--- a/.hgignore	Mon Aug 31 00:01:59 2020 +0000
+++ b/.hgignore	Sun Sep 06 22:48:09 2020 +0000
@@ -15,4 +15,6 @@
 ^ueda/utils/cutelements$
 ^ueda/utils/instfileelem$
 
+^netdiff/convert/protel2donl$
+
 ^pads2gpcb/pads2gpcb$

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/netdiff/convert/Makefile	Sun Sep 06 22:48:09 2020 +0000
@@ -0,0 +1,17 @@
+CC=	gcc
+CFLAGS=	-O2
+PROGS=	protel2donl
+BINDIR=	/usr/local/bin
+
+all:	${PROGS}
+
+${PROGS}:
+	${CC} ${CFLAGS} -o $@ $@.c
+
+install:
+	install -c -o bin -g bin -m 755 ${PROGS} ${BINDIR}
+
+clean:
+	rm -f *.[ao] a.out core errs ${PROGS}
+
+protel2donl: protel2donl.c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/netdiff/convert/protel2donl.c	Sun Sep 06 22:48:09 2020 +0000
@@ -0,0 +1,166 @@
+/*
+ * This program converts a Protel netlist (exported from Altium) into our
+ * Diff-Oriented Netlist (DONL) format.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+
+static char *infname;
+static FILE *inf;
+static char linebuf[80], netname[80];
+static int lineno;
+
+static
+get_line()
+{
+	char *cp;
+
+	if (!fgets(linebuf, sizeof linebuf, inf))
+		return(0);
+	lineno++;
+	cp = index(linebuf, '\n');
+	if (!cp) {
+		fprintf(stderr, "%s line %d: missing newline\n",
+			infname, lineno);
+		exit(1);
+	}
+	*cp = '\0';
+	if (cp > linebuf && cp[-1] == '\r')
+		*--cp = '\0';
+	return(1);
+}
+
+static void
+get_line_notfirst()
+{
+	if (!get_line()) {
+		fprintf(stderr, "error: unexpected EOF in input\n");
+		exit(1);
+	}
+	if (!strcmp(linebuf, "[")) {
+		fprintf(stderr, "%s line %d: [ NOT expected\n",
+			infname, lineno);
+		exit(1);
+	}
+	if (!strcmp(linebuf, "(")) {
+		fprintf(stderr, "%s line %d: ( NOT expected\n",
+			infname, lineno);
+		exit(1);
+	}
+}
+
+static void
+skip_component_block()
+{
+	int i;
+
+	for (i = 0; i < 6; i++) {
+		get_line_notfirst();
+		if (!strcmp(linebuf, "]")) {
+			fprintf(stderr, "%s line %d: ] NOT expected\n",
+				infname, lineno);
+			exit(1);
+		}
+		if (!strcmp(linebuf, ")")) {
+			fprintf(stderr, "%s line %d: ) NOT expected\n",
+				infname, lineno);
+			exit(1);
+		}
+	}
+	get_line_notfirst();
+	if (strcmp(linebuf, "]")) {
+		fprintf(stderr, "%s line %d: expected ]\n", infname, lineno);
+		exit(1);
+	}
+}
+
+static void
+process_net_point()
+{
+	char *cp;
+
+	cp = index(linebuf, '-');
+	if (!cp) {
+		fprintf(stderr, "%s line %d: missing \'-\' in net point\n",
+			infname, lineno);
+		exit(1);
+	}
+	if (cp == linebuf) {
+		fprintf(stderr, "%s line %d: refdes part is empty\n",
+			infname, lineno);
+		exit(1);
+	}
+	if (!cp[1]) {
+		fprintf(stderr, "%s line %d: pin number part is empty\n",
+			infname, lineno);
+		exit(1);
+	}
+	*cp = '.';	/* our PADS-like convention */
+	printf("%s\t%s\n", netname, lineno);
+}
+
+static void
+process_net_block()
+{
+	get_line_notfirst();
+	if (!strcmp(linebuf, "]")) {
+		fprintf(stderr, "%s line %d: ] NOT expected\n",
+			infname, lineno);
+		exit(1);
+	}
+	if (!strcmp(linebuf, ")")) {
+		fprintf(stderr, "%s line %d: ) NOT expected\n",
+			infname, lineno);
+		exit(1);
+	}
+	if (!linebuf[0]) {
+		fprintf(stderr, "%s line %d: empty net name\n",
+			infname, lineno);
+		exit(1);
+	}
+	strcpy(netname, linebuf);
+	for (;;) {
+		get_line_notfirst();
+		if (!strcmp(linebuf, "]")) {
+			fprintf(stderr, "%s line %d: ] NOT expected\n",
+				infname, lineno);
+			exit(1);
+		}
+		if (!strcmp(linebuf, ")"))
+			break;
+		process_net_point();
+	}
+}
+
+main(argc, argv)
+	char **argv;
+{
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s protel-netlist-file\n", argv[0]);
+		exit(1);
+	}
+	infname = argv[1];
+	inf = fopen(infname, "r");
+	if (!inf) {
+		perror(infname);
+		exit(1);
+	}
+	for (;;) {
+		if (!get_line())
+			break;
+		if (!strcmp(linebuf, "["))
+			skip_component_block();
+		else if (!strcmp(linebuf, "("))
+			process_net_block();
+		else {
+			fprintf(stderr,
+				"%s line %d: expected beginning of block\n",
+				infname, lineno);
+			exit(1);
+		}
+	}
+	exit(0);
+}