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

1.1     ! root        1: /* This example illustrates the use of the following 286DOS functions:
        !             2:  *     DOSSUBSET, DOSSUBALLOC, DOSSUBFREE
        !             3:  *
        !             4:  * This example allocates a segment <A>, and initialises it for
        !             5:  * suballocation. It suballocates a block <B> from <A>, and writes
        !             6:  * some value into a word in the block <B>. It then grows segment
        !             7:  * <A>, and notifies the suballocator of the new size. It checks
        !             8:  * that the value written into block <B> is still there, frees block
        !             9:  * <B>, frees segment <A>, and terminates.
        !            10:  *
        !            11:  * This example program is intended to illustrate the possible functions
        !            12:  * rather than do anything useful. It can run as a Family API program.
        !            13:  *
        !            14:  * Compile as: cl -AL -G0 -Lp suballoc.c
        !            15:  *
        !            16:  * Copyright (C) Microsoft Corp. 1986
        !            17:  */
        !            18: 
        !            19: #include       <doscalls.h>            /* CP/DOS function declarations      */
        !            20: #include       <dos.h>                 /* FP_OFF and FP_SEG macros          */
        !            21: 
        !            22: /* definitions used in DOSALLOCSEG call */
        !            23: #define        SIZEA   16000           /* bytes to allocate */
        !            24: #define PRIVATE 0              /* segment will not be shared */
        !            25: 
        !            26: /* definitions used in DOSSUBSET call */
        !            27: #define INIT    1              /* initialise size of subset in a segment*/
        !            28: #define INCRSIZE 0             /* increase size of subset in a segment  */
        !            29: 
        !            30: #define        SUBSIZEA 10000          /* size to suballocate */
        !            31: #define SIZER  40000           /* size to reallocate */
        !            32: #define BLKSIZE  100           /* size of block within the subset       */
        !            33: #define SUBSIZEB 20000         /* size to suballocate after realloc     */
        !            34: #define VALUEA   5             /* value to write to first word in block */
        !            35: 
        !            36: main ()
        !            37: {
        !            38:        unsigned        Selector,       /* selector for segment allocated    */
        !            39:                        BlockOffset,    /* offset to block in segment subset */
        !            40:                        *addr;          /*32 bit address to a word in segment*/
        !            41: 
        !            42:        DOSALLOCSEG (SIZEA, &Selector, PRIVATE); /* allocate a segment */
        !            43: 
        !            44:        /* subset the segment to size SUBSIZEA ( must be =< SIZEA ) */
        !            45:        DOSSUBSET (Selector, INIT, SUBSIZEA);
        !            46: 
        !            47:        DOSSUBALLOC(Selector, &BlockOffset, BLKSIZE); /* suballocate block B */
        !            48: 
        !            49:        /* write VALUEA in to first word in block B of the subset */
        !            50:        FP_SEG(addr) = Selector;
        !            51:        FP_OFF(addr) = BlockOffset;
        !            52:        *addr = VALUEA;
        !            53:        
        !            54:        DOSREALLOCSEG (SIZER, Selector); /* grow the segment to size SIZER */
        !            55: 
        !            56:        /* subset the segment to size SUBSIZEB where,
        !            57:          * (SUBSIZEB > SUBSIZEA) and (SUBSIZEB =< SIZER) */
        !            58:        DOSSUBSET(Selector, INCRSIZE, SUBSIZEB);
        !            59: 
        !            60:        /* first word in block B should still contain VALUEA */
        !            61:        if (*addr != VALUEA)
        !            62:           printf ("*** error: unexpected value in suballocated block ***\n");
        !            63: 
        !            64:        DOSSUBFREE (Selector, BlockOffset, BLKSIZE); /* free block B */
        !            65: 
        !            66:        DOSFREESEG (Selector);          /* free the segment */
        !            67: }

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