utils: add get_last_x_chars()

Reviewed-by: Pavel Březina <pbrezina@redhat.com>

5 files changed, 49 insertions, 0 deletions

diff --git a/src/tests/cmocka/test_string_utils.c b/src/tests/cmocka/test_string_utils.c
index 5d3fcf4f..4832015a 100644
--- a/src/tests/cmocka/test_string_utils.c
+++ b/src/tests/cmocka/test_string_utils.c
@@ -192,3 +192,31 @@ void test_guid_blob_to_string_buf(void **state)
         assert_string_equal(test_data[c].guid_str, str_buf);
     }
 }
+
+void test_get_last_x_chars(void **state)
+{
+    const char *s;
+
+    s = get_last_x_chars(NULL, 0);
+    assert_null(s);
+
+    s = get_last_x_chars("abc", 0);
+    assert_non_null(s);
+    assert_string_equal(s, "");
+
+    s = get_last_x_chars("abc", 1);
+    assert_non_null(s);
+    assert_string_equal(s, "c");
+
+    s = get_last_x_chars("abc", 2);
+    assert_non_null(s);
+    assert_string_equal(s, "bc");
+
+    s = get_last_x_chars("abc", 3);
+    assert_non_null(s);
+    assert_string_equal(s, "abc");
+
+    s = get_last_x_chars("abc", 4);
+    assert_non_null(s);
+    assert_string_equal(s, "abc");
+}
diff --git a/src/tests/cmocka/test_utils.c b/src/tests/cmocka/test_utils.c
index e7f97f76..d3d00fed 100644
--- a/src/tests/cmocka/test_utils.c
+++ b/src/tests/cmocka/test_utils.c
@@ -1267,6 +1267,7 @@ int main(int argc, const char *argv[])
         cmocka_unit_test(test_replace_whitespaces),
         cmocka_unit_test(test_reverse_replace_whitespaces),
         cmocka_unit_test(test_guid_blob_to_string_buf),
+        cmocka_unit_test(test_get_last_x_chars),
         cmocka_unit_test_setup_teardown(test_add_strings_lists,
                                         setup_add_strings_lists,
                                         teardown_add_strings_lists),
diff --git a/src/tests/cmocka/test_utils.h b/src/tests/cmocka/test_utils.h
index 61ef7e43..8b516316 100644
--- a/src/tests/cmocka/test_utils.h
+++ b/src/tests/cmocka/test_utils.h
@@ -30,5 +30,6 @@ void test_textual_public_key(void **state);
 void test_replace_whitespaces(void **state);
 void test_reverse_replace_whitespaces(void **state);
 void test_guid_blob_to_string_buf(void **state);
+void test_get_last_x_chars(void **state);
 
 #endif /* __TESTS__CMOCKA__TEST_UTILS_H__ */
diff --git a/src/util/string_utils.c b/src/util/string_utils.c
index 71b2a092..b6037621 100644
--- a/src/util/string_utils.c
+++ b/src/util/string_utils.c
@@ -108,3 +108,20 @@ errno_t guid_blob_to_string_buf(const uint8_t *blob, char *str_buf,
 
     return EOK;
 }
+
+const char *get_last_x_chars(const char *str, size_t x)
+{
+    size_t len;
+
+    if (str == NULL) {
+        return NULL;
+    }
+
+    len = strlen(str);
+
+    if (len < x) {
+        return str;
+    }
+
+    return (str + len - x);
+}
diff --git a/src/util/util.h b/src/util/util.h
index 786ed303..3d90cf0d 100644
--- a/src/util/util.h
+++ b/src/util/util.h
@@ -628,6 +628,8 @@ char * sss_reverse_replace_space(TALLOC_CTX *mem_ctx,
 errno_t guid_blob_to_string_buf(const uint8_t *blob, char *str_buf,
                                 size_t buf_size);
 
+const char *get_last_x_chars(const char *str, size_t x);
+
 /* from become_user.c */
 errno_t become_user(uid_t uid, gid_t gid);
 struct sss_creds;