start implementing in ts

shim.ts

@@ -0,0 +1,66 @@
+DataView.prototype.add = function (offset) {
+  return new DataView(this.buffer, offset);
+};
+DataView.prototype.writeU8 = function (val) {
+  return this.setUint8(0, val);
+};
+DataView.prototype.writeU16 = function (val) {
+  return this.setUint16(0, val);
+};
+DataView.prototype.writeU32 = function (val) {
+  return this.setUint32(0, val);
+};
+DataView.prototype.writeU64 = function (val) {
+  return this.setUint64(0, val);
+};
+DataView.prototype.readU8 = function () {
+  return this.getUint8(0);
+};
+DataView.prototype.readU16 = function () {
+  return this.getUint16(0);
+};
+DataView.prototype.readU32 = function () {
+  return this.getUint32(0);
+};
+DataView.prototype.readU64 = function () {
+  return this.getUint64(0);
+};
+const isDataView = (x: DataView | number[]): x is DataView => {
+  return x instanceof DataView;
+};
+
+DataView.prototype.writeByteArray = function (arr) {
+  const len = isDataView(arr) ? arr.byteLength : arr.length;
+  for (let i = 0; i < len; i++) {
+    this.setUint8(i, arr[i]);
+  }
+};
+DataView.prototype.readByteArray = function (len) {
+  let ret = new DataView(new ArrayBuffer(len));
+  for (let i = 0; i < len; i++) {
+    ret.setUint8(i, this.getUint8(i));
+  }
+  return ret;
+};
+
+const Memory = {
+  alloc: (len: number) => new DataView(new ArrayBuffer(len + 1)),
+  copy: (outbuf: DataView, inbuf: DataView, len: number) => outbuf.writeByteArray(inbuf.readByteArray(len)),
+};
+
+declare global {
+  interface DataView {
+    add(offset: number): DataView;
+    readByteArray(len: number): DataView;
+    readU16(): undefined;
+    readU32(): undefined;
+    readU64(): undefined;
+    readU8(): undefined;
+    writeByteArray(arr: DataView | number[]): undefined;
+    writeU16(n: number): undefined;
+    writeU32(n: number): undefined;
+    writeU64(n: number): undefined;
+    writeU8(n: number): undefined;
+  }
+}
+export default global;