Update vendor (#1414)

vendor/github.com/labstack/echo/v4/router.go

@@ -2,7 +2,6 @@ package echo
 
 import (
 	"net/http"
-	"strings"
 )
 
 type (
@@ -14,14 +13,16 @@ type (
 		echo   *Echo
 	}
 	node struct {
-		kind          kind
-		label         byte
-		prefix        string
-		parent        *node
-		children      children
-		ppath         string
-		pnames        []string
-		methodHandler *methodHandler
+		kind           kind
+		label          byte
+		prefix         string
+		parent         *node
+		staticChildren children
+		ppath          string
+		pnames         []string
+		methodHandler  *methodHandler
+		paramChild     *node
+		anyChild       *node
 	}
 	kind          uint8
 	children      []*node
@@ -41,9 +42,12 @@ type (
 )
 
 const (
-	skind kind = iota
-	pkind
-	akind
+	staticKind kind = iota
+	paramKind
+	anyKind
+
+	paramLabel = byte(':')
+	anyLabel   = byte('*')
 )
 
 // NewRouter returns a new Router instance.
@@ -69,120 +73,147 @@ func (r *Router) Add(method, path string, h HandlerFunc) {
 	pnames := []string{} // Param names
 	ppath := path        // Pristine path
 
-	for i, l := 0, len(path); i < l; i++ {
+	for i, lcpIndex := 0, len(path); i < lcpIndex; i++ {
 		if path[i] == ':' {
 			j := i + 1
 
-			r.insert(method, path[:i], nil, skind, "", nil)
-			for ; i < l && path[i] != '/'; i++ {
+			r.insert(method, path[:i], nil, staticKind, "", nil)
+			for ; i < lcpIndex && path[i] != '/'; i++ {
 			}
 
 			pnames = append(pnames, path[j:i])
 			path = path[:j] + path[i:]
-			i, l = j, len(path)
+			i, lcpIndex = j, len(path)
 
-			if i == l {
-				r.insert(method, path[:i], h, pkind, ppath, pnames)
+			if i == lcpIndex {
+				r.insert(method, path[:i], h, paramKind, ppath, pnames)
 			} else {
-				r.insert(method, path[:i], nil, pkind, "", nil)
+				r.insert(method, path[:i], nil, paramKind, "", nil)
 			}
 		} else if path[i] == '*' {
-			r.insert(method, path[:i], nil, skind, "", nil)
+			r.insert(method, path[:i], nil, staticKind, "", nil)
 			pnames = append(pnames, "*")
-			r.insert(method, path[:i+1], h, akind, ppath, pnames)
+			r.insert(method, path[:i+1], h, anyKind, ppath, pnames)
 		}
 	}
 
-	r.insert(method, path, h, skind, ppath, pnames)
+	r.insert(method, path, h, staticKind, ppath, pnames)
 }
 
 func (r *Router) insert(method, path string, h HandlerFunc, t kind, ppath string, pnames []string) {
 	// Adjust max param
-	l := len(pnames)
-	if *r.echo.maxParam < l {
-		*r.echo.maxParam = l
+	paramLen := len(pnames)
+	if *r.echo.maxParam < paramLen {
+		*r.echo.maxParam = paramLen
 	}
 
-	cn := r.tree // Current node as root
-	if cn == nil {
+	currentNode := r.tree // Current node as root
+	if currentNode == nil {
 		panic("echo: invalid method")
 	}
 	search := path
 
 	for {
-		sl := len(search)
-		pl := len(cn.prefix)
-		l := 0
+		searchLen := len(search)
+		prefixLen := len(currentNode.prefix)
+		lcpLen := 0
 
-		// LCP
-		max := pl
-		if sl < max {
-			max = sl
+		// LCP - Longest Common Prefix (https://en.wikipedia.org/wiki/LCP_array)
+		max := prefixLen
+		if searchLen < max {
+			max = searchLen
 		}
-		for ; l < max && search[l] == cn.prefix[l]; l++ {
+		for ; lcpLen < max && search[lcpLen] == currentNode.prefix[lcpLen]; lcpLen++ {
 		}
 
-		if l == 0 {
+		if lcpLen == 0 {
 			// At root node
-			cn.label = search[0]
-			cn.prefix = search
+			currentNode.label = search[0]
+			currentNode.prefix = search
 			if h != nil {
-				cn.kind = t
-				cn.addHandler(method, h)
-				cn.ppath = ppath
-				cn.pnames = pnames
+				currentNode.kind = t
+				currentNode.addHandler(method, h)
+				currentNode.ppath = ppath
+				currentNode.pnames = pnames
 			}
-		} else if l < pl {
+		} else if lcpLen < prefixLen {
 			// Split node
-			n := newNode(cn.kind, cn.prefix[l:], cn, cn.children, cn.methodHandler, cn.ppath, cn.pnames)
+			n := newNode(
+				currentNode.kind,
+				currentNode.prefix[lcpLen:],
+				currentNode,
+				currentNode.staticChildren,
+				currentNode.methodHandler,
+				currentNode.ppath,
+				currentNode.pnames,
+				currentNode.paramChild,
+				currentNode.anyChild,
+			)
 
 			// Update parent path for all children to new node
-			for _, child := range cn.children {
+			for _, child := range currentNode.staticChildren {
 				child.parent = n
 			}
+			if currentNode.paramChild != nil {
+				currentNode.paramChild.parent = n
+			}
+			if currentNode.anyChild != nil {
+				currentNode.anyChild.parent = n
+			}
 
 			// Reset parent node
-			cn.kind = skind
-			cn.label = cn.prefix[0]
-			cn.prefix = cn.prefix[:l]
-			cn.children = nil
-			cn.methodHandler = new(methodHandler)
-			cn.ppath = ""
-			cn.pnames = nil
+			currentNode.kind = staticKind
+			currentNode.label = currentNode.prefix[0]
+			currentNode.prefix = currentNode.prefix[:lcpLen]
+			currentNode.staticChildren = nil
+			currentNode.methodHandler = new(methodHandler)
+			currentNode.ppath = ""
+			currentNode.pnames = nil
+			currentNode.paramChild = nil
+			currentNode.anyChild = nil
 
-			cn.addChild(n)
+			// Only Static children could reach here
+			currentNode.addStaticChild(n)
 
-			if l == sl {
+			if lcpLen == searchLen {
 				// At parent node
-				cn.kind = t
-				cn.addHandler(method, h)
-				cn.ppath = ppath
-				cn.pnames = pnames
+				currentNode.kind = t
+				currentNode.addHandler(method, h)
+				currentNode.ppath = ppath
+				currentNode.pnames = pnames
 			} else {
 				// Create child node
-				n = newNode(t, search[l:], cn, nil, new(methodHandler), ppath, pnames)
+				n = newNode(t, search[lcpLen:], currentNode, nil, new(methodHandler), ppath, pnames, nil, nil)
 				n.addHandler(method, h)
-				cn.addChild(n)
+				// Only Static children could reach here
+				currentNode.addStaticChild(n)
 			}
-		} else if l < sl {
-			search = search[l:]
-			c := cn.findChildWithLabel(search[0])
+		} else if lcpLen < searchLen {
+			search = search[lcpLen:]
+			c := currentNode.findChildWithLabel(search[0])
 			if c != nil {
 				// Go deeper
-				cn = c
+				currentNode = c
 				continue
 			}
 			// Create child node
-			n := newNode(t, search, cn, nil, new(methodHandler), ppath, pnames)
+			n := newNode(t, search, currentNode, nil, new(methodHandler), ppath, pnames, nil, nil)
 			n.addHandler(method, h)
-			cn.addChild(n)
+			switch t {
+			case staticKind:
+				currentNode.addStaticChild(n)
+			case paramKind:
+				currentNode.paramChild = n
+			case anyKind:
+				currentNode.anyChild = n
+			}
 		} else {
 			// Node already exists
 			if h != nil {
-				cn.addHandler(method, h)
-				cn.ppath = ppath
-				if len(cn.pnames) == 0 { // Issue #729
-					cn.pnames = pnames
+				currentNode.addHandler(method, h)
+				currentNode.ppath = ppath
+				if len(currentNode.pnames) == 0 { // Issue #729
+					currentNode.pnames = pnames
 				}
 			}
 		}
@@ -190,34 +221,27 @@ func (r *Router) insert(method, path string, h HandlerFunc, t kind, ppath string
 	}
 }
 
-func newNode(t kind, pre string, p *node, c children, mh *methodHandler, ppath string, pnames []string) *node {
+func newNode(t kind, pre string, p *node, sc children, mh *methodHandler, ppath string, pnames []string, paramChildren, anyChildren *node) *node {
 	return &node{
-		kind:          t,
-		label:         pre[0],
-		prefix:        pre,
-		parent:        p,
-		children:      c,
-		ppath:         ppath,
-		pnames:        pnames,
-		methodHandler: mh,
+		kind:           t,
+		label:          pre[0],
+		prefix:         pre,
+		parent:         p,
+		staticChildren: sc,
+		ppath:          ppath,
+		pnames:         pnames,
+		methodHandler:  mh,
+		paramChild:     paramChildren,
+		anyChild:       anyChildren,
 	}
 }
 
-func (n *node) addChild(c *node) {
-	n.children = append(n.children, c)
+func (n *node) addStaticChild(c *node) {
+	n.staticChildren = append(n.staticChildren, c)
 }
 
-func (n *node) findChild(l byte, t kind) *node {
-	for _, c := range n.children {
-		if c.label == l && c.kind == t {
-			return c
-		}
-	}
-	return nil
-}
-
-func (n *node) findChildWithLabel(l byte) *node {
-	for _, c := range n.children {
+func (n *node) findStaticChild(l byte) *node {
+	for _, c := range n.staticChildren {
 		if c.label == l {
 			return c
 		}
@@ -225,12 +249,18 @@ func (n *node) findChildWithLabel(l byte) *node {
 	return nil
 }
 
-func (n *node) findChildByKind(t kind) *node {
-	for _, c := range n.children {
-		if c.kind == t {
+func (n *node) findChildWithLabel(l byte) *node {
+	for _, c := range n.staticChildren {
+		if c.label == l {
 			return c
 		}
 	}
+	if l == paramLabel {
+		return n.paramChild
+	}
+	if l == anyLabel {
+		return n.anyChild
+	}
 	return nil
 }
 
@@ -310,180 +340,152 @@ func (n *node) checkMethodNotAllowed() HandlerFunc {
 func (r *Router) Find(method, path string, c Context) {
 	ctx := c.(*context)
 	ctx.path = path
-	cn := r.tree // Current node as root
+	currentNode := r.tree // Current node as root
 
 	var (
-		search  = path
-		child   *node         // Child node
-		n       int           // Param counter
-		nk      kind          // Next kind
-		nn      *node         // Next node
-		ns      string        // Next search
-		pvalues = ctx.pvalues // Use the internal slice so the interface can keep the illusion of a dynamic slice
+		// search stores the remaining path to check for match. By each iteration we move from start of path to end of the path
+		// and search value gets shorter and shorter.
+		search      = path
+		searchIndex = 0
+		paramIndex  int           // Param counter
+		paramValues = ctx.pvalues // Use the internal slice so the interface can keep the illusion of a dynamic slice
 	)
 
-	// Search order static > param > any
+	// Backtracking is needed when a dead end (leaf node) is reached in the router tree.
+	// To backtrack the current node will be changed to the parent node and the next kind for the
+	// router logic will be returned based on fromKind or kind of the dead end node (static > param > any).
+	// For example if there is no static node match we should check parent next sibling by kind (param).
+	// Backtracking itself does not check if there is a next sibling, this is done by the router logic.
+	backtrackToNextNodeKind := func(fromKind kind) (nextNodeKind kind, valid bool) {
+		previous := currentNode
+		currentNode = previous.parent
+		valid = currentNode != nil
+
+		// Next node type by priority
+		// NOTE: With the current implementation we never backtrack from an `any` route, so `previous.kind` is
+		// always `static` or `any`
+		// If this is changed then for any route next kind would be `static` and this statement should be changed
+		nextNodeKind = previous.kind + 1
+
+		if fromKind == staticKind {
+			// when backtracking is done from static kind block we did not change search so nothing to restore
+			return
+		}
+
+		// restore search to value it was before we move to current node we are backtracking from.
+		if previous.kind == staticKind {
+			searchIndex -= len(previous.prefix)
+		} else {
+			paramIndex--
+			// for param/any node.prefix value is always `:` so we can not deduce searchIndex from that and must use pValue
+			// for that index as it would also contain part of path we cut off before moving into node we are backtracking from
+			searchIndex -= len(paramValues[paramIndex])
+		}
+		search = path[searchIndex:]
+		return
+	}
+
+	// Router tree is implemented by longest common prefix array (LCP array) https://en.wikipedia.org/wiki/LCP_array
+	// Tree search is implemented as for loop where one loop iteration is divided into 3 separate blocks
+	// Each of these blocks checks specific kind of node (static/param/any). Order of blocks reflex their priority in routing.
+	// Search order/priority is: static > param > any.
+	//
+	// Note: backtracking in tree is implemented by replacing/switching currentNode to previous node
+	// and hoping to (goto statement) next block by priority to check if it is the match.
 	for {
-		if search == "" {
+		prefixLen := 0 // Prefix length
+		lcpLen := 0    // LCP (longest common prefix) length
+
+		if currentNode.kind == staticKind {
+			searchLen := len(search)
+			prefixLen = len(currentNode.prefix)
+
+			// LCP - Longest Common Prefix (https://en.wikipedia.org/wiki/LCP_array)
+			max := prefixLen
+			if searchLen < max {
+				max = searchLen
+			}
+			for ; lcpLen < max && search[lcpLen] == currentNode.prefix[lcpLen]; lcpLen++ {
+			}
+		}
+
+		if lcpLen != prefixLen {
+			// No matching prefix, let's backtrack to the first possible alternative node of the decision path
+			nk, ok := backtrackToNextNodeKind(staticKind)
+			if !ok {
+				return // No other possibilities on the decision path
+			} else if nk == paramKind {
+				goto Param
+				// NOTE: this case (backtracking from static node to previous any node) can not happen by current any matching logic. Any node is end of search currently
+				//} else if nk == anyKind {
+				//	goto Any
+			} else {
+				// Not found (this should never be possible for static node we are looking currently)
+				return
+			}
+		}
+
+		// The full prefix has matched, remove the prefix from the remaining search
+		search = search[lcpLen:]
+		searchIndex = searchIndex + lcpLen
+
+		// Finish routing if no remaining search and we are on an leaf node
+		if search == "" && currentNode.ppath != "" {
 			break
 		}
 
-		pl := 0 // Prefix length
-		l := 0  // LCP length
-
-		if cn.label != ':' {
-			sl := len(search)
-			pl = len(cn.prefix)
-
-			// LCP
-			max := pl
-			if sl < max {
-				max = sl
-			}
-			for ; l < max && search[l] == cn.prefix[l]; l++ {
-			}
-		}
-
-		if l == pl {
-			// Continue search
-			search = search[l:]
-			// Finish routing if no remaining search and we are on an leaf node
-			if search == "" && (nn == nil || cn.parent == nil || cn.ppath != "") {
-				break
-			}
-		}
-
-		// Attempt to go back up the tree on no matching prefix or no remaining search
-		if l != pl || search == "" {
-			// Handle special case of trailing slash route with existing any route (see #1526)
-			if path[len(path)-1] == '/' && cn.findChildByKind(akind) != nil {
-				goto Any
-			}
-			if nn == nil { // Issue #1348
-				return // Not found
-			}
-			cn = nn
-			search = ns
-			if nk == pkind {
-				goto Param
-			} else if nk == akind {
-				goto Any
-			}
-		}
-
 		// Static node
-		if child = cn.findChild(search[0], skind); child != nil {
-			// Save next
-			if cn.prefix[len(cn.prefix)-1] == '/' { // Issue #623
-				nk = pkind
-				nn = cn
-				ns = search
+		if search != "" {
+			if child := currentNode.findStaticChild(search[0]); child != nil {
+				currentNode = child
+				continue
 			}
-			cn = child
-			continue
 		}
 
 	Param:
 		// Param node
-		if child = cn.findChildByKind(pkind); child != nil {
-			// Issue #378
-			if len(pvalues) == n {
-				continue
-			}
-
-			// Save next
-			if cn.prefix[len(cn.prefix)-1] == '/' { // Issue #623
-				nk = akind
-				nn = cn
-				ns = search
-			}
-
-			cn = child
+		if child := currentNode.paramChild; search != "" && child != nil {
+			currentNode = child
+			// FIXME: when param node does not have any children then param node should act similarly to any node - consider all remaining search as match
 			i, l := 0, len(search)
 			for ; i < l && search[i] != '/'; i++ {
 			}
-			pvalues[n] = search[:i]
-			n++
+			paramValues[paramIndex] = search[:i]
+			paramIndex++
 			search = search[i:]
+			searchIndex = searchIndex + i
 			continue
 		}
 
 	Any:
 		// Any node
-		if cn = cn.findChildByKind(akind); cn != nil {
-			// If any node is found, use remaining path for pvalues
-			pvalues[len(cn.pnames)-1] = search
+		if child := currentNode.anyChild; child != nil {
+			// If any node is found, use remaining path for paramValues
+			currentNode = child
+			paramValues[len(currentNode.pnames)-1] = search
 			break
 		}
 
-		// No node found, continue at stored next node
-		// or find nearest "any" route
-		if nn != nil {
-			// No next node to go down in routing (issue #954)
-			// Find nearest "any" route going up the routing tree
-			search = ns
-			np := nn.parent
-			// Consider param route one level up only
-			if cn = nn.findChildByKind(pkind); cn != nil {
-				pos := strings.IndexByte(ns, '/')
-				if pos == -1 {
-					// If no slash is remaining in search string set param value
-					pvalues[len(cn.pnames)-1] = search
-					break
-				} else if pos > 0 {
-					// Otherwise continue route processing with restored next node
-					cn = nn
-					nn = nil
-					ns = ""
-					goto Param
-				}
-			}
-			// No param route found, try to resolve nearest any route
-			for {
-				np = nn.parent
-				if cn = nn.findChildByKind(akind); cn != nil {
-					break
-				}
-				if np == nil {
-					break // no further parent nodes in tree, abort
-				}
-				var str strings.Builder
-				str.WriteString(nn.prefix)
-				str.WriteString(search)
-				search = str.String()
-				nn = np
-			}
-			if cn != nil { // use the found "any" route and update path
-				pvalues[len(cn.pnames)-1] = search
-				break
-			}
-		}
-		return // Not found
-
-	}
-
-	ctx.handler = cn.findHandler(method)
-	ctx.path = cn.ppath
-	ctx.pnames = cn.pnames
-
-	// NOTE: Slow zone...
-	if ctx.handler == nil {
-		ctx.handler = cn.checkMethodNotAllowed()
-
-		// Dig further for any, might have an empty value for *, e.g.
-		// serving a directory. Issue #207.
-		if cn = cn.findChildByKind(akind); cn == nil {
+		// Let's backtrack to the first possible alternative node of the decision path
+		nk, ok := backtrackToNextNodeKind(anyKind)
+		if !ok {
+			return // No other possibilities on the decision path
+		} else if nk == paramKind {
+			goto Param
+		} else if nk == anyKind {
+			goto Any
+		} else {
+			// Not found
 			return
 		}
-		if h := cn.findHandler(method); h != nil {
-			ctx.handler = h
-		} else {
-			ctx.handler = cn.checkMethodNotAllowed()
-		}
-		ctx.path = cn.ppath
-		ctx.pnames = cn.pnames
-		pvalues[len(cn.pnames)-1] = ""
 	}
 
+	ctx.handler = currentNode.findHandler(method)
+	ctx.path = currentNode.ppath
+	ctx.pnames = currentNode.pnames
+
+	if ctx.handler == nil {
+		ctx.handler = currentNode.checkMethodNotAllowed()
+	}
 	return
 }