1 // Copyright 2020 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/base/internal/strerror.h"
16
17 #include <array>
18 #include <cerrno>
19 #include <cstddef>
20 #include <cstdio>
21 #include <cstring>
22 #include <string>
23 #include <type_traits>
24
25 #include "absl/base/internal/errno_saver.h"
26
27 namespace absl {
28 ABSL_NAMESPACE_BEGIN
29 namespace base_internal {
30 namespace {
31
StrErrorAdaptor(int errnum,char * buf,size_t buflen)32 const char* StrErrorAdaptor(int errnum, char* buf, size_t buflen) {
33 #if defined(_WIN32)
34 int rc = strerror_s(buf, buflen, errnum);
35 buf[buflen - 1] = '\0'; // guarantee NUL termination
36 if (rc == 0 && strncmp(buf, "Unknown error", buflen) == 0) *buf = '\0';
37 return buf;
38 #else
39 // The type of `ret` is platform-specific; both of these branches must compile
40 // either way but only one will execute on any given platform:
41 auto ret = strerror_r(errnum, buf, buflen);
42 if (std::is_same<decltype(ret), int>::value) {
43 // XSI `strerror_r`; `ret` is `int`:
44 if (ret) *buf = '\0';
45 return buf;
46 } else {
47 // GNU `strerror_r`; `ret` is `char *`:
48 return reinterpret_cast<const char*>(ret);
49 }
50 #endif
51 }
52
StrErrorInternal(int errnum)53 std::string StrErrorInternal(int errnum) {
54 absl::base_internal::ErrnoSaver errno_saver;
55 char buf[100];
56 const char* str = StrErrorAdaptor(errnum, buf, sizeof buf);
57 if (*str == '\0') {
58 snprintf(buf, sizeof buf, "Unknown error %d", errnum);
59 str = buf;
60 }
61 return str;
62 }
63
64 // kSysNerr is the number of errors from a recent glibc. `StrError()` falls back
65 // to `StrErrorAdaptor()` if the value is larger than this.
66 constexpr int kSysNerr = 135;
67
NewStrErrorTable()68 std::array<std::string, kSysNerr>* NewStrErrorTable() {
69 auto* table = new std::array<std::string, kSysNerr>;
70 for (int i = 0; i < static_cast<int>(table->size()); ++i) {
71 (*table)[i] = StrErrorInternal(i);
72 }
73 return table;
74 }
75
76 } // namespace
77
StrError(int errnum)78 std::string StrError(int errnum) {
79 static const auto* table = NewStrErrorTable();
80 if (errnum >= 0 && errnum < static_cast<int>(table->size())) {
81 return (*table)[errnum];
82 }
83 return StrErrorInternal(errnum);
84 }
85
86 } // namespace base_internal
87 ABSL_NAMESPACE_END
88 } // namespace absl
89