54 lines
1.2 KiB
C++
54 lines
1.2 KiB
C++
#ifndef OSRM_UTIL_MSB_HPP
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#define OSRM_UTIL_MSB_HPP
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#include <boost/assert.hpp>
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#include <climits>
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#include <cstdint>
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#include <utility>
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namespace osrm
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{
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namespace util
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{
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// get the msb of an integer
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// return 0 for integers without msb
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template <typename T> std::size_t msb(T value)
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{
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static_assert(std::is_integral<T>::value && !std::is_signed<T>::value, "Integer required.");
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std::size_t msb = 0;
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while (value > 0)
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{
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value >>= 1u;
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msb++;
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}
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BOOST_ASSERT(msb > 0);
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return msb - 1;
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}
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#if (defined(__clang__) || defined(__GNUC__) || defined(__GNUG__))
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inline std::size_t msb(unsigned long long v)
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{
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BOOST_ASSERT(v > 0);
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constexpr auto MSB_INDEX = CHAR_BIT * sizeof(unsigned long long) - 1;
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return MSB_INDEX - __builtin_clzll(v);
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}
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inline std::size_t msb(unsigned long v)
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{
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BOOST_ASSERT(v > 0);
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constexpr auto MSB_INDEX = CHAR_BIT * sizeof(unsigned long) - 1;
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return MSB_INDEX - __builtin_clzl(v);
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}
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inline std::size_t msb(unsigned int v)
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{
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BOOST_ASSERT(v > 0);
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constexpr auto MSB_INDEX = CHAR_BIT * sizeof(unsigned int) - 1;
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return MSB_INDEX - __builtin_clz(v);
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}
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#endif
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} // namespace util
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} // namespace osrm
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#endif
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