From f8e91a2717fc617516d72d122aee26620667cfdc Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sun, 5 Aug 2018 14:38:52 +0200
Subject: Support integral points in both directions

---
 chilbert/Algorithm.hpp  |  8 ++++----
 chilbert/BigBitVec.hpp  | 36 ++++++++++++++++++------------------
 chilbert/FixBitVec.hpp  | 22 +++++++---------------
 chilbert/Operations.hpp | 15 +++++++++++++++
 4 files changed, 44 insertions(+), 37 deletions(-)

(limited to 'chilbert')

diff --git a/chilbert/Algorithm.hpp b/chilbert/Algorithm.hpp
index 0200456..e522554 100644
--- a/chilbert/Algorithm.hpp
+++ b/chilbert/Algorithm.hpp
@@ -160,7 +160,7 @@ namespace chilbert
 		e.reset();
 		d = D0;
 		l.reset();
-		h.reset();
+		h = 0U;
 
 		// Work from MSB to LSB
 		for ( i = m-1; i >= 0; i-- )
@@ -188,7 +188,7 @@ namespace chilbert
 			update2<I>(l,t,w,n,e,d);
 		}
 
-		h.grayCodeInv();
+		grayCodeInv(h);
 
 		return;
 	}
@@ -238,7 +238,7 @@ namespace chilbert
 		d = D0;
 		l.reset();
 		for ( j = 0; j < n; j++ )
-			p[j] = 0;
+			p[j] = 0U;
 
 		ho = m*n;
 		
@@ -408,7 +408,7 @@ namespace chilbert
 		d = D0;
 		l.reset();
 		for ( j = 0; j < n; j++ )
-			p[j].reset();
+			p[j] = 0;
 		
 		// Work from MSB to LSB
 		for ( i = m-1; i >= 0; i-- )
diff --git a/chilbert/BigBitVec.hpp b/chilbert/BigBitVec.hpp
index df50d6e..b5c049a 100644
--- a/chilbert/BigBitVec.hpp
+++ b/chilbert/BigBitVec.hpp
@@ -693,23 +693,6 @@ public:
 	}
 
 
-	// Gray Code Inverse
-	CBigBitVec &
-	grayCodeInv()
-	{
-		int i;
-		FBV_UINT s = 0;
-
-		for ( i = m_iRacks-1; i >= 0; i-- )
-		{
-			m_pcRacks[i].grayCodeInv();
-			if ( s ) m_pcRacks[i].flip();
-			s = m_pcRacks[i].rack() & 1;
-		}
-		return (*this);
-	}
-
-
 	// Complement
 	CBigBitVec &
 	flip()
@@ -755,7 +738,8 @@ public:
 	}
 
 	
-private:	
+private:
+	friend void grayCodeInv<CBigBitVec>(CBigBitVec&);
 
 	// Right rotates entire racks (in place).
 	void
@@ -795,6 +779,22 @@ private:
 	int m_iRacks;
 };
 
+template <>
+void
+grayCodeInv(CBigBitVec& value)
+{
+	FBV_UINT s = 0;
+
+	for (int i = value.rackCount() - 1; i >= 0; --i) {
+		CFixBitVec& rack = value.m_pcRacks[i];
+		grayCodeInv(rack);
+		if (s) {
+			rack.flip();
+		}
+		s = rack.test(0);
+	}
+}
+
 } // namespace chilbert
 
 #endif
diff --git a/chilbert/FixBitVec.hpp b/chilbert/FixBitVec.hpp
index 3cdd6ff..3a72599 100644
--- a/chilbert/FixBitVec.hpp
+++ b/chilbert/FixBitVec.hpp
@@ -355,21 +355,6 @@ public:
 		return (*this);
 	}
 
-	// Calculates the Gray Code Inverse
-	CFixBitVec &
-	grayCodeInv()
-	{
-		m_uiRack ^= (m_uiRack>>1);
-		m_uiRack ^= (m_uiRack>>2);
-		m_uiRack ^= (m_uiRack>>4);
-		m_uiRack ^= (m_uiRack>> 8);
-		m_uiRack ^= (m_uiRack>>16);
-#if FBV_BITS == 64
-		m_uiRack ^= (m_uiRack>>32);
-#endif
-		return (*this);
-	}
-
 	// Ones-complements the rack
 	CFixBitVec &
 	flip()
@@ -416,6 +401,13 @@ private:
 	FBV_UINT	m_uiRack;
 };
 
+template <>
+void
+grayCodeInv(CFixBitVec& value)
+{
+	grayCodeInv<FBV_UINT>(value.rack());
+}
+
 } // namespace chilbert
 
 #endif
diff --git a/chilbert/Operations.hpp b/chilbert/Operations.hpp
index e4a23b5..c50136a 100644
--- a/chilbert/Operations.hpp
+++ b/chilbert/Operations.hpp
@@ -22,6 +22,7 @@
 #include <cassert>
 #include <climits>
 #include <cstddef>
+#include <cstdint>
 #include <type_traits>
 
 namespace chilbert {
@@ -87,6 +88,20 @@ ffs<unsigned long long>(const unsigned long long field)
 	return __builtin_ffsll(field);
 }
 
+/// Calculates the inverse Gray Code of `value` in place
+template <typename T>
+std::enable_if_t<!std::is_integral<T>::value> grayCodeInv(T& value);
+
+/// Implementation of grayCodeInv for any integral type
+template <typename T>
+std::enable_if_t<std::is_integral<T>::value>
+grayCodeInv(T& value)
+{
+	for (T shift = 1; shift < sizeof(T) * CHAR_BIT; shift <<= 1) {
+		value ^= (value >> shift);
+	}
+}
+
 } // namespace chilbert
 
 #endif
-- 
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