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81 lines
1.9 KiB
C
81 lines
1.9 KiB
C
/**************************************************************************
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*
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* q s o r t F u n c t i o n
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* ---------------------------
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* Copyright 1982 by Digital Research Inc. All rights reserved.
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*
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* "qsort" sorts the "number" of items, each of length "size", starting
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* at "base", using function "compare" to compare 2 items in the vector.
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*
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* Calling sequence:
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* ret = qsort(base,number,size,compar)
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* Where:
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* ret = always 0
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* base -> start of items vector
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* number = number of elements in vector
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* size = number of bytes per item in vector
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* compar -> comparator function, taking ptrs to items,
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* returning WORD:
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* compar(a,b) < 0 if *a < *b
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* compar(a,b) == 0 if *a == *b
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* compar(a,b) > 0 if *a > *b
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*
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* "qsort" uses the quicksort algorithm by C.A.R. Hoare.
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* Ref: "Software Tools in Pascal" by Kernighan & Plauger.
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*****************************************************************************/
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#include <portab.h>
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#define LINEPOS(nn) ((nn)*siz + bas)
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#define EXCHANGE(aa,bb) _swap(aa,bb,siz)
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WORD qsort(bas,num,siz,cmp)
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BYTE *bas;
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WORD num;
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WORD siz;
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WORD (*cmp)();
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{
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REG WORD i,j;
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REG BYTE *pivline;
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if( num > 1 )
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{
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i = 0;
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j = num-1;
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pivline = LINEPOS(j); /* choose last line for pvt */
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do{
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while( i<j && (*cmp)(LINEPOS(i),pivline) <= 0 )
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i++;
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while( j>i && (*cmp)(LINEPOS(j),pivline) >= 0 )
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j--;
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if( i<j ) /* out of order pair */
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EXCHANGE(LINEPOS(i),LINEPOS(j));
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}while( i<j );
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EXCHANGE(LINEPOS(i),pivline);
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if( i < num-1-i ) /* sort shorter subset 1st */
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{
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qsort( bas, i, siz, cmp);
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qsort( LINEPOS(i+1), num-1-i, siz, cmp);
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} else
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{
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qsort( LINEPOS(i+1), num-1-i, siz, cmp);
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qsort( bas, i, siz, cmp);
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}
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}
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return(0);
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}
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VOID _swap(a,b,wid)
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REG BYTE *a;
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REG BYTE *b;
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REG WORD wid;
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{
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REG BYTE tmp;
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if( a != b )
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for( ; wid-- > 0; a++, b++ )
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{
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tmp = *a;
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*a = *b;
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*b = tmp;
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}
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}
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