Explore looking up the process holding a file handle.

.gitignore

@@ -22,5 +22,6 @@
 !/checkstyle.xml
 !/codenarc.groovy
 !/bootstrap
+!/native
 
 /src/**/generated

native/.gitignore

@@ -0,0 +1,8 @@
+# Ignore everything
+/*
+
+!/src
+!/.vscode
+
+!/build.gradle
+!/.gitignore

native/.vscode/c_cpp_properties.json

@@ -0,0 +1,24 @@
+{
+    "configurations": [
+        {
+            "name": "Win32",
+            "includePath": [
+                "${workspaceFolder}/**",
+                "${workspaceFolder}/../build/generated/sources/headers/java/main",
+                "${env:JAVA_HOME}/include",
+                "${env:JAVA_HOME}/include/win32"
+            ],
+            "defines": [
+                "_DEBUG",
+                "UNICODE",
+                "_UNICODE"
+            ],
+            "windowsSdkVersion": "10.0.22621.0",
+            "compilerPath": "cl.exe",
+            "cStandard": "c17",
+            "cppStandard": "c++20",
+            "intelliSenseMode": "windows-msvc-x64"
+        }
+    ],
+    "version": 4
+}

native/.vscode/settings.json

@@ -0,0 +1,70 @@
+{
+    "files.associations": {
+        "optional": "cpp",
+        "format": "cpp",
+        "system_error": "cpp",
+        "filesystem": "cpp",
+        "algorithm": "cpp",
+        "array": "cpp",
+        "atomic": "cpp",
+        "bit": "cpp",
+        "cctype": "cpp",
+        "charconv": "cpp",
+        "chrono": "cpp",
+        "clocale": "cpp",
+        "cmath": "cpp",
+        "compare": "cpp",
+        "concepts": "cpp",
+        "coroutine": "cpp",
+        "cstddef": "cpp",
+        "cstdint": "cpp",
+        "cstdio": "cpp",
+        "cstdlib": "cpp",
+        "cstring": "cpp",
+        "ctime": "cpp",
+        "cwchar": "cpp",
+        "exception": "cpp",
+        "forward_list": "cpp",
+        "initializer_list": "cpp",
+        "iomanip": "cpp",
+        "ios": "cpp",
+        "iosfwd": "cpp",
+        "istream": "cpp",
+        "iterator": "cpp",
+        "limits": "cpp",
+        "list": "cpp",
+        "locale": "cpp",
+        "map": "cpp",
+        "memory": "cpp",
+        "new": "cpp",
+        "ostream": "cpp",
+        "ratio": "cpp",
+        "sstream": "cpp",
+        "stdexcept": "cpp",
+        "stop_token": "cpp",
+        "streambuf": "cpp",
+        "string": "cpp",
+        "thread": "cpp",
+        "tuple": "cpp",
+        "type_traits": "cpp",
+        "typeinfo": "cpp",
+        "unordered_map": "cpp",
+        "utility": "cpp",
+        "vector": "cpp",
+        "xfacet": "cpp",
+        "xhash": "cpp",
+        "xiosbase": "cpp",
+        "xlocale": "cpp",
+        "xlocbuf": "cpp",
+        "xlocinfo": "cpp",
+        "xlocmes": "cpp",
+        "xlocmon": "cpp",
+        "xlocnum": "cpp",
+        "xloctime": "cpp",
+        "xmemory": "cpp",
+        "xstring": "cpp",
+        "xtr1common": "cpp",
+        "xtree": "cpp",
+        "xutility": "cpp"
+    }
+}

native/build.gradle

@@ -0,0 +1,43 @@
+plugins {
+	id 'cpp-library'
+	id 'cpp-unit-test'
+	alias(libs.plugins.spotless)
+}
+
+library {
+	targetMachines = [
+			machines.windows.x86, machines.windows.x86_64, machines.windows.architecture("aarch64")
+	]
+}
+
+library {
+	linkage = [
+		Linkage.SHARED
+	]
+}
+
+import org.gradle.internal.jvm.Jvm
+def jvmHome = Jvm.current().javaHome
+
+tasks.withType(CppCompile).configureEach {
+	includes.from(new File(jvmHome, "include"))
+	includes.from(new File(jvmHome, "include/win32"))
+	includes.from(project.rootProject.getLayout().buildDirectory.dir("generated/sources/headers/java/main"))
+
+
+	compilerArgs.addAll("/std:c++20", "/EHsc")
+}
+
+tasks.withType(AbstractLinkTask).configureEach {
+	linkerArgs.addAll("Rstrtmgr.lib")
+}
+
+spotless {
+	lineEndings = com.diffplug.spotless.LineEnding.UNIX
+
+	cpp {
+		target 'src/main/cpp/**', 'src/main/headers/**', 'src/test/cpp/**'
+		clangFormat('16.0.0')
+		licenseHeaderFile(rootProject.file("HEADER")).yearSeparator("-")
+	}
+}

native/src/main/cpp/LoomNativePlatform.cpp

@@ -0,0 +1,113 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2024 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "LoomNativePlatform.hpp"
+#include "Raii.hpp"
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+#include <restartmanager.h>
+
+namespace Loom {
+namespace {
+struct RmSessionRaiiTraits {
+  using type = DWORD;
+  static constexpr auto invalid_value = 0;
+  static void close(type t) noexcept { ::RmEndSession(t); }
+};
+using RmSession = RaiiWithInvalidValue<RmSessionRaiiTraits>;
+
+struct ProcessRaiiTraits {
+  using type = HANDLE;
+  static constexpr auto invalid_value = nullptr;
+  static void close(type t) noexcept { ::CloseHandle(t); }
+};
+using Process = RaiiWithInvalidValue<ProcessRaiiTraits>;
+
+[[noreturn]] inline void throwLastError(const std::string &message) {
+  auto lastError = GetLastError();
+  throw std::system_error(lastError, std::system_category(), message);
+}
+
+RmSession createRmSession() {
+  DWORD dwSession;
+  WCHAR szSessionKey[CCH_RM_SESSION_KEY + 1] = {0};
+
+  if (::RmStartSession(&dwSession, 0, szSessionKey) != ERROR_SUCCESS) {
+    throwLastError("RmStartSession failed");
+  }
+
+  return RmSession{dwSession};
+}
+} // namespace
+
+// https://devblogs.microsoft.com/oldnewthing/20120217-00/?p=8283
+// TODO maybe look into using:
+// https://learn.microsoft.com/en-us/windows/win32/api/shobjidl_core/nf-shobjidl_core-ifileisinuse-closefile
+std::vector<int> getPidHoldingFileLock(const std::filesystem::path &file) {
+  std::vector<int> pids;
+  RmSession session = createRmSession();
+
+  PCWSTR path_ptr = file.c_str();
+  if (::RmRegisterResources(session.get(), 1, &path_ptr, 0, NULL, 0, NULL) !=
+      ERROR_SUCCESS) {
+    throwLastError("RmRegisterResources failed");
+  }
+
+  DWORD dwError;
+  DWORD dwReason;
+  UINT nProcInfoNeeded = 64, nProcInfo;
+  std::vector<RM_PROCESS_INFO> rgpi;
+
+  do {
+    nProcInfo = 2 * nProcInfoNeeded;
+    nProcInfoNeeded = 0;
+    rgpi.resize(nProcInfo);
+    dwError = RmGetList(session.get(), &nProcInfoNeeded, &nProcInfo,
+                        rgpi.data(), &dwReason);
+  } while (dwError == ERROR_MORE_DATA);
+
+  if (dwError != ERROR_SUCCESS) {
+    throwLastError("RmGetList failed");
+  }
+
+  for (const auto &info : rgpi) {
+    Process process(::OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, FALSE,
+                                  info.Process.dwProcessId));
+    if (process) {
+      // Ensure that the process start time matches the one from the
+      // RM_PROCESS_INFO
+      FILETIME ftCreate, ftExit, ftKernel, ftUser;
+      if (GetProcessTimes(process.get(), &ftCreate, &ftExit, &ftKernel,
+                          &ftUser) &&
+          CompareFileTime(&info.Process.ProcessStartTime, &ftCreate) == 0) {
+        pids.push_back(info.Process.dwProcessId);
+      }
+    }
+  }
+
+  return pids;
+}
+} // namespace Loom

native/src/main/cpp/LoomNativePlatformJni.cpp

@@ -0,0 +1,53 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2024 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "net_fabricmc_loom_util_nativeplatform_LoomNativePlatform.h"
+
+#include "LoomNativePlatform.hpp"
+
+#include <string>
+
+namespace {
+std::wstring asWstring(JNIEnv *env, jstring string) {
+  const jchar *raw = env->GetStringChars(string, 0);
+  jsize len = env->GetStringLength(string);
+
+  std::wstring_view view(reinterpret_cast<const wchar_t *>(raw), len);
+  std::wstring value{view.begin(), view.end()};
+
+  env->ReleaseStringChars(string, raw);
+
+  return value;
+}
+} // namespace
+
+JNIEXPORT jint JNICALL
+Java_net_fabricmc_loom_util_nativeplatform_LoomNativePlatform_getPidHoldingFileLock(
+    JNIEnv *env, jclass, jstring path) {
+
+  const auto wpath = asWstring(env, path);
+  const auto pid = Loom::getPidHoldingFileLock(wpath);
+
+  return -1;
+}

native/src/main/headers/LoomNativePlatform.hpp

@@ -0,0 +1,32 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2024 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#pragma once
+
+#include <filesystem>
+#include <vector>
+
+namespace Loom {
+std::vector<int> getPidHoldingFileLock(const std::filesystem::path &file);
+}