add simple libc-based allocat to extend it in future

framework/allocator.cpp

@@ -0,0 +1,54 @@
+/*
+ * allocator.cpp
+ *
+ *  Created on: Jan 28, 2020
+ *      Author: nnosov
+ */
+
+#include <stdlib.h>
+#include <malloc.h>
+
+#include "allocator.h"
+
+void heap_free(pst_allocator& alloc, void* buff)
+{
+    alloc.size -= malloc_usable_size(buff);
+    free(buff);
+}
+
+void* heap_alloc(pst_allocator& alloc, uint32_t size)
+{
+    void* buff = malloc(size);
+    alloc.size += malloc_usable_size(buff);
+
+    return buff;
+}
+
+void* heap_realloc(pst_allocator& alloc, void* buff, uint32_t new_size)
+{
+    alloc.size -= malloc_usable_size(buff);
+    void* new_buff = realloc(buff, new_size);
+    alloc.size += malloc_usable_size(new_buff);
+
+    return new_buff;
+}
+
+void pst_alloc_init(pst_allocator& alloc)
+{
+    alloc.type = ALLOC_HEAP;
+    alloc.base = NULL;
+    alloc.size = 0;
+
+    alloc.alloc = heap_alloc;
+    alloc.free = heap_free;
+    alloc.realloc = heap_realloc;
+
+    return;
+}
+
+void pst_allocator_init_custom(pst_allocator& alloc, void* buff, uint32_t size)
+{
+    // TBD to implement custom allocator
+    return;
+}
+