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Refs.mqh
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Refs.mqh
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//+------------------------------------------------------------------+
//| EA31337 framework |
//| Copyright 2016-2019, 31337 Investments Ltd |
//| https://github.com/EA31337 |
//+------------------------------------------------------------------+
/*
* This file is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
*/
// Prevents processing this includes file for the second time.
#ifndef REFS_MQH
#define REFS_MQH
// Includes.
#include "Refs.struct.h"
/**
* For explanation about difference between strong(Ref) and weak(WeakRef) references please look at:
* @see https://medium.com/@elliotchance/strong-vs-weak-references-70356d37dfd2
*
*
*
* Usage:
*
* class Node : public Dynamic {
*
* protected:
*
* WeakRef<Node> parentNode;
* Dict<Ref<Node>> childNodes;
*
* public:
*
* void AddChild(Node* _node) {
* _node.parentNode = this;
*
* Ref<Node> ref = _node;
* childNodes.Push(ref);
* }
* };
*
*
* Ref<Node> root = new Node();
*
* Ref<Node> child1 = new Node();
* Ref<Node> child2 = new Node();
*
* root.childNodes.Push(child1);
* root.childNodes.Push(child2);
*/
// Forward class declaration.
class Dynamic;
class ReferenceCounter {
public:
/**
* Number of weak references to target object.
*/
unsigned int num_weak_refs;
/**
* Number of strong references to target object.
*/
unsigned int num_strong_refs;
/**
* Target object pointer.
*/
Dynamic* ptr_object;
/**
* Whether object has been deleted (but still have weak references).
*/
bool deleted;
/**
* Constructor.
*/
ReferenceCounter() {
num_weak_refs = 0;
num_strong_refs = 0;
ptr_object = NULL;
deleted = false;
}
/**
* ReferenceCounter class allocator.
*/
static ReferenceCounter* alloc() {
// @todo Enhance with linked-list object reuse.
return new ReferenceCounter();
}
};
/**
* Base class for reference-counted objects.
*/
class Dynamic {
public:
/**
* Pointer to object holding reference counts.
*/
ReferenceCounter* ptr_ref_counter;
/**
* Constructor.
*/
Dynamic() {
if (CheckPointer(&this) == POINTER_DYNAMIC) {
// Only dynamic objects are reference-counted.
ptr_ref_counter = ReferenceCounter::alloc();
ptr_ref_counter.ptr_object = &this;
} else {
// For objects allocated on the stack we don't use reference counting.
ptr_ref_counter = NULL;
}
}
/**
* Destructor.
*/
~Dynamic() {
if (CheckPointer(ptr_ref_counter) == POINTER_DYNAMIC && ptr_ref_counter.num_strong_refs == 0 &&
ptr_ref_counter.num_weak_refs == 0) {
// Object never been referenced.
if (ptr_ref_counter != NULL) {
delete ptr_ref_counter;
}
}
}
Dynamic(const Dynamic& right) {
ptr_ref_counter = NULL;
if (CheckPointer(&this) != POINTER_DYNAMIC && CheckPointer(&right) == POINTER_DYNAMIC) {
Print(
"Dynamic object misuse: Invoking copy constructor: STACK OBJECT = HEAP OBJECT. Remember that you can only "
"assign heap-allocated objects to heap-allocated objects!");
}
}
void operator=(const Dynamic& right) {
if (right.ptr_ref_counter != NULL /*&& CheckPointer(&right) == POINTER_DYNAMIC*/) {
Print(
"Dynamic class misuse: Invoking assignment operator for stack object with heap-allocated object on the right "
"side.");
}
}
};
#endif