791 lines
16 KiB
Go
791 lines
16 KiB
Go
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package xmlpath
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import (
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"fmt"
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"strconv"
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"unicode/utf8"
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)
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// Path is a compiled path that can be applied to a context
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// node to obtain a matching node set.
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// A single Path can be applied concurrently to any number
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// of context nodes.
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type Path struct {
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path string
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steps []pathStep
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}
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// Iter returns an iterator that goes over the list of nodes
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// that p matches on the given context.
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func (p *Path) Iter(context *Node) *Iter {
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iter := Iter{
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make([]pathStepState, len(p.steps)),
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make([]bool, len(context.nodes)),
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}
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for i := range p.steps {
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iter.state[i].step = &p.steps[i]
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}
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iter.state[0].init(context)
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return &iter
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}
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// Exists returns whether any nodes match p on the given context.
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func (p *Path) Exists(context *Node) bool {
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return p.Iter(context).Next()
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}
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// String returns the string value of the first node matched
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// by p on the given context.
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//
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// See the documentation of Node.String.
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func (p *Path) String(context *Node) (s string, ok bool) {
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iter := p.Iter(context)
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if iter.Next() {
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return iter.Node().String(), true
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}
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return "", false
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}
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// Bytes returns as a byte slice the string value of the first
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// node matched by p on the given context.
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//
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// See the documentation of Node.String.
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func (p *Path) Bytes(node *Node) (b []byte, ok bool) {
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iter := p.Iter(node)
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if iter.Next() {
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return iter.Node().Bytes(), true
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}
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return nil, false
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}
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// Iter iterates over node sets.
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type Iter struct {
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state []pathStepState
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seen []bool
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}
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// Node returns the current node.
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// Must only be called after Iter.Next returns true.
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func (iter *Iter) Node() *Node {
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state := iter.state[len(iter.state)-1]
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if state.pos == 0 {
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panic("Iter.Node called before Iter.Next")
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}
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if state.node == nil {
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panic("Iter.Node called after Iter.Next false")
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}
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return state.node
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}
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// Next iterates to the next node in the set, if any, and
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// returns whether there is a node available.
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func (iter *Iter) Next() bool {
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tip := len(iter.state) - 1
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outer:
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for {
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for !iter.state[tip].next() {
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tip--
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if tip == -1 {
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return false
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}
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}
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for tip < len(iter.state)-1 {
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tip++
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iter.state[tip].init(iter.state[tip-1].node)
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if !iter.state[tip].next() {
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tip--
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continue outer
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}
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}
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if iter.seen[iter.state[tip].node.pos] {
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continue
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}
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iter.seen[iter.state[tip].node.pos] = true
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return true
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}
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panic("unreachable")
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}
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type pathStepState struct {
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step *pathStep
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node *Node
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pos int
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idx int
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aux int
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}
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func (s *pathStepState) init(node *Node) {
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s.node = node
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s.pos = 0
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s.idx = 0
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s.aux = 0
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}
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func (s *pathStepState) next() bool {
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for s._next() {
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s.pos++
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if s.step.pred == nil || s.test(s.step.pred) {
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return true
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}
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}
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return false
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}
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func (s *pathStepState) test(pred predicate) bool {
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switch pred := pred.(type) {
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case positionPredicate:
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if pred.pos == s.pos {
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return true
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}
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case existsPredicate:
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if pred.path.Exists(s.node) {
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return true
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}
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case equalsPredicate:
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iter := pred.path.Iter(s.node)
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for iter.Next() {
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if iter.Node().equals(pred.value) {
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return true
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}
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}
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case containsPredicate:
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iter := pred.path.Iter(s.node)
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for iter.Next() {
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if iter.Node().contains(pred.value) {
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return true
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}
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}
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case notPredicate:
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iter := pred.path.Iter(s.node)
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if !iter.Next() {
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return true
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}
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case andPredicate:
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for _, sub := range pred.sub {
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if !s.test(sub) {
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return false
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}
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}
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return true
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case orPredicate:
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for _, sub := range pred.sub {
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if s.test(sub) {
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return true
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}
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}
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default:
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panic(fmt.Sprintf("internal error: unknown predicate type: %#v", s.step.pred))
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}
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return false
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}
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func (s *pathStepState) _next() bool {
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if s.node == nil {
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return false
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}
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if s.step.root && s.idx == 0 {
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for s.node.up != nil {
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s.node = s.node.up
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}
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}
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switch s.step.axis {
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case "self":
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if s.idx == 0 && s.step.match(s.node) {
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s.idx++
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return true
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}
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case "parent":
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if s.idx == 0 && s.node.up != nil && s.step.match(s.node.up) {
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s.idx++
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s.node = s.node.up
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return true
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}
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case "ancestor", "ancestor-or-self":
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if s.idx == 0 && s.step.axis == "ancestor-or-self" {
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s.idx++
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if s.step.match(s.node) {
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return true
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}
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}
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for s.node.up != nil {
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s.node = s.node.up
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s.idx++
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if s.step.match(s.node) {
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return true
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}
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}
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case "child":
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var down []*Node
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if s.idx == 0 {
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down = s.node.down
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} else {
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down = s.node.up.down
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}
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for s.idx < len(down) {
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node := down[s.idx]
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s.idx++
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if s.step.match(node) {
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s.node = node
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return true
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}
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}
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case "descendant", "descendant-or-self":
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if s.idx == 0 {
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s.idx = s.node.pos
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s.aux = s.node.end
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if s.step.axis == "descendant" {
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s.idx++
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}
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}
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for s.idx < s.aux {
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node := &s.node.nodes[s.idx]
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s.idx++
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if node.kind == attrNode {
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continue
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}
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if s.step.match(node) {
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s.node = node
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return true
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}
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}
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case "following":
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if s.idx == 0 {
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s.idx = s.node.end
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}
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for s.idx < len(s.node.nodes) {
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node := &s.node.nodes[s.idx]
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s.idx++
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if node.kind == attrNode {
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continue
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}
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if s.step.match(node) {
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s.node = node
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return true
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}
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}
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case "following-sibling":
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var down []*Node
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if s.node.up != nil {
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down = s.node.up.down
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if s.idx == 0 {
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for s.idx < len(down) {
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node := down[s.idx]
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s.idx++
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if node == s.node {
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break
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}
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}
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}
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}
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for s.idx < len(down) {
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node := down[s.idx]
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s.idx++
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if s.step.match(node) {
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s.node = node
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return true
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}
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}
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case "preceding":
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if s.idx == 0 {
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s.aux = s.node.pos // Detect ancestors.
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s.idx = s.node.pos - 1
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}
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for s.idx >= 0 {
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node := &s.node.nodes[s.idx]
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s.idx--
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if node.kind == attrNode {
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continue
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}
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if node == s.node.nodes[s.aux].up {
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s.aux = s.node.nodes[s.aux].up.pos
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continue
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}
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if s.step.match(node) {
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s.node = node
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return true
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}
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}
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case "preceding-sibling":
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var down []*Node
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if s.node.up != nil {
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down = s.node.up.down
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if s.aux == 0 {
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s.aux = 1
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for s.idx < len(down) {
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node := down[s.idx]
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s.idx++
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if node == s.node {
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s.idx--
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break
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}
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}
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}
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}
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for s.idx >= 0 {
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node := down[s.idx]
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s.idx--
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if s.step.match(node) {
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s.node = node
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return true
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}
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}
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case "attribute":
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if s.idx == 0 {
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s.idx = s.node.pos + 1
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s.aux = s.node.end
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}
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for s.idx < s.aux {
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node := &s.node.nodes[s.idx]
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s.idx++
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if node.kind != attrNode {
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break
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}
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if s.step.match(node) {
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s.node = node
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return true
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}
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}
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}
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s.node = nil
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return false
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}
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type positionPredicate struct {
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pos int
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}
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type existsPredicate struct {
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path *Path
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}
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type equalsPredicate struct {
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path *Path
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value string
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}
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type containsPredicate struct {
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path *Path
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value string
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}
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type notPredicate struct {
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path *Path
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}
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type andPredicate struct {
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sub []predicate
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}
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type orPredicate struct {
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sub []predicate
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}
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// predicate is a marker interface for predicate types.
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type predicate interface {
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predicate()
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}
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func (positionPredicate) predicate() {}
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func (existsPredicate) predicate() {}
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func (equalsPredicate) predicate() {}
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func (containsPredicate) predicate() {}
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func (notPredicate) predicate() {}
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func (andPredicate) predicate() {}
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func (orPredicate) predicate() {}
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type pathStep struct {
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root bool
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axis string
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name string
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kind nodeKind
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pred predicate
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}
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|
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func (step *pathStep) match(node *Node) bool {
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||
|
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return node.kind != endNode &&
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|
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(step.kind == anyNode || step.kind == node.kind) &&
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|
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(step.name == "*" || node.name.Local == step.name)
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}
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|
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// MustCompile returns the compiled path, and panics if
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||
|
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// there are any errors.
|
||
|
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func MustCompile(path string) *Path {
|
||
|
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e, err := Compile(path)
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|
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if err != nil {
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panic(err)
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}
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|
|
return e
|
||
|
|
}
|
||
|
|
|
||
|
|
// Compile returns the compiled path.
|
||
|
|
func Compile(path string) (*Path, error) {
|
||
|
|
c := pathCompiler{path, 0}
|
||
|
|
if path == "" {
|
||
|
|
return nil, c.errorf("empty path")
|
||
|
|
}
|
||
|
|
p, err := c.parsePath()
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
return p, nil
|
||
|
|
}
|
||
|
|
|
||
|
|
type pathCompiler struct {
|
||
|
|
path string
|
||
|
|
i int
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) errorf(format string, args ...interface{}) error {
|
||
|
|
return fmt.Errorf("compiling xml path %q:%d: %s", c.path, c.i, fmt.Sprintf(format, args...))
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) parsePath() (path *Path, err error) {
|
||
|
|
var steps []pathStep
|
||
|
|
var start = c.i
|
||
|
|
for {
|
||
|
|
step := pathStep{axis: "child"}
|
||
|
|
|
||
|
|
c.skipSpaces()
|
||
|
|
if c.i == 0 && c.skipByte('/') {
|
||
|
|
c.skipSpaces()
|
||
|
|
step.root = true
|
||
|
|
if len(c.path) == 1 {
|
||
|
|
step.name = "*"
|
||
|
|
}
|
||
|
|
}
|
||
|
|
if c.peekByte('/') {
|
||
|
|
step.axis = "descendant-or-self"
|
||
|
|
step.name = "*"
|
||
|
|
} else if c.skipByte('@') {
|
||
|
|
mark := c.i
|
||
|
|
if !c.skipName() {
|
||
|
|
return nil, c.errorf("missing name after @")
|
||
|
|
}
|
||
|
|
step.axis = "attribute"
|
||
|
|
step.name = c.path[mark:c.i]
|
||
|
|
step.kind = attrNode
|
||
|
|
} else {
|
||
|
|
mark := c.i
|
||
|
|
if c.skipName() {
|
||
|
|
step.name = c.path[mark:c.i]
|
||
|
|
c.skipSpaces()
|
||
|
|
}
|
||
|
|
if step.name == "" {
|
||
|
|
return nil, c.errorf("missing name")
|
||
|
|
} else if step.name == "*" {
|
||
|
|
step.kind = startNode
|
||
|
|
} else if step.name == "." {
|
||
|
|
step.axis = "self"
|
||
|
|
step.name = "*"
|
||
|
|
} else if step.name == ".." {
|
||
|
|
step.axis = "parent"
|
||
|
|
step.name = "*"
|
||
|
|
} else {
|
||
|
|
if c.skipByte(':') {
|
||
|
|
if !c.skipByte(':') {
|
||
|
|
return nil, c.errorf("missing ':'")
|
||
|
|
}
|
||
|
|
c.skipSpaces()
|
||
|
|
switch step.name {
|
||
|
|
case "attribute":
|
||
|
|
step.kind = attrNode
|
||
|
|
case "self", "child", "parent":
|
||
|
|
case "descendant", "descendant-or-self":
|
||
|
|
case "ancestor", "ancestor-or-self":
|
||
|
|
case "following", "following-sibling":
|
||
|
|
case "preceding", "preceding-sibling":
|
||
|
|
default:
|
||
|
|
return nil, c.errorf("unsupported axis: %q", step.name)
|
||
|
|
}
|
||
|
|
step.axis = step.name
|
||
|
|
|
||
|
|
mark = c.i
|
||
|
|
if !c.skipName() {
|
||
|
|
return nil, c.errorf("missing name")
|
||
|
|
}
|
||
|
|
step.name = c.path[mark:c.i]
|
||
|
|
|
||
|
|
c.skipSpaces()
|
||
|
|
}
|
||
|
|
if c.skipByte('(') {
|
||
|
|
c.skipSpaces()
|
||
|
|
conflict := step.kind != anyNode
|
||
|
|
switch step.name {
|
||
|
|
case "node":
|
||
|
|
// must be anyNode
|
||
|
|
case "text":
|
||
|
|
step.kind = textNode
|
||
|
|
case "comment":
|
||
|
|
step.kind = commentNode
|
||
|
|
case "processing-instruction":
|
||
|
|
step.kind = procInstNode
|
||
|
|
default:
|
||
|
|
return nil, c.errorf("unsupported expression: %s()", step.name)
|
||
|
|
}
|
||
|
|
if conflict {
|
||
|
|
return nil, c.errorf("%s() cannot succeed on axis %q", step.name, step.axis)
|
||
|
|
}
|
||
|
|
|
||
|
|
name := step.name
|
||
|
|
literal, err := c.parseLiteral()
|
||
|
|
if err == errNoLiteral {
|
||
|
|
step.name = "*"
|
||
|
|
} else if err != nil {
|
||
|
|
return nil, c.errorf("%v", err)
|
||
|
|
} else if step.kind == procInstNode {
|
||
|
|
c.skipSpaces()
|
||
|
|
step.name = literal
|
||
|
|
} else {
|
||
|
|
return nil, c.errorf("%s() has no arguments", name)
|
||
|
|
}
|
||
|
|
if !c.skipByte(')') {
|
||
|
|
return nil, c.errorf("%s() missing ')'", name)
|
||
|
|
}
|
||
|
|
c.skipSpaces()
|
||
|
|
} else if step.name == "*" && step.kind == anyNode {
|
||
|
|
step.kind = startNode
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
if c.skipByte('[') {
|
||
|
|
c.skipSpaces()
|
||
|
|
type state struct {
|
||
|
|
sub []predicate
|
||
|
|
and bool
|
||
|
|
}
|
||
|
|
var stack []state
|
||
|
|
var sub []predicate
|
||
|
|
var and bool
|
||
|
|
NextPred:
|
||
|
|
if c.skipByte('(') {
|
||
|
|
stack = append(stack, state{sub, and})
|
||
|
|
sub = nil
|
||
|
|
and = false
|
||
|
|
}
|
||
|
|
var next predicate
|
||
|
|
if pos, ok := c.parseInt(); ok {
|
||
|
|
if pos == 0 {
|
||
|
|
return nil, c.errorf("positions start at 1")
|
||
|
|
}
|
||
|
|
next = positionPredicate{pos}
|
||
|
|
} else if c.skipString("contains(") {
|
||
|
|
path, err := c.parsePath()
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
c.skipSpaces()
|
||
|
|
if !c.skipByte(',') {
|
||
|
|
return nil, c.errorf("contains() expected ',' followed by a literal string")
|
||
|
|
}
|
||
|
|
c.skipSpaces()
|
||
|
|
value, err := c.parseLiteral()
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
c.skipSpaces()
|
||
|
|
if !c.skipByte(')') {
|
||
|
|
return nil, c.errorf("contains() missing ')'")
|
||
|
|
}
|
||
|
|
next = containsPredicate{path, value}
|
||
|
|
} else if c.skipString("not(") {
|
||
|
|
// TODO Generalize to handle any predicate expression.
|
||
|
|
path, err := c.parsePath()
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
c.skipSpaces()
|
||
|
|
if !c.skipByte(')') {
|
||
|
|
return nil, c.errorf("not() missing ')'")
|
||
|
|
}
|
||
|
|
next = notPredicate{path}
|
||
|
|
} else {
|
||
|
|
path, err := c.parsePath()
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
if path.path[0] == '-' {
|
||
|
|
if _, err = strconv.Atoi(path.path); err == nil {
|
||
|
|
return nil, c.errorf("positions must be positive")
|
||
|
|
}
|
||
|
|
}
|
||
|
|
c.skipSpaces()
|
||
|
|
if c.skipByte('=') {
|
||
|
|
c.skipSpaces()
|
||
|
|
value, err := c.parseLiteral()
|
||
|
|
if err != nil {
|
||
|
|
return nil, c.errorf("%v", err)
|
||
|
|
}
|
||
|
|
next = equalsPredicate{path, value}
|
||
|
|
} else {
|
||
|
|
next = existsPredicate{path}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
HandleNext:
|
||
|
|
if and {
|
||
|
|
p := sub[len(sub)-1].(andPredicate)
|
||
|
|
p.sub = append(p.sub, next)
|
||
|
|
sub[len(sub)-1] = p
|
||
|
|
} else {
|
||
|
|
sub = append(sub, next)
|
||
|
|
}
|
||
|
|
if c.skipSpaces() {
|
||
|
|
mark := c.i
|
||
|
|
if c.skipString("and") && c.skipSpaces() {
|
||
|
|
if !and {
|
||
|
|
and = true
|
||
|
|
sub[len(sub)-1] = andPredicate{[]predicate{sub[len(sub)-1]}}
|
||
|
|
}
|
||
|
|
goto NextPred
|
||
|
|
} else if c.skipString("or") && c.skipSpaces() {
|
||
|
|
and = false
|
||
|
|
goto NextPred
|
||
|
|
} else {
|
||
|
|
c.i = mark
|
||
|
|
}
|
||
|
|
}
|
||
|
|
if c.skipByte(')') {
|
||
|
|
if len(stack) == 0 {
|
||
|
|
return nil, c.errorf("unexpected ')'")
|
||
|
|
}
|
||
|
|
if len(sub) == 1 {
|
||
|
|
next = sub[0]
|
||
|
|
} else {
|
||
|
|
next = orPredicate{sub}
|
||
|
|
}
|
||
|
|
s := stack[len(stack)-1]
|
||
|
|
stack = stack[:len(stack)-1]
|
||
|
|
sub = s.sub
|
||
|
|
and = s.and
|
||
|
|
goto HandleNext
|
||
|
|
}
|
||
|
|
if len(stack) > 0 {
|
||
|
|
return nil, c.errorf("expected ')'")
|
||
|
|
}
|
||
|
|
if len(sub) == 1 {
|
||
|
|
step.pred = sub[0]
|
||
|
|
} else {
|
||
|
|
step.pred = orPredicate{sub}
|
||
|
|
}
|
||
|
|
if !c.skipByte(']') {
|
||
|
|
return nil, c.errorf("expected ']'")
|
||
|
|
}
|
||
|
|
c.skipSpaces()
|
||
|
|
}
|
||
|
|
steps = append(steps, step)
|
||
|
|
//fmt.Printf("step: %#v\n", step)
|
||
|
|
if !c.skipByte('/') {
|
||
|
|
if (start == 0 || start == c.i) && c.i < len(c.path) {
|
||
|
|
return nil, c.errorf("unexpected %q", c.path[c.i])
|
||
|
|
}
|
||
|
|
return &Path{steps: steps, path: c.path[start:c.i]}, nil
|
||
|
|
}
|
||
|
|
}
|
||
|
|
panic("unreachable")
|
||
|
|
}
|
||
|
|
|
||
|
|
var errNoLiteral = fmt.Errorf("expected a literal string")
|
||
|
|
|
||
|
|
func (c *pathCompiler) parseLiteral() (string, error) {
|
||
|
|
if c.skipByte('"') {
|
||
|
|
mark := c.i
|
||
|
|
if !c.skipByteFind('"') {
|
||
|
|
return "", fmt.Errorf(`missing '"'`)
|
||
|
|
}
|
||
|
|
return c.path[mark : c.i-1], nil
|
||
|
|
}
|
||
|
|
if c.skipByte('\'') {
|
||
|
|
mark := c.i
|
||
|
|
if !c.skipByteFind('\'') {
|
||
|
|
return "", fmt.Errorf(`missing "'"`)
|
||
|
|
}
|
||
|
|
return c.path[mark : c.i-1], nil
|
||
|
|
}
|
||
|
|
return "", errNoLiteral
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) parseInt() (v int, ok bool) {
|
||
|
|
mark := c.i
|
||
|
|
for c.i < len(c.path) && c.path[c.i] >= '0' && c.path[c.i] <= '9' {
|
||
|
|
v *= 10
|
||
|
|
v += int(c.path[c.i]) - '0'
|
||
|
|
c.i++
|
||
|
|
}
|
||
|
|
if c.i == mark {
|
||
|
|
return 0, false
|
||
|
|
}
|
||
|
|
return v, true
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) skipByte(b byte) bool {
|
||
|
|
if c.i < len(c.path) && c.path[c.i] == b {
|
||
|
|
c.i++
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) skipByteFind(b byte) bool {
|
||
|
|
for i := c.i; i < len(c.path); i++ {
|
||
|
|
if c.path[i] == b {
|
||
|
|
c.i = i + 1
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) peekByte(b byte) bool {
|
||
|
|
return c.i < len(c.path) && c.path[c.i] == b
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) skipSpaces() bool {
|
||
|
|
mark := c.i
|
||
|
|
for c.i < len(c.path) {
|
||
|
|
if c.path[c.i] != ' ' {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
c.i++
|
||
|
|
}
|
||
|
|
return c.i != mark
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) skipString(s string) bool {
|
||
|
|
if c.i+len(s) <= len(c.path) && c.path[c.i:c.i+len(s)] == s {
|
||
|
|
c.i += len(s)
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
|
||
|
|
func (c *pathCompiler) skipName() bool {
|
||
|
|
if c.i >= len(c.path) {
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
if c.path[c.i] == '*' {
|
||
|
|
c.i++
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
start := c.i
|
||
|
|
for c.i < len(c.path) && (c.path[c.i] >= utf8.RuneSelf || isNameByte(c.path[c.i])) {
|
||
|
|
c.i++
|
||
|
|
}
|
||
|
|
return c.i > start
|
||
|
|
}
|
||
|
|
|
||
|
|
func isNameByte(c byte) bool {
|
||
|
|
return 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z' || '0' <= c && c <= '9' || c == '_' || c == '.' || c == '-'
|
||
|
|
}
|