first commit

malloc/Cpp/malloc.cpp

@@ -0,0 +1,131 @@
+#include <cstdlib>
+#include <cstdint>
+
+/* 
+ * Contains functions provided by the operating system
+ */
+namespace OurImaginaryOS
+{
+	/*
+	 * Return 1024byte aligned page of size PAGE_SIZE * pageCount
+	 * e.g. GetNewPage(1) returns a 32MiB page (PAGE_SIZE)
+	 *      GetNewPage(2) returns two contiguous pages, totaling 64MiB
+	 *      GetNewPage(0) is undefined.
+	 */
+	void *GetNewPage(size_t pageCount = 1);
+	void FreePage(void *p);
+
+	const size_t PAGE_SIZE = 32 * 1024 * 1024;
+}
+
+/* IAllocator interface for memory allocations.
+	Example Usage:
+	
+	struct Foo() {
+		IAllocator &mAllocator;
+		MyDynamicObject *mDynamicObject;
+		
+		void Foo(IAllocator &allocator) 
+			: mAllocator(allocator)
+		{
+			mDynamicObject = new(mAllocator.Alloc(sizeof(*mDynamicObject)) MyDynamicObject();
+		}
+		
+		void ~Foo()
+		{
+			mDynamicObject->~MyDynamicObject();
+			mAllocator.Free(mDynamicObject);
+		}
+	}
+*/
+class IAllocator 
+{
+public:
+	// size in bytes
+	// alignment in bytes, 0 means don't care
+	// alignOffset: offset to align returned pointer.  E.g. alignoffset of 4:
+	//   ptr        aligned start point that matches alignment parameter.
+	//    ^         ^
+	//    | 4 bytes |  Rest of block of size "size - alignOffset" |
+	// flags - currently unused
+	virtual void *Alloc(size_t size, size_t alignment = 0, size_t alignOffset = 0, int64_t flags = 0) = 0; 
+	virtual void Free(void *ptr) = 0;
+	
+	virtual ~IAllocator() = default;
+};
+
+using namespace OurImaginaryOS;
+
+class MyAllocator : public IAllocator
+{
+public:
+	MyAllocator()
+	{
+		
+	}
+
+	virtual void *Alloc(size_t size, size_t alignment = 0, size_t alignOffset = 0, int64_t flags = 0)
+	{
+        return nullptr;
+	}
+	
+	virtual void Free(void *ptr)
+	{
+	}
+	
+	virtual ~MyAllocator() 
+	{
+		
+	}
+};
+
+int main()
+{
+	return 0;
+}
+
+/*********************************************************/
+// Stuff to make coding game syntax highlighting work
+// Don't worry about what's below here.
+
+#include <vector>
+#include <mutex>
+
+namespace OurImaginaryOS
+{
+	static std::mutex s_internalPagesLock;
+	static std::vector<void *> s_internalPages;
+	
+	void *GetNewPage(size_t pageCount)
+	{
+		void *newPage = malloc(PAGE_SIZE * pageCount);
+		
+		s_internalPagesLock.lock();
+		s_internalPages.push_back(newPage);
+		s_internalPagesLock.unlock();
+		
+		return newPage;
+	}
+	
+	void FreePage(void *p)
+	{
+		void *toFree = nullptr;
+		
+		s_internalPagesLock.lock();
+		for (auto iter = s_internalPages.begin(); iter != s_internalPages.end(); iter++)
+		{
+			if (*iter == p)
+			{
+				toFree = p;
+				s_internalPages.erase(iter);
+				break;
+			}
+		}
+		s_internalPagesLock.unlock();
+		
+		if (toFree)
+		{
+			free(p);
+		}
+	}
+}