vt: separate unicode handling into vc_translate_unicode

do_con_write is complicated enough. Extract unicode handling to a
separate function. For do_con_write, 249 LOCs lowered to 183 lines.

Use diff -w -b to see the difference is neligible -- mostly whitespace
and use of 'return's instead of 'continue's.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200615074910.19267-12-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index a9e4924..caaad82 100644 (file)
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2572,6 +2572,85 @@ static inline int vc_translate_ascii(const struct vc_data *vc, int c)
        return c;
 }
 
+/**
+ * vc_translate_unicode -- Combine UTF-8 into Unicode in @vc_utf_char
+ *
+ * @vc_utf_char is the being-constructed unicode character.
+ * @vc_utf_count is the number of continuation bytes still expected to arrive.
+ * @vc_npar is the number of continuation bytes arrived so far.
+ */
+static int vc_translate_unicode(struct vc_data *vc, int c, bool *rescan)
+{
+       static const u32 utf8_length_changes[] = {
+               0x0000007f, 0x000007ff, 0x0000ffff,
+               0x001fffff, 0x03ffffff, 0x7fffffff
+       };
+
+       if ((c & 0xc0) == 0x80) {
+               /* Continuation byte received */
+               if (vc->vc_utf_count) {
+                       vc->vc_utf_char = (vc->vc_utf_char << 6) | (c & 0x3f);
+                       vc->vc_npar++;
+                       if (--vc->vc_utf_count) {
+                               /* Still need some bytes */
+                               return -1;
+                       }
+                       /* Got a whole character */
+                       c = vc->vc_utf_char;
+                       /* Reject overlong sequences */
+                       if (c <= utf8_length_changes[vc->vc_npar - 1] ||
+                                       c > utf8_length_changes[vc->vc_npar])
+                               return 0xfffd;
+               } else {
+                       /* Unexpected continuation byte */
+                       vc->vc_utf_count = 0;
+                       return 0xfffd;
+               }
+       } else {
+               /* Single ASCII byte or first byte of a sequence received */
+               if (vc->vc_utf_count) {
+                       /* Continuation byte expected */
+                       *rescan = true;
+                       vc->vc_utf_count = 0;
+                       return 0xfffd;
+               } else if (c > 0x7f) {
+                       /* First byte of a multibyte sequence received */
+                       vc->vc_npar = 0;
+                       if ((c & 0xe0) == 0xc0) {
+                               vc->vc_utf_count = 1;
+                               vc->vc_utf_char = (c & 0x1f);
+                       } else if ((c & 0xf0) == 0xe0) {
+                               vc->vc_utf_count = 2;
+                               vc->vc_utf_char = (c & 0x0f);
+                       } else if ((c & 0xf8) == 0xf0) {
+                               vc->vc_utf_count = 3;
+                               vc->vc_utf_char = (c & 0x07);
+                       } else if ((c & 0xfc) == 0xf8) {
+                               vc->vc_utf_count = 4;
+                               vc->vc_utf_char = (c & 0x03);
+                       } else if ((c & 0xfe) == 0xfc) {
+                               vc->vc_utf_count = 5;
+                               vc->vc_utf_char = (c & 0x01);
+                       } else {
+                               /* 254 and 255 are invalid */
+                               return 0xfffd;
+                       }
+                       if (vc->vc_utf_count) {
+                               /* Still need some bytes */
+                               return -1;
+                       }
+               }
+               /* Nothing to do if an ASCII byte was received */
+       }
+       /* End of UTF-8 decoding. */
+       /* c is the received character, or U+FFFD for invalid sequences. */
+       /* Replace invalid Unicode code points with U+FFFD too */
+       if ((c >= 0xd800 && c <= 0xdfff) || c == 0xfffe || c == 0xffff)
+               return 0xfffd;
+
+       return c;
+}
+
 /* acquires console_lock */
 static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int count)
 {
@@ -2628,76 +2707,10 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co
                if (vc->vc_state != ESnormal) {
                        tc = c;
                } else if (vc->vc_utf && !vc->vc_disp_ctrl) {
-                   /* Combine UTF-8 into Unicode in vc_utf_char.
-                    * vc_utf_count is the number of continuation bytes still
-                    * expected to arrive.
-                    * vc_npar is the number of continuation bytes arrived so
-                    * far
-                    */
 rescan_last_byte:
-                   if ((c & 0xc0) == 0x80) {
-                       /* Continuation byte received */
-                       static const uint32_t utf8_length_changes[] = { 0x0000007f, 0x000007ff, 0x0000ffff, 0x001fffff, 0x03ffffff, 0x7fffffff };
-                       if (vc->vc_utf_count) {
-                           vc->vc_utf_char = (vc->vc_utf_char << 6) | (c & 0x3f);
-                           vc->vc_npar++;
-                           if (--vc->vc_utf_count) {
-                               /* Still need some bytes */
-                               continue;
-                           }
-                           /* Got a whole character */
-                           c = vc->vc_utf_char;
-                           /* Reject overlong sequences */
-                           if (c <= utf8_length_changes[vc->vc_npar - 1] ||
-                                       c > utf8_length_changes[vc->vc_npar])
-                               c = 0xfffd;
-                       } else {
-                           /* Unexpected continuation byte */
-                           vc->vc_utf_count = 0;
-                           c = 0xfffd;
-                       }
-                   } else {
-                       /* Single ASCII byte or first byte of a sequence received */
-                       if (vc->vc_utf_count) {
-                           /* Continuation byte expected */
-                           rescan = true;
-                           vc->vc_utf_count = 0;
-                           c = 0xfffd;
-                       } else if (c > 0x7f) {
-                           /* First byte of a multibyte sequence received */
-                           vc->vc_npar = 0;
-                           if ((c & 0xe0) == 0xc0) {
-                               vc->vc_utf_count = 1;
-                               vc->vc_utf_char = (c & 0x1f);
-                           } else if ((c & 0xf0) == 0xe0) {
-                               vc->vc_utf_count = 2;
-                               vc->vc_utf_char = (c & 0x0f);
-                           } else if ((c & 0xf8) == 0xf0) {
-                               vc->vc_utf_count = 3;
-                               vc->vc_utf_char = (c & 0x07);
-                           } else if ((c & 0xfc) == 0xf8) {
-                               vc->vc_utf_count = 4;
-                               vc->vc_utf_char = (c & 0x03);
-                           } else if ((c & 0xfe) == 0xfc) {
-                               vc->vc_utf_count = 5;
-                               vc->vc_utf_char = (c & 0x01);
-                           } else {
-                               /* 254 and 255 are invalid */
-                               c = 0xfffd;
-                           }
-                           if (vc->vc_utf_count) {
-                               /* Still need some bytes */
+                       tc = c = vc_translate_unicode(vc, c, &rescan);
+                       if (tc == -1)
                                continue;
-                           }
-                       }
-                       /* Nothing to do if an ASCII byte was received */
-                   }
-                   /* End of UTF-8 decoding. */
-                   /* c is the received character, or U+FFFD for invalid sequences. */
-                   /* Replace invalid Unicode code points with U+FFFD too */
-                   if ((c >= 0xd800 && c <= 0xdfff) || c == 0xfffe || c == 0xffff)
-                       c = 0xfffd;
-                   tc = c;
                } else {        /* no utf or alternate charset mode */
                        tc = vc_translate_ascii(vc, c);
                }