--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libsip/get_header.c	Tue Sep 06 20:29:44 2022 -0800
@@ -0,0 +1,39 @@
+/*
+ * In this module we implement functions for retrieving individual
+ * header fields from struct sip_pkt_rx.
+ */
+
+#include <string.h>
+#include <strings.h>
+#include "parse.h"
+
+char *
+get_single_header(msg, name, altname, dupp)
+	struct sip_pkt_rx *msg;
+	char *name, *altname;
+	int *dupp;
+{
+	unsigned n;
+	char *ret;
+
+	for (n = 0; n < msg->num_hdr_fields; n++) {
+		if (!strcasecmp(msg->hdr_fields[n].field_name, name))
+			break;
+		if (altname &&
+		    !strcasecmp(msg->hdr_fields[n].field_name, altname))
+			break;
+	}
+	if (n >= msg->num_hdr_fields)
+		return 0;
+	ret = msg->hdr_fields[n].field_value;
+	if (!dupp)
+		return ret;
+	for (n++; n < msg->num_hdr_fields; n++) {
+		if (!strcasecmp(msg->hdr_fields[n].field_name, name))
+			*dupp = 1;
+		if (altname &&
+		    !strcasecmp(msg->hdr_fields[n].field_name, altname))
+			*dupp = 1;
+	}
+	return ret;
+}