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53 lines
942 B
ArmAsm
53 lines
942 B
ArmAsm
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; void* memset (void* ptr, int c, size_t n);
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;
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; Ullrich von Bassewitz, 29.05.1998
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;
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.export _memset
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.import popax
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.importzp ptr1, ptr2, tmp1, tmp2, tmp3
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_memset:
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sta tmp1 ; Save n
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stx tmp2
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jsr popax ; Get c
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sta tmp3 ; Save c
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jsr popax ; Get ptr
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sta ptr1
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stx ptr1+1 ; Save work copy
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sta ptr2
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stx ptr2+1 ; Save a copy for the function result
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lda tmp3
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ldy #0
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ldx tmp2 ; Get high byte of n
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beq L2 ; Jump if zero
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; Set 256 byte blocks
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L1: sta (ptr1),y ; Set one byte
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iny
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sta (ptr1),y ; Unroll this a bit to make it faster
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iny
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bne L1
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inc ptr1+1
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dex ; Next 256 byte block
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bne L1 ; Repeat if any
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; Set the remaining bytes if any
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L2: ldx tmp1 ; Get the low byte of n
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beq L9 ; Low byte is zero
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L3: sta (ptr1),y ; Set one byte
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iny
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dex ; Done?
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bne L3
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L9: lda ptr2 ; Load function result
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ldx ptr2+1
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rts
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