--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtest/tw5reader.c	Thu Sep 19 03:08:47 2024 +0000
@@ -0,0 +1,65 @@
+/*
+ * Here we implement our twts005_read_frame() function.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <strings.h>
+#include "tw5reader.h"
+
+static int decode_hex_digit(char c)
+{
+	if (isdigit(c))
+		return c - '0';
+	else if (isupper(c))
+		return c - 'A' + 10;
+	else
+		return c - 'a' + 10;
+}
+
+int twts005_read_frame(FILE *hexf, unsigned *lineno, uint8_t *frame,
+			unsigned *lenp)
+{
+	char linebuf[81];
+	char *cp, *np;
+	uint8_t *dp;
+	unsigned len;
+
+	for (;;) {
+		if (!fgets(linebuf, sizeof linebuf, hexf))
+			return 0;
+		(*lineno)++;
+		if (!index(linebuf, '\n'))
+			return -2;
+		for (cp = linebuf; isspace(*cp); cp++)
+			;
+		if (*cp != '\0' && *cp != '#')
+			break;
+	}
+	for (np = cp; *cp && !isspace(*cp); cp++)
+		;
+	if (*cp)
+		*cp++ = '\0';
+	while (isspace(*cp))
+		cp++;
+	if (*cp != '\0' && *cp != '#')
+		return -1;
+	if (!strcasecmp(np, "NULL")) {
+		*lenp = 0;
+		return 1;
+	}
+
+	dp = frame;
+	len = 0;
+	for (cp = np; *cp; cp += 2) {
+		if (!isxdigit(cp[0]) || !isxdigit(cp[1]))
+			return -1;
+		*dp++ = (decode_hex_digit(cp[0]) << 4) |
+			decode_hex_digit(cp[1]);
+		len++;
+	}
+	*lenp = len;
+	return 1;
+}