--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libcoding/hexdecode.c	Thu Jun 13 02:29:29 2024 +0000
@@ -0,0 +1,37 @@
+/*
+ * This library module implements decoding of long hex strings,
+ * such as SMS PDUs.
+ */
+
+#include <sys/types.h>
+#include <ctype.h>
+
+decode_hex_line(inbuf, outbuf, outmax)
+	char *inbuf;
+	u_char *outbuf;
+	unsigned outmax;
+{
+	char *inp = inbuf;
+	u_char *outp = outbuf;
+	unsigned outcnt = 0;
+	int c, d[2], i;
+
+	while (*inp) {
+		if (!isxdigit(inp[0]) || !isxdigit(inp[1]))
+			return(-1);
+		if (outcnt >= outmax)
+			break;
+		for (i = 0; i < 2; i++) {
+			c = *inp++;
+			if (isdigit(c))
+				d[i] = c - '0';
+			else if (isupper(c))
+				d[i] = c - 'A' + 10;
+			else
+				d[i] = c - 'a' + 10;
+		}
+		*outp++ = (d[0] << 4) | d[1];
+		outcnt++;
+	}
+	return outcnt;
+}