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tree.go
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// Copyright 2013 Julien Schmidt. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be found
// in the LICENSE file.
package httprouter
import (
"net/http"
"strings"
"unicode"
"unicode/utf8"
)
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
}
// Search for a wildcard segment and check the name for invalid characters.
// Returns -1 as index, if no wildcard was found.
func findWildcard(path string) (wilcard string, i int, valid bool) {
// Find start
for start, c := range []byte(path) {
// A wildcard starts with ':' (param) or '*' (catch-all)
if c != ':' && c != '*' {
continue
}
// Find end and check for invalid characters
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 countParams(path string) uint16 {
var n uint
for i := range []byte(path) {
switch path[i] {
case ':', '*':
n++
}
}
return uint16(n)
}
type nodeType uint8
const (
static nodeType = iota // default
root
param
catchAll
)
type node struct {
path string
indices string
wildChild bool
nType nodeType
priority uint32
children []*node
handle http.HandlerFunc
}
// Increments priority of the given child and reorders if necessary
func (n *node) incrementChildPrio(pos int) int {
cs := n.children
cs[pos].priority++
prio := cs[pos].priority
// Adjust position (move to front)
newPos := pos
for ; newPos > 0 && cs[newPos-1].priority < prio; newPos-- {
// Swap node positions
cs[newPos-1], cs[newPos] = cs[newPos], cs[newPos-1]
}
// Build new index char string
if newPos != pos {
n.indices = n.indices[:newPos] + // Unchanged prefix, might be empty
n.indices[pos:pos+1] + // The index char we move
n.indices[newPos:pos] + n.indices[pos+1:] // Rest without char at 'pos'
}
return newPos
}
// addRoute adds a node with the given handle to the path.
// Not concurrency-safe!
func (n *node) addRoute(path string, handle http.HandlerFunc) {
fullPath := path
n.priority++
// Empty tree
if n.path == "" && n.indices == "" {
n.insertChild(path, fullPath, handle)
n.nType = root
return
}
walk:
for {
// Find the longest common prefix.
// This also implies that the common prefix contains no ':' or '*'
// since the existing key can't contain those chars.
i := longestCommonPrefix(path, n.path)
// Split edge
if i < len(n.path) {
child := node{
path: n.path[i:],
wildChild: n.wildChild,
nType: static,
indices: n.indices,
children: n.children,
handle: n.handle,
priority: n.priority - 1,
}
n.children = []*node{&child}
// []byte for proper unicode char conversion, see #65
n.indices = string([]byte{n.path[i]})
n.path = path[:i]
n.handle = nil
n.wildChild = false
}
// Make new node a child of this node
if i < len(path) {
path = path[i:]
if n.wildChild {
n = n.children[0]
n.priority++
// Check if the wildcard matches
if len(path) >= len(n.path) && n.path == path[:len(n.path)] &&
// Adding a child to a catchAll is not possible
n.nType != catchAll &&
// Check for longer wildcard, e.g. :name and :names
(len(n.path) >= len(path) || path[len(n.path)] == '/') {
continue walk
} else {
// Wildcard conflict
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 +
"'")
}
}
idxc := path[0]
// '/' after param
if n.nType == param && idxc == '/' && len(n.children) == 1 {
n = n.children[0]
n.priority++
continue walk
}
// Check if a child with the next path byte exists
for i, c := range []byte(n.indices) {
if c == idxc {
i = n.incrementChildPrio(i)
n = n.children[i]
continue walk
}
}
// Otherwise insert it
if idxc != ':' && idxc != '*' {
// []byte for proper unicode char conversion, see #65
n.indices += string([]byte{idxc})
child := &node{}
n.children = append(n.children, child)
n.incrementChildPrio(len(n.indices) - 1)
n = child
}
n.insertChild(path, fullPath, handle)
return
}
// Otherwise add handle to current node
if n.handle != nil {
panic("a handle is already registered for path '" + fullPath + "'")
}
n.handle = handle
return
}
}
func (n *node) insertChild(path, fullPath string, handle http.HandlerFunc) {
for {
// Find prefix until first wildcard
wildcard, i, valid := findWildcard(path)
if i < 0 { // No wilcard found
break
}
// The wildcard name must not contain ':' and '*'
if !valid {
panic("only one wildcard per path segment is allowed, has: '" +
wildcard + "' in path '" + fullPath + "'")
}
// Check if the wildcard has a name
if len(wildcard) < 2 {
panic("wildcards must be named with a non-empty name in path '" + fullPath + "'")
}
// Check if this node has existing children which would be
// unreachable if we insert the wildcard here
if len(n.children) > 0 {
panic("wildcard segment '" + wildcard +
"' conflicts with existing children in path '" + fullPath + "'")
}
// param
if wildcard[0] == ':' {
if i > 0 {
// Insert prefix before the current wildcard
n.path = path[:i]
path = path[i:]
}
n.wildChild = true
child := &node{
nType: param,
path: wildcard,
}
n.children = []*node{child}
n = child
n.priority++
// If the path doesn't end with the wildcard, then there
// will be another non-wildcard subpath starting with '/'
if len(wildcard) < len(path) {
path = path[len(wildcard):]
child := &node{
priority: 1,
}
n.children = []*node{child}
n = child
continue
}
// Otherwise we're done. Insert the handle in the new leaf
n.handle = handle
return
}
// catchAll
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 + "'")
}
// Currently fixed width 1 for '/'
i--
if path[i] != '/' {
panic("no / before catch-all in path '" + fullPath + "'")
}
n.path = path[:i]
// First node: catchAll node with empty path
child := &node{
wildChild: true,
nType: catchAll,
}
n.children = []*node{child}
n.indices = string('/')
n = child
n.priority++
// Second node: node holding the variable
child = &node{
path: path[i:],
nType: catchAll,
handle: handle,
priority: 1,
}
n.children = []*node{child}
return
}
// If no wildcard was found, simply insert the path and handle
n.path = path
n.handle = handle
}
// Returns the handle registered with the given path (key). The values of
// wildcards are saved to a map.
// If no handle can be found, a TSR (trailing slash redirect) recommendation is
// made if a handle exists with an extra (without the) trailing slash for the
// given path.
func (n *node) getValue(path string, params func() *Params) (handle http.HandlerFunc, ps *Params, tsr bool) {
walk: // Outer loop for walking the tree
for {
prefix := n.path
if len(path) > len(prefix) {
if path[:len(prefix)] == prefix {
path = path[len(prefix):]
// If this node does not have a wildcard (param or catchAll)
// child, we can just look up the next child node and continue
// to walk down the tree
if !n.wildChild {
idxc := path[0]
for i, c := range []byte(n.indices) {
if c == idxc {
n = n.children[i]
continue walk
}
}
// Nothing found.
// We can recommend to redirect to the same URL without a
// trailing slash if a leaf exists for that path.
tsr = (path == "/" && n.handle != nil)
return
}
// Handle wildcard child
n = n.children[0]
switch n.nType {
case param:
// Find param end (either '/' or path end)
end := 0
for end < len(path) && path[end] != '/' {
end++
}
// Save param value
if params != nil {
if ps == nil {
ps = params()
}
// Expand slice within preallocated capacity
i := len(*ps)
*ps = (*ps)[:i+1]
(*ps)[i] = Param{
Key: n.path[1:],
Value: path[:end],
}
}
// We need to go deeper!
if end < len(path) {
if len(n.children) > 0 {
path = path[end:]
n = n.children[0]
continue walk
}
// ... but we can't
tsr = (len(path) == end+1)
return
}
if handle = n.handle; handle != nil {
return
} else if len(n.children) == 1 {
// No handle found. Check if a handle for this path + a
// trailing slash exists for TSR recommendation
n = n.children[0]
tsr = (n.path == "/" && n.handle != nil) || (n.path == "" && n.indices == "/")
}
return
case catchAll:
// Save param value
if params != nil {
if ps == nil {
ps = params()
}
// Expand slice within preallocated capacity
i := len(*ps)
*ps = (*ps)[:i+1]
(*ps)[i] = Param{
Key: n.path[2:],
Value: path,
}
}
handle = n.handle
return
default:
panic("invalid node type")
}
}
} else if path == prefix {
// We should have reached the node containing the handle.
// Check if this node has a handle registered.
if handle = n.handle; handle != nil {
return
}
// If there is no handle for this route, but this route has a
// wildcard child, there must be a handle for this path with an
// additional trailing slash
if path == "/" && n.wildChild && n.nType != root {
tsr = true
return
}
if path == "/" && n.nType == static {
tsr = true
return
}
// No handle found. Check if a handle for this path + a
// trailing slash exists for trailing slash recommendation
for i, c := range []byte(n.indices) {
if c == '/' {
n = n.children[i]
tsr = (len(n.path) == 1 && n.handle != nil) ||
(n.nType == catchAll && n.children[0].handle != nil)
return
}
}
return
}
// Nothing found. We can recommend to redirect to the same URL with an
// extra trailing slash if a leaf exists for that path
tsr = (path == "/") ||
(len(prefix) == len(path)+1 && prefix[len(path)] == '/' &&
path == prefix[:len(prefix)-1] && n.handle != nil)
return
}
}
// Makes a case-insensitive lookup of the given path and tries to find a handler.
// It can optionally also fix trailing slashes.
// It returns the case-corrected path and a bool indicating whether the lookup
// was successful.
func (n *node) findCaseInsensitivePath(path string, fixTrailingSlash bool) (fixedPath string, found bool) {
const stackBufSize = 128
// Use a static sized buffer on the stack in the common case.
// If the path is too long, allocate a buffer on the heap instead.
buf := make([]byte, 0, stackBufSize)
if l := len(path) + 1; l > stackBufSize {
buf = make([]byte, 0, l)
}
ciPath := n.findCaseInsensitivePathRec(
path,
buf, // Preallocate enough memory for new path
[4]byte{}, // Empty rune buffer
fixTrailingSlash,
)
return string(ciPath), ciPath != nil
}
// Shift bytes in array by n bytes left
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{}
}
}
// Recursive case-insensitive lookup function used by n.findCaseInsensitivePath
func (n *node) findCaseInsensitivePathRec(path string, ciPath []byte, rb [4]byte, fixTrailingSlash bool) []byte {
npLen := len(n.path)
walk: // Outer loop for walking the tree
for len(path) >= npLen && (npLen == 0 || strings.EqualFold(path[1:npLen], n.path[1:])) {
// Add common prefix to result
oldPath := path
path = path[npLen:]
ciPath = append(ciPath, n.path...)
if len(path) > 0 {
// If this node does not have a wildcard (param or catchAll) child,
// we can just look up the next child node and continue to walk down
// the tree
if !n.wildChild {
// Skip rune bytes already processed
rb = shiftNRuneBytes(rb, npLen)
if rb[0] != 0 {
// Old rune not finished
idxc := rb[0]
for i, c := range []byte(n.indices) {
if c == idxc {
// continue with child node
n = n.children[i]
npLen = len(n.path)
continue walk
}
}
} else {
// Process a new rune
var rv rune
// Find rune start.
// Runes are up to 4 byte long,
// -4 would definitely be another rune.
var off int
for max := min(npLen, 3); off < max; off++ {
if i := npLen - off; utf8.RuneStart(oldPath[i]) {
// read rune from cached path
rv, _ = utf8.DecodeRuneInString(oldPath[i:])
break
}
}
// Calculate lowercase bytes of current rune
lo := unicode.ToLower(rv)
utf8.EncodeRune(rb[:], lo)
// Skip already processed bytes
rb = shiftNRuneBytes(rb, off)
idxc := rb[0]
for i, c := range []byte(n.indices) {
// Lowercase matches
if c == idxc {
// must use a recursive approach since both the
// uppercase byte and the lowercase byte might exist
// as an index
if out := n.children[i].findCaseInsensitivePathRec(
path, ciPath, rb, fixTrailingSlash,
); out != nil {
return out
}
break
}
}
// If we found no match, the same for the uppercase rune,
// if it differs
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) {
// Uppercase matches
if c == idxc {
// Continue with child node
n = n.children[i]
npLen = len(n.path)
continue walk
}
}
}
}
// Nothing found. We can recommend to redirect to the same URL
// without a trailing slash if a leaf exists for that path
if fixTrailingSlash && path == "/" && n.handle != nil {
return ciPath
}
return nil
}
n = n.children[0]
switch n.nType {
case param:
// Find param end (either '/' or path end)
end := 0
for end < len(path) && path[end] != '/' {
end++
}
// Add param value to case insensitive path
ciPath = append(ciPath, path[:end]...)
// We need to go deeper!
if end < len(path) {
if len(n.children) > 0 {
// Continue with child node
n = n.children[0]
npLen = len(n.path)
path = path[end:]
continue
}
// ... but we can't
if fixTrailingSlash && len(path) == end+1 {
return ciPath
}
return nil
}
if n.handle != nil {
return ciPath
} else if fixTrailingSlash && len(n.children) == 1 {
// No handle found. Check if a handle for this path + a
// trailing slash exists
n = n.children[0]
if n.path == "/" && n.handle != nil {
return append(ciPath, '/')
}
}
return nil
case catchAll:
return append(ciPath, path...)
default:
panic("invalid node type")
}
} else {
// We should have reached the node containing the handle.
// Check if this node has a handle registered.
if n.handle != nil {
return ciPath
}
// No handle found.
// Try to fix the path by adding a trailing slash
if fixTrailingSlash {
for i, c := range []byte(n.indices) {
if c == '/' {
n = n.children[i]
if (len(n.path) == 1 && n.handle != nil) ||
(n.nType == catchAll && n.children[0].handle != nil) {
return append(ciPath, '/')
}
return nil
}
}
}
return nil
}
}
// Nothing found.
// Try to fix the path by adding / removing a trailing slash
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.handle != nil {
return append(ciPath, n.path...)
}
}
return nil
}