From 1b5361546c2eb1b39be984a919e1fbaa1eb958cf Mon Sep 17 00:00:00 2001
From: Joshua Chen <sidachen2003@gmail.com>
Date: Fri, 7 Jun 2024 17:35:17 +0800
Subject: [PATCH] Use DataView to access WebAssembly memory (#37)

Accompanying https://github.com/mdn/content/pull/33960

---------

Co-authored-by: Hamish Willee <hamishwillee@gmail.com>
---
 js-api-examples/memory.html                  | 12 ++++++------
 understanding-text-format/memory-export.html |  9 +++++----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/js-api-examples/memory.html b/js-api-examples/memory.html
index 1a57c7a..e11ef1f 100644
--- a/js-api-examples/memory.html
+++ b/js-api-examples/memory.html
@@ -11,14 +11,14 @@
     <script>
       const memory = new WebAssembly.Memory({
         initial: 10,
-        maximum: 100
+        maximum: 100,
       });
-
-      WebAssembly.instantiateStreaming(fetch("memory.wasm"), { js: { mem: memory } })
-      .then(obj => {
-        const summands = new Uint32Array(memory.buffer);
+      WebAssembly.instantiateStreaming(fetch("memory.wasm"), {
+        js: { mem: memory },
+      }).then((obj) => {
+        const summands = new DataView(memory.buffer);
         for (let i = 0; i < 10; i++) {
-          summands[i] = i;
+          summands.setUint32(i * 4, i, true); // WebAssembly is little endian
         }
         const sum = obj.instance.exports.accumulate(0, 10);
         console.log(sum);
diff --git a/understanding-text-format/memory-export.html b/understanding-text-format/memory-export.html
index 6116386..f638cd5 100644
--- a/understanding-text-format/memory-export.html
+++ b/understanding-text-format/memory-export.html
@@ -10,11 +10,12 @@
     <script>
       WebAssembly.instantiateStreaming(fetch("memory-export.wasm")).then(
         (object) => {
-          const values = new Uint32Array(object.instance.exports.memory.buffer);
+          const values = new DataView(object.instance.exports.memory.buffer);
+          let sum = 0;
           // views only the first ten elements of the Wasm memory
-          const summands = values.subarray(0, 10);
-          // sums the first ten elements
-          const sum = summands.reduce((sum, summand) => sum + summand);
+          for (let i = 0 ; i < 10; i++) {
+            sum += values.getUint32(i * 4, true);
+          }
           console.log(sum);
         }
       );