From dd6dfafabf6aab88d4a839b5a2877a48c09f3667 Mon Sep 17 00:00:00 2001
From: Automatic Release Builder <build@flightgear.org>
Date: Wed, 7 Oct 2020 12:21:49 +0100
Subject: [PATCH] SGPath: optimise exists() on Windows

For a very common existence only check, use a dedicated win32 API
function, to save some time.
---
 simgear/misc/sg_path.cxx | 23 ++++++++++++++++++++---
 simgear/misc/sg_path.hxx |  1 +
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/simgear/misc/sg_path.cxx b/simgear/misc/sg_path.cxx
index 48d6b638..9e74bafc 100644
--- a/simgear/misc/sg_path.cxx
+++ b/simgear/misc/sg_path.cxx
@@ -44,6 +44,7 @@
 #if defined(SG_WINDOWS)
 #  include <direct.h>
 #  include <sys/utime.h>
+#  include <Shlwapi.h>
 #endif
 
 #include "sg_path.hxx"
@@ -194,7 +195,8 @@ SGPath::SGPath(PermissionChecker validator)
     _permission_checker(validator),
     _cached(false),
     _rwCached(false),
-    _cacheEnabled(true)
+    _cacheEnabled(true),
+    _existsCached(false)
 {
 }
 
@@ -205,7 +207,8 @@ SGPath::SGPath( const std::string& p, PermissionChecker validator )
     _permission_checker(validator),
     _cached(false),
     _rwCached(false),
-    _cacheEnabled(true)
+    _cacheEnabled(true),
+    _existsCached(false)
 {
     fix();
 }
@@ -230,7 +233,8 @@ SGPath::SGPath( const SGPath& p,
     _permission_checker(validator),
     _cached(false),
     _rwCached(false),
-    _cacheEnabled(p._cacheEnabled)
+    _cacheEnabled(p._cacheEnabled),
+    _existsCached(false)
 {
     append(r);
     fix();
@@ -510,6 +514,19 @@ void SGPath::checkAccess() const
 
 bool SGPath::exists() const
 {
+#if defined(SG_WINDOWS)
+  // optimisation: _wstat is slow, eg for TerraSync
+  if (!_cached && !_existsCached) {
+      std::wstring w(wstr());
+    if ((path.length() > 1) && (path.back() == '/')) {
+	    w.pop_back();
+    }
+
+    _existsCached = true;
+    _exists = PathFileExistsW(w.c_str());
+    return _exists;
+  }
+#endif
   validate();
   return _exists;
 }
diff --git a/simgear/misc/sg_path.hxx b/simgear/misc/sg_path.hxx
index af37d6ad..205759a1 100644
--- a/simgear/misc/sg_path.hxx
+++ b/simgear/misc/sg_path.hxx
@@ -356,6 +356,7 @@ private:
     mutable bool _exists : 1;
     mutable bool _isDir : 1;
     mutable bool _isFile : 1;
+    mutable bool _existsCached : 1; ///< only used on Windows
     mutable time_t _modTime;
     mutable size_t _size;
 };