1 /*
2 * Copyright (C) 2017 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #ifndef NETUTILS_STATUS_H
18 #define NETUTILS_STATUS_H
19
20 #include <cassert>
21 #include <limits>
22 #include <ostream>
23
24 namespace android {
25 namespace netdutils {
26
27 // Simple status implementation suitable for use on the stack in low
28 // or moderate performance code. This can definitely be improved but
29 // for now short string optimization is expected to keep the common
30 // success case fast.
31 //
32 // Status is implicitly movable via the default noexcept move constructor
33 // and noexcept move-assignment operator.
34 class [[nodiscard]] Status {
35 public:
36 Status() = default;
Status(int code)37 explicit Status(int code) : mCode(code) {}
38
39 // Constructs an error Status, |code| must be non-zero.
Status(int code,std::string msg)40 Status(int code, std::string msg) : mCode(code), mMsg(std::move(msg)) { assert(!ok()); }
41
code()42 int code() const { return mCode; }
43
ok()44 bool ok() const { return code() == 0; }
45
msg()46 const std::string& msg() const { return mMsg; }
47
48 // Explicitly ignores the Status without triggering [[nodiscard]] errors.
ignoreError()49 void ignoreError() const {}
50
51 bool operator==(const Status& other) const { return code() == other.code(); }
52 bool operator!=(const Status& other) const { return !(*this == other); }
53
54 private:
55 int mCode = 0;
56 std::string mMsg;
57 };
58
59 namespace status {
60
61 const Status ok{0};
62 // EOF is not part of errno space, we'll place it far above the
63 // highest existing value.
64 const Status eof{0x10001, "end of file"};
65 const Status undefined{std::numeric_limits<int>::max(), "undefined"};
66
67 } // namespace status
68
69 // Return true if status is "OK". This is sometimes preferable to
70 // status.ok() when we want to check the state of Status-like objects
71 // that implicitly cast to Status.
isOk(const Status & status)72 inline bool isOk(const Status& status) {
73 return status.ok();
74 }
75
76 // For use only in tests.
77 #define EXPECT_OK(status) EXPECT_TRUE((status).ok())
78
79 // Documents that status is expected to be ok. This function may log
80 // (or assert when running in debug mode) if status has an unexpected value.
expectOk(const Status &)81 inline void expectOk(const Status& /*status*/) {
82 // TODO: put something here, for now this function serves solely as documentation.
83 }
84
85 // Convert POSIX errno to a Status object.
86 // If Status is extended to have more features, this mapping may
87 // become more complex.
88 Status statusFromErrno(int err, const std::string& msg);
89
90 // Helper that checks Status-like object (notably StatusOr) against a
91 // value in the errno space.
92 bool equalToErrno(const Status& status, int err);
93
94 // Helper that converts Status-like object (notably StatusOr) to a
95 // message.
96 std::string toString(const Status& status);
97
98 std::ostream& operator<<(std::ostream& os, const Status& s);
99
100 // Evaluate 'stmt' to a Status object and if it results in an error, return that
101 // error. Use 'tmp' as a variable name to avoid shadowing any variables named
102 // tmp.
103 #define RETURN_IF_NOT_OK_IMPL(tmp, stmt) \
104 do { \
105 ::android::netdutils::Status tmp = (stmt); \
106 if (!isOk(tmp)) { \
107 return tmp; \
108 } \
109 } while (false)
110
111 // Create a unique variable name to avoid shadowing local variables.
112 #define RETURN_IF_NOT_OK_CONCAT(line, stmt) RETURN_IF_NOT_OK_IMPL(__CONCAT(_status_, line), stmt)
113
114 // Macro to allow exception-like handling of error return values.
115 //
116 // If the evaluation of stmt results in an error, return that error
117 // from current function.
118 //
119 // Example usage:
120 // Status bar() { ... }
121 //
122 // RETURN_IF_NOT_OK(status);
123 // RETURN_IF_NOT_OK(bar());
124 #define RETURN_IF_NOT_OK(stmt) RETURN_IF_NOT_OK_CONCAT(__LINE__, stmt)
125
126 } // namespace netdutils
127 } // namespace android
128
129 #endif /* NETUTILS_STATUS_H */
130