/*
	Copyright 2022 Gabriel Jensen

	This file is part of rgo.

	rgo is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

	rgo is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License along with rgo. If not, see <https://www.gnu.org/licenses/>. 
*/

#include <rgo.h>

.global rgo_strlen

rgo_strlen:
#if defined(__x86_64__)
	/*
		rdi: char const * str
	*/
	/* rsi: Address of the current character. */
	movq %rdi,%rsi
	/* dl: Current character. */
.loop:
	movb (%rsi),%dl
	testb %dl,%dl
	jz .done /* Exit loop if we have reached the null-terminator. */
	incq %rsi /* Continue to the next character. */
	jmp .loop
.done:
	movq %rsi,%rax
	subq %rdi,%rax
	ret
#endif