Optimize KWSys SystemTools::FileExists on Windows

We optimize this method by using the GetFileAttributesExA native Windows
API to check for file existence when possible.  For real Windows builds
we always use it.  For Cygwin we use cygwin_conv_to_win32_path to get a
native Windows path if possible and otherwise fall back to 'access'.

Cygwin-to-Windows path conversion and cache by Wojciech Migda.
See issue #8826.

1 files changed, 65 insertions, 21 deletions

diff --git a/Source/kwsys/SystemTools.cxx b/Source/kwsys/SystemTools.cxx
index 9b7a6ed..fe0e31b 100644
--- a/Source/kwsys/SystemTools.cxx
+++ b/Source/kwsys/SystemTools.cxx
@@ -65,10 +65,15 @@
 #endif
 
 // Windows API.  Some parts used even on cygwin.
-#if defined(_WIN32)
+#if defined(_WIN32) || defined (__CYGWIN__)
 # include <windows.h>
 #endif
 
+#ifdef __CYGWIN__
+# undef _WIN32
+extern "C" void cygwin_conv_to_win32_path(const char *path, char *win32_path);
+#endif
+
 // getpwnam doesn't exist on Windows and Cray Xt3/Catamount
 // same for TIOCGWINSZ
 #if defined(_WIN32) || defined (__LIBCATAMOUNT__)
@@ -892,39 +897,69 @@ bool SystemTools::SameFile(const char* file1, const char* file2)
 #endif
 }
 
-
-// return true if the file exists
-bool SystemTools::FileExists(const char* filename, bool isFile)
+//----------------------------------------------------------------------------
+#if defined(_WIN32) || defined(__CYGWIN__)
+static bool WindowsFileExists(const char* filename)
 {
-#ifdef _MSC_VER
-# define access _access
-#endif
-#ifndef R_OK
-# define R_OK 04
+  WIN32_FILE_ATTRIBUTE_DATA fd;
+  return GetFileAttributesExA(filename, GetFileExInfoStandard, &fd) != 0;
+}
 #endif
 
-#ifdef __SYLLABLE__
-  if ((filename !=0) && (*filename == 0))
+//----------------------------------------------------------------------------
+bool SystemTools::FileExists(const char* filename)
+{
+  if(!(filename && *filename))
     {
     return false;
-  }
+    }
+#if defined(__CYGWIN__)
+  // Convert filename to native windows path if possible.
+  char winpath[MAX_PATH];
+  if(SystemTools::PathCygwinToWin32(filename, winpath))
+    {
+    return WindowsFileExists(winpath);
+    }
+  return access(filename, R_OK) == 0;
+#elif defined(_WIN32)
+  return WindowsFileExists(filename);
+#else
+  return access(filename, R_OK) == 0;
 #endif
+}
 
-  if ( access(filename, R_OK) != 0 )
+//----------------------------------------------------------------------------
+bool SystemTools::FileExists(const char* filename, bool isFile)
+{
+  if(SystemTools::FileExists(filename))
     {
-    return false;
+    // If isFile is set return not FileIsDirectory,
+    // so this will only be true if it is a file
+    return !isFile || !SystemTools::FileIsDirectory(filename);
+    }
+  return false;
+}
+
+//----------------------------------------------------------------------------
+#ifdef __CYGWIN__
+bool SystemTools::PathCygwinToWin32(const char *path, char *win32_path)
+{
+  SystemToolsTranslationMap::iterator i =
+    SystemTools::Cyg2Win32Map->find(path);
+
+  if (i != SystemTools::Cyg2Win32Map->end())
+    {
+    strncpy(win32_path, i->second.c_str(), MAX_PATH);
     }
   else
     {
-    // If isFile is set return not FileIsDirectory,
-    // so this will only be true if it is a file
-    if(isFile)
-      {
-      return !SystemTools::FileIsDirectory(filename);
-      }
-    return true;
+    cygwin_conv_to_win32_path(path, win32_path);
+    SystemToolsTranslationMap::value_type entry(path, win32_path);
+    SystemTools::Cyg2Win32Map->insert(entry);
     }
+  return win32_path[0] != 0;
 }
+#endif
 
 bool SystemTools::Touch(const char* filename, bool create)
 {
@@ -4536,6 +4571,9 @@ bool SystemTools::ParseURL( const kwsys_stl::string& URL,
 unsigned int SystemToolsManagerCount;
 SystemToolsTranslationMap *SystemTools::TranslationMap;
 SystemToolsTranslationMap *SystemTools::LongPathMap;
+#ifdef __CYGWIN__
+SystemToolsTranslationMap *SystemTools::Cyg2Win32Map;
+#endif
 
 // SystemToolsManager manages the SystemTools singleton.
 // SystemToolsManager should be included in any translation unit
@@ -4581,6 +4619,9 @@ void SystemTools::ClassInitialize()
   // Allocate the translation map first.
   SystemTools::TranslationMap = new SystemToolsTranslationMap;
   SystemTools::LongPathMap = new SystemToolsTranslationMap;
+#ifdef __CYGWIN__
+  SystemTools::Cyg2Win32Map = new SystemToolsTranslationMap;
+#endif
 
   // Add some special translation paths for unix.  These are not added
   // for windows because drive letters need to be maintained.  Also,
@@ -4637,6 +4678,9 @@ void SystemTools::ClassFinalize()
 {
   delete SystemTools::TranslationMap;
   delete SystemTools::LongPathMap;
+#ifdef __CYGWIN__
+  delete SystemTools::Cyg2Win32Map;
+#endif
 }