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Microsoft OS/2 SDK 03-01-1988

/*
 * Example of DosAllocSeg/DosFreeSeg usage.
 *
 * Shows how to allocate a segment, create a
 * pointer to it, access the segment, and free it.
 * Creates one 16K segment by default, or the number
 * specified on the command line. After all are allocated,
 * writes a 0 into the first byte of each. If you run this on
 * a system with swapping enabled you can allocate more segments
 * than fit in physcical memory, and exercise your disk.
 *
 * This program works Family API mode, although obviously
 * without the benefit of virtual memory & swapping.
 *
 * Compile as:	cl -AL -G0 -Lp alloc.c
 *
 * Created by Microsoft Corp. 1986
 */
#define INCL_DOSMEMMGR

#include <os2def.h>
#include <malloc.h>
#include <bsedos.h>

#define SEGSIZE	(16 * 1024)	/* size of each segment allocated */
#define NOTSHARED 0

main(argc, argv)
int argc;
char *argv[];
{
	USHORT *seglist;	  /* pointer to list of segments */
	char *p;		 /* pointer used to access segments */
	register int i, j;
	int rc; 		 /* system call return code */

	if(argc == 2)			/* number of segments to allocate */
		i = atoi(argv[1]);
	else
		i = 1;

	seglist = (USHORT *)malloc(2 * i);    /* list of segment selectors */

	/* allocate segment(s) */
	for(j = 0; j < i; j++) {
		rc = DosAllocSeg(SEGSIZE, (PSEL)&seglist[j], NOTSHARED);
		if(rc == 0)
			printf("allocated segment %d\n", j);
		else {
			printf("allocation failed on segment %d\n", j);
			i = j;
		}
	}

	/* write 0 into first byte of each segment */
	for(j = 0; j < i; j++) {
		SELECTOROF(p) = seglist[j];	    /* make long pointer to seg */
		OFFSETOF(p) = 0;
		printf("touching segment %d\n", j);
		p[0] = 0;			/* put zero in first byte */
	}

	/* free each segment */
	for(j = 0; j < i; j++) {
		printf("freeing segment %d\n", j);
		DosFreeSeg(seglist[j]);
	}
}

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