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/* Copyright (C) 2013 Wildfire Games.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/*
* arena allocator (variable-size blocks, no deallocation).
*/
#ifndef INCLUDED_ALLOCATORS_ARENA
#define INCLUDED_ALLOCATORS_ARENA
#include "lib/allocators/allocator_policies.h"
namespace Allocators {
/**
* allocator design parameters:
* - O(1) allocation;
* - variable-size blocks;
* - support for deallocating all objects;
* - consecutive allocations are back-to-back;
* - no extra alignment nor padding.
**/
template<class Storage = Storage_Fixed<> >
class Arena
{
NONCOPYABLE(Arena);
public:
Arena(size_t maxSize)
: storage(maxSize)
{
DeallocateAll();
}
size_t RemainingBytes() const
{
return storage.MaxCapacity() - end;
}
void* allocate(size_t size)
{
return (void*)StorageAppend(storage, end, size);
}
void deallocate(void* UNUSED(p), size_t UNUSED(size))
{
// ignored
}
void DeallocateAll()
{
end = 0;
}
// @return whether the address lies within the previously allocated range.
bool Contains(uintptr_t address) const
{
return (address - storage.Address()) < end;
}
private:
Storage storage;
size_t end;
};
LIB_API void TestArena();
/**
* allocator design parameters:
* - grow dynamically with a fixed chunkSize
* - for frequent allocations of size << chunkSize
* - no reallocations, pointers remain valid
**/
class DynamicArena
{
struct ArenaChunk
{
bool Available(size_t size) const
{
return size <= (capacity - end);
}
// Must check Available first or this may return an invalid address
uintptr_t Allocate(size_t size)
{
uintptr_t ptr = storage + end;
end += size;
return ptr;
}
uintptr_t storage;
size_t end;
size_t capacity;
ArenaChunk* next;
};
NONCOPYABLE(DynamicArena);
public:
DynamicArena(size_t chunkSize) : chunkSize(chunkSize), head(NULL)
{
AllocateNewChunk();
}
~DynamicArena()
{
ArenaChunk* chunk = head;
while (chunk != NULL)
{
ArenaChunk* next = chunk->next;
free(chunk);
chunk = next;
}
}
void AllocateNewChunk()
{
// For efficiency, do a single allocation with the ArenaChunk and its storage
ArenaChunk* next = head;
head = (ArenaChunk*)malloc(sizeof(ArenaChunk) + chunkSize);
ENSURE(head);
head->storage = sizeof(ArenaChunk) + uintptr_t(head);
head->end = 0;
head->capacity = chunkSize;
head->next = next;
}
void* allocate(size_t size)
{
if (size > chunkSize)
{
debug_warn(L"DynamicArena cannot allocate more than chunk size");
throw std::bad_alloc();
}
else if (!head->Available(size))
AllocateNewChunk();
return (void*)head->Allocate(size);
}
void deallocate(void* UNUSED(p), size_t UNUSED(size))
{
// ignored
}
private:
const size_t chunkSize;
ArenaChunk *head;
};
} // namespace Allocators
#endif // #ifndef INCLUDED_ALLOCATORS_ARENA
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