From 16f997d34c7b435d3fcf5774c700579e188b017f Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Thu, 20 Apr 2023 13:13:47 +0100
Subject: Stop putting dsfs in existing scratch int arrays.

I'm going to work towards turning 'dsf' into an opaque type, so that I
can improve its implementation without breaking clients. The first
step is to deal manually with puzzles that currently reuse a single
array of ints for multiple purposes, some of which are dsf and some
are not.

In divvy_rectangle_attempt, 'tmp' was used as an int array and later a
dsf, and I've made a new 'tmpdsf' to be the latter.

In Dominosa, solver->pc_scratch2 was sometimes a dsf, and now there's
a new solver->dsf_scratch.

In Map, parse_edge_list() needed a dsf internally and then never
exported it; it expected to be passed an array of 2*w*h ints and used
the second half as a dsf. Now it expects only w*h ints, and allocates
its own dsf internally, freeing it again before returning.

And in Tents, find_errors() was allocating a single block of 2*w*h
ints and using the second half of it as a dsf, apparently just to save
one malloc. Now we malloc and free the dsf separately.
---
 divvy.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

(limited to 'divvy.c')

diff --git a/divvy.c b/divvy.c
index 021956f..91379e4 100644
--- a/divvy.c
+++ b/divvy.c
@@ -262,7 +262,7 @@ static bool addremcommon(int w, int h, int x, int y, int *own, int val)
  */
 int *divvy_rectangle_attempt(int w, int h, int k, random_state *rs)
 {
-    int *order, *queue, *tmp, *own, *sizes, *addable, *retdsf;
+    int *order, *queue, *tmp, *own, *sizes, *addable, *retdsf, *tmpdsf;
     bool *removable;
     int wh = w*h;
     int i, j, n, x, y, qhead, qtail;
@@ -277,6 +277,7 @@ int *divvy_rectangle_attempt(int w, int h, int k, random_state *rs)
     queue = snewn(n, int);
     addable = snewn(wh*4, int);
     removable = snewn(wh, bool);
+    retdsf = tmpdsf = NULL;
 
     /*
      * Permute the grid squares into a random order, which will be
@@ -619,18 +620,18 @@ int *divvy_rectangle_attempt(int w, int h, int k, random_state *rs)
      * the ominoes really are k-ominoes and we haven't
      * accidentally split one into two disconnected pieces.
      */
-    dsf_init(tmp, wh);
+    tmpdsf = snew_dsf(wh);
     for (y = 0; y < h; y++)
 	for (x = 0; x+1 < w; x++)
 	    if (own[y*w+x] == own[y*w+(x+1)])
-		dsf_merge(tmp, y*w+x, y*w+(x+1));
+		dsf_merge(tmpdsf, y*w+x, y*w+(x+1));
     for (x = 0; x < w; x++)
 	for (y = 0; y+1 < h; y++)
 	    if (own[y*w+x] == own[(y+1)*w+x])
-		dsf_merge(tmp, y*w+x, (y+1)*w+x);
+		dsf_merge(tmpdsf, y*w+x, (y+1)*w+x);
     for (i = 0; i < wh; i++) {
 	j = dsf_canonify(retdsf, i);
-	assert(dsf_canonify(tmp, j) == dsf_canonify(tmp, i));
+	assert(dsf_canonify(tmpdsf, j) == dsf_canonify(tmpdsf, i));
     }
 
     cleanup:
@@ -640,6 +641,7 @@ int *divvy_rectangle_attempt(int w, int h, int k, random_state *rs)
      */
     sfree(order);
     sfree(tmp);
+    sfree(tmpdsf);
     sfree(own);
     sfree(sizes);
     sfree(queue);
-- 
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