如何查看Dart核心库中StringBuffer的具体实现代码？

你目前看到的是Dart核心库中StringBuffer的外部声明代码（带external关键字的方法表示其实现由底层虚拟机或平台提供，并非纯Dart代码）。要获取它的具体实现，可按以下方式操作：

• 查看Dart SDK源码

  • 针对Dart VM的底层实现：StringBuffer的核心逻辑用C++编写，位于SDK的runtime/lib/string_buffer.cc文件中，这里包含了缓冲区管理、字符串拼接优化等核心代码。
  • 针对Web平台的纯Dart实现：在SDK的lib/_internal/js_runtime/lib/js_string_buffer.dart文件中，是适配JavaScript环境的StringBuffer纯Dart实现。

• 本地SDK目录查找
  如果你已安装Dart SDK，可在本地路径中定位这些文件：

  • Windows：一般在C:\Program Files\Dart\dart-sdk
  • macOS/Linux：通常在/usr/lib/dart或~/dart-sdk
    进入后依次找到对应的runtime或_internal目录即可查看源码。

你找到的抽象声明代码如下：

// 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();
}

内容的提问来源于stack exchange，提问作者임세준