Extended hexadecimal mode.

While in hex mode (ctrl-t h) you can output hexadecimal values.
E.g.: to send 0x0A you have to type 0A (always 2 characters).

Added option -x, --hex to start in hexadecimal mode.

Added option --newline-in-hex to interpret newline characters in hex mode.
This is disabled by default, because, in my opinion, hex stream is
fundamentally different from text, so a "new line" is meaningless in this
context.

man/tio.1.in

@@ -117,6 +117,16 @@ Map NL to CR-NL on output.
 If defining more than one flag, the flags must be comma separated.
 .RE
 
+.TP
+.BR \-x ", " \-\-hex
+
+Start in hexadecimal mode.
+
+.TP
+.BR \-\-newline-in-hex
+
+Interpret new line characters ('\\r', '\\n') in hexadecimal mode.
+
 .TP
 .BR \-c ", " "\-\-color " \fI<code>
 
@@ -180,6 +190,14 @@ Toggle RTS
 .IP "\fBctrl-t v"
 Show version
 
+.SH "HEXADECIMAL MODE"
+.TP
+In hexadecimal mode each incoming byte is printed out as a hexadecimal value.
+.TP
+By default there is \fBno new line\fR in this mode, but it can be turned on using the \fB--newline-in-hex\fR option.
+.TP
+Bytes can be sent in this mode by typing the \fBtwo-character hexadecimal\fR representation of the value, e.g.: to send \fI0xA\fR you must type \fI0a\fR or \fI0A\fR.
+
 .SH "CONFIGURATION"
 .PP
 .TP 16n

src/options.c

@@ -61,6 +61,8 @@ struct option_t option =
     .socket = NULL,
     .map = "",
     .color = -1,
+    .hex_mode = false,
+    .newline_in_hex = false,
 };
 
 void print_help(char *argv[])
@@ -84,6 +86,8 @@ void print_help(char *argv[])
     printf("  -m, --map <flags>                Map special characters\n");
     printf("  -c, --color <code>               Colorize tio text\n");
     printf("  -S, --socket <socket>            Listen on socket\n");
+    printf("  -x, --hex                        Start in hexadecimal mode\n");
+    printf("      --newline-in-hex             Interpret new line characters in hex mode\n");
     printf("  -v, --version                    Display version\n");
     printf("  -h, --help                       Display help\n");
     printf("\n");
@@ -195,6 +199,8 @@ void options_parse(int argc, char *argv[])
             {"socket",           required_argument, 0, 'S'                  },
             {"map",              required_argument, 0, 'm'                  },
             {"color",            required_argument, 0, 'c'                  },
+            {"hex",              no_argument,       0, 'x'                  },
+            {"newline-in-hex",   no_argument,       0, OPT_NEWLINE_IN_HEX   },
             {"version",          no_argument,       0, 'v'                  },
             {"help",             no_argument,       0, 'h'                  },
             {0,                  0,                 0,  0                   }
@@ -204,7 +210,7 @@ void options_parse(int argc, char *argv[])
         int option_index = 0;
 
         /* Parse argument using getopt_long */
-        c = getopt_long(argc, argv, "b:d:f:s:p:o:netLlS:m:c:vh", long_options, &option_index);
+        c = getopt_long(argc, argv, "b:d:f:s:p:o:netLlS:m:c:xvh", long_options, &option_index);
 
         /* Detect the end of the options */
         if (c == -1)
@@ -301,6 +307,14 @@ void options_parse(int argc, char *argv[])
                 }
                 break;
 
+            case 'x':
+                option.hex_mode = true;
+                break;
+
+            case OPT_NEWLINE_IN_HEX:
+                option.newline_in_hex = true;
+                break;
+
             case 'v':
                 printf("tio v%s\n", VERSION);
                 printf("Copyright (c) 2014-2022 Martin Lund\n");

src/options.h

@@ -37,6 +37,8 @@ enum timestamp_t
 const char* timestamp_token(enum timestamp_t timestamp);
 enum timestamp_t timestamp_option_parse(const char *arg);
 
+#define OPT_NEWLINE_IN_HEX	1000	// "short" option for --newline-in-hex
+
 /* Options */
 struct option_t
 {
@@ -56,6 +58,8 @@ struct option_t
     const char *map;
     const char *socket;
     int color;
+    bool hex_mode;
+    bool newline_in_hex;
 };
 
 extern struct option_t option;

src/print.c

@@ -29,7 +29,7 @@ char ansi_format[30];
 
 void print_hex(char c)
 {
-  if ((c == '\n') || (c == '\r'))
+  if (((c == '\n') || (c == '\r')) && option.newline_in_hex)
   {
     printf("%c", c);
   }

src/tty.c

@@ -74,7 +74,60 @@ static bool map_i_nl_crnl = false;
 static bool map_o_cr_nl = false;
 static bool map_o_nl_crnl = false;
 static bool map_o_del_bs = false;
+static char hex_chars[2];
+static unsigned char hex_char_index = 0;
 
+static void optional_local_echo(char c)
+{
+    if (!option.local_echo)
+        return;
+    print(c);
+    fflush(stdout);
+    if (option.log)
+        log_write(c);
+}
+
+inline static bool is_valid_hex(char c)
+{
+    return ((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'));
+}
+
+inline static unsigned char char_to_nibble(char c)
+{
+    if(c >= '0' && c <= '9'){
+        return c - '0';
+    } else if(c >= 'a' && c <= 'f'){
+        return c - 'a' + 10;
+    } else if(c >= 'A' && c <= 'F'){
+        return c - 'A' + 10;
+    } else {
+        return 0;
+    }
+}
+
+static void output_hex(char c)
+{
+    hex_chars[hex_char_index++] = c;
+
+    if (hex_char_index == 2)
+    {
+        unsigned char hex_value = char_to_nibble(hex_chars[0]) << 4 | (char_to_nibble(hex_chars[1]) & 0x0F);
+        hex_char_index = 0;
+
+        optional_local_echo(hex_value);
+
+        ssize_t status = write(fd, &hex_value, 1);
+        if (status < 0)
+        {
+            warning_printf("Could not write to tty device");
+        } else
+        {
+            tx_total++;
+        }
+
+        fsync(fd);
+    }
+}
 
 static void toggle_line(const char *line_name, int mask)
 {
@@ -585,16 +638,6 @@ void tty_restore(void)
         tty_disconnect();
 }
 
-static void optional_local_echo(char c)
-{
-    if (!option.local_echo)
-        return;
-    print(c);
-    fflush(stdout);
-    if (option.log)
-        log_write(c);
-}
-
 int tty_connect(void)
 {
     fd_set rdfs;           /* Read file descriptor set */
@@ -644,6 +687,19 @@ int tty_connect(void)
     if (option.timestamp)
         next_timestamp = true;
 
+    if (option.hex_mode)
+    {
+        print = print_hex;
+        print_mode = HEX;
+        tio_printf("Switched to hexadecimal mode");
+    }
+    else
+    {
+        print = print_normal;
+        print_mode = NORMAL;
+        tio_printf("Switched to normal mode");
+    }
+
     /* Save current port settings */
     if (tcgetattr(fd, &tio_old) < 0)
         goto error_tcgetattr;
@@ -800,6 +856,15 @@ int tty_connect(void)
 
             if (forward)
             {
+                if (print_mode == HEX)
+                {
+                    if (!is_valid_hex(input_char))
+                    {
+                        warning_printf("Invalid hex character: '%c' (0x%02x)", input_char, input_char);
+                        continue;
+                    }
+                }
+
                 /* Map output character */
                 if ((output_char == 127) && (map_o_del_bs))
                     output_char = '\b';
@@ -819,6 +884,12 @@ int tty_connect(void)
                     tx_total += 2;
                     delay(option.output_delay);
                 } else
+                {
+                    if (print_mode == HEX)
+                    {
+                        output_hex(output_char);
+                    }
+                    else
                     {
                         /* Send output to tty device */
                         optional_local_echo(output_char);
@@ -829,6 +900,7 @@ int tty_connect(void)
 
                         /* Update transmit statistics */
                         tx_total++;
+                    }
 
                     /* Insert output delay */
                     delay(option.output_delay);