Remove duplicate base64 decoding code. NFC (emscripten-core#23321)

The optimized `base64Decode` was only being using by minimal runtime.
After this change it used in the regular runtime too which should speed
up decoding.

The optimized version also avoids the dependency of `atob` which means
we can also drop the atob polyfill.

Author: sbc100

eslint.config.mjs

@@ -48,7 +48,6 @@ export default [{
     'src/settings_internal.js',
     'src/arrayUtils.js',
     'src/deterministic.js',
-    'src/base64Utils.js',
     'src/base64Decode.js',
     'src/proxyWorker.js',
     'src/proxyClient.js',

src/base64Decode.js

@@ -39,7 +39,7 @@ function base64Decode(b64) {
 #if ENVIRONMENT_MAY_BE_NODE
   if (typeof ENVIRONMENT_IS_NODE != 'undefined' && ENVIRONMENT_IS_NODE) {
     var buf = Buffer.from(b64, 'base64');
-    return new Uint8Array(buf.buffer, buf.byteOffset, buf.byteLength);
+    return new Uint8Array(buf.buffer, buf.byteOffset, buf.length);
   }
 #endif
 
@@ -58,3 +58,15 @@ function base64Decode(b64) {
 }
 
 #endif // ~WASM2JS
+
+#if !MINIMAL_RUNTIME
+// If filename is a base64 data URI, parses and returns data (Buffer on node,
+// Uint8Array otherwise). If filename is not a base64 data URI, returns undefined.
+function tryParseAsDataURI(filename) {
+  if (!isDataURI(filename)) {
+    return;
+  }
+
+  return base64Decode(filename.slice(dataURIPrefix.length));
+}
+#endif

src/base64Utils.js

@@ -445,11 +445,6 @@ function exportRuntime() {
     runtimeElements.push('checkStackCookie');
   }
 
-  if (SUPPORT_BASE64_EMBEDDING) {
-    runtimeElements.push('intArrayFromBase64');
-    runtimeElements.push('tryParseAsDataURI');
-  }
-
   if (RETAIN_COMPILER_SETTINGS) {
     runtimeElements.push('getCompilerSetting');
   }

src/modules.mjs

@@ -110,6 +110,10 @@ var imports = {
 #endif // MINIFY_WASM_IMPORTED_MODULES
 };
 
+#if SINGLE_FILE && WASM == 1 && !WASM2JS
+Module['wasm'] = base64Decode('<<< WASM_BINARY_DATA >>>');
+#endif
+
 #if MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION
 // https://caniuse.com/#feat=wasm and https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/instantiateStreaming
 // Firefox 52 added Wasm support, but only Firefox 58 added instantiateStreaming.

src/polyfill/atob.js

@@ -44,10 +44,6 @@ if (typeof WebAssembly != 'object') {
 }
 #endif
 
-#if SUPPORT_BASE64_EMBEDDING || FORCE_FILESYSTEM
-#include "base64Utils.js"
-#endif
-
 // Wasm globals
 
 var wasmMemory;

src/postamble_minimal.js

@@ -32,11 +32,6 @@ if (Module['doWasm2JS']) {
 #endif
 #endif
 
-#if SINGLE_FILE && WASM == 1 && !WASM2JS
-#include "base64Decode.js"
-Module['wasm'] = base64Decode('<<< WASM_BINARY_DATA >>>');
-#endif
-
 var HEAP8, HEAP16, HEAP32, HEAPU8, HEAPU16, HEAPU32, HEAPF32, HEAPF64,
 #if WASM_BIGINT
   HEAP64, HEAPU64,

src/preamble.js

@@ -17,6 +17,10 @@
 #include "growableHeap.js"
 #endif
 
+#if SUPPORT_BASE64_EMBEDDING
+#include "base64Decode.js"
+#endif
+
 #if USE_ASAN
 #include "runtime_asan.js"
 #endif

src/preamble_minimal.js

@@ -140,7 +140,7 @@ var AUDIO_WORKLET_FILE = '';
 // Base URL the source mapfile, if relevant
 var SOURCE_MAP_BASE = '';
 
-// If set to 1, src/base64Utils.js will be included in the bundle.
+// If set to 1 then base64 decoding functions will be included in the bundle.
 // This is set internally when needed (SINGLE_FILE)
 var SUPPORT_BASE64_EMBEDDING = false;