Add serd_node_compare()

2 files changed, 39 insertions, 0 deletions

diff --git a/serd/serd.h b/serd/serd.h
index ce968a28..06bff454 100644
--- a/serd/serd.h
+++ b/serd/serd.h
@@ -643,6 +643,17 @@ bool
 serd_node_equals(const SerdNode* a, const SerdNode* 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_API
+int
+serd_node_compare(const SerdNode* a, const SerdNode* b);
+
+/**
    Create a new URI from a string.
 */
 SERD_API
diff --git a/src/node.c b/src/node.c
index 859cb0a3..b0e8f991 100644
--- a/src/node.c
+++ b/src/node.c
@@ -66,6 +66,14 @@ serd_node_pad_size(const size_t n_bytes)
 }
 
 static const SerdNode*
+serd_node_maybe_get_meta_c(const SerdNode* node)
+{
+	return (node->flags & (SERD_HAS_LANGUAGE | SERD_HAS_DATATYPE))
+		? (node + 1 + (serd_node_pad_size(node->n_bytes) / serd_node_align))
+		: NULL;
+}
+
+static const SerdNode*
 serd_node_get_meta_c(const SerdNode* node)
 {
 	return node + 1 + (serd_node_pad_size(node->n_bytes) / serd_node_align);
@@ -303,6 +311,26 @@ serd_node_equals(const SerdNode* a, const SerdNode* b)
 	return false;
 }
 
+int
+serd_node_compare(const SerdNode* a, const SerdNode* b)
+{
+	if (a == b) {
+		return 0;
+	} else if (!a || !b) {
+		return (a < b) ? -1 : (a > b) ? 1 : 0;
+	} else if (a->type != b->type) {
+		return a->type - b->type;
+	}
+
+	const int cmp = strcmp(serd_node_get_string(a), serd_node_get_string(b));
+	if (cmp) {
+		return cmp;
+	}
+
+	return serd_node_compare(serd_node_maybe_get_meta_c(a),
+	                         serd_node_maybe_get_meta_c(b));
+}
+
 static size_t
 serd_uri_string_length(const SerdURI* uri)
 {