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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102a/clib/qsort.c

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