| 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253 | // Copyright 2018 The Abseil Authors.//// Licensed under the Apache License, Version 2.0 (the "License");// you may not use this file except in compliance with the License.// You may obtain a copy of the License at////      http://www.apache.org/licenses/LICENSE-2.0//// 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 ABSL_STRINGS_INTERNAL_BITS_H_#define ABSL_STRINGS_INTERNAL_BITS_H_#include <cstdint>#if defined(_MSC_VER) && defined(_M_X64)#include <intrin.h>#pragma intrinsic(_BitScanReverse64)#endifnamespace absl {namespace strings_internal {// Returns the number of leading 0 bits in a 64-bit value.inline int CountLeadingZeros64(uint64_t n) {#if defined(__GNUC__)  static_assert(sizeof(unsigned long long) == sizeof(n),  // NOLINT(runtime/int)                "__builtin_clzll does not take 64bit arg");  return n == 0 ? 64 : __builtin_clzll(n);#elif defined(_MSC_VER) && defined(_M_X64)  unsigned long result;  // NOLINT(runtime/int)  if (_BitScanReverse64(&result, n)) {    return 63 - result;  }  return 64;#else  int zeroes = 60;  if (n >> 32) zeroes -= 32, n >>= 32;  if (n >> 16) zeroes -= 16, n >>= 16;  if (n >> 8) zeroes -= 8, n >>= 8;  if (n >> 4) zeroes -= 4, n >>= 4;  return "\4\3\2\2\1\1\1\1\0\0\0\0\0\0\0\0"[n] + zeroes;#endif}}  // namespace strings_internal}  // namespace absl#endif  // ABSL_STRINGS_INTERNAL_BITS_H_
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