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58 lines
938 B
ArmAsm
58 lines
938 B
ArmAsm
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; Ullrich von Bassewitz, 09.06.1998
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;
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; void* memchr (const void* p, int c, size_t n);
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;
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.export _memchr
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.import popax, return0
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.importzp ptr1, ptr2, tmp1
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_memchr:
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sta ptr2 ; Save n
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stx ptr2+1
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jsr popax ; get c
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sta tmp1
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jsr popax ; get p
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sta ptr1
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stx ptr1+1
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ldy #0
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lda tmp1 ; get c
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ldx ptr2 ; use X as low counter byte
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beq L3 ; check high byte
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; Search for the char
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L1: cmp (ptr1),y
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beq L5 ; jump if found
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iny
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bne L2
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inc ptr1+1
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L2: cpx #0
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beq L3
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dex
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jmp L1
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L3: ldx ptr2+1 ; Check high byte
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beq L4 ; Jump if counter off
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dec ptr2+1
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ldx #$FF
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bne L1 ; branch always
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; Character not found, return zero
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L4: jmp return0
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; Character found, calculate pointer
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L5: ldx ptr1+1 ; get high byte of pointer
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tya ; low byte offset
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clc
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adc ptr1
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bcc L6
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inx
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L6: rts
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