[PATCH 2/2] Improve on the "prefer downloaded" dive computer model

[Linus Torvalds]

From: Linus Torvalds <torvalds at linux-foundation.org>
Date: Tue, 22 Jan 2013 16:57:07 -0800
Subject: [PATCH 2/2] Improve on the "prefer downloaded" dive computer model

It used to be that when you checked the "Prefer downloaded" checkmark,
we'd throw away *any* old dive computer data.  That was good, because it
allowed us to start from a clean slate when you had some old subsurface
data with questionable dive computer data.

However, it was a bit extreme, and it's really not what you want if you
already have (good) dive computer data from other dive computers.

So this modifies the logic a bit.  Instead of throwing away all old dive
computer data, the "Prefer downloaded" checkmark now means:

 - the newly downloaded data becomes the "primary" dive computer data
   (ie the first in the list)

 - if there was old dive computer data that *could* have been from this
   new dive computer (ie it didn't have model information, or it had a
   matching model but no device ID data), we throw that away

 - but any existing dive computer data from other dive computers is left.

This seems to be much closer to what we really would want for a new
"preferred" download.

Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
---

The old "prefer downloaded" was a quick hack to allow people to override 
old subsurface data from the days before we supported multiple dive 
computers.

This modifies the logic to make much more sense in the existing subsurface 
world, where you may have valid data from multiple dive computers, but 
want to re-download some dives from one of them for some reason or other.

 dive.c | 60 ++++++++++++++++++++++++++++++++----------------------------
 1 file changed, 32 insertions(+), 28 deletions(-)

diff --git a/dive.c b/dive.c
index b61166569a97..fe9ce3a200ef 100644
--- a/dive.c
+++ b/dive.c
@@ -1323,7 +1323,24 @@ static int same_dc(struct divecomputer *a, struct divecomputer *b)
 	return eva == evb;
 }
 
-static void remove_redundant_dc(struct divecomputer *dc)
+static int might_be_same_device(struct divecomputer *a, struct divecomputer *b)
+{
+	/* No dive computer model? That matches anything */
+	if (!a->model || !b->model)
+		return 1;
+
+	/* Otherwise at least the model names have to match */
+	if (strcasecmp(a->model, b->model))
+		return 0;
+
+	/* No device ID? Match */
+	if (!a->deviceid || !b->deviceid)
+		return 1;
+
+	return a->deviceid == b->deviceid;
+}
+
+static void remove_redundant_dc(struct divecomputer *dc, int prefer_downloaded)
 {
 	do {
 		struct divecomputer **p = &dc->next;
@@ -1331,7 +1348,7 @@ static void remove_redundant_dc(struct divecomputer *dc)
 		/* Check this dc against all the following ones.. */
 		while (*p) {
 			struct divecomputer *check = *p;
-			if (same_dc(dc, check)) {
+			if (same_dc(dc, check) || (prefer_downloaded && might_be_same_device(dc, check))) {
 				*p = check->next;
 				check->next = NULL;
 				free_dc(check);
@@ -1340,7 +1357,8 @@ static void remove_redundant_dc(struct divecomputer *dc)
 			p = &check->next;
 		}
 
-		/* .. and then continue down the chain */
+		/* .. and then continue down the chain, but we */
+		prefer_downloaded = 0;
 		dc = dc->next;
 	} while (dc);
 }
@@ -1357,19 +1375,7 @@ static struct divecomputer *find_matching_computer(struct divecomputer *match, s
 	while ((p = list) != NULL) {
 		list = list->next;
 
-		/* No dive computer model? That matches anything */
-		if (!match->model || !p->model)
-			break;
-
-		/* Otherwise at least the model names have to match */
-		if (strcasecmp(match->model, p->model))
-			continue;
-
-		/* No device ID? Match */
-		if (!match->deviceid || !p->deviceid)
-			break;
-
-		if (match->deviceid == p->deviceid)
+		if (might_be_same_device(match, p))
 			break;
 	}
 	return p;
@@ -1422,9 +1428,13 @@ static void interleave_dive_computers(struct divecomputer *res,
  * name etc), we will prefer a new-style one and just throw
  * away the old. We're assuming it's a re-download.
  *
- * Otherwise, we'll just try to keep all the information.
+ * Otherwise, we'll just try to keep all the information,
+ * unless the user has specified that they prefer the
+ * downloaded computer, in which case we'll aggressively
+ * try to throw out old information that *might* be from
+ * that one.
  */
-static void join_dive_computers(struct divecomputer *res, struct divecomputer *a, struct divecomputer *b)
+static void join_dive_computers(struct divecomputer *res, struct divecomputer *a, struct divecomputer *b, int prefer_downloaded)
 {
 	struct divecomputer *tmp;
 
@@ -1449,7 +1459,7 @@ static void join_dive_computers(struct divecomputer *res, struct divecomputer *a
 	*tmp->next = *b;
 	clear_dc(b);
 
-	remove_redundant_dc(res);
+	remove_redundant_dc(res, prefer_downloaded);
 }
 
 struct dive *merge_dives(struct dive *a, struct dive *b, int offset, gboolean prefer_downloaded)
@@ -1490,18 +1500,12 @@ struct dive *merge_dives(struct dive *a, struct dive *b, int offset, gboolean pr
 	MERGE_MIN_PREFDL(res, dl, a, b, watertemp.mkelvin);
 	merge_equipment(res, a, b);
 	if (dl) {
-		res->dc = dl->dc;
-		/*
-		 * Since we copied the events and samples,
-		 * we can't free them from the source when
-		 * we free it - so make sure the source
-		 * dive computer data is cleared out.
-		 */
-		clear_dc(&dl->dc);
+		/* If we prefer downloaded, do those first, and get rid of "might be same" computers */
+		join_dive_computers(&res->dc, &dl->dc, &a->dc, 1);
 	} else if (offset)
 		interleave_dive_computers(&res->dc, &a->dc, &b->dc, offset);
 	else
-		join_dive_computers(&res->dc, &a->dc, &b->dc);
+		join_dive_computers(&res->dc, &a->dc, &b->dc, 0);
 
 	fixup_dive(res);
 	return res;
-- 
1.8.1.1.271.g02f55e6