fix: cut redirect and allow-path routing overhead

Reuse fixed-path and Allow-header buffers so redirect and OPTIONS handling stop rebuilding temporary data on every request. Cache fallback chains and add regression coverage for redirect, 404, 405, and Allow behavior to keep the faster miss paths stable.

engine.go

@@ -11,6 +11,7 @@ import (
 	"reflect"
 	"runtime"
 	"strings"
+	"unicode/utf8"
 
 	"net/http"
 
@@ -82,6 +83,11 @@ type Engine struct {
 
 	// GlobalMaxRequestBodySize 全局请求体Body大小限制
 	GlobalMaxRequestBodySize int64
+
+	notFoundChain            HandlersChain
+	notFoundNoMethodChain    HandlersChain
+	unmatchedFSChain         HandlersChain
+	unmatchedFSNoMethodChain HandlersChain
 }
 
 // HandleFunc 注册一个或多个 HTTP 方法的路由
@@ -127,10 +133,19 @@ var methodNotAllowedHandler HandlerFunc = func(c *Context) {
 	// 是否是OPTIONS方式
 	if httpMethod == http.MethodOptions {
 		// 如果是 OPTIONS 请求,尝试查找所有允许的方法
-		allowedMethods := engine.allowedMethodsForPath(requestPath)
+		allowedMethods := engine.allowedMethodsForPath(requestPath, c.allowedMethodsBuf[:0])
+		c.allowedMethodsBuf = allowedMethods[:0]
 		if len(allowedMethods) > 0 {
 			// 如果找到了允许的方法,返回 200 OK 并设置 Allow 头部
-			c.Writer.Header().Set("Allow", strings.Join(allowedMethods, ", "))
+			allowHeader := c.allowHeaderBuf[:0]
+			for i, method := range allowedMethods {
+				if i > 0 {
+					allowHeader = append(allowHeader, ',', ' ')
+				}
+				allowHeader = append(allowHeader, method...)
+			}
+			c.allowHeaderBuf = allowHeader[:0]
+			c.Writer.Header().Set("Allow", BytesToString(allowHeader))
 			c.Status(http.StatusOK)
 			return
 		}
@@ -251,6 +266,7 @@ func New() *Engine {
 		TLSServerConfigurator:    nil,
 		GlobalMaxRequestBodySize: -1,
 	}
+	engine.rebuildFallbackChains()
 	engine.shutdownCtx, engine.shutdownCancel = context.WithCancel(context.Background())
 	//engine.SetProtocols(GetDefaultProtocolsConfig())
 	engine.SetDefaultProtocols()
@@ -306,6 +322,7 @@ func (engine *Engine) SetRedirectFixedPath(enable bool) {
 // 是否开启MethodNotAllowed
 func (engine *Engine) SetHandleMethodNotAllowed(enable bool) {
 	engine.HandleMethodNotAllowed = enable
+	engine.rebuildFallbackChains()
 }
 
 // SetLogger传入实例
@@ -346,6 +363,7 @@ func (engine *Engine) SetUnMatchFSChain(fs http.FileSystem, handlers ...HandlerF
 		engine.unMatchFS.ServeUnmatchedAsFS = false
 		engine.UnMatchFSRoutes = nil
 	}
+	engine.rebuildFallbackChains()
 }
 
 // 获取默认Protocol配置
@@ -531,12 +549,52 @@ func NotFound() HandlerFunc {
 func (Engine *Engine) NoRoute(handler HandlerFunc) {
 	Engine.noRoute = handler
 	Engine.noRoutes = nil
+	Engine.rebuildFallbackChains()
 }
 
 // 传入并设置NoRoutes (这不是最后一个处理, 你仍可以next到默认的404处理)
 func (Engine *Engine) NoRoutes(handlerFuncs ...HandlerFunc) {
 	Engine.noRoute = nil
 	Engine.noRoutes = handlerFuncs
+	Engine.rebuildFallbackChains()
+}
+
+func (engine *Engine) rebuildFallbackChains() {
+	buildChain := func(includeMethodNotAllowed bool, includeUnmatchedFS bool) HandlersChain {
+		finalSize := len(engine.globalHandlers) + 1 // 最后的 NotFound
+		if includeMethodNotAllowed {
+			finalSize++
+		}
+		if includeUnmatchedFS {
+			finalSize += len(engine.UnMatchFSRoutes)
+		}
+		if engine.noRoute != nil {
+			finalSize++
+		} else {
+			finalSize += len(engine.noRoutes)
+		}
+
+		chain := make(HandlersChain, 0, finalSize)
+		chain = append(chain, engine.globalHandlers...)
+		if includeMethodNotAllowed {
+			chain = append(chain, methodNotAllowedHandler)
+		}
+		if includeUnmatchedFS {
+			chain = append(chain, engine.UnMatchFSRoutes...)
+		}
+		if engine.noRoute != nil {
+			chain = append(chain, engine.noRoute)
+		} else if len(engine.noRoutes) > 0 {
+			chain = append(chain, engine.noRoutes...)
+		}
+		chain = append(chain, notFoundHandler)
+		return chain
+	}
+
+	engine.notFoundChain = buildChain(engine.HandleMethodNotAllowed, false)
+	engine.notFoundNoMethodChain = buildChain(false, false)
+	engine.unmatchedFSChain = buildChain(engine.HandleMethodNotAllowed, engine.unMatchFS.ServeUnmatchedAsFS)
+	engine.unmatchedFSNoMethodChain = buildChain(false, engine.unMatchFS.ServeUnmatchedAsFS)
 }
 
 // combineHandlers 组合多个处理函数链为一个
@@ -553,6 +611,7 @@ func (engine *Engine) combineHandlers(h1 HandlersChain, h2 HandlersChain) Handle
 // 这些中间件将应用于所有注册的路由
 func (engine *Engine) Use(middleware ...HandlerFunc) IRouter {
 	engine.globalHandlers = append(engine.globalHandlers, middleware...)
+	engine.rebuildFallbackChains()
 	return engine
 }
 
@@ -746,48 +805,24 @@ func (engine *Engine) handleRequest(c *Context) {
 				c.Redirect(http.StatusMovedPermanently, redirectPath) // 301 永久重定向
 				return
 			}
-			if engine.RedirectFixedPath {
+			if engine.RedirectFixedPath && shouldTryFixedPathLookup(requestPath, rootNode) {
 				// 仅在启用固定路径重定向时执行大小写修复查找, 避免无意义的二次树遍历.
-				ciPath, found := rootNode.findCaseInsensitivePath(requestPath, engine.RedirectTrailingSlash)
+				ciPath, found := rootNode.findCaseInsensitivePathWithBuffer(requestPath, c.fixedPathBuf, engine.RedirectTrailingSlash)
 				if found {
+					c.fixedPathBuf = ciPath[:0]
 					c.Redirect(http.StatusMovedPermanently, BytesToString(ciPath)) // 301 永久重定向到修正后的路径
 					return
 				}
+				c.fixedPathBuf = ciPath[:0]
 			}
 		}
 	}
 
-	// 构建处理链
-	// 组合全局中间件和路由处理函数
-	handlers := engine.globalHandlers
-
-	// 如果启用了 MethodNotAllowed 处理,并且没有找到精确匹配的路由
-	// 则在全局中间件之后添加 MethodNotAllowed 处理器
-	if engine.HandleMethodNotAllowed {
-		handlers = append(handlers, MethodNotAllowed())
-	}
-
-	// 如果启用了 UnMatchFS 处理,并且没有找到精确匹配的路由和 MethodNotAllowed
-	// 则在处理链的最后添加 UnMatchFS 处理器
 	if engine.unMatchFS.ServeUnmatchedAsFS {
-		/*
-			var unMatchFSHandle = c.engine.unMatchFileServer
-			handlers = append(handlers, unMatchFSHandle)
-		*/
-		handlers = append(handlers, engine.UnMatchFSRoutes...)
+		c.handlers = engine.unmatchedFSChain
+	} else {
+		c.handlers = engine.notFoundChain
 	}
-
-	// 如果用户设置了 NoRoute 处理器,且没有匹配到任何路由、MethodNotAllowed 或 UnMatchFS
-	// 则在处理链的最后添加 NoRoute 处理器
-	if engine.noRoute != nil {
-		handlers = append(handlers, engine.noRoute)
-	} else if len(engine.noRoutes) > 0 {
-		handlers = append(handlers, engine.noRoutes...)
-	}
-
-	handlers = append(handlers, NotFound())
-
-	c.handlers = handlers
 	c.Next() // 执行处理函数链
 	//c.Writer.Flush() // 确保所有缓冲的响应数据被发送
 }
@@ -813,8 +848,28 @@ func isGeneralOptionsRequest(req *http.Request) bool {
 	return req != nil && req.Method == http.MethodOptions && req.RequestURI == "*"
 }
 
-func (engine *Engine) allowedMethodsForPath(requestPath string) []string {
-	allowedMethods := make([]string, 0, len(engine.methodTrees))
+func shouldTryFixedPathLookup(path string, root *node) bool {
+	if root != nil && root.hasCaseInsensitivePath {
+		return true
+	}
+	for i := 0; i < len(path); i++ {
+		c := path[i]
+		if c >= utf8.RuneSelf {
+			return true
+		}
+		if c >= 'A' && c <= 'Z' {
+			return true
+		}
+	}
+	return false
+}
+
+func (engine *Engine) allowedMethodsForPath(requestPath string, allowedMethods []string) []string {
+	if cap(allowedMethods) < len(engine.methodTrees) {
+		allowedMethods = make([]string, 0, len(engine.methodTrees))
+	} else {
+		allowedMethods = allowedMethods[:0]
+	}
 	for _, treeIter := range engine.methodTrees {
 		// 注意这里 treeIter.root 才是正确的,因为 treeIter 是 methodTree 类型
 		tempSkippedNodes := GetTempSkippedNodes()