1 files changed, 67 insertions, 0 deletions
diff --git a/src/js/builtins/JSBufferConstructor.ts b/src/js/builtins/JSBufferConstructor.ts
new file mode 100644
index 000000000..debc62d51
--- /dev/null
+++ b/src/js/builtins/JSBufferConstructor.ts
@@ -0,0 +1,67 @@
+export function from(items) {
+  if ($isUndefinedOrNull(items)) {
+    throw new TypeError(
+      "The first argument must be one of type string, Buffer, ArrayBuffer, Array, or Array-like Object.",
+    );
+  }
+
+  // TODO: figure out why private symbol not found
+  if (
+    typeof items === "string" ||
+    (typeof items === "object" &&
+      ($isTypedArrayView(items) ||
+        items instanceof ArrayBuffer ||
+        items instanceof SharedArrayBuffer ||
+        items instanceof String))
+  ) {
+    switch ($argumentCount()) {
+      case 1: {
+        return new $Buffer(items);
+      }
+      case 2: {
+        return new $Buffer(items, $argument(1));
+      }
+      default: {
+        return new $Buffer(items, $argument(1), $argument(2));
+      }
+    }
+  }
+
+  var arrayLike = $toObject(
+    items,
+    "The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object.",
+  ) as ArrayLike<any>;
+
+  if (!$isJSArray(arrayLike)) {
+    const toPrimitive = $tryGetByIdWithWellKnownSymbol(items, "toPrimitive");
+
+    if (toPrimitive) {
+      const primitive = toPrimitive.$call(items, "string");
+
+      if (typeof primitive === "string") {
+        switch ($argumentCount()) {
+          case 1: {
+            return new $Buffer(primitive);
+          }
+          case 2: {
+            return new $Buffer(primitive, $argument(1));
+          }
+          default: {
+            return new $Buffer(primitive, $argument(1), $argument(2));
+          }
+        }
+      }
+    }
+
+    if (!("length" in arrayLike) || $isCallable(arrayLike)) {
+      throw new TypeError(
+        "The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object.",
+      );
+    }
+  }
+
+  // Don't pass the second argument because Node's Buffer.from doesn't accept
+  // a function and Uint8Array.from requires it if it exists
+  // That means we cannot use $tailCallFowrardArguments here, sadly
+  return new $Buffer(Uint8Array.from(arrayLike).buffer);
+}