Commit a3b69a02 authored by Uli Schlachter's avatar Uli Schlachter
Browse files

pdf font subset: Generate valid font names

A hash value is encoded in base 26 with upper case letters for font

Commit ed984146 replaced "numerator = abs (hash);" with "numerator =
hash;" in this code, because hash has type uint32_t and the compiler
warned about taking the absolute value of an unsigned value.  However,
abs() is actually defined to take an int argument. Thus, there was some
implicit cast.

Since numerator has type long, i.e. is signed, it is now actually
possible to get an overflow in the implicit cast and then have a
negative number. The following code is not prepared for this and
produces non-letters when encoding the hash.

This commit fixes that problem by not using ldiv() and instead using /
and % to directly compute the needed values. This gets rid of the need
to convert to type long. Since now everything works with uint32_t, there
is no more chance for negative numbers messing things up.

Fixes: #449

Signed-off-by: Uli Schlachter's avatarUli Schlachter <>
parent 3894a1ab
......@@ -5310,18 +5310,14 @@ _create_font_subset_tag (cairo_scaled_font_subset_t *font_subset,
uint32_t hash;
int i;
long numerator;
ldiv_t d;
hash = _hash_data ((unsigned char *) font_name, strlen(font_name), 0);
hash = _hash_data ((unsigned char *) (font_subset->glyphs),
font_subset->num_glyphs * sizeof(unsigned long), hash);
numerator = hash;
for (i = 0; i < 6; i++) {
d = ldiv (numerator, 26);
numerator = d.quot;
tag[i] = 'A' + d.rem;
tag[i] = 'A' + (hash % 26);
hash /= 26;
tag[i] = 0;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment