[nautilus/ellipsization-truncation-a-united-nation: 2/4] eel: string: refactor middle truncation

[Ernestas Kulik <ernestask src gnome org>]

commit ea0998e7ac3d448fbc51c359a53711b0ba759e4d
Author: Ernestas Kulik <ernestask gnome org>
Date:   Mon Feb 19 20:32:09 2018 +0200

    eel: string: refactor middle truncation
    
    The code is a bit suboptimal in places, namely using strlen() when the
    array length is available at compile time. Another thing is wasteful
    allocation of the new string: the truncated string of the same size as
    the source string. This can be fixed by adding a couple of different
    allocations. :)
    The comments were also removed, as they’re obvious.

 eel/eel-string.c | 36 +++++++++++++-----------------------
 1 file changed, 13 insertions(+), 23 deletions(-)
---
diff --git a/eel/eel-string.c b/eel/eel-string.c
index df1209919..0694649f5 100644
--- a/eel/eel-string.c
+++ b/eel/eel-string.c
@@ -106,26 +106,21 @@ eel_str_capitalize (const char *string)
  **/
 char *
 eel_str_middle_truncate (const char *string,
-                         guint       truncate_length)
+                         size_t      truncate_length)
 {
-    char *truncated;
-    guint length;
-    guint num_left_chars;
-    guint num_right_chars;
-
-    const char delimter[] = "…";
-    const guint delimter_length = strlen (delimter);
-    const guint min_truncate_length = delimter_length + 2;
+    const char ellipsis[] = "…";
+    const size_t min_truncate_length = G_N_ELEMENTS (ellipsis) + 2;
+    size_t length;
+    size_t num_left_chars;
+    size_t num_right_chars;
+    g_autofree char *left_substring = NULL;
+    g_autofree char *right_substring = NULL;
 
     if (string == NULL)
     {
         return NULL;
     }
 
-    /* It doesnt make sense to truncate strings to less than
-     * the size of the delimiter plus 2 characters (one on each
-     * side)
-     */
     if (truncate_length < min_truncate_length)
     {
         return g_strdup (string);
@@ -133,23 +128,18 @@ eel_str_middle_truncate (const char *string,
 
     length = g_utf8_strlen (string, -1);
 
-    /* Make sure the string is not already small enough. */
     if (length <= truncate_length)
     {
         return g_strdup (string);
     }
 
-    /* Find the 'middle' where the truncation will occur. */
-    num_left_chars = (truncate_length - delimter_length) / 2;
-    num_right_chars = truncate_length - num_left_chars - delimter_length;
-
-    truncated = g_new (char, strlen (string) + 1);
+    num_left_chars = (truncate_length - G_N_ELEMENTS (ellipsis)) / 2;
+    num_right_chars = truncate_length - num_left_chars - G_N_ELEMENTS (ellipsis);
 
-    g_utf8_strncpy (truncated, string, num_left_chars);
-    strcat (truncated, delimter);
-    strcat (truncated, g_utf8_offset_to_pointer (string, length - num_right_chars));
+    left_substring = g_utf8_substring (string, 0, num_left_chars);
+    right_substring = g_utf8_substring (string, length - num_right_chars, length);
 
-    return truncated;
+    return g_strconcat (left_substring, ellipsis, right_substring, NULL);
 }
 
 char *