From 9b580f1a46571424e85b5fd9f41cb32df92ca7e0 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Thu, 20 Dec 2018 13:02:24 -0500
Subject: Add serd_node_compare()

---
 serd/serd.h | 11 +++++++++++
 src/node.c  | 25 +++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/serd/serd.h b/serd/serd.h
index e9484ec9..aaf66549 100644
--- a/serd/serd.h
+++ b/serd/serd.h
@@ -642,6 +642,17 @@ SERD_API
 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.
 */
diff --git a/src/node.c b/src/node.c
index 9851a6a7..20312815 100644
--- a/src/node.c
+++ b/src/node.c
@@ -65,6 +65,14 @@ serd_node_pad_size(const size_t n_bytes)
 	return size;
 }
 
+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)
 {
@@ -303,6 +311,23 @@ 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 : 1;
+	} else if (a->type != b->type) {
+		return (a->type < b->type) ? -1 : 1;
+	}
+
+	const int cmp = strcmp(serd_node_get_string(a), serd_node_get_string(b));
+	return cmp ? cmp
+	           : 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)
 {
-- 
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