directize

std/assembly/util/runtime.ts

@@ -0,0 +1,36 @@
+import { AL_MASK, MAX_SIZE_32 } from "./allocator";
+
+/**
+ * The common runtime object header prepended to all managed objects. Has a size of 16 bytes in
+ * WASM32 and contains a classId (e.g. for instanceof checks), the allocation size (e.g. for
+ * .byteLength and .length computation) and additional reserved fields to be used by GC. If no
+ * GC is present, the HEADER is cut into half excluding the reserved fields, as indicated by
+ * HEADER_SIZE.
+*/
+@unmanaged export class HEADER {
+  /** Unique id of the respective class or a magic value if not yet registered.*/
+  classId: u32;
+  /** Size of the allocated payload. */
+  payloadSize: u32;
+  /** Reserved field for use by GC. Only present if GC is. */
+  reserved1: usize; // itcm: tagged next
+  /** Reserved field for use by GC. Only present if GC is. */
+  reserved2: usize; // itcm: prev
+}
+
+/** Common runtime header size. */
+// @ts-ignore: decorator
+@lazy
+export const HEADER_SIZE: usize = isDefined(__ref_collect)
+  ? (offsetof<HEADER>(           ) + AL_MASK) & ~AL_MASK  // full header if GC is present
+  : (offsetof<HEADER>("reserved1") + AL_MASK) & ~AL_MASK; // half header if GC is absent
+
+/** Common runtime header magic. Used to assert registered/unregistered status. */
+// @ts-ignore: decorator
+@lazy
+export const HEADER_MAGIC: u32 = 0xA55E4B17;
+
+/** Maximum byte length of any buffer-like object. */
+// @ts-ignore
+@lazy
+export const MAX_BYTELENGTH: i32 = MAX_SIZE_32 - HEADER_SIZE;