Add reset key function for maps

Allows changing the pointer to key when they are equivalent (by cmp
function), to avoid memory leaks that could happen if we assumed either
pointer was to be freed or overwritten.

3 files changed, 46 insertions, 1 deletions

diff --git a/collections/map/map.adoc b/collections/map/map.adoc
index 2b3e2cb..2822b79 100644
--- a/collections/map/map.adoc
+++ b/collections/map/map.adoc
@@ -1,7 +1,7 @@
 Map
 ===
 Tucker Evans
-v0.3, 2020-07-06
+v0.4, 2020-07-06
 
 A basic map implemented in an AVL tree.
 
@@ -92,6 +92,27 @@ map_insert(dict, "ONE", NULL);
 assert(map_size(dict) == 1);
 ----
 
+[[map_reset_key]]
++void* map_reset_key(map *self, vaid *key)+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This replaces an equivalent key with the one passed in, the key that is
+overwritten is return so the user can free it.
+
+Examples
+^^^^^^^^
+[source,c]
+----
+#include "map.h"
+#include <string.h>
+
+map *dict = map_new((cmp_func) strcmp);
+
+map_insert(dict, strdup("ONE"), "VALUE");
+assert(map_insert(dict, "ONE", "NEW_VALUE") < 0);
+free(map_reset_key(dict "ONE"));
+assert(map_insert(dict, "ONE", "NEW_VALUE") == 0);
+----
+
 [[map_clear]]
 +void map_clear(map *self)+
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/collections/map/map.c b/collections/map/map.c
index 83a446d..7de58e4 100644
--- a/collections/map/map.c
+++ b/collections/map/map.c
@@ -82,6 +82,29 @@ void *key, *val;
 	return 0;
 }
 
+void* map_reset_key(root, key)
+map *root;
+void *key;
+{
+	void *tmp;
+	int cmp;
+
+	if (!root || !key)
+		return NULL;
+
+	cmp = root->cmp(root->key, key);
+
+	if (cmp < 0)
+		return map_reset_key(root->left, key);
+
+	if (cmp > 0)
+		return map_reset_key(root->right, key);
+
+	tmp = root->key;
+	root->key = key;
+	return tmp;
+}
+
 void map_clear(root)
 map *root;
 {
diff --git a/collections/map/map.h b/collections/map/map.h
index b389d87..a5fc816 100644
--- a/collections/map/map.h
+++ b/collections/map/map.h
@@ -12,6 +12,7 @@ int map_size(map*);
 
 /*data*/
 int map_insert(map*, void*, void*);
+void* map_reset_key(map*, void*);
 
 /*memory*/
 void map_clear(map*);