less,microcom,lineedit: use common routine to set raw termios

function                                             old     new   delta
get_termios_and_make_raw                               -     139    +139
xget1                                                 39       8     -31
read_line_input                                     3912    3867     -45
less_main                                           2525    2471     -54
set_termios_to_raw                                   116      36     -80
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/4 up/down: 139/-210)          Total: -71 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

5 files changed, 54 insertions, 49 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 06f887732..aff2825ac 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1582,6 +1582,7 @@ int tcsetattr_stdin_TCSANOW(const struct termios *tp) FAST_FUNC;
 #define TERMIOS_CLEAR_ISIG (1 << 0)
 #define TERMIOS_RAW_CRNL   (1 << 1)
 #define TERMIOS_RAW_INPUT  (1 << 2)
+int get_termios_and_make_raw(int fd, struct termios *newterm, struct termios *oldterm, int flags) FAST_FUNC;
 int set_termios_to_raw(int fd, struct termios *oldterm, int flags) FAST_FUNC;
 
 /* NB: "unsigned request" is crucial! "int request" will break some arches! */
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 17766a126..3a092ffe2 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -2259,7 +2259,7 @@ static int32_t reverse_i_search(int timeout)
  */
 int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *command, int maxsize)
 {
-	int len;
+	int len, n;
 	int timeout;
 #if ENABLE_FEATURE_TAB_COMPLETION
 	smallint lastWasTab = 0;
@@ -2274,9 +2274,10 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
 
 	INIT_S();
 
-	if (tcgetattr(STDIN_FILENO, &initial_settings) < 0
-	 || (initial_settings.c_lflag & (ECHO|ICANON)) == ICANON
-	) {
+	n = get_termios_and_make_raw(STDIN_FILENO, &new_settings, &initial_settings, 0
+		| TERMIOS_CLEAR_ISIG /* turn off INTR (ctrl-C), QUIT, SUSP */
+	);
+	if (n != 0 || (initial_settings.c_lflag & (ECHO|ICANON)) == ICANON) {
 		/* Happens when e.g. stty -echo was run before.
 		 * But if ICANON is not set, we don't come here.
 		 * (example: interactive python ^Z-backgrounded,
@@ -2329,18 +2330,6 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
 #endif
 #define command command_must_not_be_used
 
-	new_settings = initial_settings;
-	/* ~ICANON: unbuffered input (most c_cc[] are disabled, VMIN/VTIME are enabled) */
-	/* ~ECHO, ~ECHONL: turn off echoing, including newline echoing */
-	/* ~ISIG: turn off INTR (ctrl-C), QUIT, SUSP */
-	new_settings.c_lflag &= ~(ICANON | ECHO | ECHONL | ISIG);
-	/* reads will block only if < 1 char is available */
-	new_settings.c_cc[VMIN] = 1;
-	/* no timeout (reads block forever) */
-	new_settings.c_cc[VTIME] = 0;
-	/* Should be not needed if ISIG is off: */
-	/* Turn off CTRL-C */
-	/* new_settings.c_cc[VINTR] = _POSIX_VDISABLE; */
 	tcsetattr_stdin_TCSANOW(&new_settings);
 
 #if ENABLE_USERNAME_OR_HOMEDIR
diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index 1b3a1667b..d7647704e 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -311,40 +311,65 @@ int FAST_FUNC tcsetattr_stdin_TCSANOW(const struct termios *tp)
 	return tcsetattr(STDIN_FILENO, TCSANOW, tp);
 }
 
-int FAST_FUNC set_termios_to_raw(int fd, struct termios *oldterm, int flags)
+int FAST_FUNC get_termios_and_make_raw(int fd, struct termios *newterm, struct termios *oldterm, int flags)
 {
-//TODO: lineedit, microcom, slattach, less might be adapted to use this too:
-// grep for "tcsetattr"
-
-	struct termios newterm;
+//TODO: slattach, shell read might be adapted to use this too: grep for "tcsetattr", "[VTIME] = 0"
+	int r;
 
-	tcgetattr(fd, oldterm);
-	newterm = *oldterm;
+	memset(oldterm, 0, sizeof(*oldterm)); /* paranoia */
+	r = tcgetattr(fd, oldterm);
+	*newterm = *oldterm;
 
 	/* Turn off buffered input (ICANON)
 	 * Turn off echoing (ECHO)
 	 * and separate echoing of newline (ECHONL, normally off anyway)
 	 */
-	newterm.c_lflag &= ~(ICANON | ECHO | ECHONL);
+	newterm->c_lflag &= ~(ICANON | ECHO | ECHONL);
 	if (flags & TERMIOS_CLEAR_ISIG) {
 		/* dont recognize INT/QUIT/SUSP chars */
-		newterm.c_lflag &= ~ISIG;
+		newterm->c_lflag &= ~ISIG;
 	}
 	/* reads will block only if < 1 char is available */
-	newterm.c_cc[VMIN] = 1;
+	newterm->c_cc[VMIN] = 1;
 	/* no timeout (reads block forever) */
-	newterm.c_cc[VTIME] = 0;
+	newterm->c_cc[VTIME] = 0;
 	if (flags & TERMIOS_RAW_CRNL) {
+/* IXON, IXOFF, and IXANY:
+ * IXOFF=1: sw flow control is enabled on input queue:
+ * tty transmits a STOP char when input queue is close to full
+ * and transmits a START char when input queue is nearly empty.
+ * IXON=1: sw flow control is enabled on output queue:
+ * tty will stop sending if STOP char is received,
+ * and resume sending if START is received, or if any char
+ * is received and IXANY=1.
+ */
+		/* IXON=0: XON/XOFF chars are treated as normal chars (why we do this?) */
 		/* dont convert CR to NL on input */
-		newterm.c_iflag &= ~(IXON | ICRNL);
-		/* dont convert NL to CR on output */
-		newterm.c_oflag &= ~(ONLCR);
+		newterm->c_iflag &= ~(IXON | ICRNL);
+		/* dont convert NL to CR+NL on output */
+		newterm->c_oflag &= ~(ONLCR);
+		/* Maybe clear more c_oflag bits? usually, only OPOST and ONLCR are set.
+		 * OPOST  Enable implementation-defined output processing (is this reqd for all other bits to work?)
+		 * OLCUC  Map lowercase characters to uppercase on output.
+		 * OCRNL  Map CR to NL on output.
+		 * ONOCR  Don't output CR at column 0.
+		 * ONLRET Don't output CR.
+		 */
 	}
 	if (flags & TERMIOS_RAW_INPUT) {
+		/* IXOFF=0: disable sending XON/XOFF if input buf is full */
+		/* IXON=0: XON/XOFF chars are treated as normal chars */
 		/* dont convert anything on input */
-		newterm.c_iflag &= ~(BRKINT|INLCR|ICRNL|IXON|IXOFF|IUCLC|IXANY|IMAXBEL);
+		newterm->c_iflag &= ~(IXOFF|IXON|IXANY|BRKINT|INLCR|ICRNL|IUCLC|IMAXBEL);
 	}
+	return r;
+}
+
+int FAST_FUNC set_termios_to_raw(int fd, struct termios *oldterm, int flags)
+{
+	struct termios newterm;
 
+	get_termios_and_make_raw(fd, &newterm, oldterm, flags);
 	return tcsetattr(fd, TCSANOW, &newterm);
 }
 
diff --git a/miscutils/less.c b/miscutils/less.c
index d524b6c87..c6c158a51 100644
--- a/miscutils/less.c
+++ b/miscutils/less.c
@@ -1824,15 +1824,9 @@ int less_main(int argc, char **argv)
 	G.kbd_fd_orig_flags = ndelay_on(tty_fd);
 	kbd_fd = tty_fd; /* save in a global */
 
-	tcgetattr(kbd_fd, &term_orig);
-	term_less = term_orig;
-	term_less.c_lflag &= ~(ICANON | ECHO);
-	term_less.c_iflag &= ~(IXON | ICRNL);
-	/*term_less.c_oflag &= ~ONLCR;*/
-	term_less.c_cc[VMIN] = 1;
-	term_less.c_cc[VTIME] = 0;
-
-	IF_FEATURE_LESS_ASK_TERMINAL(G.winsize_err =) get_terminal_width_height(kbd_fd, &width, &max_displayed_line);
+	get_termios_and_make_raw(tty_fd, &term_less, &term_orig, TERMIOS_RAW_CRNL);
+
+	IF_FEATURE_LESS_ASK_TERMINAL(G.winsize_err =) get_terminal_width_height(tty_fd, &width, &max_displayed_line);
 	/* 20: two tabstops + 4 */
 	if (width < 20 || max_displayed_line < 3)
 		return bb_cat(argv);
diff --git a/miscutils/microcom.c b/miscutils/microcom.c
index b87f3273f..fa090057e 100644
--- a/miscutils/microcom.c
+++ b/miscutils/microcom.c
@@ -33,15 +33,11 @@
 // set raw tty mode
 static void xget1(int fd, struct termios *t, struct termios *oldt)
 {
-//TODO: use set_termios_to_raw()
-	tcgetattr(fd, oldt);
-	*t = *oldt;
-	cfmakeraw(t);
-//	t->c_lflag &= ~(ISIG|ICANON|ECHO|IEXTEN);
-//	t->c_iflag &= ~(BRKINT|IXON|ICRNL);
-//	t->c_oflag &= ~(ONLCR);
-//	t->c_cc[VMIN]  = 1;
-//	t->c_cc[VTIME] = 0;
+	get_termios_and_make_raw(fd, t, oldt, 0
+		| TERMIOS_CLEAR_ISIG /* ^C is ASCII char 3, not "interrupt me!" */
+		| TERMIOS_RAW_INPUT /* pass all chars verbatim, no special handling or translating CR->NL */
+		| TERMIOS_RAW_CRNL  /* dont convert NL<->CR on output too */
+	);
 }
 
 static int xset1(int fd, struct termios *tio, const char *device)