Add allocator interface

src/pool.h

@@ -0,0 +1,26 @@
+#pragma once
+#include "base_core.h"
+
+typedef union APoolElement APoolElement;
+union APoolElement {
+    APoolElement *next;          // offset from start to next free block (when not allocated)
+};
+
+typedef struct APool APool;
+struct APool {
+    APoolElement *free_list;  // free list
+    U8 *start;         // start of user buffer
+    Allocator *allocator;
+    U32 element_size;    // aligned size of each block
+    U32 n_elements;      // total number of blocks
+    U32 align;         // alignment
+};
+enum {
+    APOOL_AUTOGROW = 0
+};
+
+#define apool_create(arena, n_elements, type) \
+        apool_create_ex(arena, n_elements, sizeof(type), alignof(type));
+APool *apool_create_ex(Allocator *allocator, U32 n_elements, U32 element_size, uint32_t element_align);
+void *apool_alloc(APool *pool);
+void apool_free(APool *pool, void *element);