fix SwiftOldDriver#1573

Reports/2019/#79-2019.08.12.md

@@ -23,7 +23,25 @@
 
 ## 工具
 
-> 开发过程中常用的工具，及一些新工具的介绍
+### [Swift API-Digester](https://github.com/apple/swift-nio/commit/07e7e01c76be20640ddc3770d7b16e87eedf20de)
+
+[@享耳先森](https://github.com/iblacksun)：Swift 5.1 里新增了一个 `api-digester` 功能，用来打印和比较编译产物的 API，Swift-NIO 在此基础上搭建了一个 API Diff 功能，可以预见未来开源框架都会使用这个功能来生成 API Diff，帮助检验 Pull Request 对于 API 的影响，ChangeLog 的生成等等。
+
+用类似这样的命令：`swift api-digester -diagnose-sdk --input-paths "dir1" -input-paths "dir2"` 就能比较两个编译产物的 API 区别，生成类似下面的结果：
+
+> Removed Decls
+> Constructor WebSocketFrameDecoder.init(maxFrameSize:automaticErrorHandling:) has been removed
+> EnumElement WebSocketOpcode.unknownControl has been removed
+> EnumElement WebSocketOpcode.unknownNonControl has been removed
+
+> Renamed Decls
+> Func WebSocketFrameDecoder.decode(ctx:buffer:) has been renamed to Func WebSocketFrameDecoder.decode(context:buffer:)
+> Func WebSocketFrameDecoder.decodeLast(ctx:buffer:) has been renamed to Func WebSocketFrameDecoder.decodeLast(context:buffer:seenEOF:)
+> Func WebSocketFrameEncoder.write(ctx:data:promise:) has been renamed to Func WebSocketFrameEncoder.write(context:data:promise:)
+> Func WebSocketProtocolErrorHandler.errorCaught(ctx:error:) has been renamed to Func WebSocketProtocolErrorHandler.errorCaught(context:error:)
+
+> Type Changes
+> Constructor UInt8.init(webSocketOpcode:) has return type change from UInt8? to UInt8
 
 ## 代码