366 lines
12 KiB
Go
366 lines
12 KiB
Go
package xmlquery
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import (
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"bufio"
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"encoding/xml"
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"errors"
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"fmt"
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"io"
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"net/http"
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"regexp"
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"strings"
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"github.com/antchfx/xpath"
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"golang.org/x/net/html/charset"
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)
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var xmlMIMERegex = regexp.MustCompile(`(?i)((application|image|message|model)/((\w|\.|-)+\+?)?|text/)(wb)?xml`)
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// LoadURL loads the XML document from the specified URL.
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func LoadURL(url string) (*Node, error) {
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resp, err := http.Get(url)
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if err != nil {
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return nil, err
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}
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defer resp.Body.Close()
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// Make sure the Content-Type has a valid XML MIME type
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if xmlMIMERegex.MatchString(resp.Header.Get("Content-Type")) {
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return Parse(resp.Body)
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}
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return nil, fmt.Errorf("invalid XML document(%s)", resp.Header.Get("Content-Type"))
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}
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// Parse returns the parse tree for the XML from the given Reader.
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func Parse(r io.Reader) (*Node, error) {
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return ParseWithOptions(r, ParserOptions{})
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}
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// ParseWithOptions is like parse, but with custom options
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func ParseWithOptions(r io.Reader, options ParserOptions) (*Node, error) {
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p := createParser(r)
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options.apply(p)
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for {
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_, err := p.parse()
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if err == io.EOF {
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return p.doc, nil
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}
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if err != nil {
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return nil, err
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}
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}
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}
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type parser struct {
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decoder *xml.Decoder
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doc *Node
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space2prefix map[string]string
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level int
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prev *Node
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streamElementXPath *xpath.Expr // Under streaming mode, this specifies the xpath to the target element node(s).
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streamElementFilter *xpath.Expr // If specified, it provides further filtering on the target element.
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streamNode *Node // Need to remember the last target node So we can clean it up upon next Read() call.
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streamNodePrev *Node // Need to remember target node's prev so upon target node removal, we can restore correct prev.
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reader *cachedReader // Need to maintain a reference to the reader, so we can determine whether a node contains CDATA.
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}
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func createParser(r io.Reader) *parser {
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reader := newCachedReader(bufio.NewReader(r))
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p := &parser{
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decoder: xml.NewDecoder(reader),
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doc: &Node{Type: DocumentNode},
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space2prefix: make(map[string]string),
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level: 0,
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reader: reader,
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}
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// http://www.w3.org/XML/1998/namespace is bound by definition to the prefix xml.
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p.space2prefix["http://www.w3.org/XML/1998/namespace"] = "xml"
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p.decoder.CharsetReader = charset.NewReaderLabel
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p.prev = p.doc
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return p
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}
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func (p *parser) parse() (*Node, error) {
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var streamElementNodeCounter int
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for {
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tok, err := p.decoder.Token()
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if err != nil {
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return nil, err
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}
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switch tok := tok.(type) {
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case xml.StartElement:
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if p.level == 0 {
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// mising XML declaration
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node := &Node{Type: DeclarationNode, Data: "xml", level: 1}
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AddChild(p.prev, node)
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p.level = 1
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p.prev = node
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}
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// https://www.w3.org/TR/xml-names/#scoping-defaulting
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for _, att := range tok.Attr {
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if att.Name.Local == "xmlns" {
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p.space2prefix[att.Value] = ""
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} else if att.Name.Space == "xmlns" {
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p.space2prefix[att.Value] = att.Name.Local
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}
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}
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if tok.Name.Space != "" {
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if _, found := p.space2prefix[tok.Name.Space]; !found {
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return nil, errors.New("xmlquery: invalid XML document, namespace is missing")
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}
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}
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attributes := make([]Attr, len(tok.Attr))
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for i, att := range tok.Attr {
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name := att.Name
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if prefix, ok := p.space2prefix[name.Space]; ok {
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name.Space = prefix
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}
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attributes[i] = Attr{
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Name: name,
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Value: att.Value,
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NamespaceURI: att.Name.Space,
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}
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}
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node := &Node{
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Type: ElementNode,
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Data: tok.Name.Local,
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Prefix: p.space2prefix[tok.Name.Space],
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NamespaceURI: tok.Name.Space,
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Attr: attributes,
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level: p.level,
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}
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if p.level == p.prev.level {
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AddSibling(p.prev, node)
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} else if p.level > p.prev.level {
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AddChild(p.prev, node)
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} else if p.level < p.prev.level {
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for i := p.prev.level - p.level; i > 1; i-- {
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p.prev = p.prev.Parent
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}
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AddSibling(p.prev.Parent, node)
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}
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// If we're in the streaming mode, we need to remember the node if it is the target node
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// so that when we finish processing the node's EndElement, we know how/what to return to
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// caller. Also we need to remove the target node from the tree upon next Read() call so
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// memory doesn't grow unbounded.
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if p.streamElementXPath != nil {
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if p.streamNode == nil {
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if QuerySelector(p.doc, p.streamElementXPath) != nil {
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p.streamNode = node
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p.streamNodePrev = p.prev
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streamElementNodeCounter = 1
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}
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} else {
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streamElementNodeCounter++
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}
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}
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p.prev = node
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p.level++
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p.reader.StartCaching()
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case xml.EndElement:
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p.level--
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// If we're in streaming mode, and we already have a potential streaming
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// target node identified (p.streamNode != nil) then we need to check if
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// this is the real one we want to return to caller.
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if p.streamNode != nil {
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streamElementNodeCounter--
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if streamElementNodeCounter == 0 {
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// Now we know this element node is the at least passing the initial
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// p.streamElementXPath check and is a potential target node candidate.
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// We need to have 1 more check with p.streamElementFilter (if given) to
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// ensure it is really the element node we want.
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// The reason we need a two-step check process is because the following
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// situation:
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// <AAA><BBB>b1</BBB></AAA>
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// And say the p.streamElementXPath = "/AAA/BBB[. != 'b1']". Now during
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// xml.StartElement time, the <BBB> node is still empty, so it will pass
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// the p.streamElementXPath check. However, eventually we know this <BBB>
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// shouldn't be returned to the caller. Having a second more fine-grained
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// filter check ensures that. So in this case, the caller should really
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// setup the stream parser with:
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// streamElementXPath = "/AAA/BBB["
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// streamElementFilter = "/AAA/BBB[. != 'b1']"
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if p.streamElementFilter == nil || QuerySelector(p.doc, p.streamElementFilter) != nil {
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return p.streamNode, nil
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}
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// otherwise, this isn't our target node, clean things up.
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// note we also remove the underlying *Node from the node tree, to prevent
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// future stream node candidate selection error.
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RemoveFromTree(p.streamNode)
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p.prev = p.streamNodePrev
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p.streamNode = nil
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p.streamNodePrev = nil
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}
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}
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case xml.CharData:
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p.reader.StopCaching()
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// First, normalize the cache...
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cached := strings.ToUpper(string(p.reader.Cache()))
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nodeType := TextNode
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if strings.HasPrefix(cached, "<![CDATA[") {
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nodeType = CharDataNode
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}
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node := &Node{Type: nodeType, Data: string(tok), level: p.level}
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if p.level == p.prev.level {
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AddSibling(p.prev, node)
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} else if p.level > p.prev.level {
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AddChild(p.prev, node)
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} else if p.level < p.prev.level {
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for i := p.prev.level - p.level; i > 1; i-- {
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p.prev = p.prev.Parent
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}
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AddSibling(p.prev.Parent, node)
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}
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p.reader.StartCaching()
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case xml.Comment:
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node := &Node{Type: CommentNode, Data: string(tok), level: p.level}
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if p.level == p.prev.level {
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AddSibling(p.prev, node)
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} else if p.level > p.prev.level {
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AddChild(p.prev, node)
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} else if p.level < p.prev.level {
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for i := p.prev.level - p.level; i > 1; i-- {
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p.prev = p.prev.Parent
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}
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AddSibling(p.prev.Parent, node)
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}
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case xml.ProcInst: // Processing Instruction
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if p.prev.Type != DeclarationNode {
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p.level++
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}
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node := &Node{Type: DeclarationNode, Data: tok.Target, level: p.level}
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pairs := strings.Split(string(tok.Inst), " ")
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for _, pair := range pairs {
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pair = strings.TrimSpace(pair)
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if i := strings.Index(pair, "="); i > 0 {
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AddAttr(node, pair[:i], strings.Trim(pair[i+1:], `"`))
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}
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}
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if p.level == p.prev.level {
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AddSibling(p.prev, node)
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} else if p.level > p.prev.level {
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AddChild(p.prev, node)
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}
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p.prev = node
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case xml.Directive:
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}
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}
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}
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// StreamParser enables loading and parsing an XML document in a streaming
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// fashion.
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type StreamParser struct {
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p *parser
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}
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// CreateStreamParser creates a StreamParser. Argument streamElementXPath is
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// required.
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// Argument streamElementFilter is optional and should only be used in advanced
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// scenarios.
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//
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// Scenario 1: simple case:
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// xml := `<AAA><BBB>b1</BBB><BBB>b2</BBB></AAA>`
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// sp, err := CreateStreamParser(strings.NewReader(xml), "/AAA/BBB")
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// if err != nil {
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// panic(err)
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// }
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// for {
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// n, err := sp.Read()
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// if err != nil {
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// break
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// }
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// fmt.Println(n.OutputXML(true))
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// }
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// Output will be:
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// <BBB>b1</BBB>
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// <BBB>b2</BBB>
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//
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// Scenario 2: advanced case:
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// xml := `<AAA><BBB>b1</BBB><BBB>b2</BBB></AAA>`
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// sp, err := CreateStreamParser(strings.NewReader(xml), "/AAA/BBB", "/AAA/BBB[. != 'b1']")
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// if err != nil {
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// panic(err)
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// }
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// for {
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// n, err := sp.Read()
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// if err != nil {
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// break
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// }
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// fmt.Println(n.OutputXML(true))
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// }
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// Output will be:
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// <BBB>b2</BBB>
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//
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// As the argument names indicate, streamElementXPath should be used for
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// providing xpath query pointing to the target element node only, no extra
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// filtering on the element itself or its children; while streamElementFilter,
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// if needed, can provide additional filtering on the target element and its
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// children.
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//
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// CreateStreamParser returns an error if either streamElementXPath or
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// streamElementFilter, if provided, cannot be successfully parsed and compiled
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// into a valid xpath query.
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func CreateStreamParser(r io.Reader, streamElementXPath string, streamElementFilter ...string) (*StreamParser, error) {
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return CreateStreamParserWithOptions(r, ParserOptions{}, streamElementXPath, streamElementFilter...)
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}
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// CreateStreamParserWithOptions is like CreateStreamParser, but with custom options
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func CreateStreamParserWithOptions(
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r io.Reader,
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options ParserOptions,
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streamElementXPath string,
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streamElementFilter ...string,
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) (*StreamParser, error) {
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elemXPath, err := getQuery(streamElementXPath)
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if err != nil {
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return nil, fmt.Errorf("invalid streamElementXPath '%s', err: %s", streamElementXPath, err.Error())
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}
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elemFilter := (*xpath.Expr)(nil)
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if len(streamElementFilter) > 0 {
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elemFilter, err = getQuery(streamElementFilter[0])
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if err != nil {
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return nil, fmt.Errorf("invalid streamElementFilter '%s', err: %s", streamElementFilter[0], err.Error())
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}
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}
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parser := createParser(r)
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options.apply(parser)
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sp := &StreamParser{
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p: parser,
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}
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sp.p.streamElementXPath = elemXPath
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sp.p.streamElementFilter = elemFilter
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return sp, nil
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}
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// Read returns a target node that satisfies the XPath specified by caller at
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// StreamParser creation time. If there is no more satisfying target nodes after
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// reading the rest of the XML document, io.EOF will be returned. At any time,
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// any XML parsing error encountered will be returned, and the stream parsing
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// stopped. Calling Read() after an error is returned (including io.EOF) results
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// undefined behavior. Also note, due to the streaming nature, calling Read()
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// will automatically remove any previous target node(s) from the document tree.
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func (sp *StreamParser) Read() (*Node, error) {
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// Because this is a streaming read, we need to release/remove last
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// target node from the node tree to free up memory.
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if sp.p.streamNode != nil {
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// We need to remove all siblings before the current stream node,
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// because the document may contain unwanted nodes between the target
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// ones (for example new line text node), which would otherwise
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// accumulate as first childs, and slow down the stream over time
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for sp.p.streamNode.PrevSibling != nil {
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RemoveFromTree(sp.p.streamNode.PrevSibling)
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}
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sp.p.prev = sp.p.streamNode.Parent
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RemoveFromTree(sp.p.streamNode)
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sp.p.streamNode = nil
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sp.p.streamNodePrev = nil
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}
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return sp.p.parse()
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}
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