1 // Copyright 2019 The Pigweed Authors
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not
4 // use this file except in compliance with the License. You may obtain a copy of
5 // 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, WITHOUT
11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12 // License for the specific language governing permissions and limitations under
13 // the License.
14 #pragma once
15
16 #include <cstddef>
17
18 namespace pw {
19 namespace string {
20
21 // Calculates the length of a null-terminated string up to the specified maximum
22 // length. If str is nullptr, returns 0.
23 //
24 // This function is a constexpr version of C11's strnlen_s.
Length(const char * str,size_t max_len)25 constexpr size_t Length(const char* str, size_t max_len) {
26 size_t length = 0;
27
28 if (str != nullptr) {
29 for (; length < max_len; ++length) {
30 if (str[length] == '\0') {
31 break;
32 }
33 }
34 }
35
36 return length;
37 }
38
39 } // namespace string
40 } // namespace pw
41