1 // Tencent is pleased to support the open source community by making RapidJSON available. 2 // 3 // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved. 4 // 5 // Licensed under the MIT License (the "License"); you may not use this file except 6 // in compliance with the License. You may obtain a copy of the License at 7 // 8 // http://opensource.org/licenses/MIT 9 // 10 // Unless required by applicable law or agreed to in writing, software distributed 11 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 12 // CONDITIONS OF ANY KIND, either express or implied. See the License for the 13 // specific language governing permissions and limitations under the License. 14 15 #ifndef RAPIDJSON_CLZLL_H_ 16 #define RAPIDJSON_CLZLL_H_ 17 18 #include "../rapidjson.h" 19 20 #if defined(_MSC_VER) 21 #include <intrin.h> 22 #if defined(_WIN64) 23 #pragma intrinsic(_BitScanReverse64) 24 #else 25 #pragma intrinsic(_BitScanReverse) 26 #endif 27 #endif 28 29 RAPIDJSON_NAMESPACE_BEGIN 30 namespace internal { 31 32 #if (defined(__GNUC__) && __GNUC__ >= 4) || RAPIDJSON_HAS_BUILTIN(__builtin_clzll) 33 #define RAPIDJSON_CLZLL __builtin_clzll 34 #else 35 36 inline uint32_t clzll(uint64_t x) { 37 // Passing 0 to __builtin_clzll is UB in GCC and results in an 38 // infinite loop in the software implementation. 39 RAPIDJSON_ASSERT(x != 0); 40 41 #if defined(_MSC_VER) 42 unsigned long r = 0; 43 #if defined(_WIN64) 44 _BitScanReverse64(&r, x); 45 #else 46 // Scan the high 32 bits. 47 if (_BitScanReverse(&r, static_cast<uint32_t>(x >> 32))) 48 return 63 - (r + 32); 49 50 // Scan the low 32 bits. 51 _BitScanReverse(&r, static_cast<uint32_t>(x & 0xFFFFFFFF)); 52 #endif // _WIN64 53 54 return 63 - r; 55 #else 56 uint32_t r; 57 while (!(x & (static_cast<uint64_t>(1) << 63))) { 58 x <<= 1; 59 ++r; 60 } 61 62 return r; 63 #endif // _MSC_VER 64 } 65 66 #define RAPIDJSON_CLZLL RAPIDJSON_NAMESPACE::internal::clzll 67 #endif // (defined(__GNUC__) && __GNUC__ >= 4) || RAPIDJSON_HAS_BUILTIN(__builtin_clzll) 68 69 } // namespace internal 70 RAPIDJSON_NAMESPACE_END 71 72 #endif // RAPIDJSON_CLZLL_H_