Writing more real program and squashing bugs

base.kl

@@ -1,12 +1,47 @@
 #import "Windows.kl"
 
+SizeU :: #strict U64
+OS_PAGE_SIZE :: 4096
+
 OS_Memory :: struct
-  commit : U64
-  reserve: U64
+  commit : SizeU
+  reserve: SizeU
   data   : *U8
 
 Arena :: struct
   memory: OS_Memory
   alignment: U64
-  len: U64
+  len: SizeU
+
+get_align_offset :: (size: SizeU, align: SizeU): SizeU
+  mask := align - 1
+  val  := size & mask
+  if val != 0
+    val = align - val
+  return val
+
+align_up :: (size: SizeU, align: SizeU): SizeU
+  result := size + get_align_offset(size, align)
+  return result
+
+reserve :: (size: SizeU): OS_Memory
+  result := OS_Memory{reserve=align_up(size, OS_PAGE_SIZE)}
+  result.data = VirtualAlloc(0, result.reserve, MEM_RESERVE, PAGE_READWRITE)->*U8
+  return result
+
+clamp_top_sizeu :: (val: SizeU, max: SizeU): SizeU
+  if val > max
+    return max
+  return val
+
+commit :: (m: *OS_Memory, size: SizeU): Bool
+  commit_size := align_up(size, OS_PAGE_SIZE)
+  total_commit := m.commit + commit_size
+  clamped_commit := clamp_top_sizeu(total_commit, m.reserve)
+  adjusted_commit := clamped_commit - m.commit
+  if adjusted_commit != 0
+    result := VirtualFree(m.data->*void, 0, MEM_RELEASE)
+    m.commit += adjusted_commit
+    return true
+  return false