--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libcommon/alpha_decode.c	Thu Feb 11 22:28:45 2021 +0000
@@ -0,0 +1,132 @@
+/*
+ * This module contains functions for decoding and displaying alpha fields
+ * that exist in various SIM files.
+ */
+
+#include <sys/types.h>
+#include <string.h>
+#include <strings.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static char gsm7_decode_table[128] = {
+	'@', 0,   '$',  0,   0,   0,    0,   0,
+	0,   0,   '\n', 0,   0,   '\r', 0,   0,
+	0,   '_', 0,    0,   0,   0,    0,   0,
+	0,   0,   0,    0,   0,   0,    0,   0,
+	' ', '!', '"',  '#', 0,   '%',  '&', 0x27,
+	'(', ')', '*',  '+', ',', '-',  '.', '/',
+	'0', '1', '2',  '3', '4', '5',  '6', '7',
+	'8', '9', ':',  ';', '<', '=',  '>', '?',
+	0,   'A', 'B',  'C', 'D', 'E',  'F', 'G',
+	'H', 'I', 'J',  'K', 'L', 'M',  'N', 'O',
+	'P', 'Q', 'R',  'S', 'T', 'U',  'V', 'W',
+	'X', 'Y', 'Z',  0,   0,   0,    0,   0,
+	0,   'a', 'b',  'c', 'd', 'e',  'f', 'g',
+	'h', 'i', 'j',  'k', 'l', 'm',  'n', 'o',
+	'p', 'q', 'r',  's', 't', 'u',  'v', 'w',
+	'x', 'y', 'z',  0,   0,   0,    0,   0
+};
+
+static char gsm7ext_decode_table[128] = {
+	0,   0, 0, 0, 0,   0, 0, 0, 0,   0,   0, 0, 0,   0,   0,   0,
+	0,   0, 0, 0, '^', 0, 0, 0, 0,   0,   0, 0, 0,   0,   0,   0,
+	0,   0, 0, 0, 0,   0, 0, 0, '{', '}', 0, 0, 0,   0,   0,   '\\',
+	0,   0, 0, 0, 0,   0, 0, 0, 0,   0,   0, 0, '[', '~', ']', 0,
+	'|', 0, 0, 0, 0,   0, 0, 0, 0,   0,   0, 0, 0,   0,   0,   0,
+	0,   0, 0, 0, 0,   0, 0, 0, 0,   0,   0, 0, 0,   0,   0,   0,
+	0,   0, 0, 0, 0,   0, 0, 0, 0,   0,   0, 0, 0,   0,   0,   0,
+	0,   0, 0, 0, 0,   0, 0, 0, 0,   0,   0, 0, 0,   0,   0,   0
+};
+
+static
+is_gsm7_string_ok(data, nbytes)
+	u_char *data;
+	unsigned nbytes;
+{
+	u_char *dp, *endp;
+	int c;
+
+	dp = data;
+	endp = data + nbytes;
+	while (dp < endp) {
+		c = *dp++;
+		if (c == 0x1B && dp < endp)
+			c = gsm7ext_decode_table[*dp++];
+		else
+			c = gsm7_decode_table[c];
+		if (!c)
+			return(0);
+	}
+	return(1);
+}
+
+static void
+print_alpha_field_gsmdecode(data, nbytes, outf)
+	u_char *data;
+	unsigned nbytes;
+	FILE *outf;
+{
+	u_char *dp, *endp;
+	int c;
+
+	dp = data;
+	endp = data + nbytes;
+	putc('"', outf);
+	while (dp < endp) {
+		c = *dp++;
+		if (c == 0x1B && dp < endp)
+			c = gsm7ext_decode_table[*dp++];
+		else
+			c = gsm7_decode_table[c];
+		if (c == '\n') {
+			putc('\\', outf);
+			putc('n', outf);
+			continue;
+		}
+		if (c == '\r') {
+			putc('\\', outf);
+			putc('r', outf);
+			continue;
+		}
+		if (c == '"' || c == '\\')
+			putc('\\', outf);
+		putc(c, outf);
+	}
+	putc('"', outf);
+}
+
+static void
+print_alpha_field_hex(data, nbytes, outf)
+	u_char *data;
+	unsigned nbytes;
+	FILE *outf;
+{
+	u_char *dp, *endp;
+
+	fputs("HEX ", outf);
+	dp = data;
+	endp = data + nbytes;
+	while (dp < endp)
+		fprintf(outf, "%02X", *dp++);
+}
+
+void
+print_alpha_field(data, nbytes, outf)
+	u_char *data;
+	unsigned nbytes;
+	FILE *outf;
+{
+	if (!nbytes) {
+		fputs("\"\"", outf);
+		return;
+	}
+	if (data[0] & 0x80) {
+		print_alpha_field_hex(data, nbytes, outf);
+		return;
+	}
+	if (is_gsm7_string_ok(data, nbytes))
+		print_alpha_field_gsmdecode(data, nbytes, outf);
+	else
+		print_alpha_field_hex(data, nbytes, outf);
+}