memutil.cc (1648B)
1 // Copyright 2017 The Abseil Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #include "absl/strings/internal/memutil.h" 16 17 #include <cstdlib> 18 19 #include "absl/strings/ascii.h" 20 21 namespace absl { 22 ABSL_NAMESPACE_BEGIN 23 namespace strings_internal { 24 25 int memcasecmp(const char* s1, const char* s2, size_t len) { 26 const unsigned char* us1 = reinterpret_cast<const unsigned char*>(s1); 27 const unsigned char* us2 = reinterpret_cast<const unsigned char*>(s2); 28 29 for (size_t i = 0; i < len; i++) { 30 unsigned char c1 = us1[i]; 31 unsigned char c2 = us2[i]; 32 // If bytes are the same, they will be the same when converted to lower. 33 // So we only need to convert if bytes are not equal. 34 // NOTE(b/308193381): We do not use `absl::ascii_tolower` here in order 35 // to avoid its lookup table and improve performance. 36 if (c1 != c2) { 37 c1 = c1 >= 'A' && c1 <= 'Z' ? c1 - 'A' + 'a' : c1; 38 c2 = c2 >= 'A' && c2 <= 'Z' ? c2 - 'A' + 'a' : c2; 39 const int diff = int{c1} - int{c2}; 40 if (diff != 0) return diff; 41 } 42 } 43 return 0; 44 } 45 46 } // namespace strings_internal 47 ABSL_NAMESPACE_END 48 } // namespace absl