utils_test: add osmo_print_n_test()

A couple of times recently I've needed to copy out a substring to a buffer with
limited size. Use of strncpy() or osmo_strlcpy() are nontrivial here.
I wanted to have a dedicated function.

After I wrote that function with a test, I noticed that I had already
implemented the same thing a while ago, as osmo_print_n() :P
So here is just the test.

Change-Id: Ia716abdc1f58af6065b84f4f567388a32a7b39fc

3 files changed, 82 insertions, 0 deletions

diff --git a/src/utils.c b/src/utils.c
index 904f6e45..4378431b 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -509,6 +509,8 @@ uint8_t *osmo_encode_big_endian(uint64_t value, size_t data_len)
  * Copy at most \a siz bytes from \a src to \a dst, ensuring that the result is
  * NUL terminated. The NUL character is included in \a siz, i.e. passing the
  * actual sizeof(*dst) is correct.
+ *
+ * Note, a similar function that also limits the input buffer size is osmo_print_n().
  */
 size_t osmo_strlcpy(char *dst, const char *src, size_t siz)
 {
diff --git a/tests/utils/utils_test.c b/tests/utils/utils_test.c
index 55c9e7f7..69510afe 100644
--- a/tests/utils/utils_test.c
+++ b/tests/utils/utils_test.c
@@ -1138,6 +1138,59 @@ static void name_c_impl_test()
 	talloc_free(ctx);
 }
 
+static void osmo_print_n_test(void)
+{
+	struct token_test {
+		const char *src;
+		size_t token_len;
+		size_t buf_size;
+		const char *expect_token;
+		int expect_rc;
+	};
+	struct token_test tests[] = {
+		{ "foo=bar", 3, 100, "foo", 3 },
+		{ "foo", 10, 100, "foo", 3 },
+		{ "foo", 3, 100, "foo", 3 },
+		{ NULL, 10, 100, "", 0 },
+		{ "", 10, 100, "", 0 },
+		{ "foo=bar", 0, 100, "", 0 },
+
+		{ "foo=bar", 3, 2, "f", 3 },
+		{ "foo", 10, 2, "f", 3 },
+		{ "foo", 3, 2, "f", 3 },
+		{ NULL, 10, 2, "", 0 },
+		{ "", 10, 2, "", 0 },
+		{ "foo=bar", 0, 2, "", 0 },
+
+		{ "foo=bar", 3, 1, "", 3 },
+		{ "foo", 10, 1, "", 3 },
+		{ "foo", 3, 1, "", 3 },
+		{ NULL, 10, 1, "", 0 },
+		{ "", 10, 1, "", 0 },
+		{ "foo=bar", 0, 1, "", 0 },
+
+		{ "foo=bar", 3, 0, "unchanged", 3 },
+		{ "foo", 10, 0, "unchanged", 3 },
+		{ "foo", 3, 0, "unchanged", 3 },
+		{ NULL, 10, 0, "unchanged", 0 },
+		{ "", 10, 0, "unchanged", 0 },
+		{ "foo=bar", 0, 0, "unchanged", 0 },
+	};
+	struct token_test *t;
+	printf("\n%s()\n", __func__);
+	for (t = tests; t - tests < ARRAY_SIZE(tests); t++) {
+		char buf[100] = "unchanged";
+		int rc = osmo_print_n(buf, t->buf_size, t->src, t->token_len);
+		printf("%s token_len=%zu buf_size=%zu", osmo_quote_str(t->src, -1), t->token_len, t->buf_size);
+		printf(" -> token=%s rc=%d", osmo_quote_str(buf, -1), rc);
+		if (strcmp(buf, t->expect_token))
+			printf(" ERROR: expected token %s", osmo_quote_str(t->expect_token, -1));
+		if (rc != t->expect_rc)
+			printf(" ERROR: expected rc %d", t->expect_rc);
+		printf("\n");
+	}
+}
+
 int main(int argc, char **argv)
 {
 	static const struct log_info log_info = {};
@@ -1159,5 +1212,6 @@ int main(int argc, char **argv)
 	strbuf_test_nolen();
 	startswith_test();
 	name_c_impl_test();
+	osmo_print_n_test();
 	return 0;
 }
diff --git a/tests/utils/utils_test.ok b/tests/utils/utils_test.ok
index b6036476..d5cf4910 100644
--- a/tests/utils/utils_test.ok
+++ b/tests/utils/utils_test.ok
@@ -377,3 +377,29 @@ name_c_impl_test
       OSMO_NAME_C_IMPL(10, NULL) -> NULL  allocated 0
     OSMO_NAME_C_IMPL(0, "ERROR") -> "ERROR"  allocated 1  6 bytes, name 'foo_name_c_zero'
        OSMO_NAME_C_IMPL(0, NULL) -> NULL  allocated 0
+
+osmo_print_n_test()
+"foo=bar" token_len=3 buf_size=100 -> token="foo" rc=3
+"foo" token_len=10 buf_size=100 -> token="foo" rc=3
+"foo" token_len=3 buf_size=100 -> token="foo" rc=3
+NULL token_len=10 buf_size=100 -> token="" rc=0
+"" token_len=10 buf_size=100 -> token="" rc=0
+"foo=bar" token_len=0 buf_size=100 -> token="" rc=0
+"foo=bar" token_len=3 buf_size=2 -> token="f" rc=3
+"foo" token_len=10 buf_size=2 -> token="f" rc=3
+"foo" token_len=3 buf_size=2 -> token="f" rc=3
+NULL token_len=10 buf_size=2 -> token="" rc=0
+"" token_len=10 buf_size=2 -> token="" rc=0
+"foo=bar" token_len=0 buf_size=2 -> token="" rc=0
+"foo=bar" token_len=3 buf_size=1 -> token="" rc=3
+"foo" token_len=10 buf_size=1 -> token="" rc=3
+"foo" token_len=3 buf_size=1 -> token="" rc=3
+NULL token_len=10 buf_size=1 -> token="" rc=0
+"" token_len=10 buf_size=1 -> token="" rc=0
+"foo=bar" token_len=0 buf_size=1 -> token="" rc=0
+"foo=bar" token_len=3 buf_size=0 -> token="unchanged" rc=3
+"foo" token_len=10 buf_size=0 -> token="unchanged" rc=3
+"foo" token_len=3 buf_size=0 -> token="unchanged" rc=3
+NULL token_len=10 buf_size=0 -> token="unchanged" rc=0
+"" token_len=10 buf_size=0 -> token="unchanged" rc=0
+"foo=bar" token_len=0 buf_size=0 -> token="unchanged" rc=0