Add Result<T, E> type
This commit is contained in:
wheremyfoodat
parent
189d177692
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077b254a4f
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@ -19,6 +19,7 @@ include_directories(third-party/zydis/include/Zydis)
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include_directories(third-party/winpthread/include)
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include_directories(third-party/vulkan/include)
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include_directories(third-party/xxhash/include)
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include_directories(third-party/result/include)
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add_subdirectory("third-party")
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#=================== EXAMPLE ===================
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include_directories(src)
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@ -0,0 +1,201 @@
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Apache License
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Copyright {2016} {Mathieu Stefani}
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@ -0,0 +1,132 @@
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# Result
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This is an adaption of [https://github.com/oktal/result](https://github.com/oktal/result). Make sure to support the original library!
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## Overview
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`Result<T, E>` is a template type that can be used to return and propage errors. It can be used to replace
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exceptions in context where they are not allowed or too slow to be used. `Result<T, E>` is an algebraic data
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type of `Ok(T)` that represents success and `Err(E)` representing an error.
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Design of this class has been mainly inspired by Rust's [std::result](https://doc.rust-lang.org/std/result/)
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```
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struct Request {
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};
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struct Error {
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enum class Kind {
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Timeout,
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Invalid,
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TooLong
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}
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Error(Kind kind, std::string text);
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Kind kind;
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std::string text;
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};
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Result<Request, Error> parseRequest(const std::string& payload) {
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if (payload.size() > 512) return Err(Error(Kind::TooLong, "Request exceeded maximum allowed size (512 bytes)"));
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Request request;
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return Ok(request);
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}
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std::string payload = receivePayload();
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auto request = parseRequest(payload).expect("Failed to parse request");
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```
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To return a successfull `Result`, use the `Ok()` function. To return an error one, use the `Err()` function.
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## Extract and unwrap
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To extract the value from a `Result<T, E>` type, you can use the `expect()` function that will yield the value
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of an `Ok(T)` or terminate the program with an error message passed as a parameter.
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```
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Result<uint32_t, uint32_t> r1 = Ok(3u);
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auto val = r1.expect("Failed to retrieve the value");
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assert(val == 3);
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```
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`unwrap()` can also be used to extract the value of a `Result`, yielding the value of an `Ok(T)` value or terminating
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the program otherwise:
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```
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Result<uint32_t, uint32_t> r1 = Ok(3u);
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auto val = r1.unwrap();
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assert(val == 3);
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```
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Instead a terminating the program, `unwrapOr` can be used to return a default value for an `Err(E)` Result:
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```
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Result<uint32_t, uint32_t> r1 = Err(9u);
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auto val = r1.unwrapOr(0);
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assert(val == 0);
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```
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## Map and bind
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To transform (or map) a `Result<T, E>` to a `Result<U, E>`, `Result` provides a `map` member function.
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`map` will apply a function to a contained `Ok(T)` value and will return the result of the transformation,
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and will leave an `Err(E)` untouched:
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```
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std::string stringify(int val) { return std::to_string(val); }
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Result<uint32_t, uint32_t> r1 = Ok(2u);
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auto r2 = r1.map(stringify); // Maps a Result<uint32_t, uint32_t> to Result<std::string, uint32_t>
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assert(r2.unwrap(), "2");
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```
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Note that `map` should return a simple value and not a `Result<U, E>`. A function returning nothing (`void`)
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applied to a `Result<T, E>` will yield a `Result<void, E>`.
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To map a function to a contained `Err(E)` value, use the `mapError` function.
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To *bind* a `Result<T, E>` to a `Result<U, E>`, you can use the `andThen` member function:
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```
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Result<uint32_t, uint32_t> square(uint32_t val) { return Ok(val * val); }
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Result<uint32_t, uint32_t> r1 = Ok(3u);
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auto r2 = r1.andThen(square);
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assert(r2.unwrap(), 9);
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```
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Use `orElse` to apply a function to a contained `Err(E)` value:
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```
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Result<uint32_t, uint32_t> identity(uint32_t val) { return Ok(val); }
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Result<uint32_t, uint32_t> r1 = Err(3u);
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assert(r1.andThen(identity).orElse(square).unwrap(), 9);
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```
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## The TRY macro
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Like Rust, a `TRY` macro is also provided that comes in handy when writing code that calls a lot of functions returning a `Result`.
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the `TRY` macro will simply call its argument and short-cirtcuit the function returning an `Err(E)` if the operation returned an error `Result`:
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```
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Result<void, IoError> copy(int srcFd, const char* dstFile) {
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auto fd = TRY(open(dstFile));
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auto data = TRY(read(srcFd));
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TRY(write(fd, data));
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return Ok();
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}
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```
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Note that this macro uses a special extension called *compound statement* only supported by gcc and clang
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@ -0,0 +1,910 @@
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/*
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Mathieu Stefani, 03 mai 2016
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This header provides a Result type that can be used to replace exceptions in code
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that has to handle error.
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Result<T, E> can be used to return and propagate an error to the caller. Result<T, E> is an algebraic
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data type that can either Ok(T) to represent success or Err(E) to represent an error.
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*/
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#pragma once
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#include <iostream>
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#include <functional>
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#include <type_traits>
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namespace types {
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template<typename T>
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struct Ok {
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Ok(const T& val) : val(val) { }
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Ok(T&& val) : val(std::move(val)) { }
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T val;
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};
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template<>
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struct Ok<void> { };
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template<typename E>
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struct Err {
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Err(const E& val) : val(val) { }
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Err(E&& val) : val(std::move(val)) { }
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E val;
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};
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}
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template<typename T, typename CleanT = typename std::decay<T>::type>
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types::Ok<CleanT> Ok(T&& val) {
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return types::Ok<CleanT>(std::forward<T>(val));
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}
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inline types::Ok<void> Ok() {
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return types::Ok<void>();
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}
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template<typename E, typename CleanE = typename std::decay<E>::type>
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types::Err<CleanE> Err(E&& val) {
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return types::Err<CleanE>(std::forward<E>(val));
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}
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namespace Rust {
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template<typename T, typename E> struct Result;
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}
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namespace details {
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template<typename ...> struct void_t { typedef void type; };
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namespace impl {
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template<typename Func> struct result_of;
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template<typename Ret, typename Cls, typename... Args>
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struct result_of<Ret (Cls::*)(Args...)> : public result_of<Ret (Args...)> { };
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template<typename Ret, typename... Args>
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struct result_of<Ret (Args...)> {
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typedef Ret type;
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};
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}
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template<typename Func>
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struct result_of : public impl::result_of<decltype(&Func::operator())> { };
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template<typename Ret, typename Cls, typename... Args>
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struct result_of<Ret (Cls::*) (Args...) const> {
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typedef Ret type;
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};
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template<typename Ret, typename... Args>
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struct result_of<Ret (*)(Args...)> {
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typedef Ret type;
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};
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template<typename R>
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struct ResultOkType { typedef typename std::decay<R>::type type; };
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template<typename T, typename E>
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struct ResultOkType<Rust::Result<T, E>> {
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typedef T type;
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};
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template<typename R>
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struct ResultErrType { typedef R type; };
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template<typename T, typename E>
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struct ResultErrType<Rust::Result<T, E>> {
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typedef typename std::remove_reference<E>::type type;
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};
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template<typename R> struct IsResult : public std::false_type { };
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template<typename T, typename E>
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struct IsResult<Rust::Result<T, E>> : public std::true_type { };
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namespace ok {
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namespace impl {
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template<typename T> struct Map;
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template<typename Ret, typename Cls, typename Arg>
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struct Map<Ret (Cls::*)(Arg) const> : public Map<Ret (Arg)> { };
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template<typename Ret, typename Cls, typename Arg>
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struct Map<Ret (Cls::*)(Arg)> : public Map<Ret (Arg)> { };
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// General implementation
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template<typename Ret, typename Arg>
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struct Map<Ret (Arg)> {
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static_assert(!IsResult<Ret>::value,
|
||||
"Can not map a callback returning a Result, use andThen instead");
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
static Rust::Result<Ret, E> map(const Rust::Result<T, E>& result, Func func) {
|
||||
|
||||
static_assert(
|
||||
std::is_same<T, Arg>::value ||
|
||||
std::is_convertible<T, Arg>::value,
|
||||
"Incompatible types detected");
|
||||
|
||||
if (result.isOk()) {
|
||||
auto res = func(result.storage().template get<T>());
|
||||
return types::Ok<Ret>(std::move(res));
|
||||
}
|
||||
|
||||
return types::Err<E>(result.storage().template get<E>());
|
||||
}
|
||||
};
|
||||
|
||||
// Specialization for callback returning void
|
||||
template<typename Arg>
|
||||
struct Map<void (Arg)> {
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
static Rust::Result<void, E> map(const Rust::Result<T, E>& result, Func func) {
|
||||
|
||||
if (result.isOk()) {
|
||||
func(result.storage().template get<T>());
|
||||
return types::Ok<void>();
|
||||
}
|
||||
|
||||
return types::Err<E>(result.storage().template get<E>());
|
||||
}
|
||||
};
|
||||
|
||||
// Specialization for a void Result
|
||||
template<typename Ret>
|
||||
struct Map<Ret (void)> {
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
static Rust::Result<Ret, E> map(const Rust::Result<T, E>& result, Func func) {
|
||||
static_assert(std::is_same<T, void>::value,
|
||||
"Can not map a void callback on a non-void Result");
|
||||
|
||||
if (result.isOk()) {
|
||||
auto ret = func();
|
||||
return types::Ok<Ret>(std::move(ret));
|
||||
}
|
||||
|
||||
return types::Err<E>(result.storage().template get<E>());
|
||||
}
|
||||
};
|
||||
|
||||
// Specialization for callback returning void on a void Result
|
||||
template<>
|
||||
struct Map<void (void)> {
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
static Rust::Result<void, E> map(const Rust::Result<T, E>& result, Func func) {
|
||||
static_assert(std::is_same<T, void>::value,
|
||||
"Can not map a void callback on a non-void Result");
|
||||
|
||||
if (result.isOk()) {
|
||||
func();
|
||||
return types::Ok<void>();
|
||||
}
|
||||
|
||||
return types::Err<E>(result.storage().template get<E>());
|
||||
}
|
||||
};
|
||||
|
||||
// General specialization for a callback returning a Result
|
||||
template<typename U, typename E, typename Arg>
|
||||
struct Map<Rust::Result<U, E> (Arg)> {
|
||||
|
||||
template<typename T, typename Func>
|
||||
static Rust::Result<U, E> map(const Rust::Result<T, E>& result, Func func) {
|
||||
static_assert(
|
||||
std::is_same<T, Arg>::value ||
|
||||
std::is_convertible<T, Arg>::value,
|
||||
"Incompatible types detected");
|
||||
|
||||
if (result.isOk()) {
|
||||
auto res = func(result.storage().template get<T>());
|
||||
return res;
|
||||
}
|
||||
|
||||
return types::Err<E>(result.storage().template get<E>());
|
||||
}
|
||||
};
|
||||
|
||||
// Specialization for a void callback returning a Result
|
||||
template<typename U, typename E>
|
||||
struct Map<Rust::Result<U, E> (void)> {
|
||||
|
||||
template<typename T, typename Func>
|
||||
static Rust::Result<U, E> map(const Rust::Result<T, E>& result, Func func) {
|
||||
static_assert(std::is_same<T, void>::value, "Can not call a void-callback on a non-void Result");
|
||||
|
||||
if (result.isOk()) {
|
||||
auto res = func();
|
||||
return res;
|
||||
}
|
||||
|
||||
return types::Err<E>(result.storage().template get<E>());
|
||||
}
|
||||
|
||||
};
|
||||
|
||||
} // namespace impl
|
||||
|
||||
template<typename Func> struct Map : public impl::Map<decltype(&Func::operator())> { };
|
||||
|
||||
template<typename Ret, typename... Args>
|
||||
struct Map<Ret (*) (Args...)> : public impl::Map<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Map<Ret (Cls::*) (Args...)> : public impl::Map<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Map<Ret (Cls::*) (Args...) const> : public impl::Map<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename... Args>
|
||||
struct Map<std::function<Ret (Args...)>> : public impl::Map<Ret (Args...)> { };
|
||||
|
||||
} // namespace ok
|
||||
|
||||
|
||||
namespace err {
|
||||
|
||||
namespace impl {
|
||||
|
||||
template<typename T> struct Map;
|
||||
|
||||
template<typename Ret, typename Cls, typename Arg>
|
||||
struct Map<Ret (Cls::*)(Arg) const> {
|
||||
|
||||
static_assert(!IsResult<Ret>::value,
|
||||
"Can not map a callback returning a Result, use orElse instead");
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
static Rust::Result<T, Ret> map(const Rust::Result<T, E>& result, Func func) {
|
||||
if (result.isErr()) {
|
||||
auto res = func(result.storage().template get<E>());
|
||||
return types::Err<Ret>(res);
|
||||
}
|
||||
|
||||
return types::Ok<T>(result.storage().template get<T>());
|
||||
}
|
||||
|
||||
template<typename E, typename Func>
|
||||
static Rust::Result<void, Ret> map(const Rust::Result<void, E>& result, Func func) {
|
||||
if (result.isErr()) {
|
||||
auto res = func(result.storage().template get<E>());
|
||||
return types::Err<Ret>(res);
|
||||
}
|
||||
|
||||
return types::Ok<void>();
|
||||
}
|
||||
|
||||
|
||||
};
|
||||
|
||||
} // namespace impl
|
||||
|
||||
template<typename Func> struct Map : public impl::Map<decltype(&Func::operator())> { };
|
||||
|
||||
} // namespace err;
|
||||
|
||||
namespace And {
|
||||
|
||||
namespace impl {
|
||||
|
||||
template<typename Func> struct Then;
|
||||
|
||||
template<typename Ret, typename... Args>
|
||||
struct Then<Ret (*)(Args...)> : public Then<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Then<Ret (Cls::*)(Args...)> : public Then<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Then<Ret (Cls::*)(Args...) const> : public Then<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Arg>
|
||||
struct Then<Ret (Arg)> {
|
||||
static_assert(std::is_same<Ret, void>::value,
|
||||
"then() should not return anything, use map() instead");
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
static Rust::Result<T, E> then(const Rust::Result<T, E>& result, Func func) {
|
||||
if (result.isOk()) {
|
||||
func(result.storage().template get<T>());
|
||||
}
|
||||
return result;
|
||||
}
|
||||
};
|
||||
|
||||
template<typename Ret>
|
||||
struct Then<Ret (void)> {
|
||||
static_assert(std::is_same<Ret, void>::value,
|
||||
"then() should not return anything, use map() instead");
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
static Rust::Result<T, E> then(const Rust::Result<T, E>& result, Func func) {
|
||||
static_assert(std::is_same<T, void>::value, "Can not call a void-callback on a non-void Result");
|
||||
|
||||
if (result.isOk()) {
|
||||
func();
|
||||
}
|
||||
|
||||
return result;
|
||||
}
|
||||
};
|
||||
|
||||
|
||||
} // namespace impl
|
||||
|
||||
template<typename Func>
|
||||
struct Then : public impl::Then<decltype(&Func::operator())> { };
|
||||
|
||||
template<typename Ret, typename... Args>
|
||||
struct Then<Ret (*) (Args...)> : public impl::Then<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Then<Ret (Cls::*)(Args...)> : public impl::Then<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Then<Ret (Cls::*)(Args...) const> : public impl::Then<Ret (Args...)> { };
|
||||
|
||||
} // namespace And
|
||||
|
||||
namespace Or {
|
||||
|
||||
namespace impl {
|
||||
|
||||
template<typename Func> struct Else;
|
||||
|
||||
template<typename Ret, typename... Args>
|
||||
struct Else<Ret (*)(Args...)> : public Else<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Else<Ret (Cls::*)(Args...)> : public Else<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Else<Ret (Cls::*)(Args...) const> : public Else<Ret (Args...)> { };
|
||||
|
||||
template<typename T, typename F, typename Arg>
|
||||
struct Else<Rust::Result<T, F> (Arg)> {
|
||||
|
||||
template<typename E, typename Func>
|
||||
static Rust::Result<T, F> orElse(const Rust::Result<T, E>& result, Func func) {
|
||||
static_assert(
|
||||
std::is_same<E, Arg>::value ||
|
||||
std::is_convertible<E, Arg>::value,
|
||||
"Incompatible types detected");
|
||||
|
||||
if (result.isErr()) {
|
||||
auto res = func(result.storage().template get<E>());
|
||||
return res;
|
||||
}
|
||||
|
||||
return types::Ok<T>(result.storage().template get<T>());
|
||||
}
|
||||
|
||||
template<typename E, typename Func>
|
||||
static Rust::Result<void, F> orElse(const Rust::Result<void, E>& result, Func func) {
|
||||
if (result.isErr()) {
|
||||
auto res = func(result.storage().template get<E>());
|
||||
return res;
|
||||
}
|
||||
|
||||
return types::Ok<void>();
|
||||
}
|
||||
|
||||
};
|
||||
|
||||
template<typename T, typename F>
|
||||
struct Else<Rust::Result<T, F> (void)> {
|
||||
|
||||
template<typename E, typename Func>
|
||||
static Rust::Result<T, F> orElse(const Rust::Result<T, E>& result, Func func) {
|
||||
static_assert(std::is_same<T, void>::value,
|
||||
"Can not call a void-callback on a non-void Result");
|
||||
|
||||
if (result.isErr()) {
|
||||
auto res = func();
|
||||
return res;
|
||||
}
|
||||
|
||||
return types::Ok<T>(result.storage().template get<T>());
|
||||
}
|
||||
|
||||
template<typename E, typename Func>
|
||||
static Rust::Result<void, F> orElse(const Rust::Result<void, E>& result, Func func) {
|
||||
if (result.isErr()) {
|
||||
auto res = func();
|
||||
return res;
|
||||
}
|
||||
|
||||
return types::Ok<void>();
|
||||
}
|
||||
|
||||
};
|
||||
|
||||
} // namespace impl
|
||||
|
||||
template<typename Func>
|
||||
struct Else : public impl::Else<decltype(&Func::operator())> { };
|
||||
|
||||
template<typename Ret, typename... Args>
|
||||
struct Else<Ret (*) (Args...)> : public impl::Else<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Else<Ret (Cls::*)(Args...)> : public impl::Else<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Else<Ret (Cls::*)(Args...) const> : public impl::Else<Ret (Args...)> { };
|
||||
|
||||
} // namespace Or
|
||||
|
||||
namespace Other {
|
||||
|
||||
namespace impl {
|
||||
|
||||
template<typename Func> struct Wise;
|
||||
|
||||
template<typename Ret, typename... Args>
|
||||
struct Wise<Ret (*)(Args...)> : public Wise<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Wise<Ret (Cls::*)(Args...)> : public Wise<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Wise<Ret (Cls::*)(Args...) const> : public Wise<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Arg>
|
||||
struct Wise<Ret (Arg)> {
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
static Rust::Result<T, E> otherwise(const Rust::Result<T, E>& result, Func func) {
|
||||
static_assert(
|
||||
std::is_same<E, Arg>::value ||
|
||||
std::is_convertible<E, Arg>::value,
|
||||
"Incompatible types detected");
|
||||
|
||||
static_assert(std::is_same<Ret, void>::value,
|
||||
"callback should not return anything, use mapError() for that");
|
||||
|
||||
if (result.isErr()) {
|
||||
func(result.storage().template get<E>());
|
||||
}
|
||||
return result;
|
||||
}
|
||||
|
||||
};
|
||||
|
||||
} // namespace impl
|
||||
|
||||
template<typename Func>
|
||||
struct Wise : public impl::Wise<decltype(&Func::operator())> { };
|
||||
|
||||
template<typename Ret, typename... Args>
|
||||
struct Wise<Ret (*) (Args...)> : public impl::Wise<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Wise<Ret (Cls::*)(Args...)> : public impl::Wise<Ret (Args...)> { };
|
||||
|
||||
template<typename Ret, typename Cls, typename... Args>
|
||||
struct Wise<Ret (Cls::*)(Args...) const> : public impl::Wise<Ret (Args...)> { };
|
||||
|
||||
} // namespace Other
|
||||
|
||||
template<typename T, typename E, typename Func,
|
||||
typename Ret =
|
||||
Rust::Result<
|
||||
typename details::ResultOkType<
|
||||
typename details::result_of<Func>::type
|
||||
>::type,
|
||||
E>
|
||||
>
|
||||
Ret map(const Rust::Result<T, E>& result, Func func) {
|
||||
return ok::Map<Func>::map(result, func);
|
||||
}
|
||||
|
||||
template<typename T, typename E, typename Func,
|
||||
typename Ret =
|
||||
Rust::Result<T,
|
||||
typename details::ResultErrType<
|
||||
typename details::result_of<Func>::type
|
||||
>::type
|
||||
>
|
||||
>
|
||||
Ret mapError(const Rust::Result<T, E>& result, Func func) {
|
||||
return err::Map<Func>::map(result, func);
|
||||
}
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
Rust::Result<T, E> then(const Rust::Result<T, E>& result, Func func) {
|
||||
return And::Then<Func>::then(result, func);
|
||||
}
|
||||
|
||||
template<typename T, typename E, typename Func>
|
||||
Rust::Result<T, E> otherwise(const Rust::Result<T, E>& result, Func func) {
|
||||
return Other::Wise<Func>::otherwise(result, func);
|
||||
}
|
||||
|
||||
template<typename T, typename E, typename Func,
|
||||
typename Ret =
|
||||
Rust::Result<T,
|
||||
typename details::ResultErrType<
|
||||
typename details::result_of<Func>::type
|
||||
>::type
|
||||
>
|
||||
>
|
||||
Ret orElse(const Rust::Result<T, E>& result, Func func) {
|
||||
return Or::Else<Func>::orElse(result, func);
|
||||
}
|
||||
|
||||
struct ok_tag { };
|
||||
struct err_tag { };
|
||||
|
||||
template<typename T, typename E>
|
||||
struct Storage {
|
||||
static constexpr size_t Size = sizeof(T) > sizeof(E) ? sizeof(T) : sizeof(E);
|
||||
static constexpr size_t Align = sizeof(T) > sizeof(E) ? alignof(T) : alignof(E);
|
||||
|
||||
typedef typename std::aligned_storage<Size, Align>::type type;
|
||||
|
||||
Storage()
|
||||
: initialized_(false)
|
||||
{ }
|
||||
|
||||
void construct(types::Ok<T> ok)
|
||||
{
|
||||
new (&storage_) T(ok.val);
|
||||
initialized_ = true;
|
||||
}
|
||||
void construct(types::Err<E> err)
|
||||
{
|
||||
new (&storage_) E(err.val);
|
||||
initialized_ = true;
|
||||
}
|
||||
|
||||
template<typename U>
|
||||
void rawConstruct(U&& val) {
|
||||
typedef typename std::decay<U>::type CleanU;
|
||||
|
||||
new (&storage_) CleanU(std::forward<U>(val));
|
||||
initialized_ = true;
|
||||
}
|
||||
|
||||
template<typename U>
|
||||
const U& get() const {
|
||||
return *reinterpret_cast<const U *>(&storage_);
|
||||
}
|
||||
|
||||
template<typename U>
|
||||
U& get() {
|
||||
return *reinterpret_cast<U *>(&storage_);
|
||||
}
|
||||
|
||||
void destroy(ok_tag) {
|
||||
if (initialized_) {
|
||||
get<T>().~T();
|
||||
initialized_ = false;
|
||||
}
|
||||
}
|
||||
|
||||
void destroy(err_tag) {
|
||||
if (initialized_) {
|
||||
get<E>().~E();
|
||||
initialized_ = false;
|
||||
}
|
||||
}
|
||||
|
||||
type storage_;
|
||||
bool initialized_;
|
||||
};
|
||||
|
||||
template<typename E>
|
||||
struct Storage<void, E> {
|
||||
typedef typename std::aligned_storage<sizeof(E), alignof(E)>::type type;
|
||||
|
||||
void construct(types::Ok<void>)
|
||||
{
|
||||
initialized_ = true;
|
||||
}
|
||||
|
||||
void construct(types::Err<E> err)
|
||||
{
|
||||
new (&storage_) E(err.val);
|
||||
initialized_ = true;
|
||||
}
|
||||
|
||||
template<typename U>
|
||||
void rawConstruct(U&& val) {
|
||||
typedef typename std::decay<U>::type CleanU;
|
||||
|
||||
new (&storage_) CleanU(std::forward<U>(val));
|
||||
initialized_ = true;
|
||||
}
|
||||
|
||||
void destroy(ok_tag) { initialized_ = false; }
|
||||
void destroy(err_tag) {
|
||||
if (initialized_) {
|
||||
get<E>().~E(); initialized_ = false;
|
||||
}
|
||||
}
|
||||
|
||||
template<typename U>
|
||||
const U& get() const {
|
||||
return *reinterpret_cast<const U *>(&storage_);
|
||||
}
|
||||
|
||||
template<typename U>
|
||||
U& get() {
|
||||
return *reinterpret_cast<U *>(&storage_);
|
||||
}
|
||||
|
||||
type storage_;
|
||||
bool initialized_;
|
||||
};
|
||||
|
||||
template<typename T, typename E>
|
||||
struct Constructor {
|
||||
|
||||
static void move(Storage<T, E>&& src, Storage<T, E>& dst, ok_tag) {
|
||||
dst.rawConstruct(std::move(src.template get<T>()));
|
||||
src.destroy(ok_tag());
|
||||
}
|
||||
|
||||
static void copy(const Storage<T, E>& src, Storage<T, E>& dst, ok_tag) {
|
||||
dst.rawConstruct(src.template get<T>());
|
||||
}
|
||||
|
||||
static void move(Storage<T, E>&& src, Storage<T, E>& dst, err_tag) {
|
||||
dst.rawConstruct(std::move(src.template get<E>()));
|
||||
src.destroy(err_tag());
|
||||
}
|
||||
|
||||
static void copy(const Storage<T, E>& src, Storage<T, E>& dst, err_tag) {
|
||||
dst.rawConstruct(src.template get<E>());
|
||||
}
|
||||
};
|
||||
|
||||
template<typename E>
|
||||
struct Constructor<void, E> {
|
||||
static void move(Storage<void, E>&& src, Storage<void, E>& dst, ok_tag) {
|
||||
}
|
||||
|
||||
static void copy(const Storage<void, E>& src, Storage<void, E>& dst, ok_tag) {
|
||||
}
|
||||
|
||||
static void move(Storage<void, E>&& src, Storage<void, E>& dst, err_tag) {
|
||||
dst.rawConstruct(std::move(src.template get<E>()));
|
||||
src.destroy(err_tag());
|
||||
}
|
||||
|
||||
static void copy(const Storage<void, E>& src, Storage<void, E>& dst, err_tag) {
|
||||
dst.rawConstruct(src.template get<E>());
|
||||
}
|
||||
};
|
||||
|
||||
} // namespace details
|
||||
|
||||
namespace rpog {
|
||||
|
||||
template<typename T, typename = void> struct EqualityComparable : std::false_type { };
|
||||
|
||||
template<typename T>
|
||||
struct EqualityComparable<T,
|
||||
typename std::enable_if<
|
||||
true,
|
||||
typename details::void_t<decltype(std::declval<T>() == std::declval<T>())>::type
|
||||
>::type
|
||||
> : std::true_type
|
||||
{
|
||||
};
|
||||
|
||||
|
||||
} // namespace rpog
|
||||
|
||||
namespace Rust {
|
||||
template<typename T, typename E>
|
||||
struct Result {
|
||||
|
||||
static_assert(!std::is_same<E, void>::value, "void error type is not allowed");
|
||||
|
||||
typedef details::Storage<T, E> storage_type;
|
||||
|
||||
Result(types::Ok<T> ok)
|
||||
: ok_(true)
|
||||
{
|
||||
storage_.construct(std::move(ok));
|
||||
}
|
||||
|
||||
Result(types::Err<E> err)
|
||||
: ok_(false)
|
||||
{
|
||||
storage_.construct(std::move(err));
|
||||
}
|
||||
|
||||
Result(Result&& other) {
|
||||
if (other.isOk()) {
|
||||
details::Constructor<T, E>::move(std::move(other.storage_), storage_, details::ok_tag());
|
||||
ok_ = true;
|
||||
} else {
|
||||
details::Constructor<T, E>::move(std::move(other.storage_), storage_, details::err_tag());
|
||||
ok_ = false;
|
||||
}
|
||||
}
|
||||
|
||||
Result(const Result& other) {
|
||||
if (other.isOk()) {
|
||||
details::Constructor<T, E>::copy(other.storage_, storage_, details::ok_tag());
|
||||
ok_ = true;
|
||||
} else {
|
||||
details::Constructor<T, E>::copy(other.storage_, storage_, details::err_tag());
|
||||
ok_ = false;
|
||||
}
|
||||
}
|
||||
|
||||
~Result() {
|
||||
if (ok_)
|
||||
storage_.destroy(details::ok_tag());
|
||||
else
|
||||
storage_.destroy(details::err_tag());
|
||||
}
|
||||
|
||||
bool isOk() const {
|
||||
return ok_;
|
||||
}
|
||||
|
||||
bool isErr() const {
|
||||
return !ok_;
|
||||
}
|
||||
|
||||
T expect(const char* str) const {
|
||||
if (!isOk()) {
|
||||
std::fprintf(stderr, "%s\n", str);
|
||||
std::terminate();
|
||||
}
|
||||
return expect_impl(std::is_same<T, void>());
|
||||
}
|
||||
|
||||
template<typename Func,
|
||||
typename Ret =
|
||||
Result<
|
||||
typename details::ResultOkType<
|
||||
typename details::result_of<Func>::type
|
||||
>::type,
|
||||
E>
|
||||
>
|
||||
Ret map(Func func) const {
|
||||
return details::map(*this, func);
|
||||
}
|
||||
|
||||
template<typename Func,
|
||||
typename Ret =
|
||||
Result<T,
|
||||
typename details::ResultErrType<
|
||||
typename details::result_of<Func>::type
|
||||
>::type
|
||||
>
|
||||
>
|
||||
Ret mapError(Func func) const {
|
||||
return details::mapError(*this, func);
|
||||
}
|
||||
|
||||
template<typename Func>
|
||||
Result<T, E> then(Func func) const {
|
||||
return details::then(*this, func);
|
||||
}
|
||||
|
||||
template<typename Func>
|
||||
Result<T, E> otherwise(Func func) const {
|
||||
return details::otherwise(*this, func);
|
||||
}
|
||||
|
||||
template<typename Func,
|
||||
typename Ret =
|
||||
Result<T,
|
||||
typename details::ResultErrType<
|
||||
typename details::result_of<Func>::type
|
||||
>::type
|
||||
>
|
||||
>
|
||||
Ret orElse(Func func) const {
|
||||
return details::orElse(*this, func);
|
||||
}
|
||||
|
||||
storage_type& storage() {
|
||||
return storage_;
|
||||
}
|
||||
|
||||
const storage_type& storage() const {
|
||||
return storage_;
|
||||
}
|
||||
|
||||
template<typename U = T>
|
||||
typename std::enable_if<
|
||||
!std::is_same<U, void>::value,
|
||||
U
|
||||
>::type
|
||||
unwrapOr(const U& defaultValue) const {
|
||||
if (isOk()) {
|
||||
return storage().template get<U>();
|
||||
}
|
||||
return defaultValue;
|
||||
}
|
||||
|
||||
template<typename U = T>
|
||||
typename std::enable_if<
|
||||
!std::is_same<U, void>::value,
|
||||
U
|
||||
>::type
|
||||
unwrap() const {
|
||||
if (isOk()) {
|
||||
return storage().template get<U>();
|
||||
}
|
||||
|
||||
std::fprintf(stderr, "Attempting to unwrap an error Result\n");
|
||||
std::terminate();
|
||||
}
|
||||
|
||||
E unwrapErr() const {
|
||||
if (isErr()) {
|
||||
return storage().template get<E>();
|
||||
}
|
||||
|
||||
std::fprintf(stderr, "Attempting to unwrapErr an ok Result\n");
|
||||
std::terminate();
|
||||
}
|
||||
|
||||
private:
|
||||
T expect_impl(std::true_type) const { }
|
||||
T expect_impl(std::false_type) const { return storage_.template get<T>(); }
|
||||
|
||||
bool ok_;
|
||||
storage_type storage_;
|
||||
};
|
||||
|
||||
template<typename T, typename E>
|
||||
bool operator==(const Rust::Result<T, E>& lhs, const Rust::Result<T, E>& rhs) {
|
||||
static_assert(rpog::EqualityComparable<T>::value, "T must be EqualityComparable for Result to be comparable");
|
||||
static_assert(rpog::EqualityComparable<E>::value, "E must be EqualityComparable for Result to be comparable");
|
||||
|
||||
if (lhs.isOk() && rhs.isOk()) {
|
||||
return lhs.storage().template get<T>() == rhs.storage().template get<T>();
|
||||
}
|
||||
if (lhs.isErr() && rhs.isErr()) {
|
||||
return lhs.storage().template get<E>() == rhs.storage().template get<E>();
|
||||
}
|
||||
}
|
||||
|
||||
template<typename T, typename E>
|
||||
bool operator==(const Rust::Result<T, E>& lhs, types::Ok<T> ok) {
|
||||
static_assert(rpog::EqualityComparable<T>::value, "T must be EqualityComparable for Result to be comparable");
|
||||
|
||||
if (!lhs.isOk()) return false;
|
||||
|
||||
return lhs.storage().template get<T>() == ok.val;
|
||||
}
|
||||
|
||||
template<typename E>
|
||||
bool operator==(const Rust::Result<void, E>& lhs, types::Ok<void>) {
|
||||
return lhs.isOk();
|
||||
}
|
||||
|
||||
template<typename T, typename E>
|
||||
bool operator==(const Rust::Result<T, E>& lhs, types::Err<E> err) {
|
||||
static_assert(rpog::EqualityComparable<E>::value, "E must be EqualityComparable for Result to be comparable");
|
||||
if (!lhs.isErr()) return false;
|
||||
|
||||
return lhs.storage().template get<E>() == err.val;
|
||||
}
|
||||
} // end namespace Rust
|
||||
|
||||
#define TRY(...) \
|
||||
({ \
|
||||
auto res = __VA_ARGS__; \
|
||||
if (!res.isOk()) { \
|
||||
typedef details::ResultErrType<decltype(res)>::type E; \
|
||||
return types::Err<E>(res.storage().get<E>()); \
|
||||
} \
|
||||
typedef details::ResultOkType<decltype(res)>::type T; \
|
||||
res.storage().get<T>(); \
|
||||
})
|
||||
Loading…
Reference in New Issue