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
memcasecmp(const char * s1,const char * s2,size_t len)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
49