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// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
using System;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
#if NETFRAMEWORK
using Microsoft.VisualStudio.Setup.Configuration;
#endif
namespace Microsoft.DotNet.MSBuildSdkResolver
{
internal sealed class VSSettings
{
private readonly object _lock = new object();
private readonly string _settingsFilePath;
private readonly bool _disallowPrereleaseByDefault;
private FileInfo _settingsFile;
private bool _disallowPrerelease;
// In the product, this singleton is used. It must be safe to use in parallel on multiple threads.
// In tests, mock instances can be created with the test constructor below.
public static readonly VSSettings Ambient = new VSSettings();
private VSSettings()
{
#if NETFRAMEWORK
if (!Interop.RunningOnWindows)
{
return;
}
string instanceId;
string installationVersion;
bool isPrerelease;
try
{
var configuration = new SetupConfiguration();
var instance = configuration.GetInstanceForCurrentProcess();
instanceId = instance.GetInstanceId();
installationVersion = instance.GetInstallationVersion();
isPrerelease = ((ISetupInstanceCatalog)instance).IsPrerelease();
}
catch (COMException)
{
return;
}
var version = Version.Parse(installationVersion);
_settingsFilePath = Path.Combine(
Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
"Microsoft",
"VisualStudio",
version.Major + ".0_" + instanceId,
"sdk.txt");
_disallowPrereleaseByDefault = !isPrerelease;
_disallowPrerelease = _disallowPrereleaseByDefault;
#endif
}
// Test constructor
public VSSettings(string settingsFilePath, bool disallowPrereleaseByDefault)
{
_settingsFilePath = settingsFilePath;
_disallowPrereleaseByDefault = disallowPrereleaseByDefault;
_disallowPrerelease = _disallowPrereleaseByDefault;
}
public bool DisallowPrerelease()
{
if (_settingsFilePath != null)
{
Refresh();
}
return _disallowPrerelease;
}
private void Refresh()
{
Debug.Assert(_settingsFilePath != null);
var file = new FileInfo(_settingsFilePath);
// NB: All calls to Exists and LastWriteTimeUtc below will not hit the disk
// They will return data obtained during Refresh() here.
file.Refresh();
lock (_lock)
{
// File does not exist -> use default.
if (!file.Exists)
{
_disallowPrerelease = _disallowPrereleaseByDefault;
_settingsFile = file;
return;
}
// File has not changed -> reuse prior read.
if (_settingsFile?.Exists == true && file.LastWriteTimeUtc <= _settingsFile.LastWriteTimeUtc)
{
return;
}
// File has changed -> read from disk
// If we encounter an I/O exception, assume writer is in the process of updating file,
// ignore the exception, and use stale settings until the next resolution.
try
{
ReadFromDisk();
_settingsFile = file;
return;
}
catch (IOException) { }
catch (UnauthorizedAccessException) { }
}
}
private void ReadFromDisk()
{
using (var reader = new StreamReader(_settingsFilePath))
{
string line;
while ((line = reader.ReadLine()) != null)
{
int indexOfEquals = line.IndexOf('=');
if (indexOfEquals < 0 || indexOfEquals == (line.Length - 1))
{
continue;
}
string key = line.Substring(0, indexOfEquals).Trim();
string value = line.Substring(indexOfEquals + 1).Trim();
if (key.Equals("UsePreviews", StringComparison.OrdinalIgnoreCase)
&& bool.TryParse(value, out bool usePreviews))
{
_disallowPrerelease = !usePreviews;
return;
}
}
}
// File does not have UsePreviews entry -> use default
_disallowPrerelease = _disallowPrereleaseByDefault;
}
}
}
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