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CommandInfoCache.cs
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120 lines (103 loc) · 4.78 KB
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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
using System;
using System.Collections.Concurrent;
using System.Management.Automation;
using System.Linq;
namespace Microsoft.Windows.PowerShell.ScriptAnalyzer
{
/// <summary>
/// Provides threadsafe caching around CommandInfo lookups with `Get-Command -Name ...`.
/// </summary>
internal class CommandInfoCache
{
private readonly ConcurrentDictionary<CommandLookupKey, Lazy<CommandInfo>> _commandInfoCache;
private readonly Helper _helperInstance;
/// <summary>
/// Create a fresh command info cache instance.
/// </summary>
public CommandInfoCache(Helper pssaHelperInstance)
{
_commandInfoCache = new ConcurrentDictionary<CommandLookupKey, Lazy<CommandInfo>>();
_helperInstance = pssaHelperInstance;
}
/// <summary>
/// Retrieve a command info object about a command.
/// </summary>
/// <param name="commandName">Name of the command to get a commandinfo object for.</param>
/// <param name="commandTypes">What types of command are needed. If omitted, all types are retrieved.</param>
/// <returns></returns>
public CommandInfo GetCommandInfo(string commandName, CommandTypes? commandTypes = null)
{
if (string.IsNullOrWhiteSpace(commandName))
{
return null;
}
var key = new CommandLookupKey(commandName, commandTypes);
// Atomically either use PowerShell to query a command info object, or fetch it from the cache
return _commandInfoCache.GetOrAdd(key, new Lazy<CommandInfo>(() => GetCommandInfoInternal(commandName, commandTypes))).Value;
}
/// <summary>
/// Retrieve a command info object about a command.
/// </summary>
/// <param name="commandName">Name of the command to get a commandinfo object for.</param>
/// <param name="commandTypes">What types of command are needed. If omitted, all types are retrieved.</param>
/// <returns></returns>
[Obsolete("Alias lookup is expensive and should not be relied upon for command lookup")]
public CommandInfo GetCommandInfoLegacy(string commandOrAliasName, CommandTypes? commandTypes = null)
{
string commandName = _helperInstance.GetCmdletNameFromAlias(commandOrAliasName);
return string.IsNullOrEmpty(commandName)
? GetCommandInfo(commandOrAliasName, commandTypes: commandTypes)
: GetCommandInfo(commandName, commandTypes: commandTypes);
}
/// <summary>
/// Get a CommandInfo object of the given command name
/// </summary>
/// <returns>Returns null if command does not exists</returns>
private static CommandInfo GetCommandInfoInternal(string cmdName, CommandTypes? commandType)
{
// 'Get-Command ?' would return % for example due to PowerShell interpreting is a single-character-wildcard search and not just the ? alias.
// For more details see https://github.com/PowerShell/PowerShell/issues/9308
cmdName = WildcardPattern.Escape(cmdName);
using (var ps = System.Management.Automation.PowerShell.Create())
{
ps.AddCommand("Get-Command")
.AddParameter("Name", cmdName)
.AddParameter("ErrorAction", "SilentlyContinue");
if (commandType != null)
{
ps.AddParameter("CommandType", commandType);
}
return ps.Invoke<CommandInfo>()
.FirstOrDefault();
}
}
private struct CommandLookupKey : IEquatable<CommandLookupKey>
{
private readonly string Name;
private readonly CommandTypes CommandTypes;
internal CommandLookupKey(string name, CommandTypes? commandTypes)
{
Name = name;
CommandTypes = commandTypes ?? CommandTypes.All;
}
public bool Equals(CommandLookupKey other)
{
return CommandTypes == other.CommandTypes
&& Name.Equals(other.Name, StringComparison.OrdinalIgnoreCase);
}
public override int GetHashCode()
{
// Algorithm from https://stackoverflow.com/questions/1646807/quick-and-simple-hash-code-combinations
unchecked
{
int hash = 17;
hash = hash * 31 + Name.ToUpperInvariant().GetHashCode();
hash = hash * 31 + CommandTypes.GetHashCode();
return hash;
}
}
}
}
}