From 22f15f154f2180ef60770621183616a1864225bc Mon Sep 17 00:00:00 2001
From: Adam Wardynski <award@.(win7-laptop)>
Date: Sat, 13 Nov 2010 21:43:48 +0100
Subject: [PATCH] Adding non-GCC specific alternative for lowest_bit, and as
well adding a MSVC-specific one
---
libpwrutils/bitset.h | 52 ++++++++++++++++++++++++++++++++++++++------
1 file changed, 45 insertions(+), 7 deletions(-)
diff --git a/libpwrutils/bitset.h b/libpwrutils/bitset.h
index f62feeb..439a23c 100644
--- a/libpwrutils/bitset.h
+++ b/libpwrutils/bitset.h
@@ -8,6 +8,10 @@
#include <boost/pending/lowest_bit.hpp>
#include <climits>
+#ifdef _MSC_VER
+#include <intrin.h>
+#pragma intrinsic(_BitScanForward)
+#endif
namespace PwrNlp {
@@ -37,13 +41,6 @@ size_t count_bits_set(const std::bitset<S>& b)
return b.count();
}
-template <size_t S> inline
-size_t lowest_bit(const bitset<S>& b)
-{
- // GCC specific
- return b._Find_first();
-}
-
/**
* Get index of lowest set bit in an integral type
*/
@@ -55,8 +52,49 @@ inline size_t lowest_bit(const unsigned long long& t)
inline size_t lowest_bit(const unsigned long& t)
{
+#ifndef _MSC_VER
if (t <= 0) return static_cast<size_t>(-1);
return boost::lowest_bit(t);
+#else
+ unsigned long index = 0;
+ if(_BitScanForward(&index, t)) return index;
+ return static_cast<size_t>(-1);
+#endif
+}
+
+template <size_t S> inline
+size_t lowest_bit(const bitset<S>& b)
+{
+#ifdef __GNUC__
+ return b._Find_first();
+#elif _MSC_VER
+ for(size_t w = 0; w <= S / ulong_bits; ++w) {
+ unsigned long index = 0;
+ if(_BitScanForward(&index, b._Getword(w))) {
+ return index + w * PwrNlp::ulong_bits;
+ }
+ }
+ return static_cast<size_t>(-1);
+#else
+ if(b.none()) return static_cast<size_t>(-1);
+
+ const bitset<S> mask(std::numeric_limits<unsigned long>::max());
+ bitset<S> c(b);
+ unsigned long offset = 0;
+ unsigned long ul = (c & mask).to_ulong();
+ while(ul == 0) {
+ c >>= PwrNlp::ulong_bits;
+ offset += PwrNlp::ulong_bits;
+ ul = (c & mask).to_ulong();
+ }
+ return lowest_bit(ul) + offset;
+#endif
+}
+
+template<> inline
+size_t lowest_bit(const word_bitset& b)
+{
+ return lowest_bit(b.to_ulong());
}
/// Helper iterator class for iterating through set bits
--
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