[U-Boot] [PATCH v2] common: cli_readline: Improve command line editing

[James Byrne]

This improves the cread_line() function so that it will correctly
process the 'Home', 'End', 'Delete' and arrow key escape sequences
produced by various terminal emulators. This makes command line editing
a more pleasant experience.

The previous code only supported the cursor keys and the 'Home' key, and
only for certain terminal emulator configurations. This adds support for
the 'End and 'Delete' keys, and recognises a wider range of escape
sequences. For example, the left arrow key can be 'ESC O D' instead of
'ESC [ D', and the 'Home' key can be 'ESC [ H', 'ESC O H', 'ESC 1 ~' or
'ESC 7 ~', depending on what terminal emulator you use and how it is
configured.

Signed-off-by: James Byrne <james.byrne at origamienergy.com>
---
Changes for v2
   - Explicitly initialize variable to avoid spurious compiler warning.

 common/cli_readline.c | 108 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 78 insertions(+), 30 deletions(-)

diff --git a/common/cli_readline.c b/common/cli_readline.c
index c1476e4..6690c13 100644
--- a/common/cli_readline.c
+++ b/common/cli_readline.c
@@ -283,46 +283,94 @@ static int cread_line(const char *const prompt, char *buf, unsigned int *len,
 		 * handle standard linux xterm esc sequences for arrow key, etc.
 		 */
 		if (esc_len != 0) {
+			enum { ESC_REJECT, ESC_SAVE, ESC_CONVERTED } act = ESC_REJECT;
+
 			if (esc_len == 1) {
-				if (ichar == '[') {
-					esc_save[esc_len] = ichar;
-					esc_len = 2;
+				if (ichar == '[' || ichar == 'O')
+					act = ESC_SAVE;
+				else
+					act = ESC_REJECT;
+			} else if (esc_len == 2) {
+				switch (ichar) {
+				case 'D':	/* <- key */
+					ichar = CTL_CH('b');
+					act = ESC_CONVERTED;
+					break;	/* pass off to ^B handler */
+				case 'C':	/* -> key */
+					ichar = CTL_CH('f');
+					act = ESC_CONVERTED;
+					break;	/* pass off to ^F handler */
+				case 'H':	/* Home key */
+					ichar = CTL_CH('a');
+					act = ESC_CONVERTED;
+					break;	/* pass off to ^A handler */
+				case 'F':	/* End key */
+					ichar = CTL_CH('e');
+					act = ESC_CONVERTED;
+					break;	/* pass off to ^E handler */
+				case 'A':	/* up arrow */
+					ichar = CTL_CH('p');
+					act = ESC_CONVERTED;
+					break;	/* pass off to ^P handler */
+				case 'B':	/* down arrow */
+					ichar = CTL_CH('n');
+					act = ESC_CONVERTED;
+					break;	/* pass off to ^N handler */
+				case '1':
+				case '3':
+				case '4':
+				case '7':
+				case '8':
+					if (esc_save[1] == '[') {
+						/* see if next character is ~ */
+						act = ESC_SAVE;
+					} else {
+						act = ESC_REJECT;
+					}
+					break;
+				default:
+					act = ESC_REJECT;
+					break;
+				}
+			} else if (esc_len == 3) {
+				if (ichar == '~') {
+					switch (esc_save[2]) {
+					case '3':	/* Delete key */
+						ichar = CTL_CH('d');
+						act = ESC_CONVERTED;
+						break;	/* pass to ^D handler */
+					case '1':	/* Home key */
+					case '7':
+						ichar = CTL_CH('a');
+						act = ESC_CONVERTED;
+						break;	/* pass to ^A handler */
+					case '4':	/* End key */
+					case '8':
+						ichar = CTL_CH('e');
+						act = ESC_CONVERTED;
+						break;	/* pass to ^E handler */
+					default:
+						act = ESC_REJECT;
+						break;
+					}
 				} else {
-					cread_add_str(esc_save, esc_len,
-						      insert, &num, &eol_num,
-						      buf, *len);
-					esc_len = 0;
+					act = ESC_REJECT;
 				}
-				continue;
 			}
 
-			switch (ichar) {
-			case 'D':	/* <- key */
-				ichar = CTL_CH('b');
-				esc_len = 0;
-				break;
-			case 'C':	/* -> key */
-				ichar = CTL_CH('f');
-				esc_len = 0;
-				break;	/* pass off to ^F handler */
-			case 'H':	/* Home key */
-				ichar = CTL_CH('a');
-				esc_len = 0;
-				break;	/* pass off to ^A handler */
-			case 'A':	/* up arrow */
-				ichar = CTL_CH('p');
-				esc_len = 0;
-				break;	/* pass off to ^P handler */
-			case 'B':	/* down arrow */
-				ichar = CTL_CH('n');
-				esc_len = 0;
-				break;	/* pass off to ^N handler */
-			default:
+			switch (act) {
+			case ESC_SAVE:
+				esc_save[esc_len++] = ichar;
+				continue;
+			case ESC_REJECT:
 				esc_save[esc_len++] = ichar;
 				cread_add_str(esc_save, esc_len, insert,
 					      &num, &eol_num, buf, *len);
 				esc_len = 0;
 				continue;
+			case ESC_CONVERTED:
+				esc_len = 0;
+				break;
 			}
 		}
 
-- 
1.9.1