| // 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_ |