如何查看dart核心库代码(StringBuffer)？

Question

我只是想知道StringBuffer的具体代码是什么样的。

但我只能找到这样的抽象方法。好吧..。

你能让我知道具体的代码吗？谢谢!

// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of dart.core;

class StringBuffer implements StringSink {
  /// Creates a string buffer containing the provided [content].
  external StringBuffer([Object content = ""]);

  /// Returns the length of the content that has been accumulated so far.
  /// This is a constant-time operation.
  external int get length;

  /// Returns whether the buffer is empty. This is a constant-time operation.
  bool get isEmpty => length == 0;

  /// Returns whether the buffer is not empty. This is a constant-time
  /// operation.
  bool get isNotEmpty => !isEmpty;

  /// Adds the string representation of [object] to the buffer.
  external void write(Object? object);

  /// Adds the string representation of [charCode] to the buffer.
  ///
  /// Equivalent to `write(String.fromCharCode(charCode))`.
  external void writeCharCode(int charCode);

  /// Writes all [objects] separated by [separator].
  ///
  /// Writes each individual object in [objects] in iteration order,
  /// and writes [separator] between any two objects.
  external void writeAll(Iterable<dynamic> objects, [String separator = ""]);

  external void writeln([Object? obj = ""]);

  /// Clears the string buffer.
  external void clear();

  /// Returns the contents of buffer as a single string.
  external String toString();
}

Answer 1

这取决于您感兴趣的目标平台，这也是为什么要这样做的原因，因为external函数可以根据目标指向不同的实现。

在这里可以找到不同平台的实现：

https://github.com/dart-lang/sdk/tree/2.18.1/sdk/lib/_internal

因此，如果您希望看到在运行Dart VM或编译为AOT二进制文件时使用的实现，可以在这里找到StringBuffer的实现：

https://github.com/dart-lang/sdk/blob/2.18.1/sdk/lib/_internal/vm/lib/string_buffer_patch.dart

这里的另一点是，Dart VM代码通常有如下内容，您可以在StringBuffer实现的底部看到这些内容：

  @pragma("vm:external-name", "StringBuffer_createStringFromUint16Array")
  external static String _create(Uint16List buffer, int length, bool isLatin1);

这意味着我们调用Dart运行时中的C++代码(它与编译的应用程序捆绑在一起)。因此，_create调用最终将调用以下方法：

https://github.com/dart-lang/sdk/blob/2.18.1/runtime/lib/string.cc#L516-L534

如果您的目标是JavaScript，则可以在这里找到用于该实现的代码(当编译到发布就绪JS包时)：

https://github.com/dart-lang/sdk/blob/2.18.1/sdk/lib/_internal/js_runtime/lib/core_patch.dart#L632