list: New helper macros for converting entries to items

2 files changed, 65 insertions, 16 deletions

diff --git a/src/bftw.c b/src/bftw.c
index 9ff526d..aa36b87 100644
--- a/src/bftw.c
+++ b/src/bftw.c
@@ -69,14 +69,8 @@ struct bftw_file {
 };
 
 /** Move from a list entry to a bftw_file. */
-static struct bftw_file *bftw_file_entry(struct slink *link) {
-	return BFS_CONTAINER_OF(link, struct bftw_file, link);
-}
-
-/** Move from an LRU entry to a bftw_file. */
-static struct bftw_file *bftw_lru_file(struct link *link) {
-	return BFS_CONTAINER_OF(link, struct bftw_file, lru);
-}
+#define BFTW_FILE(...) \
+	LIST_ITEM(struct bftw_file, __VA_ARGS__)
 
 /**
  * A cache of open directories.
@@ -126,7 +120,7 @@ static int bftw_cache_pop(struct bftw_cache *cache) {
 		return -1;
 	}
 
-	struct bftw_file *file = bftw_lru_file(cache->list.tail);
+	struct bftw_file *file = BFTW_FILE(cache->list.tail, lru);
 	bftw_file_close(cache, file);
 	return 0;
 }
@@ -810,7 +804,7 @@ static int bftw_pop(struct bftw_state *state) {
 		return 0;
 	}
 
-	state->file = bftw_file_entry(slist_pop(&state->queue));
+	state->file = BFTW_FILE(slist_pop(&state->queue));
 
 	if (bftw_build_path(state) != 0) {
 		return -1;
@@ -974,9 +968,7 @@ static int bftw_state_destroy(struct bftw_state *state) {
 
 /** Comparison function for BFTW_SORT. */
 static bool bftw_file_cmp(struct slink *left, struct slink *right, const void *ptr) {
-	struct bftw_file *lfile = bftw_file_entry(left);
-	struct bftw_file *rfile = bftw_file_entry(right);
-	return strcoll(lfile->name, rfile->name) <= 0;
+	return strcoll(BFTW_FILE(left)->name, BFTW_FILE(right)->name) <= 0;
 }
 
 /** Finish adding a batch of files. */
diff --git a/src/list.h b/src/list.h
index 1985413..b47bed7 100644
--- a/src/list.h
+++ b/src/list.h
@@ -107,10 +107,67 @@ struct link *list_pop(struct list *list);
 /** Check if a link is attached to a list. */
 bool list_attached(const struct list *list, const struct link *link);
 
+// LIST_ITEM() helper
+#define LIST_ITEM_IMPL(type, entry, member, ...) \
+	BFS_CONTAINER_OF(entry, type, member)
+
+/**
+ * Convert a list entry to its container.
+ *
+ * @param type
+ *         The type of the list entries.
+ * @param entry
+ *         The list entry to convert.
+ * @param member
+ *         The name of the list link field (default: link).
+ * @return
+ *         The item that contains the given entry.
+ */
+#define LIST_ITEM(...) \
+	LIST_ITEM_IMPL(__VA_ARGS__, link,)
+
+// LIST_NEXT() helper
+#define LIST_NEXT_IMPL(type, entry, member, ...) \
+	LIST_ITEM(type, (entry)->member.next, member)
+
+/**
+ * Get the next item in a list.
+ *
+ * @param type
+ *         The type of the list entries.
+ * @param entry
+ *         The current entry.
+ * @param member
+ *         The name of the list link field (default: link).
+ * @return
+ *         The next item in the list.
+ */
+#define LIST_NEXT(...) \
+	LIST_NEXT_IMPL(__VA_ARGS__, link,)
+
+// LIST_PREV() helper
+#define LIST_PREV_IMPL(type, entry, member, ...) \
+	LIST_ITEM(type, (entry)->member.prev, member)
+
+/**
+ * Get the previous entry in a list.
+ *
+ * @param type
+ *         The type of the list entries.
+ * @param entry
+ *         The current entry.
+ * @param member
+ *         The name of the list link field (default: link).
+ * @return
+ *         The previous item in the list.
+ */
+#define LIST_PREV(...) \
+	LIST_PREV_IMPL(__VA_ARGS__, link,)
+
 // Helper for LIST_FOR_EACH_*()
 #define LIST_FOR_EACH_IMPL(entry, type, i, member, ...) \
-	for (type *_next, *i = BFS_CONTAINER_OF(entry, type, member); \
-	     i && (_next = BFS_CONTAINER_OF(i->member.next, type, member), true); \
+	for (type *_next, *i = LIST_ITEM(type, entry, member);	\
+	     i && (_next = LIST_NEXT(type, i, member), true); \
 	     i = _next)
 
 /**
@@ -150,7 +207,7 @@ bool list_attached(const struct list *list, const struct link *link);
 
 // Helper for LIST_DRAIN()
 #define LIST_DRAIN_IMPL(list, type, i, member, ...) \
-	for (type *i; (i = BFS_CONTAINER_OF(LIST_POP(list), type, member));)
+	for (type *i; (i = LIST_ITEM(type, LIST_POP(list), member));)
 
 /**
  * Drain the entries from a list.