mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-10-31 06:05:44 +00:00
a8939590de
The bulk of this commit was generated by running:
run-clang-tidy.py \
-checks='-*,llvm-namespace-comment' \
-header-filter=^/.../mozilla-central/.* \
-fix
144 lines
3.6 KiB
C++
144 lines
3.6 KiB
C++
/* -*- 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/. */
|
|
|
|
/* A utility for expanding a tuple into a variadic argument list.
|
|
* Based on std::index_sequence. */
|
|
|
|
/**
|
|
* Example usage:
|
|
*
|
|
* Problem:
|
|
*
|
|
* You have a variadic function Foo:
|
|
*
|
|
* template <typename... Args> void Foo(Args...);
|
|
*
|
|
* And a variadic function Bar, which contains a tuple:
|
|
*
|
|
* template <typename... Args>
|
|
* void Bar() {
|
|
* // ...
|
|
* Tuple<Args...> t;
|
|
* }
|
|
*
|
|
* And inside Bar, you want to call Foo with the elements of the tuple as
|
|
* arguments to Foo.
|
|
*
|
|
* You want to write:
|
|
*
|
|
* Foo(Get<0>(t), Get<1>(t), ..., Get<N>(t))
|
|
*
|
|
* but you can't literally write that, because N is different for different
|
|
* instantiations of Bar.
|
|
*
|
|
* Solution:
|
|
*
|
|
* Write a helper function which takes the tuple, and an index sequence
|
|
* containing indices corresponding to the tuple indices.
|
|
*
|
|
* template <typename... Args, size_t... Indices>
|
|
* void Helper(const Tuple<Args...>& t, IndexSequence<Indices>)
|
|
* {
|
|
* Foo(Get<Indices>(t)...);
|
|
* }
|
|
*
|
|
* Assuming 'Indices...' are 0, 1, ..., N - 1, where N is the size of the
|
|
* tuple, pack expansion will expand the pack 'Get<Indices>(t)...' to
|
|
* 'Get<0>(t), Get<1>(t), ..., Get<N>(t)'.
|
|
*
|
|
* Finally, call the helper, creating the index sequence to pass in like so:
|
|
*
|
|
* template <typename... Args>
|
|
* void Bar() {
|
|
* // ...
|
|
* Tuple<Args...> t;
|
|
* Helper(t, typename IndexSequenceFor<Args...>::Type());
|
|
* }
|
|
*/
|
|
|
|
#ifndef mozilla_IndexSequence_h
|
|
#define mozilla_IndexSequence_h
|
|
|
|
#include "mozilla/Attributes.h"
|
|
|
|
#include <stddef.h>
|
|
|
|
namespace mozilla {
|
|
|
|
/**
|
|
* Represents a compile-time sequence of integer indices.
|
|
*/
|
|
template<size_t... Indices>
|
|
struct IndexSequence
|
|
{
|
|
static MOZ_CONSTEXPR size_t Size() { return sizeof...(Indices); }
|
|
};
|
|
|
|
namespace detail {
|
|
|
|
// Helpers used by MakeIndexSequence.
|
|
|
|
template<size_t... Indices>
|
|
struct IndexTuple
|
|
{
|
|
typedef IndexTuple<Indices..., sizeof...(Indices)> Next;
|
|
};
|
|
|
|
// Builds IndexTuple<0, 1, ..., N - 1>.
|
|
template<size_t N>
|
|
struct BuildIndexTuple
|
|
{
|
|
typedef typename BuildIndexTuple<N - 1>::Type::Next Type;
|
|
};
|
|
|
|
template<>
|
|
struct BuildIndexTuple<0>
|
|
{
|
|
typedef IndexTuple<> Type;
|
|
};
|
|
|
|
template<size_t N, typename IndexTuple>
|
|
struct MakeIndexSequenceImpl;
|
|
|
|
template<size_t N, size_t... Indices>
|
|
struct MakeIndexSequenceImpl<N, IndexTuple<Indices...>>
|
|
{
|
|
typedef IndexSequence<Indices...> Type;
|
|
};
|
|
|
|
} // namespace detail
|
|
|
|
/**
|
|
* A utility for building an IndexSequence of consecutive indices.
|
|
* MakeIndexSequence<N>::Type evaluates to IndexSequence<0, 1, .., N - 1>.
|
|
* Note: unlike std::make_index_sequence, this is not an alias template
|
|
* to work around bugs in MSVC 2013.
|
|
*/
|
|
template<size_t N>
|
|
struct MakeIndexSequence
|
|
{
|
|
typedef typename detail::MakeIndexSequenceImpl<N,
|
|
typename detail::BuildIndexTuple<N>::Type>::Type Type;
|
|
};
|
|
|
|
/**
|
|
* A utility for building an IndexSequence of consecutive indices
|
|
* corresponding to a variadic argument list.
|
|
* IndexSequenceFor<Types...> evaluates to IndexSequence<0, 1, ..., N - 1>
|
|
* where N is the number of types in Types.
|
|
* Note: unlike std::index_sequence_for, this is not an alias template
|
|
* to work around bugs in MSVC 2013.
|
|
*/
|
|
template<typename... Types>
|
|
struct IndexSequenceFor
|
|
{
|
|
typedef typename MakeIndexSequence<sizeof...(Types)>::Type Type;
|
|
};
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif /* mozilla_IndexSequence_h */
|