/IronPython_1_1/Src/IronPython/Modules/re.cs

/* ****************************************************************************

 *

 * Copyright (c) Microsoft Corporation. 

 *

 * This source code is subject to terms and conditions of the Microsoft Public

 * License. A  copy of the license can be found in the License.html file at the

 * root of this distribution. If  you cannot locate the  Microsoft Public

 * License, please send an email to  dlr@microsoft.com. By using this source

 * code in any fashion, you are agreeing to be bound by the terms of the 

 * Microsoft Public License.

 *

 * You must not remove this notice, or any other, from this software.

 *

 * ***************************************************************************/



using System;

using System.Text;

using System.Text.RegularExpressions;

using System.Collections;

using System.Collections.Generic;

using System.Diagnostics;



using IronPython.Runtime;

using IronPython.Runtime.Operations;

using IronPython.Runtime.Exceptions;

using System.Runtime.InteropServices;



[assembly: PythonModule("re", typeof(IronPython.Modules.PythonRegex))]

namespace IronPython.Modules {



    /// <summary>

    /// Python regular expression module.

    /// </summary>

    [PythonType("re")]

    public static class PythonRegex {



        #region CONSTANTS



        // short forms

        public static object I = 0x02;

        public static object L = 0x04;

        public static object M = 0x08;

        public static object S = 0x10;

        public static object U = 0x20;

        public static object X = 0x40;



        // long forms

        public static object IGNORECASE = 0x02;

        public static object LOCALE = 0x04;

        public static object MULTILINE = 0x08;

        public static object DOTALL = 0x10;

        public static object UNICODE = 0x20;

        public static object VERBOSE = 0x40;



        #endregion



        #region Public API Surface



        [PythonName("compile")]

        public static RE_Pattern Compile(object pattern) {

            try {

                return new RE_Pattern(ValidatePattern(pattern));

            } catch (ArgumentException e) {

                throw ExceptionConverter.CreateThrowable(error, e.Message);

            }

        }



        [PythonName("compile")]

        public static RE_Pattern Compile(object pattern, object flags) {

            try {

                return new RE_Pattern(ValidatePattern(pattern), Converter.ConvertToInt32(flags));

            } catch (ArgumentException e) {

                throw ExceptionConverter.CreateThrowable(error, e.Message);

            }

        }

        public static string engine = "cli reg ex";



        public static object error = ExceptionConverter.CreatePythonException("error", "re");



        [PythonName("escape")]

        public static string Escape(string text) {

            if (text == null) throw Ops.TypeError("text must not be None");



            for (int i = 0; i < text.Length; i++) {

                if (!Char.IsLetterOrDigit(text[i])) {

                    StringBuilder sb = new StringBuilder(text, 0, i, text.Length);



                    char ch = text[i];

                    do {

                        sb.Append('\\');

                        sb.Append(ch);

                        i++;



                        int last = i;

                        while (i < text.Length) {

                            ch = text[i];

                            if (!Char.IsLetterOrDigit(ch)) {

                                break;

                            }

                            i++;

                        }

                        sb.Append(text, last, i - last);

                    } while (i < text.Length);



                    return sb.ToString();

                }

            }

            return text;

        }



        [PythonName("findall")]

        public static object FindAll(object pattern, string @string) {

            return FindAll(pattern, @string, 0);

        }



        [PythonName("findall")]

        public static object FindAll(object pattern, string @string, int flags) {

            RE_Pattern pat = new RE_Pattern(ValidatePattern(pattern), flags);

            ValidateString(@string, "string");



            MatchCollection mc = pat.FindAllWorker(@string, 0, @string.Length);

            return FixFindAllMatch(pat, mc);

        }



        private static object FixFindAllMatch(RE_Pattern pat, MatchCollection mc) {

            object[] matches = new object[mc.Count];

            int numgrps = pat.re.GetGroupNumbers().Length;

            for (int i = 0; i < mc.Count; i++) {

                if (numgrps > 2) { // CLR gives us a "bonus" group of 0 - the entire expression

                    //  at this point we have more than one group in the pattern;

                    //  need to return a list of tuples in this case



                    //  for each match item in the matchcollection, create a tuple representing what was matched

                    //  e.g. findall("(\d+)|(\w+)", "x = 99y") == [('', 'x'), ('99', ''), ('', 'y')]

                    //  in the example above, ('', 'x') did not match (\d+) as indicated by '' but did 

                    //  match (\w+) as indicated by 'x' and so on...

                    int k = 0;

                    List<object> tpl = new List<object>();

                    foreach (Group g in mc[i].Groups) {

                        //  here also the CLR gives us a "bonus" match as the first item which is the 

                        //  group that was actually matched in the tuple e.g. we get 'x', '', 'x' for 

                        //  the first match object...so we'll skip the first item when creating the 

                        //  tuple

                        if (k++ != 0) {

                            tpl.Add(g.Value);

                        }

                    }

                    matches[i] = Tuple.Make(tpl);

                } else if (numgrps == 2) {

                    //  at this point we have exactly one group in the pattern (including the "bonus" one given 

                    //  by the CLR 

                    //  skip the first match since that contains the entire match and not the group match

                    //  e.g. re.findall(r"(\w+)\s+fish\b", "green fish") will have "green fish" in the 0 

                    //  index and "green" as the (\w+) group match

                    matches[i] = mc[i].Groups[1].Value;

                } else {

                    matches[i] = mc[i].Value;

                }

            }

            return new List(matches);

        }



        [PythonName("finditer")]

        public static object FindIter(object pattern, object @string) {

            return FindIter(pattern, @string, 0);

        }



        [PythonName("finditer")]

        public static object FindIter(object pattern, object @string, int flags) {

            RE_Pattern pat = new RE_Pattern(ValidatePattern(pattern), flags);



            string str = ValidateString(@string, "string");

            return MatchIterator(pat.FindAllWorker(str, 0, str.Length), pat, str);

        }



        [PythonName("match")]

        public static object Match(object pattern, object @string) {

            return Match(pattern, @string, 0);

        }



        [PythonName("match")]

        public static object Match(object pattern, object @string, int flags) {

            return new RE_Pattern(ValidatePattern(pattern), flags).Match(ValidateString(@string, "string"));

        }



        [PythonName("search")]

        public static object Search(object pattern, object @string) {

            return Search(pattern, @string, 0);

        }

        [PythonName("search")]

        public static object Search(object pattern, object @string, int flags) {

            return new RE_Pattern(ValidatePattern(pattern), flags).Search(ValidateString(@string, "string"));

        }



        [PythonName("split")]

        public static object Split(object pattern, object @string) {

            return Split(ValidatePattern(pattern), ValidateString(@string, "string"), 0);

        }

        [PythonName("split")]

        public static object Split(object pattern, object @string, int maxsplit) {

            return new RE_Pattern(ValidatePattern(pattern)).Split(ValidateString(@string, "string"),

                maxsplit);

        }



        [PythonName("sub")]

        public static object Substitute(object pattern, object repl, object @string) {

            return Substitute(pattern, repl, @string, Int32.MaxValue);

        }



        [PythonName("sub")]

        public static object Substitute(object pattern, object repl, object @string, int count) {

            return new RE_Pattern(ValidatePattern(pattern)).Substitute(repl, ValidateString(@string, "string"), count);

        }



        [PythonName("subn")]

        public static object SubGetCount(object pattern, object repl, object @string) {

            return SubGetCount(pattern, repl, @string, Int32.MaxValue);

        }



        [PythonName("subn")]

        public static object SubGetCount(object pattern, object repl, object @string, int count) {

            return new RE_Pattern(ValidatePattern(pattern)).SubGetCount(repl, ValidateString(@string, "string"), count);



        }



        #endregion



        #region Public classes

        /// <summary>

        /// Compiled reg-ex pattern

        /// </summary>

        public class RE_Pattern : IWeakReferenceable {

            internal Regex re;

            private Dict groups;

            private int compileFlags;

            private WeakRefTracker weakRefTracker;

            internal ParsedRegex pre;



            public RE_Pattern(object pattern)

                : this(pattern, 0) {

            }



            public RE_Pattern(object pattern, int flags) {

                pre = PreParseRegex(ValidatePattern(pattern));

                try {

                    RegexOptions opts = FlagsToOption(flags);

                    this.re = new Regex(pre.Pattern, opts);

                } catch (ArgumentException e) {

                    throw ExceptionConverter.CreateThrowable(error, e.Message);

                }

                this.compileFlags = flags;

            }



            [PythonName("match")]

            public RE_Match Match(object text) {

                string input = ValidateString(text, "text");

                return RE_Match.makeMatch(re.Match(input), this, input, 0, input.Length);

            }



            private static int FixPosition(string text, int position) {

                if (position < 0) return 0;

                if (position > text.Length) return text.Length;



                return position;

            }



            [PythonName("match")]

            public RE_Match Match(object text, int pos) {                

                string input = ValidateString(text, "text");

                pos = FixPosition(input, pos);

                return RE_Match.makeMatch(re.Match(input, pos), this, input, pos, input.Length);

            }



            [PythonName("match")]

            public RE_Match Match(object text, [DefaultParameterValue(0)] int pos, int endpos) {                

                string input = ValidateString(text, "text");

                pos = FixPosition(input, pos);

                endpos = FixPosition(input, endpos);

                return RE_Match.makeMatch(

                    re.Match(input.Substring(0, endpos), pos),

                    this,

                    input,

                    pos,

                    endpos);

            }



            [PythonName("search")]

            public RE_Match Search(object text) {

                string input = ValidateString(text, "text");

                return RE_Match.make(re.Match(input), this, input);

            }



            [PythonName("search")]

            public RE_Match Search(object text, int pos) {

                string input = ValidateString(text, "text");

                return RE_Match.make(re.Match(input, pos, input.Length - pos), this, input);

            }



            [PythonName("search")]

            public RE_Match Search(object text, int pos, int endpos) {

                string input = ValidateString(text, "text");

                return RE_Match.make(re.Match(input, pos, Math.Max(endpos - pos, 0)), this, input);

            }



            [PythonName("findall")]

            public object FindAll(string @string) {

                return FindAll(@string, 0, null);

            }



            [PythonName("findall")]

            public object FindAll(string @string, int pos) {

                return FindAll(@string, pos, null);

            }



            [PythonName("findall")]

            public object FindAll(object @string, int pos, object endpos) {

                MatchCollection mc = FindAllWorker(ValidateString(@string, "text"), pos, endpos);



                return new List(FixFindAllMatch(this, mc));

            }



            internal MatchCollection FindAllWorker(string str, int pos, object endpos) {

                string against = str;

                if (endpos != null) {

                    int end = Converter.ConvertToInt32(endpos);

                    against = against.Substring(0, Math.Max(end, 0));

                }

                return re.Matches(against, pos);

            }



            [PythonName("finditer")]

            public object FindIter(object @string) {

                string input = ValidateString(@string, "string");

                return MatchIterator(FindAllWorker(input, 0, input.Length), this, input);

            }



            [PythonName("finditer")]

            public object FindIter(object @string, int pos) {

                string input = ValidateString(@string, "string");

                return MatchIterator(FindAllWorker(input, pos, input.Length), this, input);

            }



            [PythonName("finditer")]

            public object FindIter(object @string, int pos, int endpos) {

                string input = ValidateString(@string, "string");

                return MatchIterator(FindAllWorker(input, pos, endpos), this, input);

            }



            [PythonName("split")]

            public object Split(object @string) {

                return Split(@string, 0);

            }



            [PythonName("split")]

            public object Split(object @string, int maxsplit) {

                List result = new List();

                // fast path for negative maxSplit ( == "make no splits")

                if (maxsplit < 0)

                    result.AddNoLock(@string);

                else {

                    // iterate over all matches

                    string theStr = ValidateString(@string, "string");

                    MatchCollection matches = re.Matches(theStr);

                    int lastPos = 0; // is either start of the string, or first position *after* the last match

                    int nSplits = 0; // how many splits have occurred?

                    foreach (Match m in matches) {

                        if (m.Length > 0) {

                            // add substring from lastPos to beginning of current match

                            result.AddNoLock(theStr.Substring(lastPos, m.Index - lastPos));

                            // if there are subgroups of the match, add their match or None

                            if (m.Groups.Count > 1)

                                for (int i = 1; i < m.Groups.Count; i++)

                                    if (m.Groups[i].Success)

                                        result.AddNoLock(m.Groups[i].Value);

                                    else

                                        result.AddNoLock(null);

                            // update lastPos, nSplits

                            lastPos = m.Index + m.Length;

                            nSplits++;

                            if (nSplits == maxsplit)

                                break;

                        }

                    }

                    // add tail following last match

                    result.AddNoLock(theStr.Substring(lastPos));

                }

                return result;

            }



            [PythonName("sub")]

            public string Substitute(object repl, object @string) {

                return Substitute(repl, ValidateString(@string, "string"), Int32.MaxValue);

            }



            [PythonName("sub")]

            public string Substitute(object repl, object @string, int count) {

                if (repl == null) throw Ops.TypeError("NoneType is not valid repl");

                //  if 'count' is omitted or 0, all occurrences are replaced

                if (count == 0) count = Int32.MaxValue;



                string replacement = repl as string;

                if (replacement == null) {

                    if (repl is ExtensibleString) {

                        replacement = (repl as ExtensibleString).Value;

                    }

                }



                Match prev = null;

                string input = ValidateString(@string, "string");

                return re.Replace(

                    input,

                    delegate(Match match) {

                        //  from the docs: Empty matches for the pattern are replaced 

                        //  only when not adjacent to a previous match

                        if (String.IsNullOrEmpty(match.Value) && prev != null &&

                                        (prev.Index + prev.Length) == match.Index) {

                            return "";

                        };

                        prev = match;



                        if (replacement != null) return UnescapeGroups(match, replacement);

                        return Ops.Call(repl, RE_Match.make(match, this, input)) as string;

                    },

                    count);

            }



            [PythonName("subn")]

            public object SubGetCount(object repl, string @string) {

                return SubGetCount(repl, @string, Int32.MaxValue);

            }



            [PythonName("subn")]

            public object SubGetCount(object repl, object @string, int count) {

                if (repl == null) throw Ops.TypeError("NoneType is not valid repl");

                //  if 'count' is omitted or 0, all occurrences are replaced

                if (count == 0) count = Int32.MaxValue;



                int totalCount = 0;

                string res;

                string replacement = repl as string;



                if (replacement == null) {

                    if (repl is ExtensibleString) {

                        replacement = (repl as ExtensibleString).Value;

                    }

                }



                Match prev = null;

                string input = ValidateString(@string, "string");

                res = re.Replace(

                    input,

                    delegate(Match match) {

                        //  from the docs: Empty matches for the pattern are replaced 

                        //  only when not adjacent to a previous match

                        if (String.IsNullOrEmpty(match.Value) && prev != null &&

                            (prev.Index + prev.Length) == match.Index) {

                            return "";

                        };

                        prev = match;



                        totalCount++;

                        if (replacement != null) return UnescapeGroups(match, replacement);



                        return Ops.Call(repl, RE_Match.make(match, this, input)) as string;

                    },

                    count);



                return Tuple.MakeTuple(res, totalCount);

            }



            public int Flags {

                [PythonName("flags")]

                get {

                    return compileFlags;

                }

            }



            public Dict GroupIndex {

                [PythonName("groupindex")]

                get {

                    if (groups == null) {

                        Dict d = new Dict();

                        string[] names = re.GetGroupNames();

                        int[] nums = re.GetGroupNumbers();

                        for (int i = 1; i < names.Length; i++) {

                            if (Char.IsDigit(names[i][0])) continue;    // skip numeric names



                            d[names[i]] = nums[i];

                        }

                        groups = d;

                    }

                    return groups;

                }

            }



            public string Pattern {

                [PythonName("pattern")]

                get {

                    return pre.UserPattern;

                }

            }





            #region IWeakReferenceable Members



            public WeakRefTracker GetWeakRef() {

                return weakRefTracker;

            }



            public bool SetWeakRef(WeakRefTracker value) {

                weakRefTracker = value;

                return true;

            }



            public void SetFinalizer(WeakRefTracker value) {

                SetWeakRef(value);

            }



            #endregion

        }



        public class RE_Match {

            RE_Pattern pattern;

            private Match m;

            private string text;

            private int lastindex = -1;

            private int endPos;



            #region Internal makers

            internal static RE_Match make(Match m, RE_Pattern pattern, string input) {

                if (m.Success) return new RE_Match(m, pattern, input);

                return null;

            }



            internal static RE_Match makeMatch(Match m, RE_Pattern pattern, string input, int offset, int endPos) {

                if (m.Success && m.Index == offset) return new RE_Match(m, pattern, input, endPos);

                return null;

            }

            #endregion



            #region Public ctors

            public RE_Match(Match m, RE_Pattern pattern, string text) {

                this.m = m;

                this.pattern = pattern;

                this.text = text;

            }

            public RE_Match(Match m, RE_Pattern pattern, string text, int endpos) {

                this.m = m;

                this.pattern = pattern;

                this.text = text;

                this.endPos = endpos;

            }

            #endregion



            //			public override bool __nonzero__() {

            //				return m.Success;

            //			}



            #region Public API Surface



            [PythonName("end")]

            public int End() {

                return m.Index + m.Length;

            }



            [PythonName("start")]

            public int Start() {

                return m.Index;

            }



            [PythonName("start")]

            public int Start(object group) {

                int grpIndex = GetGroupIndex(group);

                if (!m.Groups[grpIndex].Success) {

                    return -1;

                }

                return m.Groups[grpIndex].Index;

            }



            [PythonName("end")]

            public int End(object group) {

                int grpIndex = GetGroupIndex(group);

                if (!m.Groups[grpIndex].Success) {

                    return -1;

                }

                return m.Groups[grpIndex].Index + m.Groups[grpIndex].Length;

            }



            [PythonName("group")]

            public object Group(object index, params object[] additional) {

                if (additional.Length == 0) return Group(index);



                object[] res = new object[additional.Length + 1];

                res[0] = m.Groups[GetGroupIndex(index)].Success ? m.Groups[GetGroupIndex(index)].Value : null;

                for (int i = 1; i < res.Length; i++) {

                    int grpIndex = GetGroupIndex(additional[i - 1]);

                    res[i] = m.Groups[grpIndex].Success ? m.Groups[grpIndex].Value : null;

                }

                return Tuple.MakeTuple(res);

            }



            [PythonName("group")]

            public object Group(object index) {

                int pos = GetGroupIndex(index);

                Group g = m.Groups[pos];

                return g.Success ? g.Value : null;



            }



            [PythonName("group")]

            public object Group() {

                return Group(0);

            }



            [PythonName("groups")]

            public object Groups() {

                return Groups(null);

            }



            [PythonName("groups")]

            public object Groups(object @default) {

                object[] ret = new object[m.Groups.Count - 1];

                for (int i = 1; i < m.Groups.Count; i++) {

                    if (!m.Groups[i].Success) {

                        ret[i - 1] = @default;

                    } else {

                        ret[i - 1] = m.Groups[i].Value;

                    }

                }

                return Ops.MakeTuple(ret);

            }



            [PythonName("expand")]

            public object Expand(object template) {

                string strTmp = ValidateString(template, "template");



                StringBuilder res = new StringBuilder();

                for (int i = 0; i < strTmp.Length; i++) {

                    if (strTmp[i] != '\\') { res.Append(strTmp[i]); continue; }

                    if (++i == strTmp.Length) { res.Append(strTmp[i - 1]); continue; }



                    if (Char.IsDigit(strTmp[i])) {

                        AppendGroup(res, (int)(strTmp[i] - '0'));

                    } else if (strTmp[i] == 'g') {

                        if (++i == strTmp.Length) { res.Append("\\g"); return res.ToString(); }

                        if (strTmp[i] != '<') {

                            res.Append("\\g<"); continue;

                        } else { // '<'

                            StringBuilder name = new StringBuilder();

                            i++;

                            while (strTmp[i] != '>' && i < strTmp.Length) {

                                name.Append(strTmp[i++]);

                            }

                            AppendGroup(res, pattern.re.GroupNumberFromName(name.ToString()));

                        }

                    } else {

                        switch (strTmp[i]) {

                            case 'n': res.Append('\n'); break;

                            case 'r': res.Append('\r'); break;

                            case 't': res.Append('\t'); break;

                            case '\\': res.Append('\\'); break;

                        }

                    }



                }

                return res.ToString();

            }



            [PythonName("groupdict")]

            public object GroupDict() {

                return GroupDict(null);

            }



            private static bool IsGroupNumber(string name) {

                foreach (char c in name) {

                    if (!Char.IsNumber(c)) return false;

                }

                return true;

            }



            [PythonName("groupdict")]

            public object GroupDict(object value) {

                string[] groupNames = this.pattern.re.GetGroupNames();

                Debug.Assert(groupNames.Length == this.m.Groups.Count);

                Dict d = new Dict();

                for (int i = 0; i < groupNames.Length; i++) {

                    if (IsGroupNumber(groupNames[i])) continue; // python doesn't report group numbers



                    if (m.Groups[i].Captures.Count != 0) {

                        d[groupNames[i]] = m.Groups[i].Value;

                    } else {

                        d[groupNames[i]] = value;

                    }

                }

                return d;

            }



            [PythonName("span")]

            public object Span() {

                return Tuple.MakeTuple(this.Start(), this.End());

            }



            [PythonName("span")]

            public object Span(object group) {

                return Tuple.MakeTuple(this.Start(group), this.End(group));

            }



            public int Position {

                [PythonName("pos")]

                get {

                    return m.Index;

                }

            }



            public int EndPosition {

                [PythonName("endpos")]

                get {

                    return endPos;

                }

            }



            public string SearchValue {

                [PythonName("string")]

                get {

                    return text;

                }

            }



            public object Regs {

                [PythonName("regs")]

                get {

                    object[] res = new object[m.Groups.Count];

                    for(int i = 0; i<res.Length; i++) {

                        res[i] = Tuple.MakeTuple(this.Start(i), this.End(i));

                    }

                                        

                    return Tuple.MakeTuple(res);

                }

            }



            public object Pattern {

                [PythonName("re")]

                get {

                    return pattern;

                }

            }



            public object LastIndex {

                [PythonName("lastindex")]

                get {

                    //   -1 : initial value of lastindex

                    //    0 : no match found

                    //other : the true lastindex



                    // Match.Groups contains "lower" level matched groups, which has to be removed

                    if (lastindex == -1) {

                        int i = 1;

                        while (i < m.Groups.Count) {

                            if (m.Groups[i].Success) {

                                lastindex = i;

                                int start = m.Groups[i].Index;

                                int end = start + m.Groups[i].Length;

                                i++;



                                // skip any group which fall into the range [start, end], 

                                // no matter match succeed or fail

                                while (i < m.Groups.Count && (m.Groups[i].Index < end)) {

                                    i++;

                                }

                            } else {

                                i++;

                            }

                        }



                        if (lastindex == -1) {

                            lastindex = 0;

                        }

                    }



                    if (lastindex == 0) {

                        return null;

                    } else {

                        return lastindex;

                    }

                }

            }



            public object LastGroup {

                [PythonName("lastgroup")]

                get {

                    if (LastIndex == null) return null;



                    // when group was not explicitly named, RegEx assigns the number as name

                    // This is different from C-Python, which returns None in such cases



                    return this.pattern.re.GroupNameFromNumber((int)LastIndex);

                }

            }

            #endregion



            #region Private helper functions

            private void AppendGroup(StringBuilder sb, int index) {

                sb.Append(m.Groups[index].Value);

            }



            private int GetGroupIndex(object group) {

                int grpIndex;

                if (!Converter.TryConvertToInt32(group, out grpIndex)) {

                    grpIndex = pattern.re.GroupNumberFromName(ValidateString(group, "group"));

                }

                if (grpIndex < 0 || grpIndex >= m.Groups.Count) {

                    throw Ops.IndexError("no such group");

                }

                return grpIndex;

            }

            #endregion

        }



        #endregion



        #region Private helper functions

        private static IEnumerator MatchIterator(MatchCollection matches, RE_Pattern pattern, string input) {

            for (int i = 0; i < matches.Count; i++) {

                yield return RE_Match.make(matches[i], pattern, input);

            }

        }



        private static RegexOptions FlagsToOption(int flags) {

            RegexOptions opts = RegexOptions.None;

            if ((flags & (int)IGNORECASE) != 0) opts |= RegexOptions.IgnoreCase;

            if ((flags & (int)MULTILINE) != 0) opts |= RegexOptions.Multiline;

            if (((flags & (int)LOCALE)) == 0) opts &= (~RegexOptions.CultureInvariant);

            if ((flags & (int)DOTALL) != 0) opts |= RegexOptions.Singleline;

            if ((flags & (int)VERBOSE) != 0) opts |= RegexOptions.IgnorePatternWhitespace;



            return opts;

        }



        internal class ParsedRegex {

            public ParsedRegex(string pattern) {

                this.UserPattern = pattern;

            }



            public string UserPattern;

            public string Pattern;

            public RegexOptions Options = RegexOptions.CultureInvariant;

        }



        /// <summary>

        /// Preparses a regular expression text returning a ParsedRegex class

        /// that can be used for further regular expressions.

        /// </summary>

        private static ParsedRegex PreParseRegex(string pattern) {

            ParsedRegex res = new ParsedRegex(pattern);



            //string newPattern;

            int cur = 0, nameIndex;

            int curGroup = 0;

            bool containsNamedGroup = false;



            for (; ; ) {

                nameIndex = pattern.IndexOf("(", cur);

                if (nameIndex > 0 && pattern[nameIndex - 1] == '\\') {

                    int curIndex = nameIndex - 2;

                    int backslashCount = 1;

                    while (curIndex >= 0 && pattern[curIndex] == '\\') {

                        backslashCount++;

                        curIndex--;

                    }

                    // odd number of back slashes, this is an optional

                    // paren that we should ignore.

                    if ((backslashCount & 0x01) != 0) {

                        cur++;

                        continue;

                    }

                }



                if (nameIndex == -1) break;

                if (nameIndex == pattern.Length - 1) break;



                switch (pattern[++nameIndex]) {

                    case '?':

                        // extension syntax

                        if (nameIndex == pattern.Length - 1) throw ExceptionConverter.CreateThrowable(error, "unexpected end of regex");

                        switch (pattern[++nameIndex]) {

                            case 'P':

                                //  named regex, .NET doesn't expect the P so we'll remove it;

                                //  also, once we see a named group i.e. ?P then we need to start artificially 

                                //  naming all unnamed groups from then on---this is to get around the fact that 

                                //  the CLR RegEx support orders all the unnamed groups before all the named 

                                //  groups, even if the named groups are before the unnamed ones in the pattern;

                                //  the artificial naming preserves the order of the groups and thus the order of

                                //  the matches

                                if (nameIndex + 1 < pattern.Length && pattern[nameIndex + 1] == '=') {

                                    // match whatever was previously matched by the named group



                                    // remove the (?P=

                                    pattern = pattern.Remove(nameIndex - 2, 4);

                                    pattern = pattern.Insert(nameIndex - 2, "\\\\k<");

                                    int tmpIndex = nameIndex;

                                    while (tmpIndex < pattern.Length && pattern[tmpIndex] != ')')

                                        tmpIndex++;



                                    if (tmpIndex == pattern.Length) throw ExceptionConverter.CreateThrowable(error, "unexpected end of regex");



                                    pattern = pattern.Substring(0, tmpIndex) + ">" + pattern.Substring(tmpIndex + 1);

                                } else {

                                    containsNamedGroup = true;

                                    pattern = pattern.Remove(nameIndex, 1);

                                }

                                break;

                            case 'i': res.Options |= RegexOptions.IgnoreCase; break;

                            case 'L': res.Options &= ~(RegexOptions.CultureInvariant); break;

                            case 'm': res.Options |= RegexOptions.Multiline; break;

                            case 's': res.Options |= RegexOptions.Singleline; break;

                            case 'u': break;

                            case 'x': res.Options |= RegexOptions.IgnorePatternWhitespace; break;

                            case ':': break; // non-capturing

                            case '=': break; // look ahead assertion

                            case '<': break; // positive look behind assertion

                            case '!': break; // negative look ahead assertion

                            case '#': break; // inline comment

                            case '(':  // yes/no if group exists, we don't support this

                            default: throw ExceptionConverter.CreateThrowable(error, "Unrecognized extension " + pattern[nameIndex]);

                        }

                        break;

                    default:

                        // just another group

                        curGroup++;

                        if (containsNamedGroup) {

                            // need to name this unnamed group

                            pattern = pattern.Insert(nameIndex, "?<Named" + GetRandomString() + ">");

                        }

                        break;

                }



                cur = nameIndex;

            }



            cur = 0;

            for (; ; ) {

                nameIndex = pattern.IndexOf('\\', cur);



                if (nameIndex == -1 || nameIndex == pattern.Length - 1) break;

                char curChar = pattern[++nameIndex];

                switch (curChar) {

                    case 'x':

                    case 'u':

                    case 'a':

                    case 'b':

                    case 'e':

                    case 'f':

                    case 'n':

                    case 'r':

                    case 't':

                    case 'v':

                    case 'c':

                    case 's':

                    case 'W':

                    case 'w':

                    case 'p':

                    case 'P':

                    case 'S':

                    case 'd':

                    case 'D':

                    case 'Z':

                        // known escape sequences, leave escaped.

                        break;

                    case '\\':

                        // escaping a \\

                        cur += 2;

                        break;

                    default:

                        System.Globalization.UnicodeCategory charClass = Char.GetUnicodeCategory(curChar);

                        switch (charClass) {

                            // recognized word characters, always unescape.

                            case System.Globalization.UnicodeCategory.ModifierLetter:

                            case System.Globalization.UnicodeCategory.LowercaseLetter:

                            case System.Globalization.UnicodeCategory.UppercaseLetter:

                            case System.Globalization.UnicodeCategory.TitlecaseLetter:

                            case System.Globalization.UnicodeCategory.OtherLetter:

                            case System.Globalization.UnicodeCategory.LetterNumber:

                            case System.Globalization.UnicodeCategory.OtherNumber:

                            case System.Globalization.UnicodeCategory.ConnectorPunctuation:

                                pattern = pattern.Remove(nameIndex - 1, 1);

                                break;

                            case System.Globalization.UnicodeCategory.DecimalDigitNumber:

                                //  actually don't want to unescape '\1', '\2' etc. which are references to groups

                                break;

                        }

                        break;

                }

                cur++;

            }



            res.Pattern = pattern;

            return res;

        }



        static Random r = new Random(DateTime.Now.Millisecond);

        private static string GetRandomString() {

            return r.Next(Int32.MaxValue / 2, Int32.MaxValue).ToString();

        }



        private static string UnescapeGroups(Match m, string text) {

            for (int i = 0; i < text.Length; i++) {

                if (text[i] == '\\') {

                    StringBuilder sb = new StringBuilder(text, 0, i, text.Length);



                    do {

                        if (text[i] == '\\') {

                            i++;

                            if (i == text.Length) { sb.Append('\\'); break; }



                            switch (text[i]) {

                                case 'n': sb.Append('\n'); break;

                                case 'r': sb.Append('\r'); break;

                                case 't': sb.Append('\t'); break;

                                case '\\': sb.Append('\\'); break;

                                case '\'': sb.Append('\''); break;

                                case '"': sb.Append('"'); break;

                                case 'b': sb.Append('\b'); break;

                                case 'g':

                                    //  \g<#>, \g<name> need to be substituted by the groups they 

                                    //  matched

                                    if (text[i + 1] == '<') {

                                        int anglebrkStart = i + 1;

                                        int anglebrkEnd = text.IndexOf('>', i + 2);

                                        if (anglebrkEnd != -1) {

                                            //  grab the # or 'name' of the group between '< >'

                                            int lengrp = anglebrkEnd - (anglebrkStart + 1);

                                            string grp = text.Substring(anglebrkStart + 1, lengrp);

                                            int num;

                                            Group g;

                                            if (Int32.TryParse(grp, out num)) {

                                                g = m.Groups[num];

                                                if (String.IsNullOrEmpty(g.Value)) {

                                                    throw Ops.IndexError("unknown group reference");

                                                }

                                                sb.Append(g.Value);

                                            } else {

                                                g = m.Groups[grp];

                                                if (String.IsNullOrEmpty(g.Value)) {

                                                    throw Ops.IndexError("unknown group reference");

                                                }

                                                sb.Append(g.Value);

                                            }

                                            i = anglebrkEnd;

                                        }

                                        break;

                                    }

                                    sb.Append('\\');

                                    sb.Append((char)text[i]);

                                    break;

                                default:

                                    if (Char.IsDigit(text[i]) && text[i] <= '7') {

                                        int val = 0;

                                        int digitCount = 0;

                                        while (i < text.Length && Char.IsDigit(text[i]) && text[i] <= '7') {

                                            digitCount++;

                                            val += val * 8 + (text[i] - '0');

                                            i++;

                                        }

                                        i--;



                                        if (digitCount == 1 && val > 0 && val < m.Groups.Count) {

                                            sb.Append(m.Groups[val].Value);

                                        } else {

                                            sb.Append((char)val);

                                        }

                                    } else {

                                        sb.Append('\\');

                                        sb.Append((char)text[i]);

                                    }

                                    break;

                            }

                        } else {

                            sb.Append(text[i]);

                        }

                    } while (++i < text.Length);

                    return sb.ToString();

                }

            }

            return text;

        }



        private static string ValidatePattern(object pattern) {

            if (pattern is string) return pattern as string;



            ExtensibleString es = pattern as ExtensibleString;

            if (es != null) return es.Value;



            RE_Pattern rep = pattern as RE_Pattern;

            if (rep != null) return rep.pre.UserPattern;



            throw Ops.TypeError("pattern must be a string or compiled pattern");

        }



        private static string ValidateString(object str, string param) {

            if (str is string) return str as string;



            ExtensibleString es = str as ExtensibleString;

            if (es != null) return es.Value;



            throw Ops.TypeError("expected string for parameter '{0}' but got '{1}'", param, Ops.GetPythonTypeName(str));

        }



        #endregion

    }

}