New repo setup

src/memory/pageallocator.h

@@ -0,0 +1,116 @@
+/**
+ * Author: Nathan Giddings
+ * 
+ * Code adapted from personal project: https://github.com/ngiddings/quark-libmalloc/blob/master/include/libmalloc/buddy_alloc.h
+ */
+#ifndef PAGE_ALLOCATOR_H
+#define PAGE_ALLOCATOR_H
+
+#include "memorymap.h"
+#include "types/physaddr.h"
+
+namespace kernel::memory
+{
+
+/**
+ * @brief Manages the reservation and freeing of physical memory pages.
+ */
+class PageAllocator
+{
+public:
+
+    static const physaddr_t NOMEM = (physaddr_t)(~0);
+
+    static unsigned long mapSize(MemoryMap& map, unsigned long blockSize);
+
+    PageAllocator();
+
+    /**
+     * @brief Constructs the page allocator's internal data structures from an
+     * existing description of the memory layout.
+     * 
+     * @param map a description of the physical memory layout
+     * @param mapBase location
+     * @param blockSize the size in bytes of a single block of memory
+     */
+    PageAllocator(MemoryMap& map, void *mapBase, unsigned long blockSize);
+
+    /**
+     * @brief Reserves a chunk of memory at least `size` bytes long. The
+     * reserved physical memory will be contiguous; therefore, the allocator
+     * can potentially fail due to fragmentation.
+     * 
+     * @param size the minimum number of bytes to reserve
+     * @return the physical address of the newly allocated chunk of memory, or
+     * NOMEM upon failure.
+     */
+    physaddr_t reserve(unsigned long size);
+
+    /**
+     * @brief 
+     * @param location 
+     * @return 
+     */
+    unsigned long free(physaddr_t location);
+
+private:
+
+    class Block
+    {
+    public:
+
+        static const unsigned long RESERVED = 0;
+
+        static const unsigned long FREE = 1;
+
+        Block();
+        
+        Block(Block *linkf, Block *linkb, unsigned long kval, unsigned long tag);
+
+        Block *linkb;
+
+        Block *linkf;
+
+        unsigned long kval;
+
+        unsigned long tag;
+
+    };
+
+    /**
+     * @brief The number of distinct block sizes that are supported. Serves
+     * as the maximum possible value of `maxKVal`, and defines the size of
+     * the largest possible block: (2 ^ (availListSize-1)) * blockSize.
+     */
+    static const int availListSize = 32;
+
+    Block availList[availListSize];
+
+    Block *blockMap;
+
+    unsigned long blockMapSize;
+
+    unsigned long maxKVal;
+
+    unsigned long blockSize;
+
+    unsigned long offset;
+
+    unsigned long freeBlockCount;
+
+    /**
+     * @brief Inserts a new block into the appropriate linked list, performing
+     * mergers with buddy blocks as needed.
+     * 
+     * @param index 
+     * @param k 
+     */
+    void insert(unsigned long index, unsigned long k);
+
+};
+
+extern PageAllocator pageAllocator;
+
+}
+
+#endif