[json-glib] [generator] Pre-compute the escape table

[Emmanuele Bassi <ebassi src gnome org>]

commit 6e706fb2b7a371f25c169ed25d4b617f2dc05b63
Author: Emmanuele Bassi <ebassi linux intel com>
Date:   Sun Jun 21 10:58:24 2009 +0100

    [generator] Pre-compute the escape table
    
    Instead of allocating the escape table to be used with g_strescape()
    for each string we can have it unrolled already in code.
    
    Thanks to: Christian Persch <chpe gnome org>
    
    Fixes bug:
    
      http://bugzilla.openedhand.com/show_bug.cgi?id=1648

 json-glib/json-generator.c |   43 +++++++++++++++++++++++++++++++++----------
 1 files changed, 33 insertions(+), 10 deletions(-)
---
diff --git a/json-glib/json-generator.c b/json-glib/json-generator.c
index c808fab..f662fbf 100644
--- a/json-glib/json-generator.c
+++ b/json-glib/json-generator.c
@@ -79,8 +79,39 @@ static gchar *dump_object (JsonGenerator *generator,
                            JsonObject    *object,
                            gsize         *length);
 
+/* non-ASCII characters can't be escaped, otherwise UTF-8
+ * chars will break, so we just pregenerate this table of
+ * high characters and then we feed it to g_strescape()
+ */
+static const char json_exceptions[] = {
+  0x7f,  0x80,  0x81,  0x82,  0x83,  0x84,  0x85,  0x86,
+  0x87,  0x88,  0x89,  0x8a,  0x8b,  0x8c,  0x8d,  0x8e,
+  0x8f,  0x90,  0x91,  0x92,  0x93,  0x94,  0x95,  0x96,
+  0x97,  0x98,  0x99,  0x9a,  0x9b,  0x9c,  0x9d,  0x9e,
+  0x9f,  0xa0,  0xa1,  0xa2,  0xa3,  0xa4,  0xa5,  0xa6,
+  0xa7,  0xa8,  0xa9,  0xaa,  0xab,  0xac,  0xad,  0xae,
+  0xaf,  0xb0,  0xb1,  0xb2,  0xb3,  0xb4,  0xb5,  0xb6,
+  0xb7,  0xb8,  0xb9,  0xba,  0xbb,  0xbc,  0xbd,  0xbe,
+  0xbf,  0xc0,  0xc1,  0xc2,  0xc3,  0xc4,  0xc5,  0xc6,
+  0xc7,  0xc8,  0xc9,  0xca,  0xcb,  0xcc,  0xcd,  0xce,
+  0xcf,  0xd0,  0xd1,  0xd2,  0xd3,  0xd4,  0xd5,  0xd6,
+  0xd7,  0xd8,  0xd9,  0xda,  0xdb,  0xdc,  0xdd,  0xde,
+  0xdf,  0xe0,  0xe1,  0xe2,  0xe3,  0xe4,  0xe5,  0xe6,
+  0xe7,  0xe8,  0xe9,  0xea,  0xeb,  0xec,  0xed,  0xee,
+  0xef,  0xf0,  0xf1,  0xf2,  0xf3,  0xf4,  0xf5,  0xf6,
+  0xf7,  0xf8,  0xf9,  0xfa,  0xfb,  0xfc,  0xfd,  0xfe,
+  0xff,
+  '\0'   /* g_strescape() expects a NUL-terminated string */
+};
+
 G_DEFINE_TYPE (JsonGenerator, json_generator, G_TYPE_OBJECT);
 
+static gchar *
+json_strescape (const gchar *str)
+{
+  return g_strescape (str, json_exceptions);
+}
+
 static void
 json_generator_finalize (GObject *gobject)
 {
@@ -266,18 +297,10 @@ dump_value (JsonGenerator *generator,
     case G_TYPE_STRING:
       {
         gchar *tmp;
-        gchar *exceptions = g_malloc (128);
-        gint chr, i;
-
-        /* non-ascii characters can't be escaped, otherwise utf-8
-         * chars will break */
-        for (i = 0, chr = 0x7f; chr <= 0xff; chr++, i++)
-          exceptions[i] = chr;
-
-        tmp = g_strescape (g_value_get_string (&value), exceptions);
-        g_free (exceptions);
 
+        tmp = json_strescape (g_value_get_string (&value));
         g_string_append_printf (buffer, "\"%s\"", tmp);
+
         g_free (tmp);
       }
       break;