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//------------------------------------------------------------------------------
// <copyright file="XPathPatternParser.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
//------------------------------------------------------------------------------
using System.Collections.Generic;
using System.Diagnostics;
using System.Xml;
using System.Xml.Xsl.Qil;
using System.Xml.Xsl.XPath;
namespace System.Xml.Xsl.Xslt {
using XPathParser = XPathParser<QilNode>;
using XPathNodeType = System.Xml.XPath.XPathNodeType;
using Res = System.Xml.Utils.Res;
internal class XPathPatternParser {
public interface IPatternBuilder : IXPathBuilder<QilNode> {
IXPathBuilder<QilNode> GetPredicateBuilder(QilNode context);
}
XPathScanner scanner;
IPatternBuilder ptrnBuilder;
XPathParser predicateParser = new XPathParser();
public QilNode Parse(XPathScanner scanner, IPatternBuilder ptrnBuilder) {
Debug.Assert(this.scanner == null && this.ptrnBuilder == null);
Debug.Assert(scanner != null && ptrnBuilder != null);
QilNode result = null;
ptrnBuilder.StartBuild();
try {
this.scanner = scanner;
this.ptrnBuilder = ptrnBuilder;
result = this.ParsePattern();
this.scanner.CheckToken(LexKind.Eof);
} finally {
result = ptrnBuilder.EndBuild(result);
#if DEBUG
this.ptrnBuilder = null;
this.scanner = null;
#endif
}
return result;
}
/*
* Pattern ::= LocationPathPattern ('|' LocationPathPattern)*
*/
private QilNode ParsePattern() {
QilNode opnd = ParseLocationPathPattern();
while (scanner.Kind == LexKind.Union) {
scanner.NextLex();
opnd = ptrnBuilder.Operator(XPathOperator.Union, opnd, ParseLocationPathPattern());
}
return opnd;
}
/*
* LocationPathPattern ::= '/' RelativePathPattern? | '//'? RelativePathPattern | IdKeyPattern (('/' | '//') RelativePathPattern)?
*/
private QilNode ParseLocationPathPattern() {
QilNode opnd;
switch (scanner.Kind) {
case LexKind.Slash :
scanner.NextLex();
opnd = ptrnBuilder.Axis(XPathAxis.Root, XPathNodeType.All, null, null);
if (XPathParser.IsStep(scanner.Kind)) {
opnd = ptrnBuilder.JoinStep(opnd, ParseRelativePathPattern());
}
return opnd;
case LexKind.SlashSlash :
scanner.NextLex();
return ptrnBuilder.JoinStep(
ptrnBuilder.Axis(XPathAxis.Root, XPathNodeType.All, null, null),
ptrnBuilder.JoinStep(
ptrnBuilder.Axis(XPathAxis.DescendantOrSelf, XPathNodeType.All, null, null),
ParseRelativePathPattern()
)
);
case LexKind.Name :
if (scanner.CanBeFunction && scanner.Prefix.Length == 0 && (scanner.Name == "id" || scanner.Name == "key")) {
opnd = ParseIdKeyPattern();
switch (scanner.Kind) {
case LexKind.Slash :
scanner.NextLex();
opnd = ptrnBuilder.JoinStep(opnd, ParseRelativePathPattern());
break;
case LexKind.SlashSlash :
scanner.NextLex();
opnd = ptrnBuilder.JoinStep(opnd,
ptrnBuilder.JoinStep(
ptrnBuilder.Axis(XPathAxis.DescendantOrSelf, XPathNodeType.All, null, null),
ParseRelativePathPattern()
)
);
break;
}
return opnd;
}
break;
}
opnd = ParseRelativePathPattern();
return opnd;
}
/*
* IdKeyPattern ::= 'id' '(' Literal ')' | 'key' '(' Literal ',' Literal ')'
*/
private QilNode ParseIdKeyPattern() {
Debug.Assert(scanner.CanBeFunction);
Debug.Assert(scanner.Prefix.Length == 0);
Debug.Assert(scanner.Name == "id" || scanner.Name == "key");
List<QilNode> args = new List<QilNode>(2);
if (scanner.Name == "id") {
scanner.NextLex();
scanner.PassToken(LexKind.LParens);
scanner.CheckToken(LexKind.String);
args.Add(ptrnBuilder.String(scanner.StringValue));
scanner.NextLex();
scanner.PassToken(LexKind.RParens);
return ptrnBuilder.Function("", "id", args);
} else {
scanner.NextLex();
scanner.PassToken(LexKind.LParens);
scanner.CheckToken(LexKind.String);
args.Add(ptrnBuilder.String(scanner.StringValue));
scanner.NextLex();
scanner.PassToken(LexKind.Comma);
scanner.CheckToken(LexKind.String);
args.Add(ptrnBuilder.String(scanner.StringValue));
scanner.NextLex();
scanner.PassToken(LexKind.RParens);
return ptrnBuilder.Function("", "key", args);
}
}
/*
* RelativePathPattern ::= StepPattern (('/' | '//') StepPattern)*
*/
//Max depth to avoid StackOverflow
const int MaxParseRelativePathDepth = 1024;
private int parseRelativePath = 0;
private QilNode ParseRelativePathPattern() {
if (++parseRelativePath > MaxParseRelativePathDepth) {
if (System.Xml.XmlConfiguration.XsltConfigSection.LimitXPathComplexity) {
throw scanner.CreateException(System.Xml.Utils.Res.Xslt_InputTooComplex);
}
}
QilNode opnd = ParseStepPattern();
if (scanner.Kind == LexKind.Slash) {
scanner.NextLex();
opnd = ptrnBuilder.JoinStep(opnd, ParseRelativePathPattern());
} else if (scanner.Kind == LexKind.SlashSlash) {
scanner.NextLex();
opnd = ptrnBuilder.JoinStep(opnd,
ptrnBuilder.JoinStep(
ptrnBuilder.Axis(XPathAxis.DescendantOrSelf, XPathNodeType.All, null, null),
ParseRelativePathPattern()
)
);
}
--parseRelativePath;
return opnd;
}
/*
* StepPattern ::= ChildOrAttributeAxisSpecifier NodeTest Predicate*
* ChildOrAttributeAxisSpecifier ::= @ ? | ('child' | 'attribute') '::'
*/
private QilNode ParseStepPattern() {
QilNode opnd;
XPathAxis axis;
switch (scanner.Kind) {
case LexKind.Dot:
case LexKind.DotDot:
throw scanner.CreateException(Res.XPath_InvalidAxisInPattern);
case LexKind.At:
axis = XPathAxis.Attribute;
scanner.NextLex();
break;
case LexKind.Axis:
axis = scanner.Axis;
if (axis != XPathAxis.Child && axis != XPathAxis.Attribute) {
throw scanner.CreateException(Res.XPath_InvalidAxisInPattern);
}
scanner.NextLex(); // Skip '::'
scanner.NextLex();
break;
case LexKind.Name:
case LexKind.Star:
// NodeTest must start with Name or '*'
axis = XPathAxis.Child;
break;
default:
throw scanner.CreateException(Res.XPath_UnexpectedToken, scanner.RawValue);
}
XPathNodeType nodeType;
string nodePrefix, nodeName;
XPathParser.InternalParseNodeTest(scanner, axis, out nodeType, out nodePrefix, out nodeName);
opnd = ptrnBuilder.Axis(axis, nodeType, nodePrefix, nodeName);
XPathPatternBuilder xpathPatternBuilder = ptrnBuilder as XPathPatternBuilder;
if (xpathPatternBuilder != null) {
//for XPathPatternBuilder, get all predicates and then build them
List<QilNode> predicates = new List<QilNode>();
while (scanner.Kind == LexKind.LBracket) {
predicates.Add(ParsePredicate(opnd));
}
if (predicates.Count > 0)
opnd = xpathPatternBuilder.BuildPredicates(opnd, predicates);
}
else {
while (scanner.Kind == LexKind.LBracket) {
opnd = ptrnBuilder.Predicate(opnd, ParsePredicate(opnd), /*reverseStep:*/false);
}
}
return opnd;
}
/*
* Predicate ::= '[' Expr ']'
*/
private QilNode ParsePredicate(QilNode context) {
Debug.Assert(scanner.Kind == LexKind.LBracket);
scanner.NextLex();
QilNode result = predicateParser.Parse(scanner, ptrnBuilder.GetPredicateBuilder(context), LexKind.RBracket);
Debug.Assert(scanner.Kind == LexKind.RBracket);
scanner.NextLex();
return result;
}
}
}
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