertex;
- op[n] |= (f == 5) ? mask & 0xA : mask;
- if (r == cbp->c_dir) {
- /* compute the multiple spot overlap values */
- switch (i) {
- case 0: /* sp1 is the first spot in A */
- if (f == 4)
- op[n] |= 0xA0;
- else if (f != 5)
- op[n] |= 0xF0;
- break;
- case 1: /* sp1 is the second spot in A */
- if (f == 5)
- op[n] |= 0xA0;
- else
- op[n] |= 0xF0;
- break;
- case 4: /* sp1 is the penultimate spot in A */
- if (f == 0)
- op[n] |= 0xC0;
- else
- op[n] |= 0xF0;
- break;
- case 5: /* sp1 is the last spot in A */
- if (f == 1)
- op[n] |= 0xC0;
- else if (f != 0)
- op[n] |= 0xF0;
- break;
- default:
- op[n] |= 0xF0;
- }
- }
+
+ int fib = (int)(spb->s_frame[rb] - frames);
+ intersect[fia * FAREA + fib] = (short)vertex;
+ u_char *op = &overlap[fia * FAREA + fib];
+ *op = adjust_overlap(*op, ra, sia, rb, sib, mask);
}
}
}
