| /* |
| * Copyright (C) 2016 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| // Portable error handling functions. This is only necessary for host-side |
| // code that needs to be cross-platform; code that is only run on Unix should |
| // just use errno and strerror() for simplicity. |
| // |
| // There is some complexity since Windows has (at least) three different error |
| // numbers, not all of which share the same type: |
| // * errno: for C runtime errors. |
| // * GetLastError(): Windows non-socket errors. |
| // * WSAGetLastError(): Windows socket errors. |
| // errno can be passed to strerror() on all platforms, but the other two require |
| // special handling to get the error string. Refer to Microsoft documentation |
| // to determine which error code to check for each function. |
| |
| #pragma once |
| |
| #include <assert.h> |
| |
| #include <string> |
| |
| namespace android { |
| namespace base { |
| |
| // Returns a string describing the given system error code. |error_code| must |
| // be errno on Unix or GetLastError()/WSAGetLastError() on Windows. Passing |
| // errno on Windows has undefined behavior. |
| std::string SystemErrorCodeToString(int error_code); |
| |
| } // namespace base |
| } // namespace android |
| |
| // Convenient macros for evaluating a statement, checking if the result is error, and returning it |
| // to the caller. |
| // |
| // Usage with Result<T>: |
| // |
| // Result<Foo> getFoo() {...} |
| // |
| // Result<Bar> getBar() { |
| // Foo foo = OR_RETURN(getFoo()); |
| // return Bar{foo}; |
| // } |
| // |
| // Usage with status_t: |
| // |
| // status_t getFoo(Foo*) {...} |
| // |
| // status_t getBar(Bar* bar) { |
| // Foo foo; |
| // OR_RETURN(getFoo(&foo)); |
| // *bar = Bar{foo}; |
| // return OK; |
| // } |
| // |
| // Actually this can be used for any type as long as the OkOrFail<T> contract is satisfied. See |
| // below. |
| // If implicit conversion compilation errors occur involving a value type with a templated |
| // forwarding ref ctor, compilation with cpp20 or explicitly converting to the desired |
| // return type is required. |
| #define OR_RETURN(expr) \ |
| ({ \ |
| decltype(expr)&& tmp = (expr); \ |
| typedef android::base::OkOrFail<std::remove_reference_t<decltype(tmp)>> ok_or_fail; \ |
| if (!ok_or_fail::IsOk(tmp)) { \ |
| return ok_or_fail::Fail(std::move(tmp)); \ |
| } \ |
| ok_or_fail::Unwrap(std::move(tmp)); \ |
| }) |
| |
| // Same as OR_RETURN, but aborts if expr is a failure. |
| #if defined(__BIONIC__) |
| #define OR_FATAL(expr) \ |
| ({ \ |
| decltype(expr)&& tmp = (expr); \ |
| typedef android::base::OkOrFail<std::remove_reference_t<decltype(tmp)>> ok_or_fail; \ |
| if (!ok_or_fail::IsOk(tmp)) { \ |
| __assert(__FILE__, __LINE__, ok_or_fail::ErrorMessage(tmp).c_str()); \ |
| } \ |
| ok_or_fail::Unwrap(std::move(tmp)); \ |
| }) |
| #else |
| #define OR_FATAL(expr) \ |
| ({ \ |
| decltype(expr)&& tmp = (expr); \ |
| typedef android::base::OkOrFail<std::remove_reference_t<decltype(tmp)>> ok_or_fail; \ |
| if (!ok_or_fail::IsOk(tmp)) { \ |
| fprintf(stderr, "%s:%d: assertion \"%s\" failed", __FILE__, __LINE__, \ |
| ok_or_fail::ErrorMessage(tmp).c_str()); \ |
| abort(); \ |
| } \ |
| ok_or_fail::Unwrap(std::move(tmp)); \ |
| }) |
| #endif |
| |
| namespace android { |
| namespace base { |
| |
| // The OkOrFail contract for a type T. This must be implemented for a type T if you want to use |
| // OR_RETURN(stmt) where stmt evalues to a value of type T. |
| template <typename T, typename = void> |
| struct OkOrFail { |
| // Checks if T is ok or fail. |
| static bool IsOk(const T&); |
| |
| // Turns T into the success value. |
| template <typename U> |
| static U Unwrap(T&&); |
| |
| // Moves T into OkOrFail<T>, so that we can convert it to other types |
| OkOrFail(T&& v); |
| OkOrFail() = delete; |
| OkOrFail(const T&) = delete; |
| |
| // And there need to be one or more conversion operators that turns the error value of T into a |
| // target type. For example, for T = Result<V, E>, there can be ... |
| // |
| // // for the case where OR_RETURN is called in a function expecting E |
| // operator E()&& { return val_.error().code(); } |
| // |
| // // for the case where OR_RETURN is called in a function expecting Result<U, E> |
| // template <typename U> |
| // operator Result<U, E>()&& { return val_.error(); } |
| |
| // Returns the string representation of the fail value. |
| static std::string ErrorMessage(const T& v); |
| }; |
| |
| } // namespace base |
| } // namespace android |