func (n *node) findCaseInsensitivePathRec(path string, ciPath []byte, rb [4]byte, fixTrailingSlash bool) []byte {
	npLen := len(n.path)
walk:  
	for len(path) >= npLen && (npLen == 0 || strings.EqualFold(path[1:npLen], n.path[1:])) {
		oldPath := path
		path = path[npLen:]
		ciPath = append(ciPath, n.path...)
		if len(path) == 0 {
			if n.handlers != nil {
				return ciPath
			}
			if fixTrailingSlash {
				for i, c := range []byte(n.indices) {
					if c == '/' {
						n = n.children[i]
						if (len(n.path) == 1 && n.handlers != nil) ||
							(n.nType == catchAll && n.children[0].handlers != nil) {
							return append(ciPath, '/')
						}
						return nil
					}
				}
			}
			return nil
		}
		if !n.wildChild {
			rb = shiftNRuneBytes(rb, npLen)
			if rb[0] != 0 {
				idxc := rb[0]
				for i, c := range []byte(n.indices) {
					if c == idxc {
						n = n.children[i]
						npLen = len(n.path)
						continue walk
					}
				}
			} else {
				var rv rune
				var off int
				for max := min(npLen, 3); off < max; off++ {
					if i := npLen - off; utf8.RuneStart(oldPath[i]) {
						rv, _ = utf8.DecodeRuneInString(oldPath[i:])
						break
					}
				}
				lo := unicode.ToLower(rv)
				utf8.EncodeRune(rb[:], lo)
				rb = shiftNRuneBytes(rb, off)
				idxc := rb[0]
				for i, c := range []byte(n.indices) {
					if c == idxc {
						if out := n.children[i].findCaseInsensitivePathRec(
							path, ciPath, rb, fixTrailingSlash,
						); out != nil {
							return out
						}
						break
					}
				}
				if up := unicode.ToUpper(rv); up != lo {
					utf8.EncodeRune(rb[:], up)
					rb = shiftNRuneBytes(rb, off)
					idxc := rb[0]
					for i, c := range []byte(n.indices) {
						if c == idxc {
							n = n.children[i]
							npLen = len(n.path)
							continue walk
						}
					}
				}
			}
			if fixTrailingSlash && path == "/" && n.handlers != nil {
				return ciPath
			}
			return nil
		}
		n = n.children[0]
		switch n.nType {
		case param:
			end := 0
			for end < len(path) && path[end] != '/' {
				end++
			}
			ciPath = append(ciPath, path[:end]...)
			if end < len(path) {
				if len(n.children) > 0 {
					n = n.children[0]
					npLen = len(n.path)
					path = path[end:]
					continue
				}
				if fixTrailingSlash && len(path) == end+1 {
					return ciPath
				}
				return nil
			}
			if n.handlers != nil {
				return ciPath
			}
			if fixTrailingSlash && len(n.children) == 1 {
				n = n.children[0]
				if n.path == "/" && n.handlers != nil {
					return append(ciPath, '/')
				}
			}
			return nil
		case catchAll:
			return append(ciPath, path...)
		default:
			panic("invalid node type")
		}
	}
	if fixTrailingSlash {
		if path == "/" {
			return ciPath
		}
		if len(path)+1 == npLen && n.path[len(path)] == '/' &&
			strings.EqualFold(path[1:], n.path[1:len(path)]) && n.handlers != nil {
			return append(ciPath, n.path...)
		}
	}
	return nil
}
Recursive case-insensitive lookup function used by n.findCaseInsensitivePath
package gin
import (
	"bytes"
	"net/url"
	"strings"
	"unicode"
	"unicode/utf8"
	"github.com/gin-gonic/gin/internal/bytesconv"
)
var (
	strColon = []byte(":")
	strStar  = []byte("*")
)
type Param struct {
	Key   string
	Value string
}
type Params []Param
func (ps Params) Get(name string) (string, bool) {
	for _, entry := range ps {
		if entry.Key == name {
			return entry.Value, true
		}
	}
	return "", false
}
func (ps Params) ByName(name string) (va string) {
	va, _ = ps.Get(name)
	return
}
type methodTree struct {
	method string
	root   *node
}
type methodTrees []methodTree
func (trees methodTrees) get(method string) *node {
	for _, tree := range trees {
		if tree.method == method {
			return tree.root
		}
	}
	return nil
}
func min(a, b int) int {
	if a <= b {
		return a
	}
	return b
}
func longestCommonPrefix(a, b string) int {
	i := 0
	max := min(len(a), len(b))
	for i < max && a[i] == b[i] {
		i++
	}
	return i
}
func (n *node) addChild(child *node) {
	if n.wildChild && len(n.children) > 0 {
		wildcardChild := n.children[len(n.children)-1]
		n.children = append(n.children[:len(n.children)-1], child, wildcardChild)
	} else {
		n.children = append(n.children, child)
	}
}
func countParams(path string) uint16 {
	var n uint16
	s := bytesconv.StringToBytes(path)
	n += uint16(bytes.Count(s, strColon))
	n += uint16(bytes.Count(s, strStar))
	return n
}
type nodeType uint8
const (
	static nodeType = iota  
	root
	param
	catchAll
)
type node struct {
	path      string
	indices   string
	wildChild bool
	nType     nodeType
	priority  uint32
	children  []*node  
	handlers  HandlersChain
	fullPath  string
}
func (n *node) incrementChildPrio(pos int) int {
	cs := n.children
	cs[pos].priority++
	prio := cs[pos].priority
	newPos := pos
	for ; newPos > 0 && cs[newPos-1].priority < prio; newPos-- {
		cs[newPos-1], cs[newPos] = cs[newPos], cs[newPos-1]
	}
	if newPos != pos {
		n.indices = n.indices[:newPos] +  
			n.indices[pos:pos+1] +  
			n.indices[newPos:pos] + n.indices[pos+1:]  
	}
	return newPos
}
func (n *node) addRoute(path string, handlers HandlersChain) {
	fullPath := path
	n.priority++
	if len(n.path) == 0 && len(n.children) == 0 {
		n.insertChild(path, fullPath, handlers)
		n.nType = root
		return
	}
	parentFullPathIndex := 0
walk:
	for {
		i := longestCommonPrefix(path, n.path)
		if i < len(n.path) {
			child := node{
				path:      n.path[i:],
				wildChild: n.wildChild,
				indices:   n.indices,
				children:  n.children,
				handlers:  n.handlers,
				priority:  n.priority - 1,
				fullPath:  n.fullPath,
			}
			n.children = []*node{&child}
			n.indices = bytesconv.BytesToString([]byte{n.path[i]})
			n.path = path[:i]
			n.handlers = nil
			n.wildChild = false
			n.fullPath = fullPath[:parentFullPathIndex+i]
		}
		if i < len(path) {
			path = path[i:]
			c := path[0]
			if n.nType == param && c == '/' && len(n.children) == 1 {
				parentFullPathIndex += len(n.path)
				n = n.children[0]
				n.priority++
				continue walk
			}
			for i, max := 0, len(n.indices); i < max; i++ {
				if c == n.indices[i] {
					parentFullPathIndex += len(n.path)
					i = n.incrementChildPrio(i)
					n = n.children[i]
					continue walk
				}
			}
			if c != ':' && c != '*' && n.nType != catchAll {
				n.indices += bytesconv.BytesToString([]byte{c})
				child := &node{
					fullPath: fullPath,
				}
				n.addChild(child)
				n.incrementChildPrio(len(n.indices) - 1)
				n = child
			} else if n.wildChild {
				n = n.children[len(n.children)-1]
				n.priority++
				if len(path) >= len(n.path) && n.path == path[:len(n.path)] &&
					n.nType != catchAll &&
					(len(n.path) >= len(path) || path[len(n.path)] == '/') {
					continue walk
				}
				pathSeg := path
				if n.nType != catchAll {
					pathSeg = strings.SplitN(pathSeg, "/", 2)[0]
				}
				prefix := fullPath[:strings.Index(fullPath, pathSeg)] + n.path
				panic("'" + pathSeg +
					"' in new path '" + fullPath +
					"' conflicts with existing wildcard '" + n.path +
					"' in existing prefix '" + prefix +
					"'")
			}
			n.insertChild(path, fullPath, handlers)
			return
		}
		if n.handlers != nil {
			panic("handlers are already registered for path '" + fullPath + "'")
		}
		n.handlers = handlers
		n.fullPath = fullPath
		return
	}
}
func findWildcard(path string) (wildcard string, i int, valid bool) {
	for start, c := range []byte(path) {
		if c != ':' && c != '*' {
			continue
		}
		valid = true
		for end, c := range []byte(path[start+1:]) {
			switch c {
			case '/':
				return path[start : start+1+end], start, valid
			case ':', '*':
				valid = false
			}
		}
		return path[start:], start, valid
	}
	return "", -1, false
}
func (n *node) insertChild(path string, fullPath string, handlers HandlersChain) {
	for {
		wildcard, i, valid := findWildcard(path)
		if i < 0 {  
			break
		}
		if !valid {
			panic("only one wildcard per path segment is allowed, has: '" +
				wildcard + "' in path '" + fullPath + "'")
		}
		if len(wildcard) < 2 {
			panic("wildcards must be named with a non-empty name in path '" + fullPath + "'")
		}
		if wildcard[0] == ':' {  
			if i > 0 {
				n.path = path[:i]
				path = path[i:]
			}
			child := &node{
				nType:    param,
				path:     wildcard,
				fullPath: fullPath,
			}
			n.addChild(child)
			n.wildChild = true
			n = child
			n.priority++
			if len(wildcard) < len(path) {
				path = path[len(wildcard):]
				child := &node{
					priority: 1,
					fullPath: fullPath,
				}
				n.addChild(child)
				n = child
				continue
			}
			n.handlers = handlers
			return
		}
		if i+len(wildcard) != len(path) {
			panic("catch-all routes are only allowed at the end of the path in path '" + fullPath + "'")
		}
		if len(n.path) > 0 && n.path[len(n.path)-1] == '/' {
			panic("catch-all conflicts with existing handle for the path segment root in path '" + fullPath + "'")
		}
		i--
		if path[i] != '/' {
			panic("no / before catch-all in path '" + fullPath + "'")
		}
		n.path = path[:i]
		child := &node{
			wildChild: true,
			nType:     catchAll,
			fullPath:  fullPath,
		}
		n.addChild(child)
		n.indices = string('/')
		n = child
		n.priority++
		child = &node{
			path:     path[i:],
			nType:    catchAll,
			handlers: handlers,
			priority: 1,
			fullPath: fullPath,
		}
		n.children = []*node{child}
		return
	}
	n.path = path
	n.handlers = handlers
	n.fullPath = fullPath
}
type nodeValue struct {
	handlers HandlersChain
	params   *Params
	tsr      bool
	fullPath string
}
func (n *node) getValue(path string, params *Params, unescape bool) (value nodeValue) {
walk:  
	for {
		prefix := n.path
		if len(path) > len(prefix) {
			if path[:len(prefix)] == prefix {
				path = path[len(prefix):]
				idxc := path[0]
				for i, c := range []byte(n.indices) {
					if c == idxc {
						n = n.children[i]
						continue walk
					}
				}
				if !n.wildChild {
					value.tsr = (path == "/" && n.handlers != nil)
					return
				}
				n = n.children[len(n.children)-1]
				switch n.nType {
				case param:
					end := 0
					for end < len(path) && path[end] != '/' {
						end++
					}
					if params != nil {
						if value.params == nil {
							value.params = params
						}
						i := len(*value.params)
						*value.params = (*value.params)[:i+1]
						val := path[:end]
						if unescape {
							if v, err := url.QueryUnescape(val); err == nil {
								val = v
							}
						}
						(*value.params)[i] = Param{
							Key:   n.path[1:],
							Value: val,
						}
					}
					if end < len(path) {
						if len(n.children) > 0 {
							path = path[end:]
							n = n.children[0]
							continue walk
						}
						value.tsr = (len(path) == end+1)
						return
					}
					if value.handlers = n.handlers; value.handlers != nil {
						value.fullPath = n.fullPath
						return
					}
					if len(n.children) == 1 {
						n = n.children[0]
						value.tsr = (n.path == "/" && n.handlers != nil)
					}
					return
				case catchAll:
					if params != nil {
						if value.params == nil {
							value.params = params
						}
						i := len(*value.params)
						*value.params = (*value.params)[:i+1]
						val := path
						if unescape {
							if v, err := url.QueryUnescape(path); err == nil {
								val = v
							}
						}
						(*value.params)[i] = Param{
							Key:   n.path[2:],
							Value: val,
						}
					}
					value.handlers = n.handlers
					value.fullPath = n.fullPath
					return
				default:
					panic("invalid node type")
				}
			}
		}
		if path == prefix {
			if value.handlers = n.handlers; value.handlers != nil {
				value.fullPath = n.fullPath
				return
			}
			if path == "/" && n.wildChild && n.nType != root {
				value.tsr = true
				return
			}
			for i, c := range []byte(n.indices) {
				if c == '/' {
					n = n.children[i]
					value.tsr = (len(n.path) == 1 && n.handlers != nil) ||
						(n.nType == catchAll && n.children[0].handlers != nil)
					return
				}
			}
			return
		}
		value.tsr = (path == "/") ||
			(len(prefix) == len(path)+1 && prefix[len(path)] == '/' &&
				path == prefix[:len(prefix)-1] && n.handlers != nil)
		return
	}
}
func (n *node) findCaseInsensitivePath(path string, fixTrailingSlash bool) ([]byte, bool) {
	const stackBufSize = 128
	buf := make([]byte, 0, stackBufSize)
	if length := len(path) + 1; length > stackBufSize {
		buf = make([]byte, 0, length)
	}
	ciPath := n.findCaseInsensitivePathRec(
		path,
		buf,        
		[4]byte{},  
		fixTrailingSlash,
	)
	return ciPath, ciPath != nil
}
func shiftNRuneBytes(rb [4]byte, n int) [4]byte {
	switch n {
	case 0:
		return rb
	case 1:
		return [4]byte{rb[1], rb[2], rb[3], 0}
	case 2:
		return [4]byte{rb[2], rb[3]}
	case 3:
		return [4]byte{rb[3]}
	default:
		return [4]byte{}
	}
}