Parse and animate all colors and alpha values like VSFilter

* Allow exactly one of these prefixes in header values:
  0x, 0X, &h, &H. Note that "0x0xFFFFFF" is a correct value,
  as the first 0x is consumed by the parser and the second by
  the string-to-number conversion following strtol semantics.

* Allow arbitrary numbers of leading & and H
 (and not h) in any order in override tag values.

* Reduce header values modulo 2**32 instead
  of saturating them to LLONG_MIN/MAX.

* Saturate override tag values to INT32_MIN/MAX
  rather than to LLONG_MIN/MAX.

* Don't fiddle with bytes in alpha override tag values.
 (They can be outside of the 0..255 range.)

Also change the byte swapping code to be more sensible.

Fixes #80.
Fixes #145.
Fixes #178.

Also fixes our behavior in the case described in
https://code.google.com/p/xy-vsfilter/issues/detail?id=80.

1 files changed, 14 insertions, 2 deletions

diff --git a/libass/ass_utils.h b/libass/ass_utils.h
index 2ad8c5b..45ebbb6 100644
--- a/libass/ass_utils.h
+++ b/libass/ass_utils.h
@@ -85,9 +85,11 @@ void skip_spaces(char **str);
 void rskip_spaces(char **str, char *limit);
 int mystrtoi(char **p, int *res);
 int mystrtoll(char **p, long long *res);
-int mystrtou32(char **p, int base, uint32_t *res);
 int mystrtod(char **p, double *res);
-uint32_t string2color(ASS_Library *library, char *p, int hex);
+int mystrtoi32(char **p, int base, int32_t *res);
+int32_t parse_alpha_tag(char *str);
+uint32_t parse_color_tag(char *str);
+uint32_t parse_color_header(char *str);
 char parse_bool(char *str);
 int parse_ycbcr_matrix(char *str);
 unsigned ass_utf8_get_char(char **str);
@@ -111,6 +113,16 @@ static inline size_t ass_align(size_t alignment, size_t s)
     return (s + (alignment - 1)) & ~(alignment - 1);
 }
 
+static inline uint32_t ass_bswap32(uint32_t x)
+{
+#ifdef _MSC_VER
+    return _byteswap_ulong(x);
+#else
+    return (x & 0x000000FF) << 24 | (x & 0x0000FF00) <<  8 |
+           (x & 0x00FF0000) >>  8 | (x & 0xFF000000) >> 24;
+#endif
+}
+
 static inline int d6_to_int(int x)
 {
     return (x + 32) >> 6;