Add serd_node_compare()

2 files changed, 37 insertions, 0 deletions

diff --git a/include/serd/serd.h b/include/serd/serd.h
index 6aeb9138..4cf00f02 100644
--- a/include/serd/serd.h
+++ b/include/serd/serd.h
@@ -1033,6 +1033,18 @@ serd_node_equals(const SerdNode* SERD_NULLABLE a,
                  const SerdNode* SERD_NULLABLE b);
 
 /**
+   Compare two nodes.
+
+   Returns less than, equal to, or greater than zero if `a` is less than, equal
+   to, or greater than `b`, respectively.  NULL is treated as less than any
+   other node.
+*/
+SERD_PURE_API
+int
+serd_node_compare(const SerdNode* SERD_NULLABLE a,
+                  const SerdNode* SERD_NULLABLE b);
+
+/**
    @}
    @defgroup serd_event Event Handlers
    @{
diff --git a/src/node.c b/src/node.c
index 4c76ed9b..268b53af 100644
--- a/src/node.c
+++ b/src/node.c
@@ -436,6 +436,31 @@ serd_node_equals(const SerdNode* a, const SerdNode* b)
   return serd_node_total_size(b) == a_size && !memcmp(a, b, a_size);
 }
 
+int
+serd_node_compare(const SerdNode* a, const SerdNode* b)
+{
+  if (a == b) {
+    return 0;
+  }
+
+  if (!a) {
+    return -1;
+  }
+
+  if (!b) {
+    return 1;
+  }
+
+  if (a->type != b->type) {
+    return (a->type < b->type) ? -1 : 1;
+  }
+
+  const int cmp = strcmp(serd_node_string(a), serd_node_string(b));
+  return cmp ? cmp
+             : serd_node_compare(serd_node_maybe_get_meta_c(a),
+                                 serd_node_maybe_get_meta_c(b));
+}
+
 SerdNode*
 serd_new_uri(const SerdStringView str)
 {