strerror.cc (2645B)
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 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 53 std::string StrErrorInternal(int errnum) { 54 char buf[100]; 55 const char* str = StrErrorAdaptor(errnum, buf, sizeof buf); 56 if (*str == '\0') { 57 snprintf(buf, sizeof buf, "Unknown error %d", errnum); 58 str = buf; 59 } 60 return str; 61 } 62 63 // kSysNerr is the number of errors from a recent glibc. `StrError()` falls back 64 // to `StrErrorAdaptor()` if the value is larger than this. 65 constexpr int kSysNerr = 135; 66 67 std::array<std::string, kSysNerr>* NewStrErrorTable() { 68 auto* table = new std::array<std::string, kSysNerr>; 69 for (size_t i = 0; i < table->size(); ++i) { 70 (*table)[i] = StrErrorInternal(static_cast<int>(i)); 71 } 72 return table; 73 } 74 75 } // namespace 76 77 std::string StrError(int errnum) { 78 absl::base_internal::ErrnoSaver errno_saver; 79 static const auto* table = NewStrErrorTable(); 80 if (errnum >= 0 && static_cast<size_t>(errnum) < table->size()) { 81 return (*table)[static_cast<size_t>(errnum)]; 82 } 83 return StrErrorInternal(errnum); 84 } 85 86 } // namespace base_internal 87 ABSL_NAMESPACE_END 88 } // namespace absl