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

@@ -1,4 +1,4 @@
-.TH "tio" "1" "June 2018"
+.TH "tio" "1" "July 2021"
 
 .SH "NAME"
 tio \- a simple TTY terminal I/O application
@@ -56,6 +56,11 @@ option is provided, tio will exit if the device is not present or an established
 
 Enable local echo.
 
+.TP
+.BR \-t ", " "\-\-timestamp
+
+Prefix each new line with a timestamp.
+
 .TP
 .BR \-l ", " "\-\-log " \fI<filename>
 
@@ -86,10 +91,21 @@ 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 \-v ", " \-\-version
 
 Display program version.
+
 .TP
 .BR \-h ", " \-\-help
 
@@ -126,6 +142,14 @@ 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 "EXAMPLES"
 .TP
 Typical use is without options. For example:

src/include/tio/options.h

@@ -27,6 +27,8 @@
 #include <termios.h>
 #include <sys/param.h>
 
+#define OPT_NEWLINE_IN_HEX	1000	// "short" option for --newline-in-hex	
+
 /* Options */
 struct option_t
 {
@@ -41,6 +43,8 @@ struct option_t
     bool log;
     bool local_echo;
     bool timestamp;
+    bool hex_mode;
+    bool newline_in_hex;
     const char *log_filename;
     const char *map;
 };

src/options.c

@@ -47,6 +47,8 @@ struct option_t option =
     false,    // No log
     false,    // No local echo
     false,    // No timestamp
+    false,    // Not starting in hex mode
+    false,    // No newlines in hex mode
     "",       // Log filename
     ""        // Map string
 };
@@ -67,6 +69,8 @@ void print_help(char *argv[])
     printf("  -t, --timestamp             Prefix each new line with a timestamp\n");
     printf("  -l, --log <filename>        Log to file\n");
     printf("  -m, --map <flags>           Map special characters\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");
@@ -117,6 +121,8 @@ void parse_options(int argc, char *argv[])
             {"timestamp",      no_argument,       0, 't'},
             {"log",            required_argument, 0, 'l'},
             {"map",            required_argument, 0, 'm'},
+            {"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 }
@@ -126,7 +132,7 @@ void parse_options(int argc, char *argv[])
         int option_index = 0;
 
         /* Parse argument using getopt_long */
-        c = getopt_long(argc, argv, "b:d:f:s:p:o:netl:m:vh", long_options, &option_index);
+        c = getopt_long(argc, argv, "b:d:f:s:p:o:netl:m:xvh", long_options, &option_index);
 
         /* Detect the end of the options */
         if (c == -1)
@@ -189,6 +195,14 @@ void parse_options(int argc, char *argv[])
                 option.map = optarg;
                 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) 2014-2018 Martin Lund\n");

src/tty.c

@@ -60,6 +60,8 @@ 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;
 
 #define tio_printf(format, args...) \
 { \
@@ -68,10 +70,58 @@ static bool map_o_del_bs = false;
     tainted = false; \
 }
 
+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 print_hex(char c)
 {
-
+    if (((c == '\n') || (c == '\r')) && option.newline_in_hex)
-    if ((c == '\n') || (c == '\r'))
         printf("%c", c);
     else
         printf("%02x ", (unsigned char) c);
@@ -601,16 +651,6 @@ 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 */
@@ -660,6 +700,19 @@ int tty_connect(void)
     if (option.timestamp)
         next_timestamp = time(NULL);
         
+    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;
@@ -759,6 +812,7 @@ int tty_connect(void)
                     goto error_read;
                 }
             }
+            
             if (FD_ISSET(STDIN_FILENO, &rdfs))
             {
                 bool forward = true;
@@ -781,6 +835,13 @@ 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';
@@ -800,8 +861,12 @@ int tty_connect(void)
                         delay(option.output_delay);
                     }
                     
+                    if(print_mode == HEX){
+                        output_hex(output_char);
+                    } else {
                         /* Send output to tty device */
                         optional_local_echo(output_char);
+                        
                         status = write(fd, &output_char, 1);
                         if (status < 0)
                             warning_printf("Could not write to tty device");
@@ -809,6 +874,7 @@ int tty_connect(void)
 
                         /* Update transmit statistics */
                         tx_total++;
+                    }
 
                     /* Insert output delay */
                     delay(option.output_delay);