Fix base64 decoding function

bin/wasm-node/javascript/src/instance/buffer.ts

@@ -60,42 +60,13 @@ function checkRange(buffer: Uint8Array, offset: number, length: number) {
  * The input is assumed to be correct.
  */
 export function trustedBase64Decode(base64: string): Uint8Array {
-    // This implementation was mostly copy-pasted (with some adjustments)
-    // from <https://developer.mozilla.org/en-US/docs/Glossary/Base64>. As indicated in the
-    // about section (<https://developer.mozilla.org/en-US/docs/MDN/About>), this code is in the
-    // public domain.
-
-    function b64ToUint6(nChr: number) {
-        return nChr > 64 && nChr < 91 ?
-            nChr - 65
-            : nChr > 96 && nChr < 123 ?
-                nChr - 71
-                : nChr > 47 && nChr < 58 ?
-                    nChr + 4
-                    : nChr === 43 ?
-                        62
-                        : nChr === 47 ?
-                            63
-                            :
-                            0;
-
-    }
-
-    const nInLen = base64.length
-    const nOutLen = nInLen * 3 + 1 >> 2
-    const taBytes = new Uint8Array(nOutLen);
-
-    for (var nMod3, nMod4, nUint24 = 0, nOutIdx = 0, nInIdx = 0; nInIdx < nInLen; nInIdx++) {
-        nMod4 = nInIdx & 3;
-        nUint24 |= b64ToUint6(base64.charCodeAt(nInIdx)) << 6 * (3 - nMod4);
-        if (nMod4 === 3 || nInLen - nInIdx === 1) {
-            for (nMod3 = 0; nMod3 < 3 && nOutIdx < nOutLen; nMod3++, nOutIdx++) {
-                taBytes[nOutIdx] = nUint24 >>> (16 >>> nMod3 & 24) & 255;
-            }
-            nUint24 = 0;
-
-        }
+    // This code is a bit sketchy due to the fact that we decode into a string, but it seems to
+    // work.
+    const binaryString = atob(base64);
+    const size = binaryString.length;
+    const bytes = new Uint8Array(size);
+    for (let i = 0; i < size; i++) {
+        bytes[i] = binaryString.charCodeAt(i);
     }
-
-    return taBytes;
+    return bytes;
 }