winansi: fix ansi emulation

The following commands (reported in GitHub issue #201):

   printf "\033[38;2;255;0;0mX\033[m\n"
   printf "\033[38;2;255;0;0m;\033[m\n"

produce different results.  The first correctly displays a red 'X'
while the second incorrectly displays a white ';'.

The problem is that process_24bit() overruns the extent of the
escape sequence.  As a result the loop in process_escape() which
handles 'ESC[...m' sequences sees the ';' in the text as a
continuation of the escape sequence.

Fix this by:

- reworking process_24bit() so that the overrun is avoided;

- changing the test in the loop in process_escape() so that even
  if an overrun happens it stops processing at the end of the escape
  sequence.

Also, save a few bytes by replacing '++str' with 'str + 1' in a
few places.

1 files changed, 13 insertions, 12 deletions

diff --git a/win32/winansi.c b/win32/winansi.c
index 971702f18..68b568b81 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -375,17 +375,18 @@ static WORD rgb_to_console(int *rgb)
 /* 24-bit colour */
 static char *process_24bit(char *str, WORD *attr)
 {
-        int count = 0;
-        int rgb[3] = {0, 0, 0};
+        int count;
+        int rgb[3];
 
-        do {
-                rgb[count++] = strtol(str, (char **)&str, 10);
-                ++str;
-        } while (*(str-1) == ';' && count < 3);
+        for (count = 0; count < 3; ++count) {
+                rgb[count] = strtol(str, (char **)&str, 10);
+                if (*str == ';')
+                        ++str;
+        }
 
         *attr = rgb_to_console(rgb);
 
-        return str;
+        return *(str - 1) == ';' ? str - 1 : str;
 }
 
 /* 8-bit colour */
@@ -435,10 +436,10 @@ static char *process_colour(char *str, WORD *attr)
         *attr = -1;     /* error return */
         switch (val) {
         case 2:
-                str = process_24bit(++str, attr);
+                str = process_24bit(str + 1, attr);
                 break;
         case 5:
-                str = process_8bit(++str, attr);
+                str = process_8bit(str + 1, attr);
                 break;
         default:
                 break;
@@ -541,7 +542,7 @@ static char *process_escape(char *pos)
                                 attr |= colour_1bit[val - 30];
                                 break;
                         case 38: /* 8/24 bit */
-                                str = process_colour(++str, &t);
+                                str = process_colour(str + 1, &t);
                                 if (t != -1) {
                                         attr &= ~(FOREGROUND_ALL|FOREGROUND_INTENSITY);
                                         attr |= t;
@@ -565,7 +566,7 @@ static char *process_escape(char *pos)
                                 attr |= colour_1bit[val - 40] << 4;
                                 break;
                         case 48: /* 8/24 bit */
-                                str = process_colour(++str, &t);
+                                str = process_colour(str + 1, &t);
                                 if (t != -1) {
                                         attr &= ~(BACKGROUND_ALL|BACKGROUND_INTENSITY);
                                         attr |= t << 4;
@@ -581,7 +582,7 @@ static char *process_escape(char *pos)
                                 return pos;
                         }
                         str++;
-                } while (*(str-1) == ';');
+                } while (str < func);
 
                 current_attr = attr;
                 if (reverse)