modem-helpers: rework AT string quote operation and add unit tests

Rework the AT string quote operation to build the output with the
GString helper, instead of manually calculating how many bytes we'll
need in the output. It just makes it clearer.

1 files changed, 28 insertions, 0 deletions

diff --git a/src/mm-modem-helpers.c b/src/mm-modem-helpers.c
index 44e8e71e..8dad5a39 100644
--- a/src/mm-modem-helpers.c
+++ b/src/mm-modem-helpers.c
@@ -454,6 +454,34 @@ mm_bcd_to_string (const guint8 *bcd, gsize bcd_len, gboolean low_nybble_first)
 
 /*****************************************************************************/
 
+gchar *
+mm_at_quote_string (const gchar *input)
+{
+    GString *str;
+    gsize    input_len;
+
+    input_len = input ? strlen (input) : 0;
+    str = g_string_sized_new (3 + 3 * input_len); /* worst case */
+    g_string_append_c (str, '"');
+
+    if (input) {
+        gsize i, len;
+
+        len = strlen (input);
+        for (i = 0 ; i < len; i++) {
+            if (input[i] < 0x20 || input[i] == '"' || input[i] == '\\')
+                g_string_append_printf (str, "\\%02X", input[i]);
+            else
+                g_string_append_c (str, input[i]);
+        }
+    }
+    g_string_append_c (str, '"');
+
+    return g_string_free (str, FALSE);
+}
+
+/*****************************************************************************/
+
 GRegex *
 mm_voice_ring_regex_get (void)
 {