AtomicFile.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / WCF / Tools / comsvcutil / AtomicFile.cs / 1305376 / AtomicFile.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// Copyright (c) Microsoft Corporation.  All rights reserved.
//-----------------------------------------------------------------------------
namespace Microsoft.Tools.ServiceModel.ComSvcConfig
{ 
    using System;
    using System.Diagnostics; 
    using System.Configuration; 
    using System.Collections;
    using System.Collections.Specialized; 
    using System.Collections.Generic;
    using System.IO;
    using System.Reflection;
    using System.Text; 
    using System.Threading;
    using System.Runtime.InteropServices; 
    using System.Security; 
    using System.ServiceModel;
    using System.ServiceModel.Configuration; 
    using Microsoft.Tools.ServiceModel;
    using Microsoft.Tools.ServiceModel.SvcUtil;

    // Usage 
    //
    // new AtomicFile 
    // GetCurrent(readOnly)+ 
    // Delete (once), OR  GetCurrent(forUpdate)+
    // Prepare 
    // Commit or Abort
    //
    // Abort may also be called before Prepare
 
    class AtomicFile
    { 
        bool prepared; 
        string originalFileName;
        bool originalFileExists; 
        string tempFileName;
        string backupOfOriginalFileName;
        bool deleteOriginalFile;
 
        public string OriginalFileName
        { 
            get { return this.originalFileName; } 
        }
 
        public bool OriginalFileExists
        {
            get { return this.originalFileExists; }
        } 

        public AtomicFile(string fileName) 
        { 
            this.originalFileName = fileName;
            this.originalFileExists = File.Exists(this.originalFileName); 
            this.tempFileName = null;
            this.backupOfOriginalFileName = null;
            this.deleteOriginalFile = false;
            this.prepared = false; 
        }
 
        public bool CurrentExists() 
        {
            if ((this.tempFileName != null)) 
            {
                return true;
            }
            else 
            {
                return this.originalFileExists; 
            } 
        }
 
        public void Delete()
        {
            if (this.tempFileName != null)
            { 
                // once you make changes, you cant ask for delete (we have no scenario to relax this restriction..)
                throw new InvalidOperationException(); 
            } 

            if (!this.originalFileExists) 
            {
                // cant delete if the original file didnt exist
                throw new InvalidOperationException();
            } 

            this.deleteOriginalFile = true; 
        } 

        public string GetCurrentFileName(bool readOnly) 
        {
            if (this.deleteOriginalFile)
            {
                // once you delete, you cant ask for this. 
                throw new InvalidOperationException();
            } 
 
            if (this.tempFileName != null)
            { 
                return this.tempFileName;
            }
            else if (this.originalFileExists)
            { 
                if (readOnly)
                { 
                    return this.originalFileName; 
                }
                else 
                {
                    this.tempFileName = GetTempFileName();
                    File.Copy(this.originalFileName, this.tempFileName);
                    return this.tempFileName; 
                }
            } 
            else // there is no original file 
            {
                if (readOnly) 
                {
                    return null;    // nothing to read, caller should tolerate this
                }
                else 
                {
                    // want to update, have no file yet, create one.. 
                    this.tempFileName = GetTempFileName(); 
                    return this.tempFileName;
                } 
            }
        }

        // must be called before Preparing 
        public bool HasBeenModified()
        { 
            return (this.tempFileName != null || (this.originalFileExists && this.deleteOriginalFile)); 
        }
 
        public void Prepare()
        {
            if (this.tempFileName != null)
            { 
                if (this.originalFileExists)
                { 
                    this.backupOfOriginalFileName = GetTempFileName(); 
                    File.Copy(this.originalFileName, this.backupOfOriginalFileName);
                    SafeDeleteFile(this.originalFileName); 
                }

                File.Copy(this.tempFileName, this.originalFileName);
                SafeDeleteFile(this.tempFileName); 
            }
            else if (this.deleteOriginalFile) 
            { 
                this.backupOfOriginalFileName = GetTempFileName();
                File.Copy(this.originalFileName, this.backupOfOriginalFileName); 
                SafeDeleteFile(this.originalFileName);
            }

            this.prepared = true; 
        }
 
        public void Commit() 
        {
            if (!this.prepared) 
            {
                throw new InvalidOperationException();
            }
 
            SafeDeleteFile(this.backupOfOriginalFileName);
        } 
 
        // keep track of whether we had a "clean" prepare / abort, if not clean we shouldnt delete the backups/tempFiles and point the user to them
        public void Abort() 
        {
            if (this.originalFileExists)
            {
                if ((this.backupOfOriginalFileName != null) && File.Exists(this.backupOfOriginalFileName)) 
                {
                    SafeDeleteFile(this.originalFileName); 
                    File.Copy(this.backupOfOriginalFileName, this.originalFileName); 
                }
            } 
            else
            {
                SafeDeleteFile(this.originalFileName);
            } 

            SafeDeleteFile(this.backupOfOriginalFileName); 
            SafeDeleteFile(this.tempFileName); 
        }
 
        // safe as in handles null, and checks for existence first
        internal static void SafeDeleteFile(string fileName)
        {
            if ((!string.IsNullOrEmpty(fileName)) && File.Exists(fileName)) 
            {
                File.Delete(fileName); 
            } 
        }
 
        // this function guarantees to return the name of a temp file that doesnt exist
        string GetTempFileName()
        {
            return Path.Combine(Path.GetTempPath(), Path.GetRandomFileName()); 
        }
    } 
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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AtomicFile.cs source code in C# .NET

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