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// Tencent is pleased to support the open source community by making RapidJSON available.
//
// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
//
// Licensed under the MIT License (the "License"); you may not use this file except
// in compliance with the License. You may obtain a copy of the License at
//
// http://opensource.org/licenses/MIT
//
// Unless required by applicable law or agreed to in writing, software distributed
// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.
#ifndef RAPIDJSON_CLZLL_H_
#define RAPIDJSON_CLZLL_H_
#include "../rapidjson.h"
#if defined(_MSC_VER) && !defined(UNDER_CE)
#include <intrin.h>
#if defined(_WIN64)
#pragma intrinsic(_BitScanReverse64)
#else
#pragma intrinsic(_BitScanReverse)
#endif
#endif
RAPIDJSON_NAMESPACE_BEGIN
namespace internal {
inline uint32_t clzll(uint64_t x) {
// Passing 0 to __builtin_clzll is UB in GCC and results in an
// infinite loop in the software implementation.
RAPIDJSON_ASSERT(x != 0);
#if defined(_MSC_VER) && !defined(UNDER_CE)
unsigned long r = 0;
#if defined(_WIN64)
_BitScanReverse64(&r, x);
#else
// Scan the high 32 bits.
if (_BitScanReverse(&r, static_cast<uint32_t>(x >> 32)))
return 63 - (r + 32);
// Scan the low 32 bits.
_BitScanReverse(&r, static_cast<uint32_t>(x & 0xFFFFFFFF));
#endif // _WIN64
return 63 - r;
#elif (defined(__GNUC__) && __GNUC__ >= 4) || RAPIDJSON_HAS_BUILTIN(__builtin_clzll)
// __builtin_clzll wrapper
return static_cast<uint32_t>(__builtin_clzll(x));
#else
// naive version
uint32_t r = 0;
while (!(x & (static_cast<uint64_t>(1) << 63))) {
x <<= 1;
++r;
}
return r;
#endif // _MSC_VER
}
#define RAPIDJSON_CLZLL RAPIDJSON_NAMESPACE::internal::clzll
} // namespace internal
RAPIDJSON_NAMESPACE_END
#endif // RAPIDJSON_CLZLL_H_