BLI_listbase: Add utils to search from string or index.

If a valid matching string is found, return that item, otherwise
fallback to the item matching the given index, if any.

This will be useful in RNA override code, and potentially other
areas where data in lists can be referenced by their names or indices.

1 files changed, 31 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/listbase.c b/source/blender/blenlib/intern/listbase.c
index 1b16f6b0aee..443bef42cc2 100644
--- a/source/blender/blenlib/intern/listbase.c
+++ b/source/blender/blenlib/intern/listbase.c
@@ -826,6 +826,37 @@ void *BLI_listbase_bytes_rfind(const ListBase *listbase,
 }
 
 /**
+ * Find the first item in the list that matches the given string, or the given index as fallback.
+ *
+ * \note The string is only used is non-NULL and non-empty.
+ *
+ * \return The found item, or NULL.
+ */
+void *BLI_listbase_string_or_index_find(const ListBase *listbase,
+                                        const char *string,
+                                        const size_t string_offset,
+                                        const int index)
+{
+  Link *link = NULL;
+  Link *link_at_index = NULL;
+
+  int index_iter;
+  for (link = listbase->first, index_iter = 0; link; link = link->next, index_iter++) {
+    if (string != NULL && string[0] != '\0') {
+      const char *string_iter = ((const char *)link) + string_offset;
+
+      if (string[0] == string_iter[0] && STREQ(string, string_iter)) {
+        return link;
+      }
+    }
+    if (index_iter == index) {
+      link_at_index = link;
+    }
+  }
+  return link_at_index;
+}
+
+/**
  * Returns the 0-based index of the first element of listbase which contains the specified
  * null-terminated string at the specified offset, or -1 if not found.
  */