39 lines
1.2 KiB
C
39 lines
1.2 KiB
C
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// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include <assert.h>
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#include <stdint.h>
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#ifdef _MSC_VER
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#include <intrin.h>
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#endif
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namespace ROCKSDB_NAMESPACE {
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template <typename T>
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inline int BitsSetToOne(T v) {
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static_assert(std::is_integral<T>::value, "non-integral type");
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#ifdef _MSC_VER
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static_assert(sizeof(T) <= sizeof(uint64_t), "type too big");
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if (sizeof(T) > sizeof(uint32_t)) {
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return static_cast<int>(__popcnt64(static_cast<uint64_t>(v)));
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} else {
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return static_cast<int>(__popcnt(static_cast<uint32_t>(v)));
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}
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#else
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static_assert(sizeof(T) <= sizeof(unsigned long long), "type too big");
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if (sizeof(T) > sizeof(unsigned long)) {
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return __builtin_popcountll(static_cast<unsigned long long>(v));
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} else if (sizeof(T) > sizeof(unsigned int)) {
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return __builtin_popcountl(static_cast<unsigned long>(v));
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} else {
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return __builtin_popcount(static_cast<unsigned int>(v));
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}
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#endif
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}
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} // namespace ROCKSDB_NAMESPACE
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