50 lines
1 KiB
ArmAsm
50 lines
1 KiB
ArmAsm
! _memmove() Author: Kees J. Bot
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! 27 Jan 1994
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.sect .text; .sect .rom; .sect .data; .sect .bss
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! void *_memmove(void *s1, const void *s2, size_t n)
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! Copy a chunk of memory. Handle overlap.
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!
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.sect .text
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.define __memmove, __memcpy
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__memmove:
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push bp
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mov bp, sp
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push si
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push di
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mov di, 4(bp) ! String s1
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mov si, 6(bp) ! String s2
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mov cx, 8(bp) ! Length
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mov ax, di
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sub ax, si
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cmp ax, cx
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jb downwards ! if (s2 - s1) < n then copy downwards
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__memcpy:
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cld ! Clear direction bit: upwards
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cmp cx, #16
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jb upbyte ! Don't bother being smart with short arrays
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mov ax, si
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or ax, di
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testb al, #1
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jnz upbyte ! Bit 0 set, use byte copy
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upword: shr cx, #1
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rep movs ! Copy words
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adc cx, cx ! One more byte?
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upbyte:
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rep movsb ! Copy bytes
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done: mov ax, 4(bp) ! Absolutely noone cares about this value
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pop di
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pop si
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pop bp
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ret
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! Handle bad overlap by copying downwards, don't bother to do word copies.
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downwards:
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std ! Set direction bit: downwards
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add si, cx
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dec si
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add di, cx
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dec di
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rep movsb ! Copy bytes
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cld
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jmp done
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