Rename heap to memory; Allocator strategies

std/assembly/memory.ts

@@ -1,24 +1,4 @@
-const ALIGN_LOG2: usize = 3;
-const ALIGN_SIZE: usize = 1 << ALIGN_LOG2;
-const ALIGN_MASK: usize = ALIGN_SIZE - 1;
-
-var HEAP_OFFSET: usize = HEAP_BASE; // HEAP_BASE is a constant generated by the compiler
-
-export function allocate_memory(size: usize): usize {
-  if (!size) return 0;
-  var len: i32 = current_memory();
-  if (HEAP_OFFSET + size > <usize>len << 16)
-    if(grow_memory(max<i32>(<i32>ceil<f64>(<f64>size / 65536), len * 2 - len)) < 0)
-      unreachable();
-  var ptr: usize = HEAP_OFFSET;
-  if ((HEAP_OFFSET += size) & ALIGN_MASK) // align next offset
-    HEAP_OFFSET = (HEAP_OFFSET | ALIGN_MASK) + 1;
-  return ptr;
-}
-
-export function free_memory(ptr: usize): void {
-  // just a big chunk of non-disposable memory for now
-}
+import "std:memory/arena";
 
 function copy_memory(dest: usize, src: usize, n: usize): void {
   // based on musl's implementation of memcpy

std/assembly/memory/arena.ts

@@ -0,0 +1,30 @@
+// An simple arena allocator that provides a `clear_memory` function to reset
+// everything to the initial state. A user must have to make sure that there
+// a no more references to cleared memory.
+
+const ALIGN_LOG2: usize = 3;
+const ALIGN_SIZE: usize = 1 << ALIGN_LOG2;
+const ALIGN_MASK: usize = ALIGN_SIZE - 1;
+
+var HEAP_OFFSET: usize = HEAP_BASE; // generated by the compiler
+
+export function allocate_memory(size: usize): usize {
+  if (!size) return 0;
+  var len: i32 = current_memory();
+  if (HEAP_OFFSET + size > <usize>len << 16)
+    if(grow_memory(max<i32>(<i32>ceil<f64>(<f64>size / 65536), len * 2 - len)) < 0)
+      unreachable();
+  var ptr: usize = HEAP_OFFSET;
+  if ((HEAP_OFFSET += size) & ALIGN_MASK) // align next offset
+    HEAP_OFFSET = (HEAP_OFFSET | ALIGN_MASK) + 1;
+  set_memory(ptr, 0, size);
+  return ptr;
+}
+
+export function free_memory(ptr: usize): void {
+  // nop
+}
+
+export function clear_memory(): void {
+  HEAP_OFFSET = HEAP_BASE;
+}