XPathScanner.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Xml / System / Xml / XPath / Internal / XPathScanner.cs / 1305376 / XPathScanner.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
 
namespace MS.Internal.Xml.XPath { 
    using System;
    using System.Xml; 
    using System.Xml.XPath;
    using System.Diagnostics;
    using System.Globalization;
    using System.Text; 
    using System.Collections;
 
    internal sealed class XPathScanner { 
        private string  xpathExpr;
        private int     xpathExprIndex; 
        private LexKind kind;
        private char    currentChar;
        private string  name;
        private string  prefix; 
        private string  stringValue;
        private double  numberValue = double.NaN; 
        private bool    canBeFunction; 
        private XmlCharType xmlCharType = XmlCharType.Instance;
 
        public XPathScanner(string xpathExpr) {
            if (xpathExpr == null) {
                throw XPathException.Create(Res.Xp_ExprExpected, string.Empty);
            } 
            this.xpathExpr = xpathExpr;
 			NextChar(); 
            NextLex(); 
        }
 
        public string SourceText { get { return this.xpathExpr; } }

        private char CurerntChar { get { return currentChar; } }
 
        private bool NextChar() {
            Debug.Assert(0 <= xpathExprIndex && xpathExprIndex <= xpathExpr.Length); 
            if (xpathExprIndex < xpathExpr.Length) { 
				currentChar = xpathExpr[xpathExprIndex ++];
				return true; 
			}
 			else  {
				currentChar = '\0';
                return false; 
            }
        } 
 
#if XML10_FIFTH_EDITION
        private char PeekNextChar() { 
            Debug.Assert(0 <= xpathExprIndex && xpathExprIndex <= xpathExpr.Length);
            if (xpathExprIndex < xpathExpr.Length) {
                return xpathExpr[xpathExprIndex];
            } 
            else {
                Debug.Assert(xpathExprIndex == xpathExpr.Length); 
                return '\0'; 
            }
        } 
#endif

        public LexKind Kind { get { return this.kind; } }
 
        public string Name {
            get { 
                Debug.Assert(this.kind == LexKind.Name || this.kind == LexKind.Axe); 
                Debug.Assert(this.name != null);
                return this.name; 
            }
        }

        public string Prefix { 
            get {
                Debug.Assert(this.kind == LexKind.Name); 
                Debug.Assert(this.prefix != null); 
                return this.prefix;
            } 
        }

        public string StringValue {
            get { 
                Debug.Assert(this.kind == LexKind.String);
                Debug.Assert(this.stringValue != null); 
                return this.stringValue; 
            }
        } 

        public double NumberValue {
            get {
                Debug.Assert(this.kind == LexKind.Number); 
                Debug.Assert(this.numberValue != double.NaN);
                return this.numberValue; 
            } 
        }
 
        // To parse PathExpr we need a way to distinct name from function.
        // THis distinction can't be done without context: "or (1 != 0)" this this a function or 'or' in OrExp
        public bool CanBeFunction {
            get { 
                Debug.Assert(this.kind == LexKind.Name);
                return this.canBeFunction; 
            } 
        }
 
        void SkipSpace() {
            while (xmlCharType.IsWhiteSpace(this.CurerntChar) && NextChar()) ;
        }
 
        public bool NextLex() {
            SkipSpace(); 
            switch (this.CurerntChar) { 
            case '\0'  :
                kind = LexKind.Eof; 
                return false;
            case ',': case '@': case '(': case ')':
            case '|': case '*': case '[': case ']':
            case '+': case '-': case '=': case '#': 
            case '$':
                kind =  (LexKind) Convert.ToInt32(this.CurerntChar, CultureInfo.InvariantCulture); 
                NextChar(); 
                break;
            case '<': 
                kind = LexKind.Lt;
                NextChar();
                if (this.CurerntChar == '=') {
                    kind = LexKind.Le; 
                    NextChar();
                } 
                break; 
            case '>':
                kind = LexKind.Gt; 
                NextChar();
                if (this.CurerntChar == '=') {
                    kind = LexKind.Ge;
                    NextChar(); 
                }
                break; 
            case '!': 
                kind = LexKind.Bang;
                NextChar(); 
                if (this.CurerntChar == '=') {
                    kind = LexKind.Ne;
                    NextChar();
                } 
                break;
            case '.': 
                kind = LexKind.Dot; 
                NextChar();
                if (this.CurerntChar == '.') { 
                    kind = LexKind.DotDot;
                    NextChar();
                }
                else if (XmlCharType.IsDigit(this.CurerntChar)) { 
                    kind = LexKind.Number;
                    numberValue = ScanFraction(); 
                } 
                break;
            case '/': 
                kind = LexKind.Slash;
                NextChar();
                if (this.CurerntChar == '/') {
                    kind = LexKind.SlashSlash; 
                    NextChar();
                } 
                break; 
            case '"':
            case '\'': 
                this.kind = LexKind.String;
                this.stringValue = ScanString();
                break;
            default: 
                if (XmlCharType.IsDigit(this.CurerntChar)) {
                    kind = LexKind.Number; 
                    numberValue = ScanNumber(); 
                }
                else if (xmlCharType.IsStartNCNameSingleChar(this.CurerntChar) 
#if XML10_FIFTH_EDITION
                    || xmlCharType.IsNCNameHighSurrogateChar(this.CurerntChar)
#endif
                    ) { 
                    kind = LexKind.Name;
                    this.name   = ScanName(); 
                    this.prefix = string.Empty; 
                    // "foo:bar" is one lexem not three because it doesn't allow spaces in between
                    // We should distinct it from "foo::" and need process "foo ::" as well 
                    if (this.CurerntChar == ':') {
                        NextChar();
                        // can be "foo:bar" or "foo::"
                        if (this.CurerntChar == ':') {   // "foo::" 
                            NextChar();
                            kind = LexKind.Axe; 
                        } 
                        else {                          // "foo:*", "foo:bar" or "foo: "
                            this.prefix = this.name; 
                            if (this.CurerntChar == '*') {
 	                            NextChar();
                                this.name = "*";
                            } 
                            else if (xmlCharType.IsStartNCNameSingleChar(this.CurerntChar)
#if XML10_FIFTH_EDITION 
                                || xmlCharType.IsNCNameHighSurrogateChar(this.CurerntChar) 
#endif
                                ) { 
                                this.name = ScanName();
                            }
                            else {
                                throw XPathException.Create(Res.Xp_InvalidName, SourceText); 
                            }
                        } 
 
                    }
                    else { 
                        SkipSpace();
                        if (this.CurerntChar == ':') {
                            NextChar();
                            // it can be "foo ::" or just "foo :" 
                            if (this.CurerntChar == ':') {
                                NextChar(); 
                                kind = LexKind.Axe; 
                            }
                            else { 
                                throw XPathException.Create(Res.Xp_InvalidName, SourceText);
                            }
                        }
                    } 
                    SkipSpace();
                    this.canBeFunction = (this.CurerntChar == '('); 
                } 
                else {
                    throw XPathException.Create(Res.Xp_InvalidToken, SourceText); 
                }
 		        break;
            }
            return true; 
        }
 
        private double ScanNumber() { 
            Debug.Assert(this.CurerntChar == '.' || XmlCharType.IsDigit(this.CurerntChar));
            int start = xpathExprIndex - 1; 
			int len = 0;
 			while (XmlCharType.IsDigit(this.CurerntChar)) {
				NextChar(); len ++;
			} 
            if (this.CurerntChar == '.') {
				NextChar(); len ++; 
 				while (XmlCharType.IsDigit(this.CurerntChar)) { 
					NextChar(); len ++;
 				} 
            }
 			return XmlConvert.ToXPathDouble(this.xpathExpr.Substring(start, len));
        }
 
        private double ScanFraction() {
            Debug.Assert(XmlCharType.IsDigit(this.CurerntChar)); 
            int start = xpathExprIndex - 2; 
            Debug.Assert(0 <= start && this.xpathExpr[start] == '.');
			int len = 1; // '.' 
 			while (XmlCharType.IsDigit(this.CurerntChar)) {
				NextChar(); len ++;
			}
			return XmlConvert.ToXPathDouble(this.xpathExpr.Substring(start, len)); 
        }
 
        private string ScanString() { 
            char endChar = this.CurerntChar;
            NextChar(); 
            int start = xpathExprIndex - 1;
 			int len = 0;
            while(this.CurerntChar != endChar) {
				if (! NextChar()) { 
 	                throw XPathException.Create(Res.Xp_UnclosedString);
 				} 
				len ++; 
 			}
            Debug.Assert(this.CurerntChar == endChar); 
            NextChar();
            return this.xpathExpr.Substring(start, len);
        }
 
        private string ScanName() {
            Debug.Assert(xmlCharType.IsStartNCNameSingleChar(this.CurerntChar) 
#if XML10_FIFTH_EDITION 
                || xmlCharType.IsNCNameHighSurrogateChar(this.CurerntChar)
#endif 
                );
            int start = xpathExprIndex - 1;
			int len = 0;
 
            for (;;) {
                if (xmlCharType.IsNCNameSingleChar(this.CurerntChar)) { 
				    NextChar(); 
                    len ++;
                } 
#if XML10_FIFTH_EDITION
                else if (xmlCharType.IsNCNameSurrogateChar(this.PeekNextChar(), this.CurerntChar)) {
                    NextChar();
                    NextChar(); 
                    len += 2;
                } 
#endif 
                else {
                    break; 
                }
			}
            return this.xpathExpr.Substring(start, len);
        } 

        public enum LexKind  { 
            Comma                 = ',', 
            Slash                 = '/',
            At                    = '@', 
            Dot                   = '.',
            LParens               = '(',
            RParens               = ')',
            LBracket              = '[', 
            RBracket              = ']',
            Star                  = '*', 
            Plus                  = '+', 
            Minus                 = '-',
            Eq                    = '=', 
            Lt                    = '<',
            Gt                    = '>',
            Bang                  = '!',
            Dollar                = '$', 
            Apos                  = '\'',
            Quote                 = '"', 
            Union                 = '|', 
            Ne                    = 'N',   // !=
            Le                    = 'L',   // <= 
            Ge                    = 'G',   // >=
            And                   = 'A',   // &&
            Or                    = 'O',   // ||
            DotDot                = 'D',   // .. 
            SlashSlash            = 'S',   // //
            Name                  = 'n',   // XML _Name 
            String                = 's',   // Quoted string constant 
            Number                = 'd',   // _Number constant
            Axe                   = 'a',   // Axe (like child::) 
            Eof                   = 'E',
        };
    }
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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