From c28ab4461fd7868cff200283cc4cf6aded0f331f Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sun, 12 Aug 2018 22:27:55 +0200
Subject: Add pop count operations

---
 chilbert/BigBitVec.hpp  | 10 ++++++++++
 chilbert/FixBitVec.hpp  |  3 +++
 chilbert/Operations.hpp | 18 ++++++++++++++++++
 3 files changed, 31 insertions(+)

(limited to 'chilbert')

diff --git a/chilbert/BigBitVec.hpp b/chilbert/BigBitVec.hpp
index 83b8a5b..8f8dc6d 100644
--- a/chilbert/BigBitVec.hpp
+++ b/chilbert/BigBitVec.hpp
@@ -422,6 +422,16 @@ public:
 		return 0;
 	}
 
+	/// Return the number of set bits
+	size_t count() const
+	{
+		size_t c = 0;
+		for (size_t i = 0; i < m_iRacks; ++i) {
+			c += static_cast<size_t>(pop_count(m_pcRacks[i]));
+		}
+		return c;
+	}
+
 	/// Flip all bits (one's complement)
 	CBigBitVec& flip()
 	{
diff --git a/chilbert/FixBitVec.hpp b/chilbert/FixBitVec.hpp
index e47b868..bba25d9 100644
--- a/chilbert/FixBitVec.hpp
+++ b/chilbert/FixBitVec.hpp
@@ -224,6 +224,9 @@ public:
 		return static_cast<size_t>(chilbert::ffs(m_rack));
 	}
 
+	/// Return the number of set bits
+	size_t count() const { return static_cast<size_t>(pop_count(m_rack)); }
+
 	/// Flip all bits (one's complement)
 	CFixBitVec& flip()
 	{
diff --git a/chilbert/Operations.hpp b/chilbert/Operations.hpp
index b2e4344..5781e6c 100644
--- a/chilbert/Operations.hpp
+++ b/chilbert/Operations.hpp
@@ -88,6 +88,24 @@ setBit(T& field, const BitsetIndex<T> index, const bool value)
 	field.set(index, value);
 }
 
+/// Return 1 + the index of the least significant 1-bit of `field`, or zero
+template <typename T>
+int pop_count(const T& field);
+
+template <>
+int
+pop_count<unsigned long>(const unsigned long& field)
+{
+	return __builtin_popcountl(field);
+}
+
+template <>
+int
+pop_count<unsigned long long>(const unsigned long long& field)
+{
+	return __builtin_popcountll(field);
+}
+
 /// Return 1 + the index of the least significant 1-bit of `field`, or zero
 template <typename T>
 int ffs(const T field);
-- 
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