From 69a635412d4787ccb96f6641f3b4d35b77d25072 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Helleu?= <flashcode@flashtux.org>
Date: Mon, 30 Jan 2023 20:54:37 +0100
Subject: [PATCH] core: add function string_get_common_bytes_count (issue
 #1877)

---
 src/core/wee-string.c                | 25 +++++++++++++++++++++++++
 src/core/wee-string.h                |  2 ++
 tests/unit/core/test-core-string.cpp | 24 +++++++++++++++++++++++-
 3 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/src/core/wee-string.c b/src/core/wee-string.c
index abe7ccd17..a6634ba7c 100644
--- a/src/core/wee-string.c
+++ b/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
diff --git a/src/core/wee-string.h b/src/core/wee-string.h
index 641855f7f..19c616e5e 100644
--- a/src/core/wee-string.h
+++ b/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,
diff --git a/tests/unit/core/test-core-string.cpp b/tests/unit/core/test-core-string.cpp
index 671a1327c..ce1468336 100644
--- a/tests/unit/core/test-core-string.cpp
+++ b/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)