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Annotation of os2sdk/demos/examples/alloc/alloc.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Example of DOSALLOCSEG/DOSFREESEG usage.
        !             3:  *
        !             4:  * Shows how to allocate a segment, create a
        !             5:  * pointer to it, access the segment, and free it.
        !             6:  * Creates one 16K segment by default, or the number
        !             7:  * specified on the command line. After all are allocated,
        !             8:  * writes a 0 into the first byte of each. If you run this on
        !             9:  * a system with swapping enabled you can allocate more segments
        !            10:  * segments than fit in physcical memory, and exercise your disk.
        !            11:  *
        !            12:  * This program works Family API mode, although obviously
        !            13:  * without the benefit of virtual memory & swapping.
        !            14:  *
        !            15:  * Compile as:  cl -AL -G2 -Lp alloc.c
        !            16:  *
        !            17:  * Copyright (C) Microsoft Corp. 1986
        !            18:  */
        !            19: 
        !            20: #include <doscalls.h>
        !            21: #include <malloc.h>
        !            22: #include <dos.h>
        !            23: 
        !            24: #define SEGSIZE        (16 * 1024)     /* size of each segment allocated */
        !            25: #define NOTSHARED 0
        !            26: 
        !            27: main(argc, argv)
        !            28: int argc;
        !            29: char *argv[];
        !            30: {
        !            31:        unsigned *seglist;      /* pointer to list of segments */
        !            32:        char *p;                /* pointer used to access segments */
        !            33:        register int i, j;
        !            34:        int rc;                 /* system call return code */
        !            35: 
        !            36:        if(argc == 2)                   /* number of segments to allocate */
        !            37:                i = atoi(argv[1]);
        !            38:        else
        !            39:                i = 1;
        !            40: 
        !            41:        seglist = (unsigned *)malloc(2 * i);    /* list of segment selectors */
        !            42: 
        !            43:        /* allocate segment(s) */
        !            44:        for(j = 0; j < i; j++) {
        !            45:                rc = DOSALLOCSEG(SEGSIZE, &seglist[j], NOTSHARED);
        !            46:                if(rc == 0)
        !            47:                        printf("allocated segment %d\n", j);
        !            48:                else {
        !            49:                        printf("allocation failed on segment %d\n", j);
        !            50:                        i = j;
        !            51:                }
        !            52:        }
        !            53: 
        !            54:        /* write 0 into first byte of each segment */
        !            55:        for(j = 0; j < i; j++) {
        !            56:                FP_SEG(p) = seglist[j];         /* make long pointer to seg */
        !            57:                FP_OFF(p) = 0;
        !            58:                printf("touching segment %d\n", j);
        !            59:                p[0] = 0;                       /* put zero in first byte */
        !            60:        }
        !            61: 
        !            62:        /* free each segment */
        !            63:        for(j = 0; j < i; j++) {
        !            64:                printf("freeing segment %d\n", j);
        !            65:                DOSFREESEG(seglist[j]);
        !            66:        }
        !            67: }

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