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.
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rillig
parent
14facc424c
commit
463eec3668
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@ -1,4 +1,4 @@
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/* $NetBSD: bdinit.c,v 1.25 2022/05/28 17:51:27 rillig Exp $ */
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/* $NetBSD: bdinit.c,v 1.26 2022/05/28 18:55:16 rillig Exp $ */
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/*
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* Copyright (c) 1994
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@ -34,7 +34,7 @@
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#include <sys/cdefs.h>
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/* from: @(#)bdinit.c 8.2 (Berkeley) 5/3/95 */
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__RCSID("$NetBSD: bdinit.c,v 1.25 2022/05/28 17:51:27 rillig Exp $");
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__RCSID("$NetBSD: bdinit.c,v 1.26 2022/05/28 18:55:16 rillig Exp $");
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#include <string.h>
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#include "gomoku.h"
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@ -160,6 +160,52 @@ init_board(void)
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init_overlap();
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}
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/*-
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* ra direction of frame A
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* ia index of the spot in frame A (0 to 5)
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* rb direction of frame B
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* ib index of the spot in frame B (0 to 5)
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*/
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static u_char
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adjust_overlap(u_char ov, int ra, int ia, int rb, int ib, int mask)
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{
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ov |= (ib == 5) ? mask & 0xA : mask;
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if (rb != ra)
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return ov;
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/* compute the multiple spot overlap values */
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switch (ia) {
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case 0:
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if (ib == 4)
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ov |= 0xA0;
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else if (ib != 5)
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ov |= 0xF0;
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break;
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case 1:
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if (ib == 5)
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ov |= 0xA0;
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else
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ov |= 0xF0;
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break;
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case 4:
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if (ib == 0)
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ov |= 0xC0;
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else
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ov |= 0xF0;
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break;
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case 5:
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if (ib == 1)
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ov |= 0xC0;
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else if (ib != 0)
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ov |= 0xF0;
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break;
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default:
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ov |= 0xF0;
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}
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return ov;
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}
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/*
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* Initialize the overlap array.
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* Each entry in the array is a bit mask with eight bits corresponding
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@ -183,69 +229,49 @@ init_overlap(void)
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memset(overlap, 0, sizeof(overlap));
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memset(intersect, 0, sizeof(intersect));
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u_char *op = &overlap[FAREA * FAREA];
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short *ip = &intersect[FAREA * FAREA];
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for (unsigned fi = FAREA; fi-- > 0; ) { /* each frame */
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struct combostr *cbp = &frames[fi];
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op -= FAREA;
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ip -= FAREA;
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int vertex = cbp->c_vertex;
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struct spotstr *sp1 = &board[vertex];
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int d1 = dd[cbp->c_dir];
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/*-
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* Variables for frames A and B:
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*
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* fi index of the frame in the global 'frames'
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* r direction: 0 = right, 1 = down right, 2 = down, 3 = down left
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* d direction delta, difference between adjacent spot indexes
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* si index of the spot in the frame, 0 to 5
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* sp data of the spot at index i
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*/
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for (unsigned fia = FAREA; fia-- > 0; ) {
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struct combostr *fa = &frames[fia];
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int vertex = fa->c_vertex;
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struct spotstr *spa = &board[vertex];
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u_char ra = fa->c_dir;
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int da = dd[ra];
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/*
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* s = 5 if closed, 6 if open.
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* At this point black & white are the same.
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* len = 5 if closed, 6 if open.
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* At this point, Black and White have the same values.
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*/
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int s = 5 + sp1->s_fval[BLACK][cbp->c_dir].cv_win;
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/* for each spot in frame A */
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for (int i = 0; i < s; i++, sp1 += d1, vertex += d1) {
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int len = 5 + spa->s_fval[BLACK][ra].cv_win;
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for (int sia = 0; sia < len; sia++, spa += da, vertex += da) {
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/* the sixth spot in frame A only overlaps if it is open */
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int mask = (i == 5) ? 0xC : 0xF;
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/* for each direction */
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for (int r = 4; --r >= 0; ) {
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struct spotstr *sp2 = sp1;
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int d2 = dd[r];
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/* for each frame that intersects at spot sp1 */
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for (int f = 0; f < 6; f++, sp2 -= d2) {
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if (sp2->s_occ == BORDER)
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int mask = (sia == 5) ? 0xC : 0xF;
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for (int rb = 4; --rb >= 0; ) {
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struct spotstr *spb = spa;
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int db = dd[rb];
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/* for each frame that intersects at spot spa */
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for (int sib = 0; sib < 6; sib++, spb -= db) {
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if (spb->s_occ == BORDER)
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break;
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if ((sp2->s_flags & BFLAG << r) != 0)
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if ((spb->s_flags & BFLAG << rb) != 0)
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continue;
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int n = (int)(sp2->s_frame[r] - frames);
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ip[n] = (short)vertex;
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op[n] |= (f == 5) ? mask & 0xA : mask;
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if (r == cbp->c_dir) {
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/* compute the multiple spot overlap values */
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switch (i) {
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case 0: /* sp1 is the first spot in A */
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if (f == 4)
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op[n] |= 0xA0;
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else if (f != 5)
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op[n] |= 0xF0;
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break;
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case 1: /* sp1 is the second spot in A */
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if (f == 5)
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op[n] |= 0xA0;
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else
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op[n] |= 0xF0;
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break;
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case 4: /* sp1 is the penultimate spot in A */
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if (f == 0)
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op[n] |= 0xC0;
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else
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op[n] |= 0xF0;
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break;
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case 5: /* sp1 is the last spot in A */
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if (f == 1)
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op[n] |= 0xC0;
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else if (f != 0)
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op[n] |= 0xF0;
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break;
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default:
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op[n] |= 0xF0;
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}
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}
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int fib = (int)(spb->s_frame[rb] - frames);
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intersect[fia * FAREA + fib] = (short)vertex;
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u_char *op = &overlap[fia * FAREA + fib];
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*op = adjust_overlap(*op, ra, sia, rb, sib, mask);
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}
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}
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}
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