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/*
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
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