Ampr: cooked-id index preload and host FD LRU cache (#725)

Preload the app0 APR index during bind and bound the open host-file cache so streaming reads stay responsive under large title archives.

tests/SharpEmu.Libs.Tests/Ampr/AmprFileRegistryTests.cs

@@ -0,0 +1,78 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.Libs.Ampr;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.Ampr;
+
+public class AmprFileRegistryTests
+{
+    [Fact]
+    public void ComputeFileId_matches_utf8_fnv1a()
+    {
+        const string relative = "CoreData/foo/bar.bin";
+        Assert.Equal(FnvUtf8("$/" + relative), AmprFileRegistry.ComputeFileId("$/" + relative));
+        Assert.Equal(FnvUtf8("/app0/" + relative), AmprFileRegistry.ComputeFileId("/app0/" + relative));
+        Assert.Equal(FnvUtf8("app0/" + relative), AmprFileRegistry.ComputeFileId("app0/" + relative));
+        Assert.Equal(FnvUtf8(relative), AmprFileRegistry.ComputeFileId(relative));
+    }
+
+    [Fact]
+    public void RegisterApp0Relative_publishes_same_ids_as_string_hashes()
+    {
+        AmprFileRegistry.ClearForTests();
+        const string relative = "misc/loadouts/test.txt";
+        var host = Path.Combine(Path.GetTempPath(), "sharpemu-ampr-test", relative);
+        AmprFileRegistry.RegisterApp0RelativeForTests(relative, host);
+
+        Assert.True(AmprFileRegistry.TryGetHostPath(
+            AmprFileRegistry.ComputeFileId("$/" + relative), out var a));
+        Assert.True(AmprFileRegistry.TryGetHostPath(
+            AmprFileRegistry.ComputeFileId("/app0/" + relative), out var b));
+        Assert.True(AmprFileRegistry.TryGetHostPath(
+            AmprFileRegistry.ComputeFileId("app0/" + relative), out var c));
+        Assert.True(AmprFileRegistry.TryGetHostPath(
+            AmprFileRegistry.ComputeFileId(relative), out var d));
+        Assert.Equal(host, a);
+        Assert.Equal(host, b);
+        Assert.Equal(host, c);
+        Assert.Equal(host, d);
+    }
+
+    [Fact]
+    public void Register_publishes_all_app0_path_aliases()
+    {
+        AmprFileRegistry.ClearForTests();
+        const string relative = "scripts/cp11/cp11main.script";
+        var host = Path.Combine(Path.GetTempPath(), "sharpemu-ampr-test2", relative);
+        AmprFileRegistry.Register("$/" + relative, host);
+
+        Assert.True(AmprFileRegistry.TryGetHostPath(
+            AmprFileRegistry.ComputeFileId("$/" + relative), out var a));
+        Assert.True(AmprFileRegistry.TryGetHostPath(
+            AmprFileRegistry.ComputeFileId("/app0/" + relative), out var b));
+        Assert.True(AmprFileRegistry.TryGetHostPath(
+            AmprFileRegistry.ComputeFileId("app0/" + relative), out var c));
+        Assert.True(AmprFileRegistry.TryGetHostPath(
+            AmprFileRegistry.ComputeFileId(relative), out var d));
+        Assert.Equal(host, a);
+        Assert.Equal(host, b);
+        Assert.Equal(host, c);
+        Assert.Equal(host, d);
+    }
+
+    private static uint FnvUtf8(string text)
+    {
+        const uint offset = 2166136261;
+        const uint prime = 16777619;
+        var hash = offset;
+        foreach (var b in System.Text.Encoding.UTF8.GetBytes(text))
+        {
+            hash ^= b;
+            hash *= prime;
+        }
+
+        return hash;
+    }
+}

tests/SharpEmu.Libs.Tests/Ampr/AprStreamingContractTests.cs

@@ -318,6 +318,53 @@ public sealed class AprStreamingContractTests
         return BinaryPrimitives.ReadUInt32LittleEndian(bytes);
     }
 
+    [Fact]
+    public void Register_AlsoPublishesApp0AndDollarPathAliases()
+    {
+        // Resolve may register "$/asset.bin" while cooked tables look up
+        // FNV("/app0/asset.bin"). Both ids must map to the same host file.
+        var hostPath = Path.Combine(Path.GetTempPath(), $"sharpemu-apr-alias-{Guid.NewGuid():N}.bin");
+        File.WriteAllBytes(hostPath, [1, 2, 3]);
+        try
+        {
+            var dollarId = AmprFileRegistry.Register("$/weapons/demo.cani", hostPath);
+            Assert.True(AmprFileRegistry.TryGetHostPath(dollarId, out var viaDollar));
+            Assert.Equal(hostPath, viaDollar);
+
+            var app0Id = AmprFileRegistry.ComputeFileId("/app0/weapons/demo.cani");
+            Assert.NotEqual(dollarId, app0Id);
+            Assert.True(AmprFileRegistry.TryGetHostPath(app0Id, out var viaApp0));
+            Assert.Equal(hostPath, viaApp0);
+        }
+        finally
+        {
+            File.Delete(hostPath);
+        }
+    }
+
+    [Fact]
+    public void EnsureApp0Indexed_PublishesCookedApp0FileIds()
+    {
+        var mountRoot = Path.Combine(
+            Path.GetTempPath(),
+            $"sharpemu-apr-index-{Guid.NewGuid():N}");
+        var relativeDir = Path.Combine(mountRoot, "weapons");
+        Directory.CreateDirectory(relativeDir);
+        var hostPath = Path.Combine(relativeDir, "demo.cani");
+        File.WriteAllBytes(hostPath, [9, 8, 7]);
+        try
+        {
+            AmprFileRegistry.EnsureApp0Indexed(mountRoot);
+            var cookedId = AmprFileRegistry.ComputeFileId("/app0/weapons/demo.cani");
+            Assert.True(AmprFileRegistry.TryGetHostPath(cookedId, out var resolved));
+            Assert.Equal(Path.GetFullPath(hostPath), Path.GetFullPath(resolved));
+        }
+        finally
+        {
+            Directory.Delete(mountRoot, recursive: true);
+        }
+    }
+
     private static ulong ReadUInt64(FakeCpuMemory memory, ulong address)
     {
         Span<byte> bytes = stackalloc byte[sizeof(ulong)];