Libs: add libSceDiscMap HLE exports (ported from Kyty) (#79)

Port the libSceDiscMap stubs from Kyty (InoriRus/Kyty, MIT) into the
SysAbiExport model. Disc-installed titles probe these NIDs on most file
accesses to decide whether a read must be redirected to the disc drive;
answering that every request is already resident on internal storage
keeps I/O on the regular file system path instead of failing with
unresolved-import errors.

- sceDiscMapIsRequestOnHDD (lbQKqsERhtE): validates args, writes 1 to
  the result pointer, returns 0
- fJgP+wqifno / ioKMruft1ek: zero-fill the three output pointers,
  return 0 (names not present in ps5_names.txt; kept as descriptive
  Unknown exports like the existing sceKernelUnknown* convention)
- DISC_MAP_ERROR_INVALID_ARGUMENT (0x81100001) on null pointers,
  matching the documented libSceDiscMap error range
- optional tracing via SHARPEMU_LOG_DISCMAP=1

Co-authored-by: j92580498-max <252151737+j92580498-max@users.noreply.github.com>

src/SharpEmu.Libs/DiscMap/DiscMapExports.cs

@@ -0,0 +1,104 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.HLE;
+
+namespace SharpEmu.Libs.DiscMap;
+
+/// <summary>
+/// HLE implementation of libSceDiscMap, ported from Kyty's LibDiscMap.cpp
+/// (https://github.com/InoriRus/Kyty, MIT). Titles installed to internal
+/// storage query these entry points on nearly every file access to decide
+/// whether a read must be redirected to the Blu-ray drive. Reporting every
+/// request as already resident on HDD lets the regular file system path
+/// service the read.
+/// </summary>
+public static class DiscMapExports
+{
+    private const int DiscMapErrorInvalidArgument = unchecked((int)0x81100001);
+    private const int DiscMapErrorLocationNotMapped = unchecked((int)0x81100002);
+    private const int DiscMapErrorFileNotFound = unchecked((int)0x81100003);
+    private const int DiscMapErrorNoBitmapInfo = unchecked((int)0x81100004);
+
+    [SysAbiExport(
+        Nid = "lbQKqsERhtE",
+        ExportName = "sceDiscMapIsRequestOnHDD",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceDiscMap")]
+    public static int DiscMapIsRequestOnHDD(CpuContext ctx)
+    {
+        var pathAddress = ctx[CpuRegister.Rdi];
+        var offset = ctx[CpuRegister.Rsi];
+        var size = ctx[CpuRegister.Rdx];
+        var resultAddress = ctx[CpuRegister.Rcx];
+
+        if (pathAddress == 0 || resultAddress == 0)
+        {
+            return DiscMapErrorInvalidArgument;
+        }
+
+        if (!ctx.TryWriteInt32(resultAddress, 1))
+        {
+            return (int)OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT;
+        }
+
+        TraceDiscMap(ctx, "sceDiscMapIsRequestOnHDD", pathAddress, offset, size);
+
+        ctx[CpuRegister.Rax] = 0;
+        return (int)OrbisGen2Result.ORBIS_GEN2_OK;
+    }
+
+    [SysAbiExport(
+        Nid = "fJgP+wqifno",
+        ExportName = "sceDiscMapUnknownFJgP",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceDiscMap")]
+    public static int DiscMapUnknownFJgP(CpuContext ctx) => WriteMappingTriple(ctx, "sceDiscMapUnknownFJgP");
+
+    [SysAbiExport(
+        Nid = "ioKMruft1ek",
+        ExportName = "sceDiscMapUnknownIoKM",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceDiscMap")]
+    public static int DiscMapUnknownIoKM(CpuContext ctx) => WriteMappingTriple(ctx, "sceDiscMapUnknownIoKM");
+
+    private static int WriteMappingTriple(CpuContext ctx, string exportName)
+    {
+        var pathAddress = ctx[CpuRegister.Rdi];
+        var offset = ctx[CpuRegister.Rsi];
+        var size = ctx[CpuRegister.Rdx];
+        var flagsAddress = ctx[CpuRegister.Rcx];
+        var outAddress1 = ctx[CpuRegister.R8];
+        var outAddress2 = ctx[CpuRegister.R9];
+
+        if (pathAddress == 0 || flagsAddress == 0 || outAddress1 == 0 || outAddress2 == 0)
+        {
+            return DiscMapErrorInvalidArgument;
+        }
+
+        if (!ctx.TryWriteUInt64(flagsAddress, 0) ||
+            !ctx.TryWriteUInt64(outAddress1, 0) ||
+            !ctx.TryWriteUInt64(outAddress2, 0))
+        {
+            return (int)OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT;
+        }
+
+        TraceDiscMap(ctx, exportName, pathAddress, offset, size);
+
+        ctx[CpuRegister.Rax] = 0;
+        return (int)OrbisGen2Result.ORBIS_GEN2_OK;
+    }
+
+    private static void TraceDiscMap(CpuContext ctx, string exportName, ulong pathAddress, ulong offset, ulong size)
+    {
+        if (!string.Equals(Environment.GetEnvironmentVariable("SHARPEMU_LOG_DISCMAP"), "1", StringComparison.Ordinal))
+        {
+            return;
+        }
+
+        var path = ctx.TryReadNullTerminatedUtf8(pathAddress, 1024, out var value)
+            ? value
+            : $"<unreadable 0x{pathAddress:X16}>";
+        Console.Error.WriteLine($"[HLE][DISCMAP] {exportName} path={path} offset=0x{offset:X} size=0x{size:X}");
+    }
+}