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