use a better way to check whether string is empty

[iuhilnehc-ynos]

call strlen twice at

rcutils/src/split.c

Lines 41 to 47 in 4c53476

	if (NULL == str || strlen(str) == 0) {
	*string_array = rcutils_get_zero_initialized_string_array();
	return RCUTILS_RET_OK;
	}
	string_array->allocator = allocator;
	size_t string_size = strlen(str);

, I believe L41 can be updated from strlen to '\0' == *str

Signed-off-by: Chen Lihui lihui.chen@sony.com

[clalancette]

In the case where this is an empty string, this may be slightly faster, since a function call doesn't have to be made.

But in the case where it is a non-empty string, this will be substantially faster; it is constant time rather than the length of the string.

Works for me. I'll run CI on it next.

[clalancette]

CI:

• Linux
• Linux-aarch64
• macOS
• Windows

[clalancette]

The macOS failure happened in the nightly as well: https://ci.ros2.org/view/nightly/job/nightly_osx_release/1869/

Windows also had failures (its a bit random on Windows, but in the last week or so all of the failures also failed): https://ci.ros2.org/view/nightly/job/nightly_win_rel/1750/

With that, I'm going to merge this. Thanks for the contribution.