[tracker/wip/carlosg/sparql-parser-ng: 25/43] libtracker-common: Add helper function to escape \u and \U sequences

[Carlos Garnacho <carlosg src gnome org>]

commit e69e9fe357de88e26adbe9b6d3378c801dd9e8ab
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Sep 22 22:40:05 2018 +0200

    libtracker-common: Add helper function to escape \u and \U sequences

 src/libtracker-common/tracker-utils.c | 89 +++++++++++++++++++++++++++++++++++
 src/libtracker-common/tracker-utils.h |  2 +
 2 files changed, 91 insertions(+)
---
diff --git a/src/libtracker-common/tracker-utils.c b/src/libtracker-common/tracker-utils.c
index a9cb70643..c5a5721c7 100644
--- a/src/libtracker-common/tracker-utils.c
+++ b/src/libtracker-common/tracker-utils.c
@@ -236,3 +236,92 @@ tracker_utf8_truncate (const gchar  *str,
 
        return retv;
 }
+
+static gboolean
+range_is_xdigit (const gchar *str,
+                 gssize       start,
+                 gssize       end)
+{
+       gssize i;
+
+       g_assert (end > start);
+
+       for (i = start; i < end; i++) {
+               if (!g_ascii_isxdigit (str[i]))
+                       return FALSE;
+       }
+
+       return TRUE;
+}
+
+static gunichar
+xdigit_to_unichar (const gchar *str,
+                  gssize       start,
+                  gssize       end)
+{
+       gunichar ch = 0;
+       gssize i;
+
+       g_assert (end > start);
+
+       for (i = start; i < end; i++) {
+               ch |= g_ascii_xdigit_value (str[i]);
+               if (i < end - 1)
+                       ch <<= 4;
+       }
+
+       return ch;
+}
+
+/*
+ * tracker_unescape_unichars:
+ * @str: Input string
+ * @len: Length
+ *
+ * Unescapes \u and \U sequences into their respective unichars.
+ *
+ * Returns: a string with no \u nor \U sequences
+ */
+gchar *
+tracker_unescape_unichars (const gchar  *str,
+                           gssize        len)
+{
+       GString *copy;
+       gunichar ch;
+       gssize i = 0;
+
+       if (len < 0)
+               len = strlen (str);
+
+       copy = g_string_new (NULL);
+
+       while (i < len) {
+               if (len - i >= 2 &&
+                   str[i] == '\\' &&
+                   g_ascii_tolower (str[i + 1]) != 'u') {
+                       /* Not an unicode escape sequence */
+                       g_string_append_c (copy, str[i]);
+                       g_string_append_c (copy, str[i + 1]);
+                       i += 2;
+               } if (len - i >= 6 &&
+                   strncmp (&str[i], "\\u", 2) == 0 &&
+                   range_is_xdigit (&str[i], 2, 6)) {
+                       ch = xdigit_to_unichar (&str[i], 2, 6);
+                       g_string_append_unichar (copy, ch);
+                       i += 6;
+                       continue;
+               } else if (len - i >= 10 &&
+                          strncmp (&str[i], "\\U", 2) == 0 &&
+                          range_is_xdigit (&str[i], 2, 10)) {
+                       ch = xdigit_to_unichar (&str[i], 2, 10);
+                       g_string_append_unichar (copy, ch);
+                       i += 10;
+                       continue;
+               } else {
+                       g_string_append_c (copy, str[i]);
+                       i++;
+               }
+       }
+
+       return g_string_free (copy, FALSE);
+}
diff --git a/src/libtracker-common/tracker-utils.h b/src/libtracker-common/tracker-utils.h
index 87ca7b395..2cb78e5ba 100644
--- a/src/libtracker-common/tracker-utils.h
+++ b/src/libtracker-common/tracker-utils.h
@@ -45,6 +45,8 @@ gchar *  tracker_strhex                     (const guint8 *data,
                                              gchar         delimiter);
 gchar *  tracker_utf8_truncate              (const gchar  *str,
                                              gsize         max_size);
+gchar *  tracker_unescape_unichars          (const gchar  *str,
+                                            gssize        len);
 
 G_END_DECLS