--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/calypso/main.c	Sun Mar 14 05:07:34 2021 +0000
@@ -0,0 +1,104 @@
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+
+static
+is_string_all_hex(str)
+	char *str;
+{
+	char *cp;
+
+	for (cp = str; *cp; cp++)
+		if (!isxdigit(*cp))
+			return(0);
+	return(1);
+}
+
+cmd_exchange(input)
+	char *input;
+{
+	char *targv[3];
+	int rc;
+
+	targv[0] = "X";
+	targv[1] = input;
+	targv[2] = 0;
+
+	tpinterf_make_cmd(targv);
+	rc = tpinterf_send_cmd();
+	if (rc < 0)
+		return(rc);
+	return tpinterf_pass_output(20);
+}
+
+cmd_atr()
+{
+	static char *atr_argv[2] = {"atr", 0};
+	int rc;
+
+	tpinterf_make_cmd(atr_argv);
+	rc = tpinterf_send_cmd();
+	if (rc < 0)
+		return(rc);
+	return tpinterf_pass_output(1);
+}
+
+cmd_poweroff()
+{
+	static char *poweroff_argv[2] = {"poweroff", 0};
+
+	tpinterf_make_cmd(poweroff_argv);
+	tpinterf_send_cmd();
+}
+
+main(argc, argv)
+	char **argv;
+{
+	char inbuf[576], *cp;
+	unsigned len;
+
+	parse_target_fd_opt(argc, argv);
+	putchar('\n');
+
+	while (fgets(inbuf, sizeof inbuf, stdin)) {
+		cp = index(inbuf, '\n');
+		if (!cp) {
+			printf("back end error: missing newline on input\n");
+			continue;
+		}
+		*cp = '\0';
+		if (!strcmp(inbuf, "atr")) {
+			cmd_atr();
+			continue;
+		}
+		if (!strcmp(inbuf, "poweroff")) {
+			cmd_poweroff();
+			exit(0);
+		}
+		if (!is_string_all_hex(inbuf)) {
+			printf("back end error: input is not all hex\n");
+			continue;
+		}
+		len = strlen(inbuf);
+		if (len & 1) {
+			printf(
+			"back end error: input has odd number of hex digits\n");
+			continue;
+		}
+		if (len < 10) {
+			printf(
+		"back end error: input is too short for command APDU\n");
+			continue;
+		}
+		if (len > 520) {
+			printf(
+			"back end error: input is too long for command APDU\n");
+			continue;
+		}
+		cmd_exchange(inbuf);
+	}
+
+	exit(0);
+}