From 0e932ba27417037ae4bdab3fa2dfe542250163d3 Mon Sep 17 00:00:00 2001
From: "Unknown W. Brackets" <checkins@unknownbrackets.org>
Date: Tue, 1 Mar 2022 19:36:36 -0800
Subject: [PATCH 1/2] Windows: Create SYSTEM directory early.

On UNC, we see paths as absolute and don't auto-create this on config
load.  We should really create it here anyway.
---
 Core/System.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Core/System.cpp b/Core/System.cpp
index e3952524d6..859ca3f6b7 100644
--- a/Core/System.cpp
+++ b/Core/System.cpp
@@ -731,6 +731,7 @@ void InitSysDirectories() {
 	File::CreateDir(GetSysDirectory(DIRECTORY_GAME));
 	File::CreateDir(GetSysDirectory(DIRECTORY_SAVEDATA));
 	File::CreateDir(GetSysDirectory(DIRECTORY_SAVESTATE));
+	File::CreateDir(GetSysDirectory(DIRECTORY_SYSTEM));
 
 	if (g_Config.currentDirectory.empty()) {
 		g_Config.currentDirectory = GetSysDirectory(DIRECTORY_GAME);

From 73ece5b5cafced4afc9dab9dbc57612ee0dc5c3b Mon Sep 17 00:00:00 2001
From: "Unknown W. Brackets" <checkins@unknownbrackets.org>
Date: Tue, 1 Mar 2022 21:07:17 -0800
Subject: [PATCH 2/2] Windows: Correct root vol handling for UNC paths.

Otherwise CreateFullPath() fails.
---
 Common/File/Path.cpp  | 11 +++++++++++
 unittest/UnitTest.cpp |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/Common/File/Path.cpp b/Common/File/Path.cpp
index 7324118068..d0bda53328 100644
--- a/Common/File/Path.cpp
+++ b/Common/File/Path.cpp
@@ -307,6 +307,17 @@ Path Path::GetRootVolume() const {
 		std::string path = path_.substr(0, 2);
 		return Path(path);
 	}
+	// Support UNC and device paths.
+	if (path_[0] == '/' && path_[1] == '/') {
+		size_t next = 2;
+		if ((path_[2] == '.' || path_[2] == '?') && path_[3] == '/') {
+			// Device path, or "\\.\UNC" path, skip the dot and consider the device the root.
+			next = 4;
+		}
+
+		size_t len = path_.find_first_of('/', next);
+		return Path(path_.substr(0, len));
+	}
 #endif
 	return Path("/");
 }
diff --git a/unittest/UnitTest.cpp b/unittest/UnitTest.cpp
index fba781084b..ec5a92a845 100644
--- a/unittest/UnitTest.cpp
+++ b/unittest/UnitTest.cpp
@@ -608,6 +608,10 @@ static bool TestPath() {
 	EXPECT_EQ_STR(Path("C:\\Yo").GetFilename(), std::string("Yo"));
 	EXPECT_EQ_STR(Path("C:\\Yo\\Lo").GetDirectory(), std::string("C:/Yo"));
 	EXPECT_EQ_STR(Path("C:\\Yo\\Lo").GetFilename(), std::string("Lo"));
+
+	EXPECT_EQ_STR(Path(R"(\\host\share\filename)").GetRootVolume().ToString(), std::string("//host"));
+	EXPECT_EQ_STR(Path(R"(\\?\UNC\share\filename)").GetRootVolume().ToString(), std::string("//?/UNC"));
+	EXPECT_EQ_STR(Path(R"(\\?\C:\share\filename)").GetRootVolume().ToString(), std::string("//?/C:"));
 #endif
 
 	std::string computedPath;