template<typename Type>
class Grid
{
public:
Grid() : memory(nullptr)
{ }
//Construct and call Resize().
Grid(const cRect &newBounds, const Type &value = Type()) : memory(nullptr)
{
this->Resize(newBounds, value);
}
~Grid()
{
//Clear the grid, calling the destructors on any constructed elements.
this->Clear();
//Deallocate any reserved memory.
this->deallocate(this->memory);
}
//Erases the grid, resetting the bounds to (0,0,0,0).
//Does not free the reserved capacity. Call Conserve() afterward to do that.
void Clear()
{
this->Resize(cRect(0,0,0,0));
}
//================================================================
//Resizes the grid to 'newBounds', constructing the new elements with 'value' (or the default constructor if 'value' is not set).
//If Grid doesn't have enough capacity, it'll reallocate storage and move the elements to new memory addresses.
//Throws std::bad_alloc if the allocation failed, and rethrows any exceptions thrown by element constructors or destructors.
void Resize(const cRect &newBounds, const Type &value = Type())
{
try
{
//[CAN THROW - Make sure no member variables are changed before these function calls]
cRect newCapacity = this->ensureCapacity(newBounds, true);
//[CAN THROW - Make sure no member variables are changed before these function calls]
this->constructAdditions(this->bounds, newBounds, value);
//Record the new capacity, after we are sure no exceptions were thrown and everything succeeded.
this->capacity = newCapacity;
}
catch(std::exception &exception)
{
Log::Message("...blah..."); //exception.what()
throw;
}
catch(...)
{
Log::Message("...blah..."); //Unknown exception
throw;
}
this->bounds = newBounds;
}
//================================================================
private:
//Constructs all the new elements between oldBounds and newBounds setting them to 'value'.
//If 'newBounds' is smaller than 'oldBounds', deconstructs the old elements.
void constructAdditions(const cRect &oldBounds, const cRect &newBounds, const Type &value = Type())
{
//The largest extent of both rects.
cRect totalArea = cRect::Encompassing(oldBounds, newBounds);
//The overlapping portion of both rects (if any).
cRect reducedArea = cRect::Intersection(oldBounds, newBounds);
//-------------------------------------------
//If a constructor throws an exception, we want to know which element it was,
//so we keep track of what the last point was before the exception was thrown.
cPoint lastPoint;
try
{
for(cPoint point : newBounds)
{
if(reducedArea.Contains(point))
{
//Do nothing - this area is already constructed.
}
else
{
lastPoint = point;
//Needs to be constructed.
this->construct((*this)[point], value);
}
}
}
catch(...)
{
//Since we caught an exception, destruct every element we had previously constructed.
for(cPoint point : newBounds)
{
if(reducedArea.Contains(point))
{
//Do nothing - this area is already constructed.
}
else if(point == lastPoint)
{
//Stop here - we didn't construct anything beyond this element.
break;
}
else
{
//Destruct the element we previously constructed.
this->destruct((*this)[point]);
}
}
throw;
}
//-------------------------------------------
//Destruct any elements that we no longer want (if we're resizing smaller than our previous size).
for(cPoint point : oldBounds)
{
if(reducedArea.Contains(point))
{
//Do nothing - we're preserving these elements.
}
else
{
//Needs to be destructed.
this->destruct((*this)[point]);
}
}
}
//================================================================
//Construct a single element.
void construct(Type &element, const Type &value = Type())
{
new (&element) Type(value); //Call constructor.
}
//Constructs an element with move semantics.
void moveConstruct(Type &element, Type &&value)
{
new (&element) Type(value); //Call move constructor.
}
//Destruct a single element.
void destruct(Type &element)
{
element.~Type(); //Call destructor.
}
//================================================================
//Ensures *at least* enough room for 'bounds'. Returns the resulting capacity.
//If 'addExtra' is true, includes even more capacity for future growth.
cRect ensureCapacity(const cRect &bounds, bool addExtra)
{
//Check whether we have enough capacity to resize.
if(!this->capacity.Contains(bounds))
{
cRect desiredCapacity = bounds;
if(addExtra)
{
//If we're bothering to grow in size, we might as well reserve a little extra for future growth.
int quarterWidth = (bounds.size.width / 4) + 1;
int quarterHeight = (bounds.size.height / 4) + 1;
desiredCapacity.Pad(quarterWidth, quarterWidth, quarterHeight, quarterHeight);
}
//Allocate and move the elements.
//[CAN THROW - Make sure no member variables are changed before this function call]
this->reallocateMemory(desiredCapacity);
//Return the new capacity.
return desiredCapacity;
}
//Return the current capacity.
return this->capacity;
}
//================================================================
//This allocates enough memory for 'capacity', without constructing any elements.
Type *allocate(const cRect &capacity)
{
//Allocate the new memory.
size_t numElements = capacity.size.Area();
size_t numBytes = (sizeof(Type) * numElements);
void *data = ::operator new(numBytes);
return static_cast<Type*>(data);
}
//This deallocates 'memory', without calling any destructors.
void deallocate(Type *data)
{
::operator delete(data);
}
//================================================================
//Reallocates the memory and migrates the elements over using moveElements().
//Throws std::bad_alloc if the allocation failed, and throws any exceptions thrown by element constructors.
void reallocateMemory(const cRect &newCapacity)
{
if(!this->memory)
{
//If we don't have any memory, just allocate some and don't worry about moving any elements.
//[CAN THROW - Make sure no member variables are changed before this function call]
this->memory = this->allocate(newCapacity);
}
else if(newCapacity.IsEmpty())
{
//Free all the memory.
this->deallocate(this->memory);
this->memory = nullptr;
}
else
{
//Allocate the new memory.
//Note: I put the allocated memory into a unique_ptr here, incase moveElements() throws.
//This way, the new memory is properly released.
//[CAN THROW - Make sure no member variables are changed before this function call]
std::unique_ptr<Type, use_operator_delete> newMemory = this->allocate(newCapacity);
//A few extra variables for readability.
Type *oldMemory = this->memory;
const cRect &oldCapacity = this->capacity;
//Move the elements.
//[CAN THROW - Make sure no member variables are changed before this function call]
this->moveElements(oldMemory, oldCapacity, newMemory.get(), newCapacity, this->bounds);
//Delete the old memory.
this->deallocate(oldMemory);
//And store the new pointer. Have the unique_ptr release ownership of the memory as well.
this->memory = newMemory.release();
}
//Record the new capacity.
this->capacity = newCapacity;
}
//Called by 'reallocateMemory' only.
void moveElements(Type *oldMemory, const cRect &oldCapacity, Type *newMemory,
const cRect &newCapacity, const cRect &bounds)
{
//Insanity preservation.
//Assert that our elements are actually within the capacity of both the new and old blocks of memory.
BOOST_ASSERT(oldCapacity.Contains(bounds));
BOOST_ASSERT(newCapacity.Contains(bounds));
//Assert that neither block of memory's size is empty (they have to have a positive non-zero width and height).
BOOST_ASSERT(!oldCapacity.IsEmpty());
BOOST_ASSERT(!newCapacity.IsEmpty());
//Assert that neither pointer to the allocated memory is empty.
BOOST_ASSERT(oldMemory != nullptr);
BOOST_ASSERT(newMemory != nullptr);
//The length of each 'row' of the grid's capacity in memory.
size_t oldStride = oldCapacity.size.width;
size_t newStride = newCapacity.size.width;
//The initial offset of the actual bounds from the memory capacity.
size_t oldOffset = oldCapacity.Index(bounds.position);
size_t newOffset = newCapacity.Index(bounds.position);
//The number of rows and columns of actual elements we need to move.
size_t rows = bounds.size.height;
size_t columns = bounds.size.width;
//=================================================================
//Incase a constructor throws an exception, keep track of the last row and column.
size_t lastRow = 0;
size_t lastColumn = 0;
try
{
//Move-construct all the new elements.
for(size_t row = 0; row < rows; lastRow = row++)
{
for(size_t column = 0; column < columns; lastColumn = column++)
{
size_t oldIndex = (row * oldStride) + column;
oldIndex += oldOffset;
size_t newIndex = (row * newStride) + column;
newIndex += newOffset;
//Construct the new location, and move the element.
this->moveConstruct(newMemory[newIndex], std::move(oldMemory[oldIndex]));
}
}
}
catch(...)
{
//Since we just caught an exception thrown from one of the element move-constructors,
//destruct all the new elements we just constructed, up until the failed constructor.
for(size_t row = 0; row < lastRow; row++)
{
for(size_t column = 0; column < lastColumn; column++)
{
size_t newIndex = (row * newStride) + column;
newIndex += newOffset;
//Destruct the element we constructed in the previous for() loops.
this->destruct(newMemory[newIndex]);
}
}
throw;
}
//=================================================================
//Destruct all the old elements.
for(size_t row = 0; row < rows; row++)
{
for(size_t column = 0; column < columns; column++)
{
size_t oldIndex = (row * oldStride) + column;
oldIndex += oldOffset;
//Destruct old location.
this->destruct(oldMemory[oldIndex]);
}
}
}
//================================================================
private:
Type *memory;
cRect bounds; //Current grid boundaries.
cRect capacity; //Currently allocated memory capacity, guaranteed to be at least 'bounds' and maybe larger.
};