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55 lines
962 B
ArmAsm
55 lines
962 B
ArmAsm
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; size_t __fastcall__ strnlen (const char* s, size_t maxlen);
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.export _strnlen
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.import popax
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.importzp ptr1, tmp1, tmp2, tmp3, tmp4
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.proc _strnlen
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; Fetch string pointer.
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sta ptr1
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stx ptr1+1
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; Clear return value.
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lda #0
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sta tmp1
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sta tmp2
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; Get maximum length.
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jsr popax
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sta tmp3
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inc tmp3
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inx
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stx tmp4
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;;; Loop over string.
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ldy #0
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; Decrement maximum length.
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next: dec tmp3
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bne l2
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dec tmp4
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beq done
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l2:
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lda (ptr1),y
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beq done
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; Step to next character.
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inc ptr1
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bne l1
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inc ptr1+1
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l1:
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; Increment return value.
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inc tmp1
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bne next
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inc tmp2
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jmp next
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done: lda tmp1
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ldx tmp2
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rts
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.endproc
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