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
15 #include "pw_string/format.h"
16
17 #include <cstdio>
18
19 namespace pw::string {
20
Format(std::span<char> buffer,const char * format,...)21 StatusWithSize Format(std::span<char> buffer, const char* format, ...) {
22 va_list args;
23 va_start(args, format);
24 const StatusWithSize result = FormatVaList(buffer, format, args);
25 va_end(args);
26
27 return result;
28 }
29
FormatVaList(std::span<char> buffer,const char * format,va_list args)30 StatusWithSize FormatVaList(std::span<char> buffer,
31 const char* format,
32 va_list args) {
33 if (buffer.empty()) {
34 return StatusWithSize::ResourceExhausted();
35 }
36
37 const int result = std::vsnprintf(buffer.data(), buffer.size(), format, args);
38
39 // If an error occurred, the number of characters written is unknown.
40 // Discard any output by terminating the buffer.
41 if (result < 0) {
42 buffer[0] = '\0';
43 return StatusWithSize::InvalidArgument();
44 }
45
46 // If result >= buffer.size(), the output was truncated and null-terminated.
47 if (static_cast<unsigned>(result) >= buffer.size()) {
48 return StatusWithSize::ResourceExhausted(buffer.size() - 1);
49 }
50
51 return StatusWithSize(result);
52 }
53
54 } // namespace pw::string
55