From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 21:33:14 +0200
Subject: Adding upstream version 115.7.0esr.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 mfbt/ResultExtensions.h | 371 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 371 insertions(+)
 create mode 100644 mfbt/ResultExtensions.h

(limited to 'mfbt/ResultExtensions.h')

diff --git a/mfbt/ResultExtensions.h b/mfbt/ResultExtensions.h
new file mode 100644
index 0000000000..97f197d800
--- /dev/null
+++ b/mfbt/ResultExtensions.h
@@ -0,0 +1,371 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Extensions to the Result type to enable simpler handling of XPCOM/NSPR
+ * results. */
+
+#ifndef mozilla_ResultExtensions_h
+#define mozilla_ResultExtensions_h
+
+#include "mozilla/Assertions.h"
+#include "nscore.h"
+#include "prtypes.h"
+#include "mozilla/dom/quota/RemoveParen.h"
+
+namespace mozilla {
+
+struct ErrorPropagationTag;
+
+// Allow nsresult errors to automatically convert to nsresult values, so MOZ_TRY
+// can be used in XPCOM methods with Result<T, nserror> results.
+template <>
+class [[nodiscard]] GenericErrorResult<nsresult> {
+  nsresult mErrorValue;
+
+  template <typename V, typename E2>
+  friend class Result;
+
+ public:
+  explicit GenericErrorResult(nsresult aErrorValue) : mErrorValue(aErrorValue) {
+    MOZ_ASSERT(NS_FAILED(aErrorValue));
+  }
+
+  GenericErrorResult(nsresult aErrorValue, const ErrorPropagationTag&)
+      : GenericErrorResult(aErrorValue) {}
+
+  operator nsresult() const { return mErrorValue; }
+};
+
+// Allow MOZ_TRY to handle `PRStatus` values.
+template <typename E = nsresult>
+inline Result<Ok, E> ToResult(PRStatus aValue);
+
+}  // namespace mozilla
+
+#include "mozilla/Result.h"
+
+namespace mozilla {
+
+template <typename ResultType>
+struct ResultTypeTraits;
+
+template <>
+struct ResultTypeTraits<nsresult> {
+  static nsresult From(nsresult aValue) { return aValue; }
+};
+
+template <typename E>
+inline Result<Ok, E> ToResult(nsresult aValue) {
+  if (NS_FAILED(aValue)) {
+    return Err(ResultTypeTraits<E>::From(aValue));
+  }
+  return Ok();
+}
+
+template <typename E>
+inline Result<Ok, E> ToResult(PRStatus aValue) {
+  if (aValue == PR_SUCCESS) {
+    return Ok();
+  }
+  return Err(ResultTypeTraits<E>::From(NS_ERROR_FAILURE));
+}
+
+namespace detail {
+template <typename R>
+auto ResultRefAsParam(R& aResult) {
+  return &aResult;
+}
+
+template <typename R, typename E, typename RArgMapper, typename Func,
+          typename... Args>
+Result<R, E> ToResultInvokeInternal(const Func& aFunc,
+                                    const RArgMapper& aRArgMapper,
+                                    Args&&... aArgs) {
+  // XXX Thereotically, if R is a pointer to a non-refcounted type, this might
+  // be a non-owning pointer, but unless we find a case where this actually is
+  // relevant, it's safe to forbid any raw pointer result.
+  static_assert(
+      !std::is_pointer_v<R>,
+      "Raw pointer results are not supported, please specify a smart pointer "
+      "result type explicitly, so that getter_AddRefs is used");
+
+  R res;
+  nsresult rv = aFunc(std::forward<Args>(aArgs)..., aRArgMapper(res));
+  if (NS_FAILED(rv)) {
+    return Err(ResultTypeTraits<E>::From(rv));
+  }
+  return res;
+}
+
+template <typename T>
+struct outparam_as_pointer;
+
+template <typename T>
+struct outparam_as_pointer<T*> {
+  using type = T*;
+};
+
+template <typename T>
+struct outparam_as_reference;
+
+template <typename T>
+struct outparam_as_reference<T*> {
+  using type = T&;
+};
+
+template <typename R, typename E, template <typename> typename RArg,
+          typename Func, typename... Args>
+using to_result_retval_t =
+    decltype(std::declval<Func&>()(
+                 std::declval<Args&&>()...,
+                 std::declval<typename RArg<decltype(ResultRefAsParam(
+                     std::declval<R&>()))>::type>()),
+             Result<R, E>(Err(ResultTypeTraits<E>::From(NS_ERROR_FAILURE))));
+
+// There are two ToResultInvokeSelector overloads, which cover the cases of a) a
+// pointer-typed output parameter, and b) a reference-typed output parameter,
+// using to_result_retval_t in connection with outparam_as_pointer and
+// outparam_as_reference type traits. These type traits may be specialized for
+// types other than raw pointers to allow calling functions with argument types
+// that implicitly convert/bind to a raw pointer/reference. The overload that is
+// used is selected by expression SFINAE: the decltype expression in
+// to_result_retval_t is only valid in either case.
+template <typename R, typename E, typename Func, typename... Args>
+auto ToResultInvokeSelector(const Func& aFunc, Args&&... aArgs)
+    -> to_result_retval_t<R, E, outparam_as_pointer, Func, Args...> {
+  return ToResultInvokeInternal<R, E>(
+      aFunc, [](R& res) -> decltype(auto) { return ResultRefAsParam(res); },
+      std::forward<Args>(aArgs)...);
+}
+
+template <typename R, typename E, typename Func, typename... Args>
+auto ToResultInvokeSelector(const Func& aFunc, Args&&... aArgs)
+    -> to_result_retval_t<R, E, outparam_as_reference, Func, Args...> {
+  return ToResultInvokeInternal<R, E>(
+      aFunc, [](R& res) -> decltype(auto) { return *ResultRefAsParam(res); },
+      std::forward<Args>(aArgs)...);
+}
+
+}  // namespace detail
+
+/**
+ * Adapts a function with a nsresult error type and an R* output parameter as
+ * the last parameter to a function returning a mozilla::Result<R, nsresult>
+ * object.
+ *
+ * This can also be used with member functions together with std::men_fn, e.g.
+ *
+ *    nsCOMPtr<nsIFile> file = ...;
+ *    auto existsOrErr = ToResultInvoke<bool>(std::mem_fn(&nsIFile::Exists),
+ *                                            *file);
+ *
+ * but it is more convenient to use the member function version, which has the
+ * additional benefit of enabling the deduction of the success result type:
+ *
+ *    nsCOMPtr<nsIFile> file = ...;
+ *    auto existsOrErr = ToResultInvokeMember(*file, &nsIFile::Exists);
+ */
+template <typename R, typename E = nsresult, typename Func, typename... Args>
+Result<R, E> ToResultInvoke(const Func& aFunc, Args&&... aArgs) {
+  return detail::ToResultInvokeSelector<R, E, Func, Args&&...>(
+      aFunc, std::forward<Args>(aArgs)...);
+}
+
+namespace detail {
+template <typename T>
+struct tag {
+  using type = T;
+};
+
+template <typename... Ts>
+struct select_last {
+  using type = typename decltype((tag<Ts>{}, ...))::type;
+};
+
+template <typename... Ts>
+using select_last_t = typename select_last<Ts...>::type;
+
+template <>
+struct select_last<> {
+  using type = void;
+};
+
+template <typename E, typename RArg, typename T, typename Func,
+          typename... Args>
+auto ToResultInvokeMemberInternal(T& aObj, const Func& aFunc, Args&&... aArgs) {
+  if constexpr (std::is_pointer_v<RArg> ||
+                (std::is_lvalue_reference_v<RArg> &&
+                 !std::is_const_v<std::remove_reference_t<RArg>>)) {
+    auto lambda = [&](RArg res) {
+      return (aObj.*aFunc)(std::forward<Args>(aArgs)..., res);
+    };
+    return detail::ToResultInvokeSelector<
+        std::remove_reference_t<std::remove_pointer_t<RArg>>, E,
+        decltype(lambda)>(lambda);
+  } else {
+    // No output parameter present, return a Result<Ok, E>
+    return mozilla::ToResult<E>((aObj.*aFunc)(std::forward<Args>(aArgs)...));
+  }
+}
+
+// For use in MOZ_TO_RESULT_INVOKE_MEMBER/MOZ_TO_RESULT_INVOKE_MEMBER_TYPED.
+template <typename T>
+auto DerefHelper(const T&) -> T&;
+
+template <typename T>
+auto DerefHelper(T*) -> T&;
+
+template <template <class> class SmartPtr, typename T,
+          typename = decltype(*std::declval<const SmartPtr<T>>())>
+auto DerefHelper(const SmartPtr<T>&) -> T&;
+
+template <typename T>
+using DerefedType =
+    std::remove_reference_t<decltype(DerefHelper(std::declval<const T&>()))>;
+}  // namespace detail
+
+template <typename E = nsresult, typename T, typename U, typename... XArgs,
+          typename... Args,
+          typename = std::enable_if_t<std::is_base_of_v<U, T>>>
+auto ToResultInvokeMember(T& aObj, nsresult (U::*aFunc)(XArgs...),
+                          Args&&... aArgs) {
+  return detail::ToResultInvokeMemberInternal<E,
+                                              detail::select_last_t<XArgs...>>(
+      aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, typename T, typename U, typename... XArgs,
+          typename... Args,
+          typename = std::enable_if_t<std::is_base_of_v<U, T>>>
+auto ToResultInvokeMember(const T& aObj, nsresult (U::*aFunc)(XArgs...) const,
+                          Args&&... aArgs) {
+  return detail::ToResultInvokeMemberInternal<E,
+                                              detail::select_last_t<XArgs...>>(
+      aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, typename T, typename U, typename... XArgs,
+          typename... Args>
+auto ToResultInvokeMember(T* const aObj, nsresult (U::*aFunc)(XArgs...),
+                          Args&&... aArgs) {
+  return ToResultInvokeMember<E>(*aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, typename T, typename U, typename... XArgs,
+          typename... Args>
+auto ToResultInvokeMember(const T* const aObj,
+                          nsresult (U::*aFunc)(XArgs...) const,
+                          Args&&... aArgs) {
+  return ToResultInvokeMember<E>(*aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, template <class> class SmartPtr, typename T,
+          typename U, typename... XArgs, typename... Args,
+          typename = std::enable_if_t<std::is_base_of_v<U, T>>,
+          typename = decltype(*std::declval<const SmartPtr<T>>())>
+auto ToResultInvokeMember(const SmartPtr<T>& aObj,
+                          nsresult (U::*aFunc)(XArgs...), Args&&... aArgs) {
+  return ToResultInvokeMember<E>(*aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, template <class> class SmartPtr, typename T,
+          typename U, typename... XArgs, typename... Args,
+          typename = std::enable_if_t<std::is_base_of_v<U, T>>,
+          typename = decltype(*std::declval<const SmartPtr<T>>())>
+auto ToResultInvokeMember(const SmartPtr<const T>& aObj,
+                          nsresult (U::*aFunc)(XArgs...) const,
+                          Args&&... aArgs) {
+  return ToResultInvokeMember<E>(*aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+#if defined(XP_WIN) && !defined(_WIN64)
+template <typename E = nsresult, typename T, typename U, typename... XArgs,
+          typename... Args,
+          typename = std::enable_if_t<std::is_base_of_v<U, T>>>
+auto ToResultInvokeMember(T& aObj, nsresult (__stdcall U::*aFunc)(XArgs...),
+                          Args&&... aArgs) {
+  return detail::ToResultInvokeMemberInternal<E,
+                                              detail::select_last_t<XArgs...>>(
+      aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, typename T, typename U, typename... XArgs,
+          typename... Args,
+          typename = std::enable_if_t<std::is_base_of_v<U, T>>>
+auto ToResultInvokeMember(const T& aObj,
+                          nsresult (__stdcall U::*aFunc)(XArgs...) const,
+                          Args&&... aArgs) {
+  return detail::ToResultInvokeMemberInternal<E,
+                                              detail::select_last_t<XArgs...>>(
+      aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, typename T, typename U, typename... XArgs,
+          typename... Args>
+auto ToResultInvokeMember(T* const aObj,
+                          nsresult (__stdcall U::*aFunc)(XArgs...),
+                          Args&&... aArgs) {
+  return ToResultInvokeMember<E>(*aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, typename T, typename U, typename... XArgs,
+          typename... Args>
+auto ToResultInvokeMember(const T* const aObj,
+                          nsresult (__stdcall U::*aFunc)(XArgs...) const,
+                          Args&&... aArgs) {
+  return ToResultInvokeMember<E>(*aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, template <class> class SmartPtr, typename T,
+          typename U, typename... XArgs, typename... Args,
+          typename = std::enable_if_t<std::is_base_of_v<U, T>>,
+          typename = decltype(*std::declval<const SmartPtr<T>>())>
+auto ToResultInvokeMember(const SmartPtr<T>& aObj,
+                          nsresult (__stdcall U::*aFunc)(XArgs...),
+                          Args&&... aArgs) {
+  return ToResultInvokeMember<E>(*aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+
+template <typename E = nsresult, template <class> class SmartPtr, typename T,
+          typename U, typename... XArgs, typename... Args,
+          typename = std::enable_if_t<std::is_base_of_v<U, T>>,
+          typename = decltype(*std::declval<const SmartPtr<T>>())>
+auto ToResultInvokeMember(const SmartPtr<const T>& aObj,
+                          nsresult (__stdcall U::*aFunc)(XArgs...) const,
+                          Args&&... aArgs) {
+  return ToResultInvokeMember<E>(*aObj, aFunc, std::forward<Args>(aArgs)...);
+}
+#endif
+
+// Macro version of ToResultInvokeMember for member functions. The macro has
+// the advantage of not requiring spelling out the member function's declarator
+// type name, at the expense of having a non-standard syntax. It can be used
+// like this:
+//
+//     nsCOMPtr<nsIFile> file;
+//     auto existsOrErr = MOZ_TO_RESULT_INVOKE_MEMBER(file, Exists);
+#define MOZ_TO_RESULT_INVOKE_MEMBER(obj, methodname, ...)                \
+  ::mozilla::ToResultInvokeMember(                                       \
+      (obj), &::mozilla::detail::DerefedType<decltype(obj)>::methodname, \
+      ##__VA_ARGS__)
+
+// Macro version of ToResultInvokeMember for member functions, where the result
+// type does not match the output parameter type. The macro has the advantage
+// of not requiring spelling out the member function's declarator type name, at
+// the expense of having a non-standard syntax. It can be used like this:
+//
+//     nsCOMPtr<nsIFile> file;
+//     auto existsOrErr =
+//         MOZ_TO_RESULT_INVOKE_MEMBER_TYPED(nsCOMPtr<nsIFile>, file, Clone);
+#define MOZ_TO_RESULT_INVOKE_MEMBER_TYPED(resultType, obj, methodname, ...) \
+  ::mozilla::ToResultInvoke<MOZ_REMOVE_PAREN(resultType)>(                  \
+      ::std::mem_fn(                                                        \
+          &::mozilla::detail::DerefedType<decltype(obj)>::methodname),      \
+      (obj), ##__VA_ARGS__)
+
+}  // namespace mozilla
+
+#endif  // mozilla_ResultExtensions_h
-- 
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