Switch ccm matrix to use a thread_local

There are other ways to pass this around, but this is the simplest
change. The old way was a race condition in CFC. 😱

Probably will want to revisit this in the future. The shared global
state feels a big gross.

Author: sz3

src/lib/cimb_translator/CimbDecoder.cpp

@@ -65,18 +65,23 @@ CimbDecoder::CimbDecoder(unsigned symbol_bits, unsigned color_bits, unsigned col
 	load_tiles();
 }
 
-const color_correction& CimbDecoder::get_ccm() const
+// protected
+color_correction& CimbDecoder::internal_ccm() const
 {
-	// testing purposes only.
-	// this returning a thread local would be fine, iff we only use it for debugging!
+	static thread_local color_correction _ccm;
 	return _ccm;
 }
 
+// public
+const color_correction& CimbDecoder::get_ccm() const
+{
+	// testing/debugging purposes only!!!!
+	return internal_ccm();
+}
+
 void CimbDecoder::update_color_correction(cv::Matx<float, 3, 3>&& ccm)
 {
-	// TODO: threadlocal?
-	// because this is dubious to begin with...
-	_ccm.update(std::move(ccm));
+	internal_ccm().update(std::move(ccm));
 }
 
 uint64_t CimbDecoder::get_tile_hash(unsigned symbol) const
@@ -163,9 +168,9 @@ std::tuple<uchar,uchar,uchar> CimbDecoder::get_color(int i) const
 unsigned CimbDecoder::get_best_color(float r, float g, float b) const
 {
 	// transform color with ccm
-	if (_ccm.active())
+	if (internal_ccm().active())
 	{
-		std::tuple<float, float, float> color = _ccm.transform(r, g, b);
+		std::tuple<float, float, float> color = internal_ccm().transform(r, g, b);
 		r = std::get<0>(color);
 		g = std::get<1>(color);
 		b = std::get<2>(color);

src/lib/cimb_translator/CimbDecoder.h

@@ -31,6 +31,8 @@ class CimbDecoder
 	unsigned symbol_bits() const;
 
 protected:
+	color_correction& internal_ccm() const;
+
 	uint64_t get_tile_hash(unsigned symbol) const;
 	bool load_tiles();
 
@@ -45,5 +47,4 @@ class CimbDecoder
 	unsigned _colorMode;
 	bool _dark;
 	uchar _ahashThreshold;
-	color_correction _ccm;
 };

src/lib/cimb_translator/test/CimbReaderTest.cpp

@@ -24,7 +24,7 @@ namespace {
 	{
 	public:
 		using CimbDecoder::CimbDecoder;
-		using CimbDecoder::_ccm;
+		using CimbDecoder::internal_ccm;
 	};
 }
 #include "serialize/str_join.h"
@@ -143,6 +143,7 @@ TEST_CASE( "CimbReaderTest/testCCM", "[unit]" )
 	cv::Mat sample = TestCimbar::loadSample("b/ex2434.jpg");
 
 	TestableCimbDecoder decoder(4, 2);
+	decoder.internal_ccm() = color_correction();
 	CimbReader cr(sample, decoder);
 
 	// this is the header value for the sample -- we could imitate what the Decoder does
@@ -151,10 +152,10 @@ TEST_CASE( "CimbReaderTest/testCCM", "[unit]" )
 	cr.update_metadata((char*)md.data(), md.md_size);
 	cr.init_ccm(2, cimbar::Config::interleave_blocks(), cimbar::Config::interleave_partitions(), cimbar::Config::fountain_chunks_per_frame(6, false));
 
-	assertTrue( decoder._ccm.active() );
+	assertTrue( decoder.get_ccm().active() );
 
 	std::stringstream ss;
-	ss << decoder._ccm.mat();
+	ss << decoder.get_ccm().mat();
 	assertEquals("[2.3991191, -0.41846275, -0.54654282;\n "
 				 "-0.42976046, 2.632102, -0.76466882;\n "
 				 "-0.54299992, -0.20199311, 2.2753253]", ss.str());
@@ -176,9 +177,10 @@ TEST_CASE( "CimbReaderTest/testCCM.Disabled", "[unit]" )
 	cv::Mat sample = TestCimbar::loadSample("b/ex2434.jpg");
 
 	TestableCimbDecoder decoder(4, 2);
+	decoder.internal_ccm() = color_correction();
 	CimbReader cr(sample, decoder, false, false);
 
-	assertFalse( decoder._ccm.active() );
+	assertFalse( decoder.get_ccm().active() );
 
 	std::array<unsigned, 6> expectedColors = {0, 1, 1, 2, 2, 2};
 	for (unsigned i = 0; i < expectedColors.size(); ++i)
@@ -197,6 +199,7 @@ TEST_CASE( "CimbReaderTest/testCCM.VeryNecessary", "[unit]" )
 	cv::Mat sample = TestCimbar::loadSample("b/ex380.jpg");
 
 	TestableCimbDecoder decoder(4, 2);
+	decoder.internal_ccm() = color_correction();
 	CimbReader cr(sample, decoder);
 
 	// this is the header value for the sample -- we could imitate what the Decoder does
@@ -205,10 +208,10 @@ TEST_CASE( "CimbReaderTest/testCCM.VeryNecessary", "[unit]" )
 	cr.update_metadata((char*)md.data(), md.md_size);
 	cr.init_ccm(2, cimbar::Config::interleave_blocks(), cimbar::Config::interleave_partitions(), cimbar::Config::fountain_chunks_per_frame(6, false));
 
-	assertTrue( decoder._ccm.active() );
+	assertTrue( decoder.get_ccm().active() );
 
 	std::stringstream ss;
-	ss << decoder._ccm.mat();
+	ss << decoder.get_ccm().mat();
 	assertEquals("[1.6250746, 0.0024788622, -0.45772526;\n "
 				 "-0.29126319, 2.2922182, -0.67037439;\n "
 				 "-1.2192062, -2.7447209, 5.0476217]", ss.str());