core: add function string_get_common_bytes_count (issue #1877)

src/core/wee-string.c

@@ -3960,6 +3960,31 @@ string_input_for_buffer (const char *string)
     return NULL;
 }
 
+/*
+ * Returns the number of bytes in common between two strings (this function
+ * works with bytes and not UTF-8 chars).
+ */
+
+int
+string_get_common_bytes_count (const char *string1, const char *string2)
+{
+    const char *ptr_str1;
+    int found;
+
+    if (!string1 || !string2)
+        return 0;
+
+    found = 0;
+    ptr_str1 = string1;
+    while (ptr_str1[0])
+    {
+        if (strchr (string2, ptr_str1[0]))
+            found++;
+        ptr_str1++;
+    }
+    return found;
+}
+
 /*
  * Returns the distance between two strings using the Levenshtein algorithm.
  * See: https://en.wikipedia.org/wiki/Levenshtein_distance

src/core/wee-string.h

@@ -134,6 +134,8 @@ extern char *string_hex_dump (const char *data, int data_size,
                               const char *prefix, const char *suffix);
 extern int string_is_command_char (const char *string);
 extern const char *string_input_for_buffer (const char *string);
+extern int string_get_common_bytes_count (const char *string1,
+                                          const char *string2);
 extern int string_levenshtein (const char *string1, const char *string2,
                                int case_sensitive);
 extern char *string_replace_with_callback (const char *string,

tests/unit/core/test-core-string.cpp

@@ -2542,7 +2542,29 @@ TEST(CoreString, InputForBuffer)
 
 /*
  * Tests functions:
- *    string_levenshtein
+ *   string_get_common_bytes_count
+ */
+
+TEST(CoreString, GetCommonBytesCount)
+{
+    LONGS_EQUAL(0, string_get_common_bytes_count (NULL, NULL));
+    LONGS_EQUAL(0, string_get_common_bytes_count ("", NULL));
+    LONGS_EQUAL(0, string_get_common_bytes_count (NULL, ""));
+    LONGS_EQUAL(0, string_get_common_bytes_count ("", ""));
+
+    LONGS_EQUAL(1, string_get_common_bytes_count ("a", "a"));
+    LONGS_EQUAL(0, string_get_common_bytes_count ("a", "b"));
+
+    LONGS_EQUAL(3, string_get_common_bytes_count ("abc", "abc"));
+
+    LONGS_EQUAL(3, string_get_common_bytes_count ("abcdef", "fac"));
+
+    LONGS_EQUAL(4, string_get_common_bytes_count ("noël", "noïl"));
+}
+
+/*
+ * Tests functions:
+ *   string_levenshtein
  */
 
 TEST(CoreString, Levenshtein)