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[sfnt] Fix charmap type 2 iterator (#52646).

The subsetted demo font of the report that exhibits the bug has a
very unusual type 2 cmap for Unicode(!): It contains only two
sub-headers, one for one-byte characters (covering the range 0x20 to
0xFA), and a second one for higher byte 0x01 (just for character
code U+0131).

Before this commit, the iterator wasn't able to correctly handle a
sub-header for higher byte 0x01.

* src/sfnt/ttcmap.c (tt_cmap2_char_next): Fix character increment
for outer loop.

git/fs: mount .git/fs: mount/attach disallowed

--- a/ChangeLog

+++ b/ChangeLog

@@ -1,3 +1,19 @@

+2017-12-18  Werner Lemberg  <[email protected]>

+

+	[sfnt] Fix charmap type 2 iterator (#52646).

+

+	The subsetted demo font of the report that exhibits the bug has a

+	very unusual type 2 cmap for Unicode(!): It contains only two

+	sub-headers, one for one-byte characters (covering the range 0x20 to

+	0xFA), and a second one for higher byte 0x01 (just for character

+	code U+0131).

+

+	Before this commit, the iterator wasn't able to correctly handle a

+	sub-header for higher byte 0x01.

+

+	* src/sfnt/ttcmap.c (tt_cmap2_char_next): Fix character increment

+	for outer loop.

+

 2017-12-18  Matthias Clasen  <[email protected]>

 	[truetype] Minor code beautification.

--- a/src/sfnt/ttcmap.c

+++ b/src/sfnt/ttcmap.c

@@ -547,9 +547,19 @@

         }

       }

-      /* jump to next sub-header, i.e. higher byte value */

+      /* If `charcode' is <= 0xFF, retry with `charcode + 1'.  If        */

+      /* `charcode' is 0x100 after the loop, do nothing since we have    */

+      /* just reached the first sub-header for two-byte character codes. */

+      /*                                                                 */

+      /* For all other cases, we jump to the next sub-header and adjust  */

+      /* `charcode' accordingly.                                         */

     Next_SubHeader:

-      charcode = FT_PAD_FLOOR( charcode, 256 ) + 256;

+      if ( charcode <= 0xFF )

+        charcode++;

+      else if ( charcode == 0x100 )

+        ;

+      else

+        charcode = FT_PAD_FLOOR( charcode, 0x100 ) + 0x100;

     }

   Exit: