utf8: introduce git_utf8_char_length

Introduce a function to determine the number of Unicode characters in a
given UTF-8 string.

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/core/utf8.c b/tests/core/utf8.c
new file mode 100644
index 000000000..021828e9e
--- /dev/null
+++ b/tests/core/utf8.c
@@ -0,0 +1,19 @@
+#include "clar_libgit2.h"
+
+void test_core_utf8__char_length(void)
+{
+	cl_assert_equal_i(0, git_utf8_char_length("", 0));
+	cl_assert_equal_i(1, git_utf8_char_length("$", 1));
+	cl_assert_equal_i(5, git_utf8_char_length("abcde", 5));
+	cl_assert_equal_i(1, git_utf8_char_length("\xc2\xa2", 2));
+	cl_assert_equal_i(2, git_utf8_char_length("\x24\xc2\xa2", 3));
+	cl_assert_equal_i(1, git_utf8_char_length("\xf0\x90\x8d\x88", 4));
+
+	/* uncontinued character counted as single characters */
+	cl_assert_equal_i(2, git_utf8_char_length("\x24\xc2", 2));
+	cl_assert_equal_i(3, git_utf8_char_length("\x24\xc2\xc2\xa2", 4));
+
+	/* invalid characters are counted as single characters */
+	cl_assert_equal_i(4, git_utf8_char_length("\x24\xc0\xc0\x34", 4));
+	cl_assert_equal_i(4, git_utf8_char_length("\x24\xf5\xfd\xc2", 4));
+}