performance patch: reduce stat () call if all cache files can be trusted

[Mike FABIAN <mfabian@xxxxxxx>]

Takashi IWAI <tiwai@xxxxxxx> made a patch to reduce the amount of stat
() calls in the case when one is absolutely sure that all cache files
are OK and up-to-date and can be trusted. 

For details see

    http://bugzilla.novell.com/show_bug.cgi?id=148361

from comment #20 on.

There are problems if the cache files are not correct of course,
but nevertheless Takashi's patch might be a useful performance hack
if a user is able to make sure that all cache files can be trusted.

--- src/fcint.h-dist	2006-02-08 20:57:29.000000000 +0100
+++ src/fcint.h	2006-02-08 20:58:06.000000000 +0100
@@ -414,6 +414,10 @@ struct _FcConfig {
      */
     time_t	rescanTime;	    /* last time information was scanned */
     int		rescanInterval;	    /* interval between scans */
+    /*
+     * Validate cache files at each open?
+     */
+    FcBool	validateCache;
 };
  
 extern FcConfig	*_fcConfig;
--- src/fccfg.c-dist	2006-02-08 21:07:16.000000000 +0100
+++ src/fccfg.c	2006-02-08 21:07:38.000000000 +0100
@@ -117,6 +117,7 @@ FcConfigCreate (void)
 
     config->rescanTime = time(0);
     config->rescanInterval = 30;    
+    config->validateCache = 1;
     
     return config;
 
--- src/fcxml.c-dist	2006-02-08 20:55:00.000000000 +0100
+++ src/fcxml.c	2006-02-08 20:57:18.000000000 +0100
@@ -293,6 +293,7 @@ typedef enum _FcElement {
 	
     FcElementBlank,
     FcElementRescan,
+    FcElementValidatecache,
 
     FcElementPrefer,
     FcElementAccept,
@@ -353,6 +354,7 @@ static struct {
     
     { "blank",		FcElementBlank },
     { "rescan",		FcElementRescan },
+    { "validatecache",	FcElementValidatecache },
 
     { "prefer",		FcElementPrefer },
     { "accept",		FcElementAccept },
@@ -1099,6 +1101,20 @@ FcParseRescan (FcConfigParse *parse)
 }
 
 static void
+FcParseValidatecache (FcConfigParse *parse)
+{
+    int	    n = FcVStackElements (parse);
+    while (n-- > 0)
+    {
+	FcVStack    *v = FcVStackFetch (parse, n);
+	if (v->tag != FcVStackBool)
+	    FcConfigMessage (parse, FcSevereWarning, "non-boolean validatecache");
+	else
+	    parse->config->validateCache = v->u.bool;
+    }
+}
+
+static void
 FcParseInt (FcConfigParse *parse)
 {
     FcChar8 *s, *end;
@@ -2086,6 +2102,9 @@ FcEndElement(void *userData, const XML_C
     case FcElementRescan:
 	FcParseRescan (parse);
 	break;
+    case FcElementValidatecache:
+	FcParseValidatecache (parse);
+	break;
 	
     case FcElementPrefer:
 	FcParseFamilies (parse, FcVStackPrefer);
--- src/fccache.c-dist	2006-02-08 20:58:21.000000000 +0100
+++ src/fccache.c	2006-02-08 21:38:23.000000000 +0100
@@ -221,9 +221,10 @@ FcGlobalCacheLoad (FcGlobalCache    *cac
 
 	/* Directory must be older than the global cache file; also
 	   cache must be newer than the config file. */
-        if (stat ((char *) name_buf, &dir_stat) < 0 || 
-            dir_stat.st_mtime > cache_stat.st_mtime ||
-	    (config_time.set && cache_stat.st_mtime < config_time.time))
+        if (config->validateCache &&
+	    (stat ((char *) name_buf, &dir_stat) < 0 || 
+	     dir_stat.st_mtime > cache_stat.st_mtime ||
+	     (config_time.set && cache_stat.st_mtime < config_time.time)))
         {
             FcCache md;
 	    off_t off;
@@ -876,6 +877,27 @@ FcCacheReadDirs (FcConfig * config, FcGl
 	    continue;
 	}
 	
+	if (! config->validateCache)
+	{
+	    /* We trust cache files -- if not found, just ignore that directory
+	     */
+	    if ((cache && FcGlobalCacheReadDir (set, subdirs, cache, (char *)dir,
+						config)) ||
+		FcDirCacheRead (set, subdirs, dir, config))
+	    {
+		sublist = FcStrListCreate (subdirs);
+		FcStrSetDestroy (subdirs);
+		if (!sublist)
+		{
+		    fprintf (stderr, "Can't create subdir list in \"%s\"\n", dir);
+		    ret++;
+		    continue;
+		}
+		ret += FcCacheReadDirs (config, cache, sublist, set, processed_dirs);
+	    }
+	    continue;
+	}
+
 	if (access ((char *) dir, X_OK) < 0)
 	{
 	    switch (errno) {
--- fonts.dtd-dist	2006-02-08 21:12:11.000000000 +0100
+++ fonts.dtd	2006-02-08 21:14:00.000000000 +0100
@@ -40,7 +40,7 @@
 <!--
     Global library configuration data
  -->
-<!ELEMENT config (blank|rescan)*>
+<!ELEMENT config (blank|rescan|validatecache)*>
 
 <!--
     Specify the set of Unicode encoding values which
@@ -82,6 +82,13 @@
 <!ELEMENT rescan (int)>
 
 <!--
+    Validate cache files dynamically
+    If this is set to false, fontconfig trusts cache files and never
+    checks the timestamp or changes of contents.
+ -->
+<!ELEMENT validatecache (bool)>
+
+<!--
     Edit list of available fonts at startup/reload time
  -->
 <!ELEMENT selectfont (rejectfont | acceptfont)* >

-- 
Mike FABIAN   <mfabian@xxxxxxx>   http://www.suse.de/~mfabian
睡眠不足はいい仕事の敵だ。

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