322 lines
11 KiB
C#
322 lines
11 KiB
C#
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//------------------------------------------------------------------------------
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// <copyright file="WriteFileContext.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//------------------------------------------------------------------------------
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namespace System.Configuration.Internal {
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using System.Configuration;
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using System.IO;
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using System.Security.Permissions;
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using System.Reflection;
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using System.Threading;
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using System.Security;
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using System.CodeDom.Compiler;
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using Microsoft.Win32;
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#if !FEATURE_PAL
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using System.Security.AccessControl;
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#endif
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internal class WriteFileContext {
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private const int SAVING_TIMEOUT = 10000; // 10 seconds
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private const int SAVING_RETRY_INTERVAL = 100; // 100 milliseconds
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private static volatile bool _osPlatformDetermined;
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private static volatile PlatformID _osPlatform;
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private TempFileCollection _tempFiles;
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private string _tempNewFilename;
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private string _templateFilename;
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internal WriteFileContext(string filename, string templateFilename) {
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string directoryname = UrlPath.GetDirectoryOrRootName(filename);
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_templateFilename = templateFilename;
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_tempFiles = new TempFileCollection(directoryname);
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try {
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_tempNewFilename = _tempFiles.AddExtension("newcfg");
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}
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catch {
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((IDisposable)_tempFiles).Dispose();
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_tempFiles = null;
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throw;
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}
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}
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static WriteFileContext() {
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_osPlatformDetermined = false;
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}
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internal string TempNewFilename {
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get {return _tempNewFilename;}
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}
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// Complete
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//
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// Cleanup the WriteFileContext object based on either success
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// or failure
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//
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// Note: The current algorithm guarantess
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// 1) The file we are saving to will always be present
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// on the file system (ie. there will be no window
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// during saving in which there won't be a file there)
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// 2) It will always be available for reading from a
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// client and it will be complete and accurate.
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//
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// ... This means that writing is a bit more complicated, and may
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// have to be retried (because of reading lock), but I don't see
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// anyway to get around this given 1 and 2.
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//
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internal void Complete(string filename, bool success) {
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try {
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if (success) {
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if ( File.Exists( filename ) ) {
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// Test that we can write to the file
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ValidateWriteAccess( filename );
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// Copy Attributes from original
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DuplicateFileAttributes( filename, _tempNewFilename );
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}
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else {
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if ( _templateFilename != null ) {
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// Copy Acl from template file
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DuplicateTemplateAttributes( _templateFilename, _tempNewFilename );
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}
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}
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ReplaceFile(_tempNewFilename, filename);
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// Don't delete, since we just moved it.
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_tempFiles.KeepFiles = true;
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}
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}
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finally {
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((IDisposable)_tempFiles).Dispose();
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_tempFiles = null;
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}
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}
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// DuplicateFileAttributes
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//
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// Copy all the files attributes that we care about from the source
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// file to the destination file
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//
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private void DuplicateFileAttributes( string source, string destination )
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{
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#if !FEATURE_PAL
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FileAttributes attributes;
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DateTime creationTime;
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// Copy File Attributes, ie. Hidden, Readonly, etc.
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attributes = File.GetAttributes( source );
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File.SetAttributes( destination, attributes );
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// Copy Creation Time
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creationTime = File.GetCreationTimeUtc( source );
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File.SetCreationTimeUtc( destination, creationTime );
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// Copy ACL's
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DuplicateTemplateAttributes( source, destination );
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#endif // FEATURE_PAL
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}
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// DuplicateTemplateAttributes
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//
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// Copy over all the attributes you would want copied from a template file.
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// As of right now this is just acl's
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//
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private void DuplicateTemplateAttributes( string source, string destination ) {
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#if !FEATURE_PAL
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if (IsWinNT) {
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FileSecurity fileSecurity;
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// Copy Security information
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fileSecurity = File.GetAccessControl( source, AccessControlSections.Access );
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// Mark dirty, so effective for write
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fileSecurity.SetAccessRuleProtection( fileSecurity.AreAccessRulesProtected, true );
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File.SetAccessControl( destination, fileSecurity );
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}
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else {
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FileAttributes fileAttributes;
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fileAttributes = File.GetAttributes( source );
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File.SetAttributes( destination, fileAttributes );
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}
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#endif // FEATURE_PAL
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}
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// ValidateWriteAccess
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//
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// Validate that we can write to the file. This will enforce the ACL's
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// on the file. Since we do our moving of files to replace, this is
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// nice to ensure we are not by-passing some security permission
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// that someone set (although that could bypass this via move themselves)
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//
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// Note: 1) This is really just a nice to have, since with directory permissions
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// they could do the same thing we are doing
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//
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// 2) We are depending on the current behavior that if the file is locked
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// and we can not open it, that we will get an UnauthorizedAccessException
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// and not the IOException.
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//
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private void ValidateWriteAccess( string filename ) {
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FileStream fs = null;
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try {
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// Try to open file for write access
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fs = new FileStream( filename,
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FileMode.Open,
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FileAccess.Write,
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FileShare.ReadWrite );
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}
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catch ( UnauthorizedAccessException ) {
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// Access was denied, make sure we throw this
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throw;
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}
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catch ( IOException ) {
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// Someone else was using the file. Since we did not get
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// the unauthorizedAccessException we have access to the file
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}
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catch ( Exception ) {
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// Unexpected, so just throw for safety sake
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throw;
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}
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finally {
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if ( fs != null ) {
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fs.Close();
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}
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}
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}
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// ReplaceFile
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//
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// Replace one file with another using MoveFileEx. This will
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// retry the operation if the file is locked because someone
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// is reading it
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//
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private void ReplaceFile( string Source, string Target )
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{
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bool WriteSucceeded = false;
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int Duration = 0;
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WriteSucceeded = AttemptMove( Source, Target );
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// The file may be open for read, if it is then
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// lets try again because maybe they will finish
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// soon, and we will be able to replace
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while ( !WriteSucceeded &&
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( Duration < SAVING_TIMEOUT ) &&
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File.Exists( Target ) &&
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!FileIsWriteLocked( Target ) ) {
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Thread.Sleep( SAVING_RETRY_INTERVAL );
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Duration += SAVING_RETRY_INTERVAL;
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WriteSucceeded = AttemptMove( Source, Target );
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}
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if ( !WriteSucceeded ) {
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throw new ConfigurationErrorsException(
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SR.GetString(SR.Config_write_failed, Target) );
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}
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}
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// AttemptMove
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//
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// Attempt to move a file from one location to another
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//
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// Return Values:
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// TRUE - Move Successful
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// FALSE - Move Failed
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private bool AttemptMove( string Source, string Target ) {
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bool MoveSuccessful = false;
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if ( IsWinNT ) {
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// We can only call this when we have kernel32.dll
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MoveSuccessful = UnsafeNativeMethods.MoveFileEx(
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Source,
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Target,
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UnsafeNativeMethods.MOVEFILE_REPLACE_EXISTING );
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}
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else {
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try {
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// VSWhidbey 548017:
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// File.Move isn't supported on Win9x. We'll use File.Copy
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// instead. Please note that Source is a temporary file which
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// will be deleted when _tempFiles is disposed.
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File.Copy(Source, Target, true);
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MoveSuccessful = true;
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}
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catch {
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MoveSuccessful = false;
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}
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}
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return MoveSuccessful;
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}
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// FileIsWriteLocked
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//
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// Is the file write locked or not?
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//
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private bool FileIsWriteLocked( string FileName ) {
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Stream FileStream = null;
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bool WriteLocked = true;
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if (!FileUtil.FileExists(FileName, true)) {
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// It can't be locked if it doesn't exist
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return false;
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}
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try {
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FileShare fileShare = FileShare.Read;
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if (IsWinNT) {
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fileShare |= FileShare.Delete;
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}
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// Try to open for shared reading
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FileStream = new FileStream( FileName,
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FileMode.Open,
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FileAccess.Read,
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fileShare);
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// If we can open it for shared reading, it is not
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// write locked
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WriteLocked = false;
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}
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finally {
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if ( FileStream != null ) {
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FileStream.Close();
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FileStream = null;
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}
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}
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return WriteLocked;
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}
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// IsWinNT
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//
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// Are we running in WinNT or not?
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//
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private bool IsWinNT {
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get {
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if ( !_osPlatformDetermined ) {
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_osPlatform = Environment.OSVersion.Platform;
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_osPlatformDetermined = true;
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}
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return ( _osPlatform == System.PlatformID.Win32NT );
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}
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}
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}
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}
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