55 lines
1.6 KiB
C
55 lines
1.6 KiB
C
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#include "sb.h"
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/* BCOPY(from,to,cnt) - Copy string of bytes.
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* Normally this routine is an assembly-language library routine,
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* but not all systems have it. Hence this C-language version
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* which tries to be fairly machine-independent.
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* Attempts to be clever about using word moves instead of byte moves.
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* Does not hack overlapping backward moves.
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*/
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bcopy(from, to, cnt) /* Copy count bytes from -> to */
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register SBMA from;
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register SBMA to;
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register unsigned cnt;
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{
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if(!cnt)
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return;
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while(rndrem((int)from)) /* Get source aligned */
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{ *to++ = *from++;
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if(--cnt == 0) return;
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}
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if(rndrem((int)to) == 0) /* Do word move if dest now aligned */
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{ register unsigned tmp;
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tmp = cnt;
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if((cnt = rnddiv(cnt)) > 4)
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{ sbm_wcpy((int *)from, (int *)to, cnt);
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if((cnt = rndrem(tmp)) == 0)
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return; /* No leftover bytes, all done */
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tmp -= cnt; /* Ugh, must update pointers */
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from += tmp;
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to += tmp;
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}
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else cnt = tmp; /* Not worth call overhead */
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}
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do { *to++ = *from++; } /* Finish up with byte loop */
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while(--cnt);
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}
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/* SBM_WCPY - word-move auxiliary routine.
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* This is a separate routine so that machines with only a few
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* registers have a chance to use them for the word copy loop.
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* This cannot be made part of BCOPY without doing some
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* unnecessary pointer conversions and using extra variables
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* (since most compilers will not accept type casts on lvalues,
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* which are needed to treat (char *) as (int *)).
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*/
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sbm_wcpy(from, to, cnt)
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register int *from, *to;
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register unsigned cnt;
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{
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if(cnt)
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do { *to++ = *from++; }
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while(--cnt);
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}
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