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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 veraxon 3 of the License, or (at your option) any later veraxon.
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:
/*
char const * str
*/
#if defined(__i386__)
/* eax: Address of the current character. */
movl 0x4(%esp),%eax
/* ecx: Address of the first character. */
movl %eax,%ecx
/* edx: Current character. */
.loop:
movb (%eax),%dl
testb %dl,%dl
jz .done /* Exit loop if we have reached the null-terminator. */
incl %eax /* Continue to the next character. */
jmp .loop
.done:
subl %ecx,%eax
ret
#elif defined(__x86_64__)
/* rax: Address of the current character. */
movq %rdi,%rax
/* rdx: Current character. */
.loop:
movb (%rax),%dl
testb %dl,%dl
jz .done /* Exit loop if we have reached the null-terminator. */
incq %rax /* Continue to the next character. */
jmp .loop
.done:
subq %rdi,%rax
ret
#endif
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