[glib] Make g_strerror() do less work

[Dan Winship <danw src gnome org>]

commit 96675446c5fc9b47265124e479cc300f7a7ced65
Author: Dan Winship <danw gnome org>
Date:   Thu Aug 6 15:39:22 2015 -0400

    Make g_strerror() do less work
    
    Store the (translated, UTF-8-encoded) error strings in a hash table to
    avoid doing translation and (possibly) g_locale_to_utf8() in every
    g_strerror() call.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=754788

 glib/gstrfuncs.c |   55 +++++++++++++++++++++++++++++++++--------------------
 1 files changed, 34 insertions(+), 21 deletions(-)
---
diff --git a/glib/gstrfuncs.c b/glib/gstrfuncs.c
index 7d6e8ef..dde6126 100644
--- a/glib/gstrfuncs.c
+++ b/glib/gstrfuncs.c
@@ -1253,40 +1253,53 @@ g_ascii_strtoll (const gchar *nptr,
 const gchar *
 g_strerror (gint errnum)
 {
-  gchar buf[1024];
-  gchar *msg;
-  gchar *tofree = NULL;
-  const gchar *ret;
+  static GHashTable *errors;
+  G_LOCK_DEFINE_STATIC (errors);
+  const gchar *msg;
   gint saved_errno = errno;
-  GError *error = NULL;
+
+  G_LOCK (errors);
+  if (errors)
+    msg = g_hash_table_lookup (errors, GINT_TO_POINTER (errnum));
+  else
+    {
+      errors = g_hash_table_new (NULL, NULL);
+      msg = NULL;
+    }
+
+  if (!msg)
+    {
+      gchar buf[1024];
+      GError *error = NULL;
 
 #if defined(G_OS_WIN32)
-  strerror_s (buf, sizeof (buf), errnum);
-  msg = buf;
+      strerror_s (buf, sizeof (buf), errnum);
+      msg = buf;
 #elif defined(HAVE_STRERROR_R)
       /* Match the condition in strerror_r(3) for glibc */
 #  if defined(__GLIBC__) && !((_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && ! _GNU_SOURCE)
-  msg = strerror_r (errnum, buf, sizeof (buf));
+      msg = strerror_r (errnum, buf, sizeof (buf));
 #  else
-  strerror_r (errnum, buf, sizeof (buf));
-  msg = buf;
+      strerror_r (errnum, buf, sizeof (buf));
+      msg = buf;
 #  endif /* HAVE_STRERROR_R */
 #else
-  g_strlcpy (buf, strerror (errnum), sizeof (buf));
-  msg = buf;
+      g_strlcpy (buf, strerror (errnum), sizeof (buf));
+      msg = buf;
 #endif
-  if (!g_get_charset (NULL))
-    {
-      msg = tofree = g_locale_to_utf8 (msg, -1, NULL, NULL, &error);
-      if (error)
-        g_print ("%s\n", error->message);
-    }
+      if (!g_get_charset (NULL))
+        {
+          msg = g_locale_to_utf8 (msg, -1, NULL, NULL, &error);
+          if (error)
+            g_print ("%s\n", error->message);
+        }
 
-  ret = g_intern_string (msg);
-  g_free (tofree);
+      g_hash_table_insert (errors, GINT_TO_POINTER (errnum), (char *) msg);
+    }
+  G_UNLOCK (errors);
 
   errno = saved_errno;
-  return ret;
+  return msg;
 }
 
 /**