162 lines
4.0 KiB
Go
162 lines
4.0 KiB
Go
package xpath
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import (
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"errors"
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"fmt"
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)
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// NodeType represents a type of XPath node.
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type NodeType int
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const (
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// RootNode is a root node of the XML document or node tree.
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RootNode NodeType = iota
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// ElementNode is an element, such as <element>.
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ElementNode
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// AttributeNode is an attribute, such as id='123'.
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AttributeNode
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// TextNode is the text content of a node.
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TextNode
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// CommentNode is a comment node, such as <!-- my comment -->
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CommentNode
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// allNode is any types of node, used by xpath package only to predicate match.
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allNode
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)
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// NodeNavigator provides cursor model for navigating XML data.
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type NodeNavigator interface {
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// NodeType returns the XPathNodeType of the current node.
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NodeType() NodeType
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// LocalName gets the Name of the current node.
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LocalName() string
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// Prefix returns namespace prefix associated with the current node.
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Prefix() string
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// Value gets the value of current node.
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Value() string
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// Copy does a deep copy of the NodeNavigator and all its components.
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Copy() NodeNavigator
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// MoveToRoot moves the NodeNavigator to the root node of the current node.
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MoveToRoot()
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// MoveToParent moves the NodeNavigator to the parent node of the current node.
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MoveToParent() bool
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// MoveToNextAttribute moves the NodeNavigator to the next attribute on current node.
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MoveToNextAttribute() bool
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// MoveToChild moves the NodeNavigator to the first child node of the current node.
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MoveToChild() bool
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// MoveToFirst moves the NodeNavigator to the first sibling node of the current node.
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MoveToFirst() bool
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// MoveToNext moves the NodeNavigator to the next sibling node of the current node.
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MoveToNext() bool
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// MoveToPrevious moves the NodeNavigator to the previous sibling node of the current node.
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MoveToPrevious() bool
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// MoveTo moves the NodeNavigator to the same position as the specified NodeNavigator.
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MoveTo(NodeNavigator) bool
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}
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// NodeIterator holds all matched Node object.
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type NodeIterator struct {
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node NodeNavigator
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query query
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}
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// Current returns current node which matched.
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func (t *NodeIterator) Current() NodeNavigator {
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return t.node
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}
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// MoveNext moves Navigator to the next match node.
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func (t *NodeIterator) MoveNext() bool {
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n := t.query.Select(t)
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if n != nil {
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if !t.node.MoveTo(n) {
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t.node = n.Copy()
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}
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return true
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}
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return false
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}
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// Select selects a node set using the specified XPath expression.
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// This method is deprecated, recommend using Expr.Select() method instead.
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func Select(root NodeNavigator, expr string) *NodeIterator {
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exp, err := Compile(expr)
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if err != nil {
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panic(err)
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}
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return exp.Select(root)
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}
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// Expr is an XPath expression for query.
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type Expr struct {
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s string
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q query
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}
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type iteratorFunc func() NodeNavigator
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func (f iteratorFunc) Current() NodeNavigator {
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return f()
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}
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// Evaluate returns the result of the expression.
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// The result type of the expression is one of the follow: bool,float64,string,NodeIterator).
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func (expr *Expr) Evaluate(root NodeNavigator) interface{} {
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val := expr.q.Evaluate(iteratorFunc(func() NodeNavigator { return root }))
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switch val.(type) {
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case query:
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return &NodeIterator{query: expr.q.Clone(), node: root}
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}
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return val
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}
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// Select selects a node set using the specified XPath expression.
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func (expr *Expr) Select(root NodeNavigator) *NodeIterator {
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return &NodeIterator{query: expr.q.Clone(), node: root}
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}
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// String returns XPath expression string.
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func (expr *Expr) String() string {
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return expr.s
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}
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// Compile compiles an XPath expression string.
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func Compile(expr string) (*Expr, error) {
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if expr == "" {
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return nil, errors.New("expr expression is nil")
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}
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qy, err := build(expr)
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if err != nil {
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return nil, err
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}
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if qy == nil {
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return nil, fmt.Errorf(fmt.Sprintf("undeclared variable in XPath expression: %s", expr))
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}
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return &Expr{s: expr, q: qy}, nil
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}
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// MustCompile compiles an XPath expression string and ignored error.
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func MustCompile(expr string) *Expr {
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exp, err := Compile(expr)
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if err != nil {
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return &Expr{s: expr, q: nopQuery{}}
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}
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return exp
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}
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