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#include "deimos/core/temp_allocator.h"
#include "deimos/core/api_registry.h"
#include "deimos/core/allocator.h"
#include "deimos/core/os.h"
static deimos::OsApi* os_api;
namespace deimos
{
class TempAllocatorImpl : public ITempAllocator
{
static constexpr int64_t kDefaultAlign = 8;
static constexpr int64_t kPageSize = 1 * Megabytes;
static constexpr int64_t kReserveSize = 256 * Megabytes;
gsl::owner<void*> m_base{};
void* m_commit_end{};
void* m_reserve_end{};
// @Todo Last allocation optimization
void* m_current{};
public:
gsl::owner<void*> Reallocate(TempAllocatorTag tag,
gsl::owner<void*> old_ptr, int64_t old_size, int64_t new_size) override
{
void* tag_ptr = std::bit_cast<void*>(tag.tag);
Expects(tag_ptr >= m_base && tag_ptr <= m_commit_end && tag_ptr <= m_current);
if (new_size <= old_size) { return (new_size == 0) ? nullptr : old_ptr; }
void* new_current = OffsetBytes(m_current, AlignUp(new_size, kDefaultAlign));
if (new_current > m_reserve_end)
{
deimos_Panic("Ran out of temporary memory");
}
if (new_current > m_commit_end)
{
const int64_t new_commit_size = AlignUp(
(int64_t)(std::bit_cast<uintptr_t>(new_current) - std::bit_cast<uintptr_t>(m_base)), // NOLINT
kPageSize);
os_api->virtual_memory->Commit(m_base, new_commit_size);
m_commit_end = OffsetBytes(m_base, new_commit_size);
Ensures(m_commit_end <= m_reserve_end);
}
if (old_ptr != nullptr)
{
MemoryCopy(m_current, old_ptr, old_size);
}
return std::exchange(m_current, new_current);
}
TempAllocator Acquire()
{
if (m_base == nullptr)
{
m_base = os_api->virtual_memory->Reserve(kReserveSize);
m_current = m_base;
m_commit_end = m_base;
m_reserve_end = OffsetBytes(m_base, kReserveSize);
}
return TempAllocator(this, {std::bit_cast<uintptr_t>(m_current)});
}
void Release(TempAllocatorTag tag) override
{
void* rewind_base = std::bit_cast<void*>(tag.tag);
Expects(rewind_base >= m_base && rewind_base <= m_commit_end);
Expects(rewind_base <= m_current);
m_current = rewind_base;
}
};
static thread_local TempAllocatorImpl g_impl;
class TempAllocatorApiImpl : public TempAllocatorApi
{
public:
TempAllocator Acquire() override
{
return g_impl.Acquire();
}
};
void RegisterTempAllocatorApi(ApiRegistry* api_registry)
{
os_api = api_registry->Get<OsApi>();
auto* allocator = api_registry->Get<AllocatorApi>()->system;
gsl::owner<TempAllocatorApi*> temp_allocator_api = allocator->New<TempAllocatorApiImpl>();
api_registry->Set(temp_allocator_api);
}
} // namespace deimos
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