util: add fast path for text-decoder fatal flag

PR-URL: https://github.com/nodejs/node/pull/45803
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michael Dawson <midawson@redhat.com>

benchmark/util/text-decoder.js

@@ -5,13 +5,14 @@ const common = require('../common.js');
 const bench = common.createBenchmark(main, {
   encoding: ['utf-8', 'latin1', 'iso-8859-3'],
   ignoreBOM: [0, 1],
+  fatal: [0, 1],
   len: [256, 1024 * 16, 1024 * 512],
   n: [1e2],
   type: ['SharedArrayBuffer', 'ArrayBuffer', 'Buffer']
 });
 
-function main({ encoding, len, n, ignoreBOM, type }) {
-  const decoder = new TextDecoder(encoding, { ignoreBOM });
+function main({ encoding, len, n, ignoreBOM, type, fatal }) {
+  const decoder = new TextDecoder(encoding, { ignoreBOM, fatal });
   let buf;
 
   switch (type) {
@@ -31,7 +32,11 @@ function main({ encoding, len, n, ignoreBOM, type }) {
 
   bench.start();
   for (let i = 0; i < n; i++) {
-    decoder.decode(buf);
+    try {
+      decoder.decode(buf);
+    } catch {
+      // eslint-disable no-empty
+    }
   }
   bench.end(n);
 }

lib/internal/encoding.js

@@ -29,6 +29,7 @@ const kFlags = Symbol('flags');
 const kEncoding = Symbol('encoding');
 const kDecoder = Symbol('decoder');
 const kEncoder = Symbol('encoder');
+const kFatal = Symbol('kFatal');
 const kUTF8FastPath = Symbol('kUTF8FastPath');
 const kIgnoreBOM = Symbol('kIgnoreBOM');
 
@@ -396,17 +397,16 @@ function makeTextDecoderICU() {
         flags |= options.ignoreBOM ? CONVERTER_FLAGS_IGNORE_BOM : 0;
       }
 
-      // Only support fast path for UTF-8 without FATAL flag
-      const fastPathAvailable = enc === 'utf-8' && !(options?.fatal);
-
       this[kDecoder] = true;
       this[kFlags] = flags;
       this[kEncoding] = enc;
       this[kIgnoreBOM] = Boolean(options?.ignoreBOM);
-      this[kUTF8FastPath] = fastPathAvailable;
+      this[kFatal] = Boolean(options?.fatal);
+      // Only support fast path for UTF-8.
+      this[kUTF8FastPath] = enc === 'utf-8';
       this[kHandle] = undefined;
 
-      if (!fastPathAvailable) {
+      if (!this[kUTF8FastPath]) {
         this.#prepareConverter();
       }
     }
@@ -425,7 +425,7 @@ function makeTextDecoderICU() {
       this[kUTF8FastPath] &&= !(options?.stream);
 
       if (this[kUTF8FastPath]) {
-        return decodeUTF8(input, this[kIgnoreBOM]);
+        return decodeUTF8(input, this[kIgnoreBOM], this[kFatal]);
       }
 
       this.#prepareConverter();

src/node_buffer.cc

@@ -28,6 +28,7 @@
 #include "node_internals.h"
 
 #include "env-inl.h"
+#include "simdutf.h"
 #include "string_bytes.h"
 #include "string_search.h"
 #include "util-inl.h"
@@ -583,10 +584,20 @@ void DecodeUTF8(const FunctionCallbackInfo<Value>& args) {
   ArrayBufferViewContents<char> buffer(args[0]);
 
   bool ignore_bom = args[1]->IsTrue();
+  bool has_fatal = args[2]->IsTrue();
 
   const char* data = buffer.data();
   size_t length = buffer.length();
 
+  if (has_fatal) {
+    auto result = simdutf::validate_utf8_with_errors(data, length);
+
+    if (result.error) {
+      return node::THROW_ERR_ENCODING_INVALID_ENCODED_DATA(
+          env->isolate(), "The encoded data was not valid for encoding utf-8");
+    }
+  }
+
   if (!ignore_bom && length >= 3) {
     if (memcmp(data, "\xEF\xBB\xBF", 3) == 0) {
       data += 3;