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Avoid allocating strings in DefaultViewLocationCache
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Fixes #3135
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@pranavkm
pranavkm committed Sep 17, 2015
1 parent 0007552 commit 1c4614c
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Showing 2 changed files with 475 additions and 135 deletions.
136 changes: 106 additions & 30 deletions src/Microsoft.AspNet.Mvc.Razor/DefaultViewLocationCache.cs
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Expand Up @@ -3,8 +3,7 @@

using System;
using System.Collections.Concurrent;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using Microsoft.Framework.Internal;

namespace Microsoft.AspNet.Mvc.Razor
Expand All @@ -14,23 +13,22 @@ namespace Microsoft.AspNet.Mvc.Razor
/// </summary>
public class DefaultViewLocationCache : IViewLocationCache
{
private const char CacheKeySeparator = ':';

// A mapping of keys generated from ViewLocationExpanderContext to view locations.
private readonly ConcurrentDictionary<string, ViewLocationCacheResult> _cache;
private readonly ConcurrentDictionary<ViewLocationCacheKey, ViewLocationCacheResult> _cache;

/// <summary>
/// Initializes a new instance of <see cref="DefaultViewLocationCache"/>.
/// </summary>
public DefaultViewLocationCache()
{
_cache = new ConcurrentDictionary<string, ViewLocationCacheResult>(StringComparer.Ordinal);
_cache = new ConcurrentDictionary<ViewLocationCacheKey, ViewLocationCacheResult>(
ViewLocationCacheKeyComparer.Instance);
}

/// <inheritdoc />
public ViewLocationCacheResult Get([NotNull] ViewLocationExpanderContext context)
{
var cacheKey = GenerateKey(context);
var cacheKey = GenerateKey(context, copyViewExpanderValues: false);
ViewLocationCacheResult result;
if (_cache.TryGetValue(cacheKey, out result))
{
Expand All @@ -45,46 +43,124 @@ public ViewLocationCacheResult Get([NotNull] ViewLocationExpanderContext context
[NotNull] ViewLocationExpanderContext context,
[NotNull] ViewLocationCacheResult value)
{
var cacheKey = GenerateKey(context);
var cacheKey = GenerateKey(context, copyViewExpanderValues: true);
_cache.TryAdd(cacheKey, value);
}

internal static string GenerateKey(ViewLocationExpanderContext context)
// Internal for unit testing
internal static ViewLocationCacheKey GenerateKey(
ViewLocationExpanderContext context,
bool copyViewExpanderValues)
{
var keyBuilder = new StringBuilder();
var routeValues = context.ActionContext.RouteData.Values;
var controller = RazorViewEngine.GetNormalizedRouteValue(
context.ActionContext,
RazorViewEngine.ControllerKey);

// format is "{viewName}:{isPartial}:{controllerName}:{areaName}:"
keyBuilder.Append(context.ViewName)
.Append(CacheKeySeparator)
.Append(context.IsPartial ? 1 : 0)
.Append(CacheKeySeparator)
.Append(controller);
var area = RazorViewEngine.GetNormalizedRouteValue(
context.ActionContext,
RazorViewEngine.AreaKey);


var area = RazorViewEngine.GetNormalizedRouteValue(context.ActionContext, RazorViewEngine.AreaKey);
if (!string.IsNullOrEmpty(area))
var values = context.Values;
if (values != null && copyViewExpanderValues)
{
keyBuilder.Append(CacheKeySeparator)
.Append(area);
// When performing a Get, avoid creating a copy of the values dictionary
values = new Dictionary<string, string>(values, StringComparer.Ordinal);
}

if (context.Values != null)
return new ViewLocationCacheKey(
context.ViewName,
controller,
area,
context.IsPartial,
values);
}

// Internal for unit testing
internal class ViewLocationCacheKeyComparer : IEqualityComparer<ViewLocationCacheKey>
{
public static readonly ViewLocationCacheKeyComparer Instance = new ViewLocationCacheKeyComparer();

public bool Equals(ViewLocationCacheKey x, ViewLocationCacheKey y)
{
var valuesDictionary = context.Values;
foreach (var item in valuesDictionary.OrderBy(k => k.Key, StringComparer.Ordinal))
if (x.IsPartial != y.IsPartial ||
!string.Equals(x.ViewName, y.ViewName, StringComparison.Ordinal) ||
!string.Equals(x.ControllerName, y.ControllerName, StringComparison.Ordinal) ||
!string.Equals(x.AreaName, y.AreaName, StringComparison.Ordinal))
{
keyBuilder.Append(CacheKeySeparator)
.Append(item.Key)
.Append(CacheKeySeparator)
.Append(item.Value);
return false;
}

if (ReferenceEquals(x.Values, y.Values))
{
return true;
}

if (x.Values == null || y.Values == null || (x.Values.Count != y.Values.Count))
{
return false;
}

foreach (var item in x.Values)
{
string yValue;
if (!y.Values.TryGetValue(item.Key, out yValue) ||
!string.Equals(item.Value, yValue, StringComparison.Ordinal))
{
return false;
}
}

return true;
}

var cacheKey = keyBuilder.ToString();
return cacheKey;
public int GetHashCode(ViewLocationCacheKey key)
{
var hashCodeCombiner = HashCodeCombiner.Start();
hashCodeCombiner.Add(key.IsPartial ? 1 : 0);
hashCodeCombiner.Add(key.ViewName, StringComparer.Ordinal);
hashCodeCombiner.Add(key.ControllerName, StringComparer.Ordinal);
hashCodeCombiner.Add(key.AreaName, StringComparer.Ordinal);

if (key.Values != null)
{
foreach (var item in key.Values)
{
hashCodeCombiner.Add(item.Key, StringComparer.Ordinal);
hashCodeCombiner.Add(item.Value, StringComparer.Ordinal);
}
}

return hashCodeCombiner;
}
}

// Internal for unit testing
internal struct ViewLocationCacheKey
{
public ViewLocationCacheKey(
string viewName,
string controllerName,
string areaName,
bool isPartial,
IDictionary<string, string> values)
{
ViewName = viewName;
ControllerName = controllerName;
AreaName = areaName;
IsPartial = isPartial;
Values = values;
}

public string ViewName { get; }

public string ControllerName { get; }

public string AreaName { get; }

public bool IsPartial { get; }

public IDictionary<string, string> Values { get; }
}
}
}

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