libbb: shrink lineedit_read_key()

function                                             old     new   delta
lineedit_read_key                                    237     231      -6

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

include/libbb.h

@@ -1900,6 +1900,8 @@ enum {
  * (unless fd is in non-blocking mode),
  * subsequent reads will time out after a few milliseconds.
  * Return of -1 means EOF or error (errno == 0 on EOF).
+ * Nonzero errno is not preserved across the call:
+ * if there was no error, errno will be cleared to 0.
  * buffer[0] is used as a counter of buffered chars and must be 0
  * on first call.
  * timeout:

libbb/lineedit.c

@@ -2155,7 +2155,7 @@ static int lineedit_read_key(char *read_key_buffer, int timeout)
 #endif
 
 	fflush_all();
-	while (1) {
+	for (;;) {
 		/* Wait for input. TIMEOUT = -1 makes read_key wait even
 		 * on nonblocking stdin, TIMEOUT = 50 makes sure we won't
 		 * insist on full MB_CUR_MAX buffer to declare input like
@@ -2167,24 +2167,30 @@ static int lineedit_read_key(char *read_key_buffer, int timeout)
 		 *
 		 * Note: read_key sets errno to 0 on success.
 		 */
-		do {
+		for (;;) {
 			if ((state->flags & LI_INTERRUPTIBLE) && bb_got_signal) {
 				errno = EINTR;
 				return -1;
 			}
 //FIXME: still races here with signals, but small window to poll() inside read_key
 			IF_FEATURE_EDITING_WINCH(S.ok_to_redraw = 1;)
+			/* errno = 0; - read_key does this itself */
 			ic = read_key(STDIN_FILENO, read_key_buffer, timeout);
 			IF_FEATURE_EDITING_WINCH(S.ok_to_redraw = 0;)
-		} while (!(state->flags & LI_INTERRUPTIBLE) && errno == EINTR);
+			if (errno != EINTR)
-
+				break;
-		if (errno) {
+			if (state->flags & LI_INTERRUPTIBLE) {
-			/* LI_INTERRUPTIBLE can bail out with EINTR here,
+				/* LI_INTERRUPTIBLE bails out on EINTR,
 				 * but nothing really guarantees that bb_got_signal
 				 * is nonzero. Follow the least surprise principle:
 				 */
-			if (errno == EINTR && bb_got_signal == 0)
+				if (bb_got_signal == 0)
-				bb_got_signal = 255; /* something nonzero */
+					bb_got_signal = 255;
+				goto ret;
+			}
+		}
+
+		if (errno) {
 #if ENABLE_UNICODE_SUPPORT
 			if (errno == EAGAIN && unicode_idx != 0)
 				goto pushback;
@@ -2251,7 +2257,7 @@ static int lineedit_read_key(char *read_key_buffer, int timeout)
 #endif
 		break;
 	}
-
+ ret:
 	return ic;
 }
 

libbb/read_key.c

@@ -291,6 +291,7 @@ int64_t FAST_FUNC safe_read_key(int fd, char *buffer, int timeout)
 {
 	int64_t r;
 	do {
+		/* errno = 0; - read_key does this itself */
 		r = read_key(fd, buffer, timeout);
 	} while (errno == EINTR);
 	return r;