.Parts was returning parts in reverse order, reworked code to be fast…

…er (via spans) and return values in the correct order.
Nexus-Mods · Aug 30, 2023 · 8586a7e · 8586a7e
1 parent c0f4fd1
commit 8586a7e
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Showing 3 changed files with 33 additions and 6 deletions.
diff --git a/src/NexusMods.Paths/RelativePath.cs b/src/NexusMods.Paths/RelativePath.cs
@@ -4,6 +4,7 @@
 using System.Runtime.CompilerServices;
 using JetBrains.Annotations;
 using NexusMods.Paths.Extensions;
+using NexusMods.Paths.HighPerformance.CommunityToolkit;
 using NexusMods.Paths.Utilities;
 
 namespace NexusMods.Paths;
@@ -72,12 +73,36 @@ public IEnumerable<RelativePath> Parts
     {
         get
         {
-            var currentPath = this;
-            while (currentPath.Path != Empty)
+            // Double iteration because we can't have iterators and spans in the same method.
+            ReadOnlySpan<char> path = Path;
+
+            if (path.Length == 0)
+                return Array.Empty<RelativePath>();
+
+            // Find the number of parts.
+            var partCount = 0;
+            for (var idx = 0; idx < path.Length; idx++)
+                if (path.DangerousGetReferenceAt(idx) == PathHelpers.DirectorySeparatorChar)
+                    partCount++;
+
+            // Allocate the array and fill it.
+            var parts = new RelativePath[partCount + 1];
+
+            var prev = 0;
+            var partIdx = 0;
+            for (var idx = 0; idx < path.Length; idx++)
             {
-                yield return currentPath.Name;
-                currentPath = currentPath.Parent;
+                var ch = path.DangerousGetReferenceAt(idx);
+                if (ch != PathHelpers.DirectorySeparatorChar) continue;
+
+                parts[partIdx] = new RelativePath(new string(path.SliceFast(prev, idx - prev)));
+                partIdx += 1;
+                idx += 1;
+                prev = idx;
             }
+
+            parts[partIdx] = new RelativePath(new string(path.SliceFast(prev)));
+            return parts;
         }
     }
 

diff --git a/tests/NexusMods.Paths.Tests/AbsolutePathTests.cs b/tests/NexusMods.Paths.Tests/AbsolutePathTests.cs
@@ -94,7 +94,8 @@ public void Test_Parts(bool isUnix, string input, string[] expectedParts)
     {
         var path = CreatePath(input, isUnix);
         var actualParts = path.Parts;
-        actualParts.Should().BeEquivalentTo(expectedParts.Select(p => new RelativePath(p)));
+        actualParts.Should().BeEquivalentTo(expectedParts.Select(p => new RelativePath(p)),
+            opts => opts.WithStrictOrdering());
     }
 
     [Theory]

diff --git a/tests/NexusMods.Paths.Tests/RelativePathTests.cs b/tests/NexusMods.Paths.Tests/RelativePathTests.cs
@@ -144,7 +144,8 @@ public void Test_GetRootComponent(string input, string expectedRootComponent)
     public void Test_Parts(string input, string[] expectedParts)
     {
         var path = new RelativePath(input);
-        path.Parts.Should().BeEquivalentTo(expectedParts.Select(x => new RelativePath(x)));
+        path.Parts.Should().BeEquivalentTo(expectedParts.Select(x => new RelativePath(x)),
+            opts => opts.WithStrictOrdering());
     }
 
     [Theory]