Add new alpm_list_remove_item() function

This takes in the list and a list item, and does the pointer dance necessary
to remove it from the list regardless of whether it is first, last, or
somewhere in the middle. It is useful for callers that already know what
item needs to be removed and have a pointer to it rather than doing a search
by data that the plain alpm_list_remove() does.

Refactor alpm_list_remove() to use this function as well.

Signed-off-by: Dan McGee <dan@archlinux.org>

lib/libalpm/alpm_list.c

@@ -285,6 +285,53 @@ alpm_list_t SYMEXPORT *alpm_list_msort(alpm_list_t *list, size_t n, alpm_list_fn
 	return(list);
 }
 
+/**
+ * @brief Remove an item from the list.
+ * item is not freed; this is the respnsiblity of the caller.
+ *
+ * @param haystack the list to remove the item from
+ * @param item the item to remove from the list
+ *
+ * @return the resultant list
+ */
+alpm_list_t SYMEXPORT *alpm_list_remove_item(alpm_list_t *haystack,
+		alpm_list_t *item)
+{
+	if(haystack == NULL || item == NULL) {
+		return(haystack);
+	}
+
+	if(item == haystack) {
+		/* Special case: removing the head node which has a back reference to
+		 * the tail node */
+		haystack = item->next;
+		if(haystack) {
+			haystack->prev = item->prev;
+		}
+		item->prev = NULL;
+	} else if(item == haystack->prev) {
+		/* Special case: removing the tail node, so we need to fix the back
+		 * reference on the head node. We also know tail != head. */
+		if(item->prev) {
+			/* i->next should always be null */
+			item->prev->next = item->next;
+			haystack->prev = item->prev;
+			item->prev = NULL;
+		}
+	} else {
+		/* Normal case, non-head and non-tail node */
+		if(item->next) {
+			item->next->prev = item->prev;
+		}
+		if(item->prev) {
+			item->prev->next = item->next;
+		}
+	}
+
+	return(haystack);
+}
+
+
 /**
  * @brief Remove an item from the list.
  *
@@ -295,9 +342,10 @@ alpm_list_t SYMEXPORT *alpm_list_msort(alpm_list_t *list, size_t n, alpm_list_fn
  *
  * @return the resultant list
  */
-alpm_list_t SYMEXPORT *alpm_list_remove(alpm_list_t *haystack, const void *needle, alpm_list_fn_cmp fn, void **data)
+alpm_list_t SYMEXPORT *alpm_list_remove(alpm_list_t *haystack,
+		const void *needle, alpm_list_fn_cmp fn, void **data)
 {
-	alpm_list_t *i = haystack, *tmp = NULL;
+	alpm_list_t *i = haystack;
 
 	if(data) {
 		*data = NULL;
@@ -312,44 +360,16 @@ alpm_list_t SYMEXPORT *alpm_list_remove(alpm_list_t *haystack, const void *needl
 			i = i->next;
 			continue;
 		}
-		tmp = i->next;
 		if(fn(i->data, needle) == 0) {
-			/* we found a matching item */
+			haystack = alpm_list_remove_item(haystack, i);
-			if(i == haystack) {
-				/* Special case: removing the head node which has a back reference to
-				 * the tail node */
-				haystack = i->next;
-				if(haystack) {
-					haystack->prev = i->prev;
-				}
-				i->prev = NULL;
-			} else if(i == haystack->prev) {
-				/* Special case: removing the tail node, so we need to fix the back
-				 * reference on the head node. We also know tail != head. */
-				if(i->prev) {
-					/* i->next should always be null */
-					i->prev->next = i->next;
-					haystack->prev = i->prev;
-					i->prev = NULL;
-				}
-			} else {
-				/* Normal case, non-head and non-tail node */
-				if(i->next) {
-					i->next->prev = i->prev;
-				}
-				if(i->prev) {
-					i->prev->next = i->next;
-				}
-			}
 
 			if(data) {
 				*data = i->data;
 			}
-			i->data = NULL;
 			free(i);
-			i = NULL;
+			break;
 		} else {
-			i = tmp;
+			i = i->next;
 		}
 	}
 

lib/libalpm/alpm_list.h

@@ -57,6 +57,7 @@ alpm_list_t *alpm_list_add_sorted(alpm_list_t *list, void *data, alpm_list_fn_cm
 alpm_list_t *alpm_list_join(alpm_list_t *first, alpm_list_t *second);
 alpm_list_t *alpm_list_mmerge(alpm_list_t *left, alpm_list_t *right, alpm_list_fn_cmp fn);
 alpm_list_t *alpm_list_msort(alpm_list_t *list, size_t n, alpm_list_fn_cmp fn);
+alpm_list_t *alpm_list_remove_item(alpm_list_t *haystack, alpm_list_t *item);
 alpm_list_t *alpm_list_remove(alpm_list_t *haystack, const void *needle, alpm_list_fn_cmp fn, void **data);
 alpm_list_t *alpm_list_remove_str(alpm_list_t *haystack, const char *needle, char **data);
 alpm_list_t *alpm_list_remove_dupes(const alpm_list_t *list);