From fce8afabfb0629d88ae02c87e62cb27e666c7010 Mon Sep 17 00:00:00 2001
From: Alibek Omarov <a1ba.omarov@gmail.com>
Date: Thu, 25 Aug 2022 20:33:16 +0300
Subject: [PATCH] filesystem: allow acquiring C interface through
 CreateInterface export

---
 filesystem/VFileSystem009.cpp    | 12 ++++++++++++
 filesystem/filesystem.c          |  2 +-
 filesystem/filesystem.h          |  1 +
 filesystem/filesystem_internal.h |  1 +
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/filesystem/VFileSystem009.cpp b/filesystem/VFileSystem009.cpp
index ffcffe40..7bfee6ba 100644
--- a/filesystem/VFileSystem009.cpp
+++ b/filesystem/VFileSystem009.cpp
@@ -492,6 +492,18 @@ extern "C" void EXPORT *CreateInterface( const char *interface, int *retval )
 		return &g_VFileSystem009;
 	}
 
+	if( !Q_strcmp( interface, FS_API_CREATEINTERFACE_TAG ))
+	{
+		// return a copy, to disallow overriding
+		static fs_api_t copy = { 0 };
+
+		if( !copy.InitStdio )
+			memcpy( &copy, &g_api, sizeof( copy ));
+
+		if( retval ) *retval = 0;
+		return &copy;
+	}
+
 	if( retval ) *retval = 1;
 	return NULL;
 }
diff --git a/filesystem/filesystem.c b/filesystem/filesystem.c
index 66a9b5ae..5e9e3926 100644
--- a/filesystem/filesystem.c
+++ b/filesystem/filesystem.c
@@ -2868,7 +2868,7 @@ static qboolean FS_InitInterface( int version, fs_interface_t *engfuncs )
 	return true;
 }
 
-static fs_api_t g_api =
+fs_api_t g_api =
 {
 	FS_InitStdio,
 	FS_ShutdownStdio,
diff --git a/filesystem/filesystem.h b/filesystem/filesystem.h
index 6a7a1f4c..54eac76c 100644
--- a/filesystem/filesystem.h
+++ b/filesystem/filesystem.h
@@ -29,6 +29,7 @@ extern "C"
 #endif // __cplusplus
 
 #define FS_API_VERSION 1 // not stable yet!
+#define FS_API_CREATEINTERFACE_TAG "XashFileSystem001" // follow FS_API_VERSION!!!
 
 // search path flags
 enum
diff --git a/filesystem/filesystem_internal.h b/filesystem/filesystem_internal.h
index 3cf5a462..5f11f52f 100644
--- a/filesystem/filesystem_internal.h
+++ b/filesystem/filesystem_internal.h
@@ -86,6 +86,7 @@ extern qboolean      fs_ext_path;
 extern char          fs_rodir[MAX_SYSPATH];
 extern char          fs_rootdir[MAX_SYSPATH];
 extern char          fs_writedir[MAX_SYSPATH];
+extern fs_api_t      g_api;
 
 #define GI FI.GameInfo