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tree.go
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/*
Copyright (c) 2013 Julien Schmidt. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* The names of the contributors may not be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL JULIEN SCHMIDT BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package siesta
import (
"strings"
"unicode"
)
func min(a, b int) int {
if a <= b {
return a
}
return b
}
func countParams(path string) uint8 {
var n uint
for i := 0; i < len(path); i++ {
if path[i] != ':' && path[i] != '*' {
continue
}
n++
}
if n >= 255 {
return 255
}
return uint8(n)
}
type nodeType uint8
const (
static nodeType = 0
param nodeType = 1
catchAll nodeType = 2
)
type node struct {
path string
wildChild bool
nType nodeType
maxParams uint8
indices []byte
children []*node
handle contextHandler
priority uint32
}
// increments priority of the given child and reorders if necessary
func (n *node) incrementChildPrio(i int) int {
n.children[i].priority++
prio := n.children[i].priority
// adjust position (move to front)
for j := i - 1; j >= 0 && n.children[j].priority < prio; j-- {
// swap node positions
tmpN := n.children[j]
n.children[j] = n.children[i]
n.children[i] = tmpN
tmpI := n.indices[j]
n.indices[j] = n.indices[i]
n.indices[i] = tmpI
i--
}
return i
}
// addRoute adds a node with the given handle to the path.
// Not concurrency-safe!
func (n *node) addRoute(path string, handle contextHandler) {
n.priority++
numParams := countParams(path)
// non-empty tree
if len(n.path) > 0 || len(n.children) > 0 {
WALK:
for {
// Update maxParams of the current node
if numParams > n.maxParams {
n.maxParams = numParams
}
// Find the longest common prefix.
// This also implies that the commom prefix contains no ':' or '*'
// since the existing key can't contain this chars.
i := 0
for max := min(len(path), len(n.path)); i < max && path[i] == n.path[i]; i++ {
}
// Split edge
if i < len(n.path) {
child := node{
path: n.path[i:],
wildChild: n.wildChild,
indices: n.indices,
children: n.children,
handle: n.handle,
priority: n.priority - 1,
}
// Update maxParams (max of all children)
for i := range child.children {
if child.children[i].maxParams > child.maxParams {
child.maxParams = child.children[i].maxParams
}
}
n.children = []*node{&child}
n.indices = []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++
// Update maxParams of the child node
if numParams > n.maxParams {
n.maxParams = numParams
}
numParams--
// Check if the wildcard matches
if len(path) >= len(n.path) && n.path == path[:len(n.path)] {
// check for longer wildcard, e.g. :name and :names
if len(n.path) >= len(path) || path[len(n.path)] == '/' {
continue WALK
}
}
panic("conflict with wildcard route")
}
c := path[0]
// slash after param
if n.nType == param && c == '/' && len(n.children) == 1 {
n = n.children[0]
n.priority++
continue WALK
}
// Check if a child with the next path byte exists
for i, index := range n.indices {
if c == index {
i = n.incrementChildPrio(i)
n = n.children[i]
continue WALK
}
}
// Otherwise insert it
if c != ':' && c != '*' {
n.indices = append(n.indices, c)
child := &node{
maxParams: numParams,
}
n.children = append(n.children, child)
n.incrementChildPrio(len(n.indices) - 1)
n = child
}
n.insertChild(numParams, path, handle)
return
} else if i == len(path) { // Make node a (in-path) leaf
if n.handle != nil {
panic("a Handle is already registered for this path")
}
n.handle = handle
}
return
}
} else { // Empty tree
n.insertChild(numParams, path, handle)
}
}
func (n *node) insertChild(numParams uint8, path string, handle contextHandler) {
var offset int // already handled bytes of the path
// find prefix until first wildcard (beginning with ':'' or '*'')
for i, max := 0, len(path); numParams > 0; i++ {
c := path[i]
if c != ':' && c != '*' {
continue
}
// check if this Node existing children which would be
// unreachable if we insert the wildcard here
if len(n.children) > 0 {
panic("wildcard route conflicts with existing children")
}
// find wildcard end (either '/' or path end)
end := i + 1
for end < max && path[end] != '/' {
switch path[end] {
// the wildcard name must not contain ':' and '*'
case ':', '*':
panic("only one wildcard per path segment is allowed")
default:
end++
}
}
// check if the wildcard has a name
if end-i < 2 {
panic("wildcards must be named with a non-empty name")
}
if c == ':' { // param
// split path at the beginning of the wildcard
if i > 0 {
n.path = path[offset:i]
offset = i
}
child := &node{
nType: param,
maxParams: numParams,
}
n.children = []*node{child}
n.wildChild = true
n = child
n.priority++
numParams--
// if the path doesn't end with the wildcard, then there
// will be another non-wildcard subpath starting with '/'
if end < max {
n.path = path[offset:end]
offset = end
child := &node{
maxParams: numParams,
priority: 1,
}
n.children = []*node{child}
n = child
}
} else { // catchAll
if end != max || numParams > 1 {
panic("catch-all routes are only allowed at the end of the path")
}
if len(n.path) > 0 && n.path[len(n.path)-1] == '/' {
panic("catch-all conflicts with existing handle for the path segment root")
}
// currently fixed width 1 for '/'
i--
if path[i] != '/' {
panic("no / before catch-all")
}
n.path = path[offset:i]
// first node: catchAll node with empty path
child := &node{
wildChild: true,
nType: catchAll,
maxParams: 1,
}
n.children = []*node{child}
n.indices = []byte{path[i]}
n = child
n.priority++
// second node: node holding the variable
child = &node{
path: path[i:],
nType: catchAll,
maxParams: 1,
handle: handle,
priority: 1,
}
n.children = []*node{child}
return
}
}
// insert remaining path part and handle to the leaf
n.path = path[offset:]
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) (handle contextHandler, p routeParams, tsr bool) {
walk: // Outer loop for walking the tree
for {
if len(path) > len(n.path) {
if path[:len(n.path)] == n.path {
path = path[len(n.path):]
// 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 {
c := path[0]
for i, index := range n.indices {
if c == index {
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 p == nil {
// lazy allocation
p = make(routeParams, 0, n.maxParams)
}
i := len(p)
p = p[:i+1] // expand slice within preallocated capacity
p[i].Key = n.path[1:]
p[i].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)
}
return
case catchAll:
// save param value
if p == nil {
// lazy allocation
p = make(routeParams, 0, n.maxParams)
}
i := len(p)
p = p[:i+1] // expand slice within preallocated capacity
p[i].Key = n.path[2:]
p[i].Value = path
handle = n.handle
return
default:
panic("Invalid node type")
}
}
} else if path == n.path {
// We should have reached the node containing the handle.
// Check if this node has a handle registered.
if handle = n.handle; handle != nil {
return
}
// No handle found. Check if a handle for this path + a
// trailing slash exists for trailing slash recommendation
for i, index := range n.indices {
if index == '/' {
n = n.children[i]
tsr = (n.path == "/" && 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(n.path) == len(path)+1 && n.path[len(path)] == '/' &&
path == n.path[:len(n.path)-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 wether the lookup
// was successful.
func (n *node) findCaseInsensitivePath(path string, fixTrailingSlash bool) (ciPath []byte, found bool) {
ciPath = make([]byte, 0, len(path)+1) // preallocate enough memory
// Outer loop for walking the tree
for len(path) >= len(n.path) && strings.ToLower(path[:len(n.path)]) == strings.ToLower(n.path) {
path = path[len(n.path):]
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 {
r := unicode.ToLower(rune(path[0]))
for i, index := range n.indices {
// must use recursive approach since both index and
// ToLower(index) could exist. We must check both.
if r == unicode.ToLower(rune(index)) {
out, found := n.children[i].findCaseInsensitivePath(path, fixTrailingSlash)
if found {
return append(ciPath, out...), true
}
}
}
// Nothing found. We can recommend to redirect to the same URL
// without a trailing slash if a leaf exists for that path
found = (fixTrailingSlash && path == "/" && n.handle != nil)
return
}
n = n.children[0]
switch n.nType {
case param:
// find param end (either '/' or path end)
k := 0
for k < len(path) && path[k] != '/' {
k++
}
// add param value to case insensitive path
ciPath = append(ciPath, path[:k]...)
// we need to go deeper!
if k < len(path) {
if len(n.children) > 0 {
path = path[k:]
n = n.children[0]
continue
}
// ... but we can't
if fixTrailingSlash && len(path) == k+1 {
return ciPath, true
}
return
}
if n.handle != nil {
return ciPath, true
} 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, '/'), true
}
}
return
case catchAll:
return append(ciPath, path...), true
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, true
}
// No handle found.
// Try to fix the path by adding a trailing slash
if fixTrailingSlash {
for i, index := range n.indices {
if index == '/' {
n = n.children[i]
if (n.path == "/" && n.handle != nil) ||
(n.nType == catchAll && n.children[0].handle != nil) {
return append(ciPath, '/'), true
}
return
}
}
}
return
}
}
// Nothing found.
// Try to fix the path by adding / removing a trailing slash
if fixTrailingSlash {
if path == "/" {
return ciPath, true
}
if len(path)+1 == len(n.path) && n.path[len(path)] == '/' &&
strings.ToLower(path) == strings.ToLower(n.path[:len(path)]) &&
n.handle != nil {
return append(ciPath, n.path...), true
}
}
return
}