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Add a non-intrinsic version of findFirstSet to the EightBit library.
Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
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@ -1,5 +1,8 @@
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#pragma once
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#include <cassert>
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#include <bitset>
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#ifdef _MSC_VER
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# include <intrin.h>
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#endif
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@ -9,9 +12,9 @@
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#endif
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namespace EightBit {
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[[nodiscard]] int countBits(uint8_t value) noexcept ;
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[[nodiscard]] bool oddParity(uint8_t value) noexcept ;
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[[nodiscard]] int findFirstSet(int value) noexcept ;
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[[nodiscard]] int countBits(uint8_t value) noexcept;
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[[nodiscard]] bool oddParity(uint8_t value) noexcept;
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[[nodiscard]] int findFirstSet(unsigned long value) noexcept;
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constexpr void assume(int expression);
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}
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@ -39,7 +42,7 @@ inline bool EightBit::oddParity(const uint8_t value) noexcept {
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return countBits(value) % 2;
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}
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inline int EightBit::findFirstSet(const int value) noexcept {
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inline int EightBit::findFirstSet(const unsigned long value) noexcept {
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#ifdef _MSC_VER
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unsigned long index;
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if (_BitScanForward(&index, value))
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@ -48,7 +51,11 @@ inline int EightBit::findFirstSet(const int value) noexcept {
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#elif defined(__GNUG__)
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return __builtin_ffs(value);
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#else
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# error Find first set not implemented
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std::bitset<sizeof(unsigned long) * 8> bits(value);
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for (size_t i = bits.size() - 1; i >= 0; --i)
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if (bits.test(i))
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return i + 1;
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return 0;
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#endif
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}
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