From 540eae22a6b42a3985e36f0f1d068e0ba748a41a Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Wed, 10 Aug 2022 20:58:19 +0200
Subject: [PATCH] Fix parsing of SSA colour tags which have their leading zeros
 omitted.

---
 src/ssa_reader.cc       | 24 ++++++++++++++++--------
 test/ssa_reader_test.cc | 17 +++--------------
 2 files changed, 19 insertions(+), 22 deletions(-)

diff --git a/src/ssa_reader.cc b/src/ssa_reader.cc
index 8632251..07d592a 100644
--- a/src/ssa_reader.cc
+++ b/src/ssa_reader.cc
@@ -25,6 +25,7 @@
 #include "compose.hpp"
 #include <boost/algorithm/string.hpp>
 #include <boost/bind/bind.hpp>
+#include <cstdlib>
 #include <iostream>
 #include <vector>
 
@@ -55,17 +56,24 @@ SSAReader::SSAReader (FILE* f)
 Colour
 h_colour (string s)
 {
-	/* There are both BGR and ABGR versions of these colours */
-	if ((s.length() != 8 && s.length() != 10) || s[0] != '&' || s[1] != 'H') {
+	if (s.empty() || s[0] != '&' || s[1] != 'H') {
 		throw SSAError(String::compose("Badly formatted colour tag %1", s));
 	}
-	int ir, ig, ib;
-	/* XXX: ignoring alpha channel here; note that 00 is opaque and FF is transparent */
-	int const off = s.length() == 10 ? 4 : 2;
-	if (sscanf(s.c_str() + off, "%2x%2x%2x", &ib, &ig, &ir) < 3) {
-		throw SSAError(String::compose("Badly formatted colour tag %1", s));
+
+	auto start = s.c_str();
+	auto const end = start + s.length();
+	while (start < end && (*start == '&' || *start == 'H')) {
+		++start;
 	}
-	return sub::Colour(ir / 255.0, ig / 255.0, ib / 255.0);
+
+	auto const colour = strtoll(start, nullptr, 16);
+
+	/* XXX: ignoring alpha channel here; note that 00 is opaque and FF is transparent */
+	return sub::Colour(
+		((colour & 0x000000ff) >> 0) / 255.0,
+		((colour & 0x0000ff00) >> 8) / 255.0,
+		((colour & 0x00ff0000) >> 16) / 255.0
+		);
 }
 
 class Style
diff --git a/test/ssa_reader_test.cc b/test/ssa_reader_test.cc
index 82d3a33..e6da697 100644
--- a/test/ssa_reader_test.cc
+++ b/test/ssa_reader_test.cc
@@ -650,21 +650,10 @@ BOOST_AUTO_TEST_CASE (ssa_reader_c)
 {
 	test_c("&H00FFFF&", "ffff00");
 	test_c("&H123456&", "563412");
+	test_c("&H0&", "000000");
+	test_c("&HFF&", "ff0000");
+	test_c("&HFF00&", "00ff00");
 	test_c("&HFF0000&", "0000ff");
 	test_c("&HFFFFFF&", "ffffff");
 }
 
-
-/** Test invalid \c */
-BOOST_AUTO_TEST_CASE (ssa_reader_c_bad)
-{
-	sub::RawSubtitle base;
-	BOOST_CHECK_THROW(
-		sub::SSAReader::parse_line(
-			base,
-			"{\\c&H0}Dieser Untertitel ist gelb",
-			1920, 1080
-			),
-		sub::SSAError
-		);
-}
-- 
2.30.2