-/* Copyright (c) 2015-2016. The SimGrid Team.
- * All rights reserved. */
+/* Copyright (c) 2015-2017. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
#include <cstdlib>
#include <cstring>
+#include <array>
#include <exception>
#include <functional>
#include <memory>
#include <string>
#include <tuple>
+#include <type_traits>
#include <utility>
#include <vector>
-#include <xbt/sysdep.h>
-#include <xbt/utility.hpp>
+#include "xbt/sysdep.h"
+#include "xbt/utility.hpp"
namespace simgrid {
namespace xbt {
code_(std::move(code)),
args_(std::make_shared<const std::vector<std::string>>(std::move(args)))
{}
- int operator()() const
+ void operator()() const
{
const int argc = args_->size();
std::vector<std::string> args = *args_;
- std::unique_ptr<char*[]> argv(new char*[argc + 1]);
- for (int i = 0; i != argc; ++i)
- argv[i] = args[i].empty() ? const_cast<char*>(""): &args[i].front();
- argv[argc] = nullptr;
- return code_(argc, argv.get());
+ if (not args.empty()) {
+ char noarg[] = {'\0'};
+ std::unique_ptr<char* []> argv(new char*[argc + 1]);
+ for (int i = 0; i != argc; ++i)
+ argv[i] = args[i].empty() ? noarg : &args[i].front();
+ argv[argc] = nullptr;
+ code_(argc, argv.get());
+ } else
+ code_(argc, nullptr);
}
};
*
* auto args = std::make_tuple(1, false);
* int res = apply(foo, args);
- * @encode
+ * @endcode
**/
template <class F, class Tuple>
constexpr auto apply(F&& f, Tuple&& t)
template<class T> class Task;
-namespace bits {
-
- // Something similar exist in C++14:
- template<class T>
- constexpr T max(T a, T b)
- {
- return (a > b) ? a : b;
- }
- template<class T, class... Args>
- constexpr T max(T a, Args... b)
- {
- return max(std::forward<T>(a), max(std::forward<Args>(b)...));
- }
-
- struct whatever {};
-
- // What we can store in a Task:
- typedef void* ptr_callback;
- struct funcptr_callback {
- // Placeholder for any function pointer:
- void(*callback)();
- void* data;
- };
- struct member_funcptr_callback {
- // Placeholder for any pointer to member function:
- void (whatever::* callback)();
- whatever* data;
- };
- typedef char any_callback[max(
- sizeof(ptr_callback),
- sizeof(funcptr_callback),
- sizeof(member_funcptr_callback)
- )];
-
- // Union of what we can store in a Task:
- union TaskErasure {
- ptr_callback ptr;
- funcptr_callback funcptr;
- member_funcptr_callback member_funcptr;
- any_callback any;
- };
-
- // Can we copy F in Task (or do we have to use the heap)?
- template<class F>
- constexpr bool isUsableDirectlyInTask()
- {
- // The only types we can portably store directly in the Task are the
- // trivially copyable ones (we can memcpy) which are small enough to fit:
- return std::is_trivially_copyable<F>::value &&
- sizeof(F) <= sizeof(bits::any_callback);
- }
-
-}
-
/** Type-erased run-once task
*
* * Like std::function but callable only once.
class Task<R(Args...)> {
private:
- typedef bits::TaskErasure TaskErasure;
- struct TaskErasureVtable {
- // Call (and possibly destroy) the function:
- R (*call)(TaskErasure&, Args...);
- // Destroy the function:
- void (*destroy)(TaskErasure&);
+ // Placeholder for some class type:
+ struct whatever {};
+
+ // Union used for storage:
+#if 0
+ typedef typename std::aligned_union<0,
+ void*,
+ std::pair<void(*)(),void*>,
+ std::pair<void(whatever::*)(), whatever*>
+ >::type TaskUnion;
+#else
+ union TaskUnion {
+ void* ptr;
+ std::pair<void(*)(),void*> funcptr;
+ std::pair<void(whatever::*)(), whatever*> memberptr;
+ char any1[sizeof(std::pair<void(*)(),void*>)];
+ char any2[sizeof(std::pair<void(whatever::*)(), whatever*>)];
+ TaskUnion() { /* Nothing to do */}
+ ~TaskUnion() { /* Nothing to do */}
+ };
+#endif
+
+ // Is F suitable for small buffer optimization?
+ template<class F>
+ static constexpr bool canSBO()
+ {
+ return sizeof(F) <= sizeof(TaskUnion) &&
+ alignof(F) <= alignof(TaskUnion);
+ }
+
+ static_assert(canSBO<std::reference_wrapper<whatever>>(),
+ "SBO not working for reference_wrapper");
+
+ // Call (and possibly destroy) the function:
+ typedef R (*call_function)(TaskUnion&, Args...);
+ // Destroy the function (of needed):
+ typedef void (*destroy_function)(TaskUnion&);
+ // Move the function (otherwise memcpy):
+ typedef void (*move_function)(TaskUnion& dest, TaskUnion& src);
+
+ // Vtable of functions for manipulating whatever is in the TaskUnion:
+ struct TaskVtable {
+ call_function call;
+ destroy_function destroy;
+ move_function move;
};
- TaskErasure code_;
- const TaskErasureVtable* vtable_ = nullptr;
+ TaskUnion buffer_;
+ const TaskVtable* vtable_ = nullptr;
+
+ void clear()
+ {
+ if (vtable_ && vtable_->destroy)
+ vtable_->destroy(buffer_);
+ }
public:
- Task() {}
- Task(std::nullptr_t) {}
+ Task() { /* Nothing to do */}
+ explicit Task(std::nullptr_t) { /* Nothing to do */}
~Task()
{
- if (vtable_ && vtable_->destroy)
- vtable_->destroy(code_);
+ this->clear();
}
Task(Task const&) = delete;
- Task& operator=(Task const&) = delete;
Task(Task&& that)
{
- std::memcpy(&code_, &that.code_, sizeof(code_));
+ if (that.vtable_ && that.vtable_->move)
+ that.vtable_->move(buffer_, that.buffer_);
+ else
+ std::memcpy(static_cast<void*>(&buffer_), static_cast<void*>(&that.buffer_), sizeof(buffer_));
+
vtable_ = that.vtable_;
that.vtable_ = nullptr;
}
- Task& operator=(Task&& that)
+ Task& operator=(Task that)
{
- if (vtable_ && vtable_->destroy)
- vtable_->destroy(code_);
- std::memcpy(&code_, &that.code_, sizeof(code_));
+ this->clear();
+ if (that.vtable_ && that.vtable_->move)
+ that.vtable_->move(buffer_, that.buffer_);
+ else
+ std::memcpy(static_cast<void*>(&buffer_), static_cast<void*>(&that.buffer_), sizeof(buffer_));
vtable_ = that.vtable_;
that.vtable_ = nullptr;
return *this;
}
- template<class F,
- typename = typename std::enable_if<bits::isUsableDirectlyInTask<F>()>::type>
- Task(F const& code)
+private:
+
+ template<class F>
+ typename std::enable_if<canSBO<F>()>::type
+ init(F code)
{
- const static TaskErasureVtable vtable {
+ const static TaskVtable vtable {
// Call:
- [](TaskErasure& erasure, Args... args) -> R {
- // We need to wrap F un a union because F might not have a default
- // constructor: this is especially the case for lambdas.
- union no_ctor {
- no_ctor() {}
- ~no_ctor() {}
- F code ;
- } code;
- if (!std::is_empty<F>::value)
- // AFAIU, this is safe as per [basic.types]:
- std::memcpy(&code.code, &erasure.any, sizeof(code.code));
- code.code(std::forward<Args>(args)...);
+ [](TaskUnion& buffer, Args... args) {
+ F* src = reinterpret_cast<F*>(&buffer);
+ F code = std::move(*src);
+ src->~F();
+ return code(std::forward<Args>(args)...);
},
// Destroy:
- nullptr
+ std::is_trivially_destructible<F>::value ?
+ static_cast<destroy_function>(nullptr) :
+ [](TaskUnion& buffer) {
+ F* code = reinterpret_cast<F*>(&buffer);
+ code->~F();
+ },
+ // Move:
+ [](TaskUnion& dst, TaskUnion& src) {
+ F* src_code = reinterpret_cast<F*>(&src);
+ F* dst_code = reinterpret_cast<F*>(&dst);
+ new(dst_code) F(std::move(*src_code));
+ src_code->~F();
+ }
};
- if (!std::is_empty<F>::value)
- std::memcpy(&code_.any, &code, sizeof(code));
+ new(&buffer_) F(std::move(code));
vtable_ = &vtable;
}
- template<class F,
- typename = typename std::enable_if<!bits::isUsableDirectlyInTask<F>()>::type>
- Task(F code)
+ template <class F> typename std::enable_if<not canSBO<F>()>::type init(F code)
{
- const static TaskErasureVtable vtable {
+ const static TaskVtable vtable {
// Call:
- [](TaskErasure& erasure, Args... args) -> R {
+ [](TaskUnion& buffer, Args... args) {
// Delete F when we go out of scope:
- std::unique_ptr<F> code(static_cast<F*>(erasure.ptr));
- (*code)(std::forward<Args>(args)...);
+ std::unique_ptr<F> code(*reinterpret_cast<F**>(&buffer));
+
return (*code)(std::forward<Args>(args)...);
},
// Destroy:
- [](TaskErasure& erasure) {
- F* code = static_cast<F*>(erasure.ptr);
+ [](TaskUnion& buffer) {
+ F* code = *reinterpret_cast<F**>(&buffer);
delete code;
- }
- };
- code_.ptr = new F(std::move(code));
- vtable_ = &vtable;
- }
-
- template<class F>
- Task(std::reference_wrapper<F> code)
- {
- const static TaskErasureVtable vtable {
- // Call:
- [](TaskErasure& erasure, Args... args) -> R {
- F* code = static_cast<F*>(erasure.ptr);
- (*code)(std::forward<Args>(args)...);
},
- // Destroy:
+ // Move:
nullptr
};
- code.code_.ptr = code.get();
+ *reinterpret_cast<F**>(&buffer_) = new F(std::move(code));
vtable_ = &vtable;
}
+public:
+ template <class F> explicit Task(F code) { this->init(std::move(code)); }
+
operator bool() const { return vtable_ != nullptr; }
bool operator!() const { return vtable_ == nullptr; }
R operator()(Args... args)
{
- if (!vtable_)
+ if (vtable_ == nullptr)
throw std::bad_function_call();
- const TaskErasureVtable* vtable = vtable_;
+ const TaskVtable* vtable = vtable_;
vtable_ = nullptr;
- return vtable->call(
code_, std::forward<Args>(args)...);
+ return vtable->call(
buffer_, std::forward<Args>(args)...);
}
};
-> Task< decltype(code(std::move(args)...))() >
{
TaskImpl<F, Args...> task(std::move(code), std::make_tuple(std::move(args)...));
- return std::move(task);
+ return Task<decltype(code(std::move(args)...))()>(std::move(task));
}
}
