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