PieceNameHelper.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ Dotnetfx_Vista_SP2 / Dotnetfx_Vista_SP2 / 8.0.50727.4016 / DEVDIV / depot / DevDiv / releases / Orcas / QFE / wpf / src / Base / MS / Internal / IO / Packaging / PieceNameHelper.cs / 1 / PieceNameHelper.cs

                            //------------------------------------------------------------------------------ 
//  Microsoft Avalon
//  Copyright (c) Microsoft Corporation, 2005
//
//  File:           PieceNameHelper.cs 
//
//  Description:    The static class PieceNameHelper contains utilities to parse 
//                  and create piece names in an adaptor-independent way. 
//                  This file also contains PieceNameInfo, a structured representation
//                  of a piece name, and its subclass PieceInfo, which provides 
//                  piece name and zip file info for a piece.
//
//  History:        05/15/05 - johnlarc - initial implementation
//----------------------------------------------------------------------------- 

using System; 
using System.IO; 
using System.IO.Packaging;                  // For ZipPackagePart, etc.
using System.Windows;                       // for ExceptionStringTable 
using System.Globalization;                 // For CultureInfo
using System.Collections.Generic;           // IEqualityComparer

using MS.Internal;                          // For Invariant 
using MS.Internal.IO.Zip;                   // For ZipFileInfo
using System.Diagnostics;                   // For Debug.Assert 
 
namespace MS.Internal.IO.Packaging
{ 
    #region class PieceInfo

    /// 
    /// A piece descriptor, made up of a ZipFileInfo and a PieceNameInfo. 
    /// 
    ///  
    /// PieceNameHelper implements IComparable in such a way as to enforce 
    /// case-insensitive lexicographical order on <name, number, isLast> triples.
    ///  
    internal class PieceInfo
    {
        //-----------------------------------------------------
        // 
        //   Constructors
        // 
        //----------------------------------------------------- 

        #region Constructors 

        internal PieceInfo(ZipFileInfo zipFileInfo, PackUriHelper.ValidatedPartUri partUri, string prefixName, int pieceNumber, bool isLastPiece)
        {
            Debug.Assert(zipFileInfo != null); 
            Debug.Assert(prefixName != null && prefixName != String.Empty);
            Debug.Assert(pieceNumber >= 0); 
 
            _zipFileInfo = zipFileInfo;
 
            // partUri can be null to indicate that the prefixname is not a valid part name
            _partUri = partUri;
            _prefixName = prefixName;
            _pieceNumber = pieceNumber; 
            _isLastPiece = isLastPiece;
 
            // Currently as per the book, the prefix names/ logical names should be 
            // compared in a case-insensitive manner.
            _normalizedPieceNamePrefix = _prefixName.ToUpperInvariant(); 
        }

        #endregion Constructors
 
        //------------------------------------------------------
        // 
        //   public methods 
        //
        //----------------------------------------------------- 
        // None
        //------------------------------------------------------
        //
        //   Internal properties 
        //
        //------------------------------------------------------ 
 
        #region Internal properties
 
        internal string NormalizedPrefixName
        {
            get
            { 
                return _normalizedPieceNamePrefix;
            } 
        } 

        internal string PrefixName 
        {
            get
            {
                return _prefixName; 
            }
        } 
 
        internal int PieceNumber
        { 
            get
            {
                return _pieceNumber;
            } 
        }
 
        internal bool IsLastPiece 
        {
            get 
            {
                return _isLastPiece;
            }
        } 

        internal PackUriHelper.ValidatedPartUri PartUri 
        { 
            get
            { 
                return _partUri;
            }
        }
 
        internal ZipFileInfo ZipFileInfo
        { 
            get 
            {
                return _zipFileInfo; 
            }
        }

        #endregion Internal properties 

        //----------------------------------------------------- 
        // 
        //   Private members
        // 
        //------------------------------------------------------

        #region Private members
 
        private PackUriHelper.ValidatedPartUri _partUri;
        private string           _prefixName; 
        private int              _pieceNumber; 
        private bool             _isLastPiece;
        private ZipFileInfo      _zipFileInfo; 
        private string           _normalizedPieceNamePrefix;

        #endregion Private members
    } 

    #endregion class PieceInfo 
 
    #region class PieceNameHelper
 
    /// 
    /// The static class PieceNameHelper contains utilities to parse and create piece names
    /// in an adaptor-independent way.
    ///  
    internal static class PieceNameHelper
    { 
        #region Internal Properties 

        internal static PieceNameComparer PieceNameComparer 
        {
            get
            {
                return _pieceNameComparer; 
            }
        } 
 
        #endregion Internal Properties
 
        #region Internal Methods

        /// 
        /// Build a piece name from its constituents: part name, piece number 
        /// and terminal status.
        /// The linearized result obeys the piece name syntax: 
        ///   piece_name = prefix_name "/" "[" 1*digit "]" [".last"] ".piece" 
        /// 
        /// A part name or the zip item name corresponding to a part name. 
        /// The 0-based order number of the piece.
        /// Whether the piece is last in the part.
        /// A Metro piece name.
        /// If partName is a piece uri. 
        /// If pieceNumber is negative.
        internal static string CreatePieceName(string partName, int pieceNumber, bool isLastPiece) 
        { 
            Invariant.Assert(pieceNumber >= 0, "Negative piece number.");
 
            return string.Format(CultureInfo.InvariantCulture, "{0}/[{1:D}]{2}.piece",
                partName,
                pieceNumber,
                isLastPiece ? ".last" : ""); 
        }
 
        ///  
        /// Return true and create a PieceInfo if the name in the input ZipFileInfo parses
        /// as a piece name. 
        /// 
        /// 
        /// No Uri validation is carried out at this level. All that is checked is valid piece
        /// syntax. So the _prefixName returned as part of the PieceInfo will not necessarily 
        /// a part name. For example, it could be the name of the content type stream.
        ///  
        internal static bool TryCreatePieceInfo(ZipFileInfo zipFileInfo, out PieceInfo pieceInfo) 
        {
            Invariant.Assert(zipFileInfo != null); 

            pieceInfo = null;

            // Try to parse as a piece name. 
            PieceNameInfo pieceNameConstituents;
            bool result = PieceNameHelper.TryParseAsPieceName(zipFileInfo.Name, 
                out pieceNameConstituents); 

            // Return the result and the output parameter. 
            if(result)
                pieceInfo = new PieceInfo(zipFileInfo,
                    pieceNameConstituents.PartUri,
                    pieceNameConstituents.PrefixName, 
                    pieceNameConstituents.PieceNumber,
                    pieceNameConstituents.IsLastPiece); 
 
            return result;
        } 

        #endregion Internal Methods

        #region Private Methods 

        //----------------------------------------------------- 
        // 
        //   Private Methods
        // 
        //-----------------------------------------------------

        #region Scan Steps
 
        // The functions in this region conform to the delegate type ScanStepDelegate
        // and implement the following automaton for scanning a piece name from right to left: 
 
        //   state                      transition      new state
        //   -----                      ----------      --------- 
        //   FindPieceExtension         ".piece"        FindIsLast
        //   FindIsLast                 "].last"        FindPieceNumber
        //   FindIsLast                 "]"             FindPieceNumber
        //   FindPieceNumber            "/[" 1*digit    FindPartName (terminal state) 

        // On entering the step, position is at the beginning of the last portion that was recognized. 
        // So left-to-right scanning starts at position - 1 in each step. 
        private delegate bool ScanStepDelegate(
            string path, ref int position, ref ScanStepDelegate nextStep, ref PieceNameInfo parseResults); 

        // Look for ".piece".
        private static bool FindPieceExtension(string path, ref int position, ref ScanStepDelegate nextStep,
            ref PieceNameInfo parseResults) 
        {
            if (!FindString(path, ref position, ".piece")) 
                return false; 

            nextStep = FindIsLast; 
            return true;
        }

        // Look for "]" or "].last". 
        private static bool FindIsLast(string path, ref int position, ref ScanStepDelegate nextStep,
            ref PieceNameInfo parseResults) 
        { 
            // Case of no ".last" member:
            if (path[position - 1] == ']') 
            {
                parseResults.IsLastPiece = false;
                --position;
                nextStep = FindPieceNumber; 
                return true;
            } 
 
            // There has to be "].last".
            if (!FindString(path, ref position, "].last")) 
                return false;

            parseResults.IsLastPiece = true;
            nextStep = FindPieceNumber; 
            return true;
        } 
 
        // Look for "/[" followed by decimal digits.
        private static bool FindPieceNumber(string path, ref int position, ref ScanStepDelegate nextStep, 
            ref PieceNameInfo parseResults)
        {
            if (!char.IsDigit(path[position - 1]))
                return false; 

            int pieceNumber = 0; 
            int multiplier = 1; // rightmost digit is for units 
            --position;
            do 
            {
                pieceNumber += multiplier * (int)char.GetNumericValue(path[position]);
                multiplier *= 10;
            } while (char.IsDigit(path[--position])); 

            // Point to the last digit found. 
            ++position; 

            //If we have a leading 0, then its not correct piecename syntax 
            if (multiplier > 10 && (int)char.GetNumericValue(path[position]) == 0)
                return false;

            if (!FindString(path, ref position, "/[")) 
                return false;
 
            parseResults.PieceNumber = pieceNumber; 
            nextStep = FindPartName;
            return true; 
        }

        // Retrieve part name. The position points to the slash past the part name.
        // So simply return the prefix up to that slash. 
        private static bool FindPartName(string path, ref int position, ref ScanStepDelegate nextStep,
            ref PieceNameInfo parseResults) 
        { 
            parseResults.PrefixName = path.Substring(0, position);
 
            // Subtract the length of the part name from position.
            position = 0;

            if (parseResults.PrefixName.Length == 0) 
                return false;
 
            Uri partUri = new Uri(ZipPackage.GetOpcNameFromZipItemName(parseResults.PrefixName), UriKind.Relative); 
            PackUriHelper.TryValidatePartUri(partUri, out parseResults.PartUri);
            return true; 
        }

        #endregion Scan Steps
 
        /// 
        /// Attempts to parse a name as a piece name. Returns true and places the 
        /// output in pieceNameConstituents. Otherwise, returns false and returns 
        /// the default constituent values pieceName, 0, and false.
        ///  
        /// The input string.
        /// An object containing the prefix name (i.e. generally the part name), the 0-based order number of the piece, and whether the piece is last in the part.
        /// True for parse success.
        ///  
        /// Syntax of a piece name:
        ///   piece_name = part_name "/" "[" 1*digit "]" [".last"] ".piece" 
        ///  
        private static bool TryParseAsPieceName(string path, out PieceNameInfo parseResults)
        { 
            parseResults = new PieceNameInfo(); // initialize to CLR default values

            // Start from the end and look for ".piece".
            int position = path.Length; 
            ScanStepDelegate nextStep = new ScanStepDelegate(FindPieceExtension);
 
            // Scan backward until the whole path has been scanned. 
            while (position > 0)
            { 
                if (!nextStep.Invoke(path, ref position, ref nextStep, ref parseResults))
                {
                    // Scan step failed. Return false.
                    parseResults.IsLastPiece = false; 
                    parseResults.PieceNumber = 0;
                    parseResults.PrefixName = path; 
                    parseResults.PartUri = null; 
                    return false;
                } 
            }

            return true;
        } 

        ///  
        /// Look for 'query' backward in 'input' starting at 'position'. 
        /// 
        private static bool FindString(string input, ref int position, string query) 
        {
            int queryPosition = query.Length;

            //The input string should have length that is greater than or equal to the 
            //length of the query string.
            if (position < queryPosition) 
                return false; 

            while (--queryPosition >= 0) 
            {
                --position;
                if (Char.ToUpperInvariant(input[position]) != Char.ToUpperInvariant(query[queryPosition]))
                    return false; 
            }
            return true; 
        } 

        #endregion Private Methods 

        #region Private Member Variables

        //----------------------------------------------------- 
        //
        //   Private Variables 
        // 
        //------------------------------------------------------
 
        private static PieceNameComparer _pieceNameComparer = new PieceNameComparer();

        #endregion Private Member Variables
 
        #region Private Struct : PieceNameInfo
 
        ///  
        /// The result of parsing a piece name as returned by the parsing methods of PieceNameHelper.
        ///  
        /// 
        ///         /// The first member, _prefixName, will be a part name if the input to parse begins with
        /// a part name, and a zip item name if it starts with a zip item name.
        ///  
        /// 
        /// In other words, all that precedes the suffixes is returned unanalyzed as an "prefix name" 
        /// by the parse functions of the PieceNameHelper. 
        /// 
        ///  
        private struct PieceNameInfo
        {
            internal PackUriHelper.ValidatedPartUri PartUri;
            internal string PrefixName; 
            internal int PieceNumber;
            internal bool IsLastPiece; 
        } 

        #endregion Private Struct : PieceNameInfo 
    }

    #endregion class PieceNameHelper
 
    #region class PieceNameComparer
 
    internal sealed class PieceNameComparer : IComparer 
    {
        //For comparing the piece names we consider the prefix name and piece numbers 
        //Pieces that are terminal and non terminal with the same number and same prefix
        //number will be treated as equivalent.
        //For example - /partA/[number].piece and /partA[number].last.piece will be treated
        //to be equivalent, as in a well-formed package either one of them can be present, 
        //not both.
        int IComparer.Compare(PieceInfo pieceInfoA, PieceInfo pieceInfoB) 
        { 
            //Even though most comparers allow for comparisons with null, we assert here, as
            //this is an internal class and we are sure that pieceInfoA and pieceInfoB passed 
            //in here should be non-null, else it would be a logical error.
            Invariant.Assert(pieceInfoA != null);
            Invariant.Assert(pieceInfoB != null);
 
            int result = string.Compare(
                pieceInfoA.NormalizedPrefixName, 
                pieceInfoB.NormalizedPrefixName, 
                StringComparison.Ordinal);
 
            if (result != 0)
                return result;

            result = pieceInfoA.PieceNumber - pieceInfoB.PieceNumber; 

            return result; 
        } 
    }
 
    #endregion class PieceNameComparer

}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
//------------------------------------------------------------------------------ 
//  Microsoft Avalon
//  Copyright (c) Microsoft Corporation, 2005
//
//  File:           PieceNameHelper.cs 
//
//  Description:    The static class PieceNameHelper contains utilities to parse 
//                  and create piece names in an adaptor-independent way. 
//                  This file also contains PieceNameInfo, a structured representation
//                  of a piece name, and its subclass PieceInfo, which provides 
//                  piece name and zip file info for a piece.
//
//  History:        05/15/05 - johnlarc - initial implementation
//----------------------------------------------------------------------------- 

using System; 
using System.IO; 
using System.IO.Packaging;                  // For ZipPackagePart, etc.
using System.Windows;                       // for ExceptionStringTable 
using System.Globalization;                 // For CultureInfo
using System.Collections.Generic;           // IEqualityComparer

using MS.Internal;                          // For Invariant 
using MS.Internal.IO.Zip;                   // For ZipFileInfo
using System.Diagnostics;                   // For Debug.Assert 
 
namespace MS.Internal.IO.Packaging
{ 
    #region class PieceInfo

    /// 
    /// A piece descriptor, made up of a ZipFileInfo and a PieceNameInfo. 
    /// 
    ///  
    /// PieceNameHelper implements IComparable in such a way as to enforce 
    /// case-insensitive lexicographical order on <name, number, isLast> triples.
    ///  
    internal class PieceInfo
    {
        //-----------------------------------------------------
        // 
        //   Constructors
        // 
        //----------------------------------------------------- 

        #region Constructors 

        internal PieceInfo(ZipFileInfo zipFileInfo, PackUriHelper.ValidatedPartUri partUri, string prefixName, int pieceNumber, bool isLastPiece)
        {
            Debug.Assert(zipFileInfo != null); 
            Debug.Assert(prefixName != null && prefixName != String.Empty);
            Debug.Assert(pieceNumber >= 0); 
 
            _zipFileInfo = zipFileInfo;
 
            // partUri can be null to indicate that the prefixname is not a valid part name
            _partUri = partUri;
            _prefixName = prefixName;
            _pieceNumber = pieceNumber; 
            _isLastPiece = isLastPiece;
 
            // Currently as per the book, the prefix names/ logical names should be 
            // compared in a case-insensitive manner.
            _normalizedPieceNamePrefix = _prefixName.ToUpperInvariant(); 
        }

        #endregion Constructors
 
        //------------------------------------------------------
        // 
        //   public methods 
        //
        //----------------------------------------------------- 
        // None
        //------------------------------------------------------
        //
        //   Internal properties 
        //
        //------------------------------------------------------ 
 
        #region Internal properties
 
        internal string NormalizedPrefixName
        {
            get
            { 
                return _normalizedPieceNamePrefix;
            } 
        } 

        internal string PrefixName 
        {
            get
            {
                return _prefixName; 
            }
        } 
 
        internal int PieceNumber
        { 
            get
            {
                return _pieceNumber;
            } 
        }
 
        internal bool IsLastPiece 
        {
            get 
            {
                return _isLastPiece;
            }
        } 

        internal PackUriHelper.ValidatedPartUri PartUri 
        { 
            get
            { 
                return _partUri;
            }
        }
 
        internal ZipFileInfo ZipFileInfo
        { 
            get 
            {
                return _zipFileInfo; 
            }
        }

        #endregion Internal properties 

        //----------------------------------------------------- 
        // 
        //   Private members
        // 
        //------------------------------------------------------

        #region Private members
 
        private PackUriHelper.ValidatedPartUri _partUri;
        private string           _prefixName; 
        private int              _pieceNumber; 
        private bool             _isLastPiece;
        private ZipFileInfo      _zipFileInfo; 
        private string           _normalizedPieceNamePrefix;

        #endregion Private members
    } 

    #endregion class PieceInfo 
 
    #region class PieceNameHelper
 
    /// 
    /// The static class PieceNameHelper contains utilities to parse and create piece names
    /// in an adaptor-independent way.
    ///  
    internal static class PieceNameHelper
    { 
        #region Internal Properties 

        internal static PieceNameComparer PieceNameComparer 
        {
            get
            {
                return _pieceNameComparer; 
            }
        } 
 
        #endregion Internal Properties
 
        #region Internal Methods

        /// 
        /// Build a piece name from its constituents: part name, piece number 
        /// and terminal status.
        /// The linearized result obeys the piece name syntax: 
        ///   piece_name = prefix_name "/" "[" 1*digit "]" [".last"] ".piece" 
        /// 
        /// A part name or the zip item name corresponding to a part name. 
        /// The 0-based order number of the piece.
        /// Whether the piece is last in the part.
        /// A Metro piece name.
        /// If partName is a piece uri. 
        /// If pieceNumber is negative.
        internal static string CreatePieceName(string partName, int pieceNumber, bool isLastPiece) 
        { 
            Invariant.Assert(pieceNumber >= 0, "Negative piece number.");
 
            return string.Format(CultureInfo.InvariantCulture, "{0}/[{1:D}]{2}.piece",
                partName,
                pieceNumber,
                isLastPiece ? ".last" : ""); 
        }
 
        ///  
        /// Return true and create a PieceInfo if the name in the input ZipFileInfo parses
        /// as a piece name. 
        /// 
        /// 
        /// No Uri validation is carried out at this level. All that is checked is valid piece
        /// syntax. So the _prefixName returned as part of the PieceInfo will not necessarily 
        /// a part name. For example, it could be the name of the content type stream.
        ///  
        internal static bool TryCreatePieceInfo(ZipFileInfo zipFileInfo, out PieceInfo pieceInfo) 
        {
            Invariant.Assert(zipFileInfo != null); 

            pieceInfo = null;

            // Try to parse as a piece name. 
            PieceNameInfo pieceNameConstituents;
            bool result = PieceNameHelper.TryParseAsPieceName(zipFileInfo.Name, 
                out pieceNameConstituents); 

            // Return the result and the output parameter. 
            if(result)
                pieceInfo = new PieceInfo(zipFileInfo,
                    pieceNameConstituents.PartUri,
                    pieceNameConstituents.PrefixName, 
                    pieceNameConstituents.PieceNumber,
                    pieceNameConstituents.IsLastPiece); 
 
            return result;
        } 

        #endregion Internal Methods

        #region Private Methods 

        //----------------------------------------------------- 
        // 
        //   Private Methods
        // 
        //-----------------------------------------------------

        #region Scan Steps
 
        // The functions in this region conform to the delegate type ScanStepDelegate
        // and implement the following automaton for scanning a piece name from right to left: 
 
        //   state                      transition      new state
        //   -----                      ----------      --------- 
        //   FindPieceExtension         ".piece"        FindIsLast
        //   FindIsLast                 "].last"        FindPieceNumber
        //   FindIsLast                 "]"             FindPieceNumber
        //   FindPieceNumber            "/[" 1*digit    FindPartName (terminal state) 

        // On entering the step, position is at the beginning of the last portion that was recognized. 
        // So left-to-right scanning starts at position - 1 in each step. 
        private delegate bool ScanStepDelegate(
            string path, ref int position, ref ScanStepDelegate nextStep, ref PieceNameInfo parseResults); 

        // Look for ".piece".
        private static bool FindPieceExtension(string path, ref int position, ref ScanStepDelegate nextStep,
            ref PieceNameInfo parseResults) 
        {
            if (!FindString(path, ref position, ".piece")) 
                return false; 

            nextStep = FindIsLast; 
            return true;
        }

        // Look for "]" or "].last". 
        private static bool FindIsLast(string path, ref int position, ref ScanStepDelegate nextStep,
            ref PieceNameInfo parseResults) 
        { 
            // Case of no ".last" member:
            if (path[position - 1] == ']') 
            {
                parseResults.IsLastPiece = false;
                --position;
                nextStep = FindPieceNumber; 
                return true;
            } 
 
            // There has to be "].last".
            if (!FindString(path, ref position, "].last")) 
                return false;

            parseResults.IsLastPiece = true;
            nextStep = FindPieceNumber; 
            return true;
        } 
 
        // Look for "/[" followed by decimal digits.
        private static bool FindPieceNumber(string path, ref int position, ref ScanStepDelegate nextStep, 
            ref PieceNameInfo parseResults)
        {
            if (!char.IsDigit(path[position - 1]))
                return false; 

            int pieceNumber = 0; 
            int multiplier = 1; // rightmost digit is for units 
            --position;
            do 
            {
                pieceNumber += multiplier * (int)char.GetNumericValue(path[position]);
                multiplier *= 10;
            } while (char.IsDigit(path[--position])); 

            // Point to the last digit found. 
            ++position; 

            //If we have a leading 0, then its not correct piecename syntax 
            if (multiplier > 10 && (int)char.GetNumericValue(path[position]) == 0)
                return false;

            if (!FindString(path, ref position, "/[")) 
                return false;
 
            parseResults.PieceNumber = pieceNumber; 
            nextStep = FindPartName;
            return true; 
        }

        // Retrieve part name. The position points to the slash past the part name.
        // So simply return the prefix up to that slash. 
        private static bool FindPartName(string path, ref int position, ref ScanStepDelegate nextStep,
            ref PieceNameInfo parseResults) 
        { 
            parseResults.PrefixName = path.Substring(0, position);
 
            // Subtract the length of the part name from position.
            position = 0;

            if (parseResults.PrefixName.Length == 0) 
                return false;
 
            Uri partUri = new Uri(ZipPackage.GetOpcNameFromZipItemName(parseResults.PrefixName), UriKind.Relative); 
            PackUriHelper.TryValidatePartUri(partUri, out parseResults.PartUri);
            return true; 
        }

        #endregion Scan Steps
 
        /// 
        /// Attempts to parse a name as a piece name. Returns true and places the 
        /// output in pieceNameConstituents. Otherwise, returns false and returns 
        /// the default constituent values pieceName, 0, and false.
        ///  
        /// The input string.
        /// An object containing the prefix name (i.e. generally the part name), the 0-based order number of the piece, and whether the piece is last in the part.
        /// True for parse success.
        ///  
        /// Syntax of a piece name:
        ///   piece_name = part_name "/" "[" 1*digit "]" [".last"] ".piece" 
        ///  
        private static bool TryParseAsPieceName(string path, out PieceNameInfo parseResults)
        { 
            parseResults = new PieceNameInfo(); // initialize to CLR default values

            // Start from the end and look for ".piece".
            int position = path.Length; 
            ScanStepDelegate nextStep = new ScanStepDelegate(FindPieceExtension);
 
            // Scan backward until the whole path has been scanned. 
            while (position > 0)
            { 
                if (!nextStep.Invoke(path, ref position, ref nextStep, ref parseResults))
                {
                    // Scan step failed. Return false.
                    parseResults.IsLastPiece = false; 
                    parseResults.PieceNumber = 0;
                    parseResults.PrefixName = path; 
                    parseResults.PartUri = null; 
                    return false;
                } 
            }

            return true;
        } 

        ///  
        /// Look for 'query' backward in 'input' starting at 'position'. 
        /// 
        private static bool FindString(string input, ref int position, string query) 
        {
            int queryPosition = query.Length;

            //The input string should have length that is greater than or equal to the 
            //length of the query string.
            if (position < queryPosition) 
                return false; 

            while (--queryPosition >= 0) 
            {
                --position;
                if (Char.ToUpperInvariant(input[position]) != Char.ToUpperInvariant(query[queryPosition]))
                    return false; 
            }
            return true; 
        } 

        #endregion Private Methods 

        #region Private Member Variables

        //----------------------------------------------------- 
        //
        //   Private Variables 
        // 
        //------------------------------------------------------
 
        private static PieceNameComparer _pieceNameComparer = new PieceNameComparer();

        #endregion Private Member Variables
 
        #region Private Struct : PieceNameInfo
 
        ///  
        /// The result of parsing a piece name as returned by the parsing methods of PieceNameHelper.
        ///  
        /// 
        ///         /// The first member, _prefixName, will be a part name if the input to parse begins with
        /// a part name, and a zip item name if it starts with a zip item name.
        ///  
        /// 
        /// In other words, all that precedes the suffixes is returned unanalyzed as an "prefix name" 
        /// by the parse functions of the PieceNameHelper. 
        /// 
        ///  
        private struct PieceNameInfo
        {
            internal PackUriHelper.ValidatedPartUri PartUri;
            internal string PrefixName; 
            internal int PieceNumber;
            internal bool IsLastPiece; 
        } 

        #endregion Private Struct : PieceNameInfo 
    }

    #endregion class PieceNameHelper
 
    #region class PieceNameComparer
 
    internal sealed class PieceNameComparer : IComparer 
    {
        //For comparing the piece names we consider the prefix name and piece numbers 
        //Pieces that are terminal and non terminal with the same number and same prefix
        //number will be treated as equivalent.
        //For example - /partA/[number].piece and /partA[number].last.piece will be treated
        //to be equivalent, as in a well-formed package either one of them can be present, 
        //not both.
        int IComparer.Compare(PieceInfo pieceInfoA, PieceInfo pieceInfoB) 
        { 
            //Even though most comparers allow for comparisons with null, we assert here, as
            //this is an internal class and we are sure that pieceInfoA and pieceInfoB passed 
            //in here should be non-null, else it would be a logical error.
            Invariant.Assert(pieceInfoA != null);
            Invariant.Assert(pieceInfoB != null);
 
            int result = string.Compare(
                pieceInfoA.NormalizedPrefixName, 
                pieceInfoB.NormalizedPrefixName, 
                StringComparison.Ordinal);
 
            if (result != 0)
                return result;

            result = pieceInfoA.PieceNumber - pieceInfoB.PieceNumber; 

            return result; 
        } 
    }
 
    #endregion class PieceNameComparer

}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
                        

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