source: trunk/minix/commands/elle/sbvall.c@ 15

/* VALLOC - Aligned memory allocator
 *      Emulation of the 4.2BSD library routine of the same name.
 *      Copyright 1985 by Ken Harrenstien, SRI International
 *      This software is quasi-public; it may be used freely with
 *      like software, but may NOT be sold or made part of licensed
 *      products without permission of the author.  In all cases
 *      the source code and any modifications thereto must remain
 *      available to any user.
 *
 *      This is part of the SB library package.
 *      Any software using the SB library must likewise be made
 *      quasi-public, with freely available sources.
 */

#include "sb.h"

char *
valloc(size)
unsigned size;
{       register int pagmsk;
        register SBMO i;
        register struct smblk *sm, *smr;
        struct smblk *sbm_mget(), *sbm_split();

        pagmsk = getpagesize() - 1;     /* Get page size in bytes, less 1 */
        if(!(sm = sbm_mget(size+pagmsk, size+pagmsk))) /* Get area big enuf */
                return(0);
        /* Now find # bytes prior to 1st page boundary.
         * This expression gives 0 if already at boundary, else #-1.
         */
        i = pagmsk - ((int)(sm->smaddr) & pagmsk);
        if(i)           /* If need to split off preceding stuff, */
          {     smr = sbm_split(sm, i+1);       /* do so (note i adjusted) */
                sbm_mfree(sm);                  /* Release preceding mem */
                if(!(sm = smr)) return(0);      /* If couldn't split, fail */
          }
        if(i = (sm->smlen - size))      /* See if any trailing stuff */
          {     smr = sbm_split(sm, size);      /* Yeah, split it off too */
                if(smr) sbm_mfree(smr); /* If couldn't split, excess OK. */
          }
        return((char *)(sm->smaddr));
}