Making the hashing buffer reusable instead of malloc every file

arena.h

@@ -293,7 +293,8 @@ typedef enum arena_commit_policy {
 typedef struct arena_params {
   u64 reserve_size; // size of one arena block
   u64 commit_size;  // initial commit size
-  u64 align;        // allocation alignment (0 = default)
+  u64 align; // allocation alignment, 0 to disable and ARENA_ALIGN to align
+             // according to architecture
 
   // Element size rules:
   // - stack mode        : push_size > 0 (mandatory)