util: Add new helpers for pipe resources

They will be handy for drivers supporting multi-planar formats.

Cc: mesa-stable
Reviewed-by: Italo Nicola <italonicola@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26109>

src/gallium/auxiliary/util/u_resource.c

@@ -64,3 +64,35 @@ util_resource_size(const struct pipe_resource *res)
 
    return size;
 }
+
+/**
+ * Return the number of the resources.
+ */
+unsigned
+util_resource_num(const struct pipe_resource *res)
+{
+   const struct pipe_resource *cur;
+   unsigned count;
+
+   for (count = 0, cur = res; cur; cur = cur->next)
+      count++;
+
+   return count;
+}
+
+/**
+ * Return the resource at the given index.
+ */
+struct pipe_resource *
+util_resource_at_index(const struct pipe_resource *res, unsigned index)
+{
+   const struct pipe_resource *cur;
+   unsigned count;
+
+   for (count = 0, cur = res; cur; cur = cur->next) {
+      if (count++ == index)
+         return (struct pipe_resource *)cur;
+   }
+
+   return NULL;
+}

src/gallium/auxiliary/util/u_resource.h

@@ -31,6 +31,12 @@
 unsigned
 util_resource_size(const struct pipe_resource *res);
 
+unsigned
+util_resource_num(const struct pipe_resource *res);
+
+struct pipe_resource *
+util_resource_at_index(const struct pipe_resource *res, unsigned index);
+
 /**
  * Return true if the texture target is an array type.
  *