1 files changed, 90 insertions, 0 deletions
diff --git a/src/allocator.cc b/src/allocator.cc
new file mode 100644
index 0000000..77736cc
--- /dev/null
+++ b/src/allocator.cc
@@ -0,0 +1,90 @@
+#include "allocator.h"
+
+static MemoryAllocator* mem_alloc = nullptr;
+
+MemoryAllocator::MemoryAllocator(uint32_t start, size_t size) {
+  if (size < sizeof(MemoryChunk)) {
+    begin = nullptr;
+    return;
+  }
+  begin = new (reinterpret_cast<void*>(start)) MemoryChunk{.size = static_cast<size_t>(size - sizeof(MemoryChunk))};
+  if (mem_alloc == nullptr) mem_alloc = this;
+}
+
+void* MemoryAllocator::malloc(size_t size) {
+  // TODO spinlock
+  // TODO memset 0 over allocated memory
+  MemoryChunk* result = nullptr;
+
+  // find the first chunk that is at least size and not allocated
+  for (auto* iter = begin; iter != nullptr; iter = iter->next) {
+    if (iter->size >= size && !iter->allocated) {
+      result = iter;
+
+      // split chunk if there is at least one byte left over
+      if (result->size >= size + sizeof(MemoryChunk) + 1) {
+        auto* _new = new (result + sizeof(MemoryChunk) + size) MemoryChunk{
+            .prev = result, .next = result->next, .size = static_cast<size_t>(result->size - sizeof(MemoryChunk))};
+        result->next = _new;
+      }
+
+      break;
+    }
+  }
+
+  return result + sizeof(MemoryChunk);
+}
+void MemoryAllocator::free(void* ptr) {
+  auto* chunk = reinterpret_cast<MemoryChunk*>(reinterpret_cast<uint32_t>(ptr) - sizeof(MemoryChunk));
+  chunk->allocated = false;
+
+  // merge in next chunk
+  if (chunk->next != nullptr && !chunk->next->allocated) {
+    chunk->size += chunk->next->size + sizeof(MemoryChunk);
+    chunk->next = chunk->next->next;
+    if (chunk->next != nullptr) chunk->next->prev = chunk;
+  }
+
+  // merge into previous chunk
+  if (chunk->prev != nullptr && !chunk->prev->allocated) {
+    chunk->prev->size += chunk->size + sizeof(MemoryChunk);
+    chunk->prev->next = chunk->next;
+    if (chunk->next != nullptr) chunk->next->prev = chunk->prev;
+  }
+};
+
+size_t MemoryAllocator::free_space() const {
+  size_t r = 0;
+  for (auto* iter = begin; iter != nullptr; iter = iter->next)
+    if (!iter->allocated) r += iter->size;
+  return r;
+}
+size_t MemoryAllocator::used_space() const {
+  size_t r = 0;
+  for (auto* iter = begin; iter != nullptr; iter = iter->next)
+    if (iter->allocated) r += iter->size;
+  return r;
+}
+
+void* operator new(unsigned sz, const std::nothrow_t&) noexcept {
+  if (mem_alloc == nullptr) return nullptr;
+  return mem_alloc->malloc(sz);
+}
+void* operator new[](unsigned sz, const std::nothrow_t&) noexcept {
+  if (mem_alloc == nullptr) return nullptr;
+  return mem_alloc->malloc(sz);
+}
+
+void operator delete(void* ptr) {
+  if (mem_alloc != nullptr) mem_alloc->free(ptr);
+}
+void operator delete[](void* ptr) {
+  if (mem_alloc != nullptr) mem_alloc->free(ptr);
+}
+
+void* operator new(unsigned /* size_bytes */, void* ptr) {
+  return ptr;
+}
+void* operator new[](unsigned /* size_bytes */, void* ptr) {
+  return ptr;
+}