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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.
 //
 // 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_