change file writing semantics in smarty_core_write_file()

This avoids unlink() unless rename() fails or a Windows system is detected

see: http://www.phpinsider.com/smarty-forum/viewtopic.php?t=6956

Thanks to c960657 from the forums.

NEWS

@@ -1,3 +1,5 @@
+- change file writing semantics in smarty_core_write_file() to unlink() only
+  when rename() fails or a Windows system is detected (c960657, boots) 
 - update debug.tpl to xhtml 1.1 compliance, fix javascript escaping in debug
   output and apply a Smarty based color scheme (cybot, boots)
 - enhance reporting precision of debug_print_var modifier (cybot, boots) 

libs/internals/core.write_file.php

@@ -23,8 +23,7 @@ function smarty_core_write_file($params, &$smarty)
         smarty_core_create_dir_structure($_params, $smarty);
     }
 
-    // write to tmp file, then rename it to avoid
-    // file locking race condition
+    // write to tmp file, then rename it to avoid file locking race condition
     $_tmp_file = tempnam($_dirname, 'wrt');
 
     if (!($fd = @fopen($_tmp_file, 'wb'))) {
@@ -38,12 +37,13 @@ function smarty_core_write_file($params, &$smarty)
     fwrite($fd, $params['contents']);
     fclose($fd);
 
-    // Delete the file if it allready exists (this is needed on Win,
-    // because it cannot overwrite files with rename()
-    if (file_exists($params['filename'])) {
+    if (PHP_OS == 'Windows' || !@rename($_tmp_file, $params['filename'])) {
+        // On platforms and filesystems that cannot overwrite with rename() 
+        // delete the file before renaming it -- because windows always suffers
+        // this, it is short-circuited to avoid the initial rename() attempt
         @unlink($params['filename']);
+        @rename($_tmp_file, $params['filename']);
     }
-    @rename($_tmp_file, $params['filename']);
     @chmod($params['filename'], $smarty->_file_perms);
 
     return true;
@@ -51,4 +51,4 @@ function smarty_core_write_file($params, &$smarty)
 
 /* vim: set expandtab: */
 
-?>
+?>