Proper memory commitment

src/arena.h

@@ -7,6 +7,7 @@ typedef U32 ArenaFlags; // no flags defined yets
 typedef struct ArenaParams ArenaParams;
 struct ArenaParams {
     U32 size;
+    U32 commit_size;
     ArenaFlags flags; // No flags defined yet
 };
 
@@ -14,15 +15,17 @@ typedef struct MemoryBlock MemoryBlock;
 struct MemoryBlock {
     U8 *base;
     U32 size;
-    U32 base_pos;     // absolute position of base relative to the first linked arena
     U32 pos;          // start of next allocation
+    U32 base_pos;     // absolute position of base relative to the first linked arena
+    U32 committed_pos;
     MemoryBlock *prev;
 };
 
 typedef struct Arena Arena;
 struct Arena {
     MemoryBlock *current;
-    U32 requested_size;
+    U32 block_size;
+    U32 commit_size;
     ArenaFlags flags;
     S32 checkpoint_level;
 };
@@ -50,7 +53,8 @@ ArenaCheckPoint arena_temp_begin(Arena *arena);
 void arena_temp_end(ArenaCheckPoint *checkpoint);
 void arena_pop_to(Arena *arena, U32 abs_pos);
 void arena_reset(Arena *arena);
-MemoryBlock *memoryblock_allocate(size_t size);
+MemoryBlock *memoryblock_allocate(size_t size, size_t commit_size);
+
 
 static INLINE U32 memoryblock_available(const MemoryBlock *block)
 {