mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-03 10:49:58 +00:00
17 lines
509 B
ArmAsm
17 lines
509 B
ArmAsm
.file "strlen.S"
|
|
|
|
.section .text
|
|
|
|
.global _strlen
|
|
.type _strlen,@function
|
|
_strlen:
|
|
add #0, r1, r4 ; Save a copy of the string start address and set the condition flags.
|
|
beq null_string ; Test for a NULL pointer.
|
|
mov #-1, r3 ; Set a limit on the number of bytes examined.
|
|
mov #0, r2 ; Stop searching when we find a NUL byte.
|
|
suntil.b ; Search until *r1 == r2
|
|
sub #1, r1 ; suntil.b leaves r1 pointing to the byte beyond the match.
|
|
null_string:
|
|
sub r4, r1 ; Compute the length.
|
|
rts
|