Improve Node file load speed.

CHANGELOG.md

@@ -66,6 +66,8 @@
 
 * Error out if a function is passed an unknown named parameter.
 
+* Improve the speed of loading large files on Node.
+
 ## 1.0.0-alpha.8
 
 * Add the `content-exists()` function.

lib/sass.dart

@@ -5,8 +5,9 @@
 import 'package:path/path.dart' as p;
 
 import 'src/ast/sass.dart';
+import 'src/exception.dart';
+import 'src/io.dart';
 import 'src/sync_package_resolver.dart';
-import 'src/utils.dart';
 import 'src/visitor/perform.dart';
 import 'src/visitor/serialize.dart';
 
@@ -23,7 +24,7 @@ import 'src/visitor/serialize.dart';
 /// Finally throws a [SassException] if conversion fails.
 String render(String path,
     {bool color: false, SyncPackageResolver packageResolver}) {
-  var contents = readSassFile(path);
+  var contents = readFile(path);
   var url = p.toUri(path);
   var sassTree = p.extension(path) == '.sass'
       ? new Stylesheet.parseSass(contents, url: url, color: color)

lib/src/executable.dart

@@ -106,7 +106,7 @@ Future<String> _loadVersion() async {
 
   var libDir =
       p.fromUri(await Isolate.resolvePackageUri(Uri.parse('package:sass/')));
-  var pubspec = readFileAsString(p.join(libDir, '..', 'pubspec.yaml'));
+  var pubspec = readFile(p.join(libDir, '..', 'pubspec.yaml'));
   return pubspec
       .split("\n")
       .firstWhere((line) => line.startsWith('version: '))

lib/src/io/interface.dart

@@ -17,7 +17,7 @@ class Stderr {
   void flush() {}
 }
 
-/// An error thrown by [readFileAsBytes] and [readFileAsString].
+/// An error thrown by [readFile].
 class FileSystemException {
   String get message => null;
 }
@@ -28,11 +28,11 @@ Stderr get stderr => null;
 /// Returns whether or not stdout is connected to an interactive terminal.
 bool get hasTerminal => false;
 
-/// Reads the file at [path] as a list of bytes.
-List<int> readFileAsBytes(String path) => null;
-
 /// Reads the file at [path] as a UTF-8 encoded string.
-String readFileAsString(String path) => null;
+///
+/// Throws a [FileSystemException] if reading fails, and a [SassException] if
+/// the file isn't valid UTF-8.
+String readFile(String path) => null;
 
 /// Returns whether a file at [path] exists.
 bool fileExists(String path) => null;

lib/src/io/node.dart

@@ -2,9 +2,14 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import 'dart:convert';
 import 'dart:typed_data';
 
 import 'package:js/js.dart';
+import 'package:path/path.dart' as p;
+import 'package:source_span/source_span.dart';
+
+import '../exception.dart';
 
 @JS()
 class _FS {
@@ -51,14 +56,28 @@ external _FS _require(String name);
 
 final _fs = _require("fs");
 
-List<int> readFileAsBytes(String path) => _readFile(path) as Uint8List;
+String readFile(String path) {
+  // TODO(nweiz): explicitly decode the bytes as UTF-8 like we do in the VM when
+  // it doesn't cause a substantial performance degradation for large files. See
+  // also dart-lang/sdk#25377.
+  var contents = _readFile(path, 'utf8');
+  if (!contents.contains("�")) return contents;
+
+  var sourceFile = new SourceFile(contents, url: p.toUri(path));
+  for (var i = 0; i < contents.length; i++) {
+    if (contents.codeUnitAt(i) != 0xFFFD) continue;
+    throw new SassException(
+        "Invalid UTF-8.", sourceFile.location(i).pointSpan());
+  }
 
-String readFileAsString(String path) => _readFile(path, 'utf8') as String;
+  // This should be unreachable.
+  return string;
+}
 
 /// Wraps `fs.readFileSync` to throw a [FileSystemException].
 _readFile(String path, [String encoding]) {
   try {
-    return _fs.readFileSync(path);
+    return _fs.readFileSync(path, encoding);
   } catch (error) {
     throw new FileSystemException._(_cleanErrorMessage(error as _SystemError));
   }

lib/src/io/vm.dart

@@ -10,9 +10,28 @@ io.Stdout get stderr => io.stderr;
 
 bool get hasTerminal => io.stdout.hasTerminal;
 
-List<int> readFileAsBytes(String path) => new io.File(path).readAsBytesSync();
-
-String readFileAsString(String path) => new io.File(path).readAsStringSync();
+String readFile(String path) {
+  var bytes = readFile(path);
+
+  try {
+    return UTF8.decode(bytes);
+  } on FormatException {
+    var decoded = UTF8.decode(bytes, allowMalformed: true);
+    var sourceFile = new SourceFile(decoded, url: p.toUri(path));
+
+    // TODO(nweiz): Use [FormatException.offset] instead when
+    // dart-lang/sdk#28293 is fixed.
+    for (var i = 0; i < bytes.length; i++) {
+      if (decoded.codeUnitAt(i) != 0xFFFD) continue;
+      throw new SassException(
+          "Invalid UTF-8.", sourceFile.location(i).pointSpan());
+    }
+
+    // This should be unreachable, but we'll rethrow the original exception just
+    // in case.
+    rethrow;
+  }
+}
 
 bool fileExists(String path) => new io.File(path).existsSync();
 

lib/src/utils.dart

@@ -3,16 +3,13 @@
 // https://opensource.org/licenses/MIT.
 
 import 'dart:collection';
-import 'dart:convert';
 import 'dart:math' as math;
 
 import 'package:charcode/charcode.dart';
 import 'package:collection/collection.dart';
-import 'package:path/path.dart' as p;
 import 'package:source_span/source_span.dart';
 
 import 'ast/node.dart';
-import 'exception.dart';
 import 'io.dart';
 import 'util/character.dart';
 
@@ -257,31 +254,6 @@ List/*<T>*/ longestCommonSubsequence/*<T>*/(
   }
 }
 
-/// Reads a Sass source file from diskx, and throws a [SassException] if UTF-8
-/// decoding fails.
-String readSassFile(String path) {
-  var bytes = readFileAsBytes(path);
-
-  try {
-    return UTF8.decode(bytes);
-  } on FormatException {
-    var decoded = UTF8.decode(bytes, allowMalformed: true);
-    var sourceFile = new SourceFile(decoded, url: p.toUri(path));
-
-    // TODO(nweiz): Use [FormatException.offset] instead when
-    // dart-lang/sdk#28293 is fixed.
-    for (var i = 0; i < bytes.length; i++) {
-      if (decoded.codeUnitAt(i) != 0xFFFD) continue;
-      throw new SassException(
-          "Invalid UTF-8.", sourceFile.location(i).pointSpan());
-    }
-
-    // This should be unreachable, but we'll rethrow the original exception just
-    // in case.
-    rethrow;
-  }
-}
-
 /// Prints a warning to standard error, associated with [span].
 ///
 /// If [color] is `true`, this uses terminal colors.

lib/src/visitor/perform.dart

@@ -636,7 +636,7 @@ class _PerformVisitor
     return _importedFiles.putIfAbsent(path, () {
       String contents;
       try {
-        contents = readSassFile(path);
+        contents = readFile(path);
       } on SassException catch (error) {
         var frames = _stack.toList()..add(_stackFrame(import.span));
         throw new SassRuntimeException(