// Copyright Oliver Kowalke 2014.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
namespace detail {
template< typename Ctx, typename Fn >
transfer_t context_ontop_void( transfer_t);
template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
fcontext_t context_create_void( StackAlloc &&, Fn &&, Params && ...);
template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
fcontext_t context_create_void( preallocated, StackAlloc &&, Fn &&, Params && ...);
template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
class record_void {
private:
typename std::decay< StackAlloc >::type salloc_;
stack_context sctx_;
typename std::decay< Fn >::type fn_;
std::tuple< typename std::decay< Params >::type ... > params_;
static void destroy( record_void * p) noexcept {
typename std::decay< StackAlloc >::type salloc = std::move( p->salloc_);
stack_context sctx = p->sctx_;
// deallocate record
p->~record_void();
// destroy stack with stack allocator
salloc.deallocate( sctx);
}
public:
record_void( stack_context sctx, StackAlloc && salloc,
Fn && fn, Params && ... params) noexcept :
salloc_( std::forward< StackAlloc >( salloc) ),
sctx_( sctx),
fn_( std::forward< Fn >( fn) ),
params_( std::forward< Params >( params) ... ) {
}
record_void( record_void const&) = delete;
record_void & operator=( record_void const&) = delete;
void deallocate() noexcept {
destroy( this);
}
transfer_t run( transfer_t t) {
Ctx from{ t.fctx };
// invoke context-function
#if defined(BOOST_NO_CXX17_STD_APPLY)
Ctx cc = apply( fn_, std::tuple_cat( params_, std::forward_as_tuple( std::move( from) ) ) );
#else
Ctx cc = std::apply( fn_, std::tuple_cat( params_, std::forward_as_tuple( std::move( from) ) ) );
#endif
return { exchange( cc.fctx_, nullptr), nullptr };
}
};
}
template<>
class execution_context< void > {
private:
friend class ontop_error;
template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
friend class detail::record_void;
template< typename Ctx, typename Fn >
friend detail::transfer_t detail::context_ontop_void( detail::transfer_t);
detail::fcontext_t fctx_{ nullptr };
execution_context( detail::fcontext_t fctx) noexcept :
fctx_( fctx) {
}
public:
execution_context() noexcept = default;
#if defined(BOOST_USE_SEGMENTED_STACKS)
// segmented-stack requires to preserve the segments of the `current` context
// which is not possible (no global pointer to current context)
template< typename Fn, typename ... Params >
execution_context( std::allocator_arg_t, segmented_stack, Fn &&, Params && ...) = delete;
template< typename Fn, typename ... Params >
execution_context( std::allocator_arg_t, preallocated, segmented_stack, Fn &&, Params && ...) = delete;
#else
template< typename Fn,
typename ... Params,
typename = detail::disable_overload< execution_context, Fn >
>
execution_context( Fn && fn, Params && ... params) :
// deferred execution of fn and its arguments
// arguments are stored in std::tuple<>
// non-type template parameter pack via std::index_sequence_for<>
// preserves the number of arguments
// used to extract the function arguments from std::tuple<>
fctx_( detail::context_create_void< execution_context >(
fixedsize_stack(),
std::forward< Fn >( fn),
std::forward< Params >( params) ... ) ) {
}
template< typename StackAlloc,
typename Fn,
typename ... Params
>
execution_context( std::allocator_arg_t, StackAlloc && salloc, Fn && fn, Params && ... params) :
// deferred execution of fn and its arguments
// arguments are stored in std::tuple<>
// non-type template parameter pack via std::index_sequence_for<>
// preserves the number of arguments
// used to extract the function arguments from std::tuple<>
fctx_( detail::context_create_void< execution_context >(
std::forward< StackAlloc >( salloc),
std::forward< Fn >( fn),
std::forward< Params >( params) ... ) ) {
}
template< typename StackAlloc,
typename Fn,
typename ... Params
>
execution_context( std::allocator_arg_t, preallocated palloc, StackAlloc && salloc, Fn && fn, Params && ... params) :
// deferred execution of fn and its arguments
// arguments are stored in std::tuple<>
// non-type template parameter pack via std::index_sequence_for<>
// preserves the number of arguments
// used to extract the function arguments from std::tuple<>
fctx_( detail::context_create_void< execution_context >(
palloc, std::forward< StackAlloc >( salloc),
std::forward< Fn >( fn),
std::forward< Params >( params) ... ) ) {
}
#endif
~execution_context() {
if ( nullptr != fctx_) {
detail::ontop_fcontext( detail::exchange( fctx_, nullptr), nullptr, detail::context_unwind);
}
}
execution_context( execution_context && other) noexcept :
fctx_( other.fctx_) {
other.fctx_ = nullptr;
}
execution_context & operator=( execution_context && other) noexcept {
if ( this != & other) {
execution_context tmp = std::move( other);
swap( tmp);
}
return * this;
}
execution_context( execution_context const& other) noexcept = delete;
execution_context & operator=( execution_context const& other) noexcept = delete;
execution_context operator()() {
BOOST_ASSERT( nullptr != fctx_);
detail::transfer_t t = detail::jump_fcontext( detail::exchange( fctx_, nullptr), nullptr);
if ( nullptr != t.data) {
std::exception_ptr * eptr = static_cast< std::exception_ptr * >( t.data);
try {
std::rethrow_exception( * eptr);
} catch (...) {
std::throw_with_nested( ontop_error{ t.fctx } );
}
}
return execution_context( t.fctx);
}
template< typename Fn >
execution_context operator()( exec_ontop_arg_t, Fn && fn) {
BOOST_ASSERT( nullptr != fctx_);
auto p = std::make_tuple( fn, std::exception_ptr{} );
detail::transfer_t t = detail::ontop_fcontext(
detail::exchange( fctx_, nullptr),
& p,
detail::context_ontop_void< execution_context, Fn >);
if ( nullptr != t.data) {
std::exception_ptr * eptr = static_cast< std::exception_ptr * >( t.data);
try {
std::rethrow_exception( * eptr);
} catch (...) {
std::throw_with_nested( ontop_error{ t.fctx } );
}
}
return execution_context( t.fctx);
}
explicit operator bool() const noexcept {
return nullptr != fctx_;
}
bool operator!() const noexcept {
return nullptr == fctx_;
}
bool operator==( execution_context const& other) const noexcept {
return fctx_ == other.fctx_;
}
bool operator!=( execution_context const& other) const noexcept {
return fctx_ != other.fctx_;
}
bool operator<( execution_context const& other) const noexcept {
return fctx_ < other.fctx_;
}
bool operator>( execution_context const& other) const noexcept {
return other.fctx_ < fctx_;
}
bool operator<=( execution_context const& other) const noexcept {
return ! ( * this > other);
}
bool operator>=( execution_context const& other) const noexcept {
return ! ( * this < other);
}
template< typename charT, class traitsT >
friend std::basic_ostream< charT, traitsT > &
operator<<( std::basic_ostream< charT, traitsT > & os, execution_context const& other) {
if ( nullptr != other.fctx_) {
return os << other.fctx_;
} else {
return os << "{not-a-context}";
}
}
void swap( execution_context & other) noexcept {
std::swap( fctx_, other.fctx_);
}
};
namespace detail {
template< typename Ctx, typename Fn >
transfer_t context_ontop_void( transfer_t t) {
auto p = static_cast< std::tuple< Fn, std::exception_ptr > * >( t.data);
BOOST_ASSERT( nullptr != p);
typename std::decay< Fn >::type fn = std::forward< Fn >( std::get< 0 >( * p) );
try {
// execute function
fn();
} catch (...) {
std::get< 1 >( * p) = std::current_exception();
return { t.fctx, & std::get< 1 >( * p ) };
}
return { exchange( t.fctx, nullptr), nullptr };
}
template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
fcontext_t context_create_void( StackAlloc && salloc, Fn && fn, Params && ... params) {
typedef record_void< Ctx, StackAlloc, Fn, Params ... > record_t;
auto sctx = salloc.allocate();
// reserve space for control structure
#if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
const std::size_t size = sctx.size - sizeof( record_t);
void * sp = static_cast< char * >( sctx.sp) - sizeof( record_t);
#else
constexpr std::size_t func_alignment = 64; // alignof( record_t);
constexpr std::size_t func_size = sizeof( record_t);
// reserve space on stack
void * sp = static_cast< char * >( sctx.sp) - func_size - func_alignment;
// align sp pointer
std::size_t space = func_size + func_alignment;
sp = std::align( func_alignment, func_size, sp, space);
BOOST_ASSERT( nullptr != sp);
// calculate remaining size
const std::size_t size = sctx.size - ( static_cast< char * >( sctx.sp) - static_cast< char * >( sp) );
#endif
// create fast-context
const fcontext_t fctx = make_fcontext( sp, size, & context_entry< record_t >);
BOOST_ASSERT( nullptr != fctx);
// placment new for control structure on context-stack
auto rec = ::new ( sp) record_t{
sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn), std::forward< Params >( params) ... };
// transfer control structure to context-stack
return jump_fcontext( fctx, rec).fctx;
}
template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
fcontext_t context_create_void( preallocated palloc, StackAlloc && salloc, Fn && fn, Params && ... params) {
typedef record_void< Ctx, StackAlloc, Fn, Params ... > record_t;
// reserve space for control structure
#if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
const std::size_t size = palloc.size - sizeof( record_t);
void * sp = static_cast< char * >( palloc.sp) - sizeof( record_t);
#else
constexpr std::size_t func_alignment = 64; // alignof( record_t);
constexpr std::size_t func_size = sizeof( record_t);
// reserve space on stack
void * sp = static_cast< char * >( palloc.sp) - func_size - func_alignment;
// align sp pointer
std::size_t space = func_size + func_alignment;
sp = std::align( func_alignment, func_size, sp, space);
BOOST_ASSERT( nullptr != sp);
// calculate remaining size
const std::size_t size = palloc.size - ( static_cast< char * >( palloc.sp) - static_cast< char * >( sp) );
#endif
// create fast-context
const fcontext_t fctx = make_fcontext( sp, size, & context_entry< record_t >);
BOOST_ASSERT( nullptr != fctx);
// placment new for control structure on context-stack
auto rec = ::new ( sp) record_t{
palloc.sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn), std::forward< Params >( params) ... };
// transfer control structure to context-stack
return jump_fcontext( fctx, rec).fctx;
}
}