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.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
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