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jaredcnancejaredcnance
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refactor(LinkBuilder): reduce allocations
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‎benchmarks/BenchmarkDotNet.Artifacts/results/Benchmarks.LinkBuilder.LinkBuilder_GetNamespaceFromPath_Benchmarks-report-github.md

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``` ini
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BenchmarkDotNet=v0.10.10, OS=Mac OS X 10.12
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Processor=Intel Core i5-5257U CPU 2.70GHz (Broadwell), ProcessorCount=4
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.NET Core SDK=2.1.4
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[Host] : .NET Core 2.0.5 (Framework 4.6.0.0), 64bit RyuJIT
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Job-XFMVNE : .NET Core 2.0.5 (Framework 4.6.0.0), 64bit RyuJIT
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LaunchCount=3 TargetCount=20 WarmupCount=10
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```
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| Method | Mean | Error | StdDev | Gen 0 | Allocated |
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|--------------------------- |-----------:|----------:|----------:|-------:|----------:|
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| UsingSplit | 1,197.6 ns | 11.929 ns | 25.933 ns | 0.9251 | 1456 B |
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| UsingSpanWithStringBuilder | 1,542.0 ns | 15.249 ns | 33.792 ns | 0.9460 | 1488 B |
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| UsingSpanWithNoAlloc | 272.6 ns | 2.265 ns | 5.018 ns | 0.0863 | 136 B |

‎benchmarks/LinkBuilder/LinkBuilder_ GetNamespaceFromPath_Benchmarks.cs

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using System;
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using System.Diagnostics;
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using System.Text;
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using System.Threading;
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using BenchmarkDotNet.Attributes;
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using BenchmarkDotNet.Attributes.Exporters;
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using BenchmarkDotNet.Attributes.Jobs;
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using JsonApiDotNetCore.Extensions;
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namespace Benchmarks.LinkBuilder
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{
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[MarkdownExporter, SimpleJob(launchCount : 3, warmupCount : 10, targetCount : 20), MemoryDiagnoser]
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public class LinkBuilder_GetNamespaceFromPath_Benchmarks
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{
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private const string PATH = "/api/some-really-long-namespace-path/resources/current/articles";
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private const string ENTITY_NAME = "articles";
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[Benchmark]
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public void UsingSplit() => GetNamespaceFromPath_BySplitting(PATH, ENTITY_NAME);
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[Benchmark]
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public void UsingSpanWithStringBuilder() => GetNamespaceFromPath_Using_Span_With_StringBuilder(PATH, ENTITY_NAME);
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[Benchmark]
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public void UsingSpanWithNoAlloc() => GetNamespaceFromPath_Using_Span_No_Alloc(PATH, ENTITY_NAME);
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public static string GetNamespaceFromPath_BySplitting(string path, string entityName)
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{
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var nSpace = string.Empty;
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var segments = path.Split('/');
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for (var i = 1; i < segments.Length; i++)
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{
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if (segments[i].ToLower() == entityName)
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break;
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nSpace += $"/{segments[i]}";
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}
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return nSpace;
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}
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public static string GetNamespaceFromPath_Using_Span_No_Alloc(string path, string entityName)
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{
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var entityNameSpan = entityName.AsSpan();
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var pathSpan = path.AsSpan();
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const char delimiter = '/';
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for (var i = 0; i < pathSpan.Length; i++)
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{
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if(pathSpan[i].Equals(delimiter))
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{
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var nextPosition = i+1;
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if(pathSpan.Length > i + entityNameSpan.Length)
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{
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var possiblePathSegment = pathSpan.Slice(nextPosition, entityNameSpan.Length);
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if (entityNameSpan.SequenceEqual(possiblePathSegment))
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{
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// check to see if it's the last position in the string
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// or if the next character is a /
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var lastCharacterPosition = nextPosition + entityNameSpan.Length;
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if(lastCharacterPosition == pathSpan.Length || pathSpan.Length >= lastCharacterPosition + 2 && pathSpan[lastCharacterPosition + 1].Equals(delimiter))
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{
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return pathSpan.Slice(0, i).ToString();
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}
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}
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}
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}
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}
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return string.Empty;
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}
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public static string GetNamespaceFromPath_Using_Span_With_StringBuilder(string path, string entityName)
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{
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var sb = new StringBuilder();
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var entityNameSpan = entityName.AsSpan();
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var subSpans = path.SpanSplit('/');
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for (var i = 1; i < subSpans.Count; i++)
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{
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var span = subSpans[i];
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if (entityNameSpan.SequenceEqual(span))
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break;
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sb.Append($"/{span.ToString()}");
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}
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return sb.ToString();
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}
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}
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}

‎benchmarks/Program.cs

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using BenchmarkDotNet.Running;
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using Benchmarks.LinkBuilder;
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using Benchmarks.Query;
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using Benchmarks.Serialization;
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var switcher = new BenchmarkSwitcher(new[] {
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typeof(JsonApiDeserializer_Benchmarks),
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typeof(JsonApiSerializer_Benchmarks),
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typeof(QueryParser_Benchmarks)
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typeof(QueryParser_Benchmarks),
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typeof(LinkBuilder_GetNamespaceFromPath_Benchmarks)
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});
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switcher.Run(args);
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}

‎src/JsonApiDotNetCore/Builders/LinkBuilder.cs

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using System;
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using System.Text;
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using JsonApiDotNetCore.Extensions;
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using JsonApiDotNetCore.Internal;
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using JsonApiDotNetCore.Services;
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using Microsoft.AspNetCore.Http;
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{
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var r = context.Request;
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return (_context.Options.RelativeLinks)
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? $"{GetNamespaceFromPath(r.Path, entityName)}"
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? GetNamespaceFromPath(r.Path, entityName)
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: $"{r.Scheme}://{r.Host}{GetNamespaceFromPath(r.Path, entityName)}";
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}
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private static string GetNamespaceFromPath(string path, string entityName)
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{
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var sb = new StringBuilder();
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var entityNameSpan = entityName.AsSpan();
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var subSpans = path.SpanSplit('/');
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for (var i = 1; i < subSpans.Count; i++)
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var pathSpan = path.AsSpan();
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const char delimiter = '/';
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for (var i = 0; i < pathSpan.Length; i++)
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{
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var span = subSpans[i];
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if (entityNameSpan.SequenceEqual(span)) break;
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sb.Append($"/{span.ToString()}");
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if(pathSpan[i].Equals(delimiter))
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{
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var nextPosition = i + 1;
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if(pathSpan.Length > i + entityNameSpan.Length)
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{
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var possiblePathSegment = pathSpan.Slice(nextPosition, entityNameSpan.Length);
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if (entityNameSpan.SequenceEqual(possiblePathSegment))
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{
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// check to see if it's the last position in the string
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// or if the next character is a /
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var lastCharacterPosition = nextPosition + entityNameSpan.Length;
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if(lastCharacterPosition == pathSpan.Length || pathSpan.Length >= lastCharacterPosition + 2 && pathSpan[lastCharacterPosition].Equals(delimiter))
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{
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return pathSpan.Slice(0, i).ToString();
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}
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}
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}
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}
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}
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return sb.ToString();
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return string.Empty;
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}
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public string GetSelfRelationLink(string parent, string parentId, string child)

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