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#include "SimpleMalloc.h"
#include "Assertions.h"
#include "Types.h"
#include <sys/mman.h>
#include <cstring>
#include <cstdio>
namespace SimpleMalloc {
class AllocationBitmap {
public:
static AllocationBitmap wrap(byte* data, unsigned size)
{
return AllocationBitmap(data, size);
}
~AllocationBitmap()
{
}
unsigned size() const { return m_size; }
bool get(unsigned index) const
{
ASSERT(index < m_size);
return 0 != (m_data[index / 8] & (1u << (index % 8)));
}
void set(unsigned index, bool value) const
{
ASSERT(index < m_size);
if (value)
m_data[index / 8] |= static_cast<byte>((1u << (index % 8)));
else
m_data[index / 8] &= static_cast<byte>(~(1u << (index % 8)));
}
private:
AllocationBitmap(byte* data, unsigned size)
: m_data(data)
, m_size(size)
{
}
byte* m_data { nullptr };
unsigned m_size { 0 };
};
template<dword chunkSize>
class ChunkAllocator {
public:
void initialize(byte* base)
{
m_base = base;
m_free = capacity_in_allocations();
dump();
}
static constexpr dword capacity_in_allocations()
{
return 1048576 / chunkSize;
}
static constexpr dword capacity_in_bytes()
{
return capacity_in_allocations() * chunkSize;
}
byte* allocate()
{
auto bitmap = this->bitmap();
for (dword i = 0; i < capacity_in_allocations(); ++i) {
if (!bitmap.get(i)) {
bitmap.set(i, true);
--m_free;
return pointer_to_chunk(i);
}
}
return nullptr;
}
void dump() const
{
printf("ChunkAllocator<%u> @ %p, free: %u\n", chunkSize, m_base, m_free);
}
void free(byte* ptr)
{
ASSERT(is_in_allocator(ptr));
auto bitmap = this->bitmap();
auto chunk_index = chunk_index_from_pointer(ptr);
ASSERT(bitmap.get(chunk_index));
bitmap.set(chunk_index, false);
++m_free;
}
bool is_in_allocator(byte* ptr)
{
return ptr >= pointer_to_chunk(0) && ptr <= address_after_this_allocator();
}
dword chunk_index_from_pointer(byte* ptr)
{
return (ptr - pointer_to_chunk(0)) / chunkSize;
}
byte* pointer_to_chunk(dword index)
{
return m_base + size_of_allocation_bitmap_in_bytes() + (index * chunkSize);
}
AllocationBitmap bitmap()
{
return AllocationBitmap::wrap(m_base, capacity_in_allocations());
}
static constexpr dword size_of_allocation_bitmap_in_bytes()
{
return capacity_in_allocations() / 8;
}
byte* address_after_this_allocator() const
{
return m_base + size_of_allocation_bitmap_in_bytes() + capacity_in_bytes();
}
dword number_of_free_chunks() const
{
return m_free;
}
private:
byte* m_base { nullptr };
dword m_free { capacity_in_allocations() };
};
struct Allocator {
void initialize();
void initialize_if_needed();
void dump();
ChunkAllocator<8> alloc8;
ChunkAllocator<16> alloc16;
ChunkAllocator<4096> alloc4096;
ChunkAllocator<16384> alloc16384;
byte* space;
bool initialized { false };
};
static Allocator allocator;
void Allocator::initialize_if_needed()
{
if (initialized)
return;
initialize();
initialized = true;
}
void Allocator::initialize()
{
space = (byte*)mmap((void*)0x20000000, 32 * MB, PROT_WRITE | PROT_READ | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
ASSERT(space != MAP_FAILED);
alloc8.initialize(space + 0x10000);
alloc16.initialize(alloc8.address_after_this_allocator());
alloc4096.initialize(alloc16.address_after_this_allocator());
alloc16384.initialize(alloc4096.address_after_this_allocator());
}
void Allocator::dump()
{
alloc8.dump();
alloc16.dump();
alloc4096.dump();
alloc16384.dump();
}
void initialize()
{
allocator.initialize();
}
void dump()
{
allocator.dump();
}
byte* allocate(dword size)
{
if (!size)
return nullptr;
allocator.initialize_if_needed();
if (size <= 8) {
if (auto* ptr = allocator.alloc8.allocate())
return ptr;
}
if (size <= 16) {
if (auto* ptr = allocator.alloc16.allocate())
return ptr;
}
if (size <= 4096) {
if (auto* ptr = allocator.alloc4096.allocate())
return ptr;
}
if (size <= 16384) {
if (auto* ptr = allocator.alloc16384.allocate())
return ptr;
}
printf("SimpleMalloc: unsupported alloc size: %u\n", size);
ASSERT_NOT_REACHED();
return nullptr;
}
byte* allocate_zeroed(dword size)
{
auto* ptr = allocate(size);
if (!ptr)
return nullptr;
memset(ptr, 0, size);
return ptr;
}
byte* reallocate(byte* ptr, dword size)
{
// FIXME;
(void) ptr;
(void) size;
ASSERT_NOT_REACHED();
return nullptr;
}
void free(byte* ptr)
{
if (!ptr)
return;
allocator.initialize_if_needed();
if (allocator.alloc8.is_in_allocator(ptr)) {
allocator.alloc8.free(ptr);
return;
}
if (allocator.alloc16.is_in_allocator(ptr)) {
allocator.alloc16.free(ptr);
return;
}
if (allocator.alloc4096.is_in_allocator(ptr)) {
allocator.alloc4096.free(ptr);
return;
}
if (allocator.alloc16384.is_in_allocator(ptr)) {
allocator.alloc16384.free(ptr);
return;
}
ASSERT_NOT_REACHED();
}
}
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