css parser: Reuse one GString

Instead of creating a new one for every ident, name and string, just
create one GString and reuse it. This means the GString we keep around
will grow to the maximum size of any ident, name or string we parse,
which is still not terribly large.

gtk/gtkcssparser.c

@@ -44,6 +44,9 @@ struct _GtkCssParser
 
   const char            *line_start;
   guint                  line;
+
+  /* Use this for parsing identifiers, names and strings. */
+  GString               *ident_str;
 };
 
 GtkCssParser *
@@ -68,6 +71,8 @@ _gtk_css_parser_new (const char            *data,
   parser->line_start = data;
   parser->line = 0;
 
+  parser->ident_str = NULL;
+
   return parser;
 }
 
@@ -79,6 +84,9 @@ _gtk_css_parser_free (GtkCssParser *parser)
   if (parser->file)
     g_object_unref (parser->file);
 
+  if (parser->ident_str)
+    g_string_free (parser->ident_str, TRUE);
+
   g_slice_free (GtkCssParser, parser);
 }
 
@@ -390,6 +398,21 @@ _gtk_css_parser_read_char (GtkCssParser *parser,
   return FALSE;
 }
 
+static char *
+_gtk_css_parser_get_ident (GtkCssParser *parser)
+{
+  char *result;
+  gsize len;
+
+  len = parser->ident_str->len;
+
+  result = g_new (char, len + 1);
+  memcpy (result, parser->ident_str->str, len + 1);
+  g_string_set_size (parser->ident_str, 0);
+
+  return result;
+}
+
 char *
 _gtk_css_parser_try_name (GtkCssParser *parser,
                           gboolean      skip_whitespace)
@@ -398,7 +421,10 @@ _gtk_css_parser_try_name (GtkCssParser *parser,
 
   g_return_val_if_fail (GTK_IS_CSS_PARSER (parser), NULL);
 
-  name = g_string_new (NULL);
+  if (parser->ident_str == NULL)
+    parser->ident_str = g_string_new (NULL);
+
+  name = parser->ident_str;
 
   while (_gtk_css_parser_read_char (parser, name, NMCHAR))
     ;
@@ -406,7 +432,7 @@ _gtk_css_parser_try_name (GtkCssParser *parser,
   if (skip_whitespace)
     _gtk_css_parser_skip_whitespace (parser);
 
-  return g_string_free (name, FALSE);
+  return _gtk_css_parser_get_ident (parser);
 }
 
 char *
@@ -420,7 +446,10 @@ _gtk_css_parser_try_ident (GtkCssParser *parser,
 
   start = parser->data;
   
-  ident = g_string_new (NULL);
+  if (parser->ident_str == NULL)
+    parser->ident_str = g_string_new (NULL);
+
+  ident = parser->ident_str;
 
   if (*parser->data == '-')
     {
@@ -431,7 +460,7 @@ _gtk_css_parser_try_ident (GtkCssParser *parser,
   if (!_gtk_css_parser_read_char (parser, ident, NMSTART))
     {
       parser->data = start;
-      g_string_free (ident, TRUE);
+      g_string_set_size (ident, 0);
       return NULL;
     }
 
@@ -441,7 +470,7 @@ _gtk_css_parser_try_ident (GtkCssParser *parser,
   if (skip_whitespace)
     _gtk_css_parser_skip_whitespace (parser);
 
-  return g_string_free (ident, FALSE);
+  return _gtk_css_parser_get_ident (parser);
 }
 
 gboolean
@@ -469,7 +498,12 @@ _gtk_css_parser_read_string (GtkCssParser *parser)
     }
   
   parser->data++;
-  str = g_string_new (NULL);
+
+  if (parser->ident_str == NULL)
+    parser->ident_str = g_string_new (NULL);
+
+  str = parser->ident_str;
+  g_assert (str->len == 0);
 
   while (TRUE)
     {
@@ -490,7 +524,7 @@ _gtk_css_parser_read_string (GtkCssParser *parser)
             {
               parser->data++;
               _gtk_css_parser_skip_whitespace (parser);
-              return g_string_free (str, FALSE);
+              return _gtk_css_parser_get_ident (parser);
             }
           
           g_string_append_c (str, *parser->data);
@@ -499,12 +533,12 @@ _gtk_css_parser_read_string (GtkCssParser *parser)
         case '\0':
           /* FIXME: position */
           _gtk_css_parser_error (parser, "Missing end quote in string.");
-          g_string_free (str, TRUE);
+          g_string_set_size (str, 0);
           return NULL;
         default:
           _gtk_css_parser_error (parser, 
                                  "Invalid character in string. Must be escaped.");
-          g_string_free (str, TRUE);
+          g_string_set_size (str, 0);
           return NULL;
         }
     }