Add a buddy allocator

src/base/lalloc.h

@@ -0,0 +1,41 @@
+#pragma once
+#include "core.h"
+
+// Internal header added in front of each allocation
+typedef struct LBlockHeader LBlockHeader;
+struct LBlockHeader {
+    U32 next;            // offset from base
+    U32 prev;            // offset from base
+    U32 size_and_flags;  // size | free_bit
+    // Padding to ensure we always return 16 byte aligned pointers.
+    uint8_t pad[4];
+};
+_Static_assert(sizeof(LBlockHeader) == 16, "sizeof(BlockHeader) is not 16");
+
+/**
+ * General purpose allocator from a pre-defined backing store
+ * - Allocated pointers are aligned to 16 bytes.
+ * - Backing buffer must be aligned to 16 bytes
+ * - 4Gb - 16 is max for the allocator backing buffer.
+ * - Allocation of > 0 bytes returns a size aligned up to 16 bytes
+ * - Allocation of 0 bytes returns a valid pointer with 0 usable space
+ * The allocator maintains a doubly linked list of blocks,
+ * when blocks are free'd, adjacent blocks are merged to keep.
+ * This is also known as a buddy allocator
+ * fragmentation to a minimum
+ */
+typedef struct LAlloc LAlloc;
+struct LAlloc {
+    uint8_t *base;              // backing store
+    U32 size;                   // total size
+    LBlockHeader *next_alloc;   // start of free block search
+};
+
+void lalloc_init(LAlloc *allocator, void *backing_store, U32 size);
+
+void *lalloc(LAlloc *allocator, U32 size);
+void lfree(LAlloc *allocator, void *ptr);
+
+LBlockHeader *lblock_from_offset(const LAlloc *allocator, U32 offset);
+U32 lblock_size(const LBlockHeader *block);
+int lblock_is_free(const LBlockHeader *block);