Rev 1408 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1627 | serge | 1 | /* _memmove() Author: Kees J. Bot */ |
| 2 | /* 2 Jan 1994 */ |
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| 1408 | serge | 3 | |
| 1627 | serge | 4 | /* void *_memmove(void *s1, const void *s2, size_t n) */ |
| 5 | /* Copy a chunk of memory. Handle overlap. */ |
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| 6 | /* */ |
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| 1408 | serge | 7 | |
| 1627 | serge | 8 | #include "asm.h" |
| 1408 | serge | 9 | |
| 1627 | serge | 10 | ENTRY(_memmove) |
| 11 | push %ebp |
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| 12 | movl %esp, %ebp |
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| 13 | push %esi |
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| 14 | push %edi |
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| 15 | movl 8(%ebp), %edi /* String s1 */ |
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| 16 | movl 12(%ebp), %esi /* String s2 */ |
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| 17 | movl 16(%ebp), %ecx /* Length */ |
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| 18 | movl %edi, %eax |
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| 19 | subl %esi, %eax |
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| 20 | cmpl %ecx, %eax |
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| 21 | jb downwards /* if (s2 - s1) < n then copy downwards */ |
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| 22 | LABEL(_memcpy) |
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| 23 | cld /* Clear direction bit: upwards */ |
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| 24 | cmpl $16, %ecx |
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| 25 | jb upbyte /* Don't bother being smart with short arrays */ |
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| 26 | movl %esi, %eax |
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| 27 | orl %edi, %eax |
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| 28 | testb $1, %al |
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| 29 | jne upbyte /* Bit 0 set, use byte copy */ |
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| 30 | testb $2, %al |
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| 31 | jne upword /* Bit 1 set, use word copy */ |
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| 32 | uplword: |
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| 33 | shrdl $2, %ecx, %eax /* Save low 2 bits of ecx in eax */ |
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| 34 | shrl $2, %ecx |
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| 1408 | serge | 35 | |
| 1627 | serge | 36 | rep movsl /* Copy longwords. */ |
| 37 | shldl $2, %eax, %ecx /* Restore excess count */ |
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| 38 | upword: |
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| 39 | shrl $1, %ecx |
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| 1408 | serge | 40 | |
| 1627 | serge | 41 | rep movsw /* Copy words */ |
| 42 | adcl %ecx, %ecx /* One more byte? */ |
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| 1408 | serge | 43 | upbyte: |
| 1627 | serge | 44 | rep movsb /* Copy bytes */ |
| 1408 | serge | 45 | done: |
| 1627 | serge | 46 | movl 8(%ebp), %eax /* Absolutely noone cares about this value */ |
| 47 | pop %edi |
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| 48 | pop %esi |
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| 49 | pop %ebp |
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| 50 | ret |
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| 1408 | serge | 51 | |
| 1627 | serge | 52 | /* Handle bad overlap by copying downwards, don't bother to do word copies. */ |
| 53 | downwards: |
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| 54 | std /* Set direction bit: downwards */ |
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| 55 | leal -1(%esi,%ecx,1), %esi |
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| 56 | leal -1(%edi,%ecx,1), %edi |
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| 1408 | serge | 57 | |
| 1627 | serge | 58 | rep movsb /* Copy bytes */ |
| 59 | cld |
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| 60 | jmp done |