Add function to calculate lev distance between strings

diff --git a/src/libutil/str_util.c b/src/libutil/str_util.c
index 780339e375a169497e9e7d7f173737470a94e940..00ef4e4ed80339403a84a41404a2a407a71e1cdc 100644 (file)
--- a/src/libutil/str_util.c
+++ b/src/libutil/str_util.c
@@ -795,3 +795,52 @@ rspamd_decode_url (gchar *dst, const gchar *src, gsize size)
 
        return (d - dst);
 }
+#define MIN3(a, b, c) ((a) < (b) ? ((a) < (c) ? (a) : (c)) : ((b) < (c) ? (b) : (c)))
+
+gint
+rspamd_strings_levenshtein_distance (const gchar *s1, gsize s1len,
+               const gchar *s2, gsize s2len)
+{
+       guint x, y, lastdiag, olddiag;
+       gchar c1, c2;
+       guint *column;
+       gint eq;
+       static const guint max_cmp = 8192;
+
+       g_assert (s1 != NULL);
+       g_assert (s2 != NULL);
+
+       if (s1len == 0) {
+               s1len = strlen (s1);
+       }
+       if (s2len == 0) {
+               s2len = strlen (s2);
+       }
+
+       if (MAX(s1len, s2len) > max_cmp) {
+               /* Cannot compare too many characters */
+               return 0;
+       }
+
+       column = g_alloca ((s1len + 1) * sizeof (guint));
+
+       for (y = 1; y <= s1len; y++) {
+               column[y] = y;
+       }
+
+       for (x = 1; x <= s2len; x++) {
+               column[0] = x;
+
+               for (y = 1, lastdiag = x - 1; y <= s1len; y++) {
+                       olddiag = column[y];
+                       c1 = s1[y - 1];
+                       c2 = s2[x - 1];
+                       eq = (c1 == c2) ? 0 : 1;
+                       column[y] = MIN3 (column[y] + 1, column[y - 1] + 1,
+                                       lastdiag + (eq));
+                       lastdiag = olddiag;
+               }
+       }
+
+       return column[s1len];
+}

diff --git a/src/libutil/str_util.h b/src/libutil/str_util.h
index 986fc7f03c863e2e5dd22aa4c3dfd8271936b5dd..e07c51701cb84c17714948deadf14499a72e32ef 100644 (file)
--- a/src/libutil/str_util.h
+++ b/src/libutil/str_util.h
@@ -141,4 +141,15 @@ gsize rspamd_decode_url (gchar *dst, const gchar *src, gsize size);
 #   define g_tolower(x) (((x) >= 'A' && (x) <= 'Z') ? (x) - 'A' + 'a' : (x))
 #endif
 
+/**
+ * Return levenstein distance between two strings
+ * @param s1
+ * @param s1len
+ * @param s2
+ * @param s2len
+ * @return
+ */
+gint rspamd_strings_levenshtein_distance (const gchar *s1, gsize s1len,
+               const gchar *s2, gsize s2len);
+
 #endif /* SRC_LIBUTIL_STR_UTIL_H_ */