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Annotation of coherent/b/lib/libc/gen/malloc/realloc.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * realloc.c
        !             3:  * Fits System V requirements.
        !             4:  * Knows format of malloc arena.
        !             5:  */
        !             6: 
        !             7: #include <stdio.h>
        !             8: #include <sys/malloc.h>
        !             9: 
        !            10: extern char *malloc();
        !            11: 
        !            12: char *
        !            13: realloc(cp, size) register char *cp; unsigned size;
        !            14: {
        !            15:        register unsigned len, needed, nlen;
        !            16:        register MBLOCK *mp, *nmp;
        !            17: 
        !            18:        if (cp == NULL)
        !            19:                return malloc(size);
        !            20:        else if (size == 0) {
        !            21:                free(cp);
        !            22:                return NULL;
        !            23:        }
        !            24: 
        !            25:        /* Add space for blksize, round up to word boundary, fail if too big. */
        !            26:        needed = roundup(size + sizeof(unsigned), BLOCKSIZE);
        !            27:        if (needed < size)
        !            28:                return NULL;
        !            29: 
        !            30:        /* Find mblock of the given cp and its length. */
        !            31:        mp = mblockp(cp);
        !            32:        len = realsize(mp->blksize);
        !            33: 
        !            34:        /* Request to shrink. */
        !            35:        if (len >= needed) {
        !            36:                if ((len -= needed) > LEASTFREE) {
        !            37:                        /* Split block into used and free parts. */
        !            38:                        mp->blksize = needed;
        !            39:                        mp = bumpp(mp, needed);
        !            40:                        mp->blksize = (len|FREE);
        !            41:                        __a_count++;
        !            42:                }
        !            43:                return cp;
        !            44:        }
        !            45: 
        !            46:        /* Request to grow. */
        !            47:        nmp = bumpp(mp, len);           /* next block */
        !            48:        nlen = nmp->blksize;            /* length of next block (+1 if free) */
        !            49:        if (isfree(nlen) && (nlen += len) > needed) {
        !            50:                /* The next block is free and the two are big enough. */
        !            51:                if ((nlen - needed) > LEASTFREE) {
        !            52:                        /* Combine blocks, split into used and free parts. */
        !            53:                        mp->blksize = needed;
        !            54:                        mp = bumpp(mp, needed);
        !            55:                        mp->blksize = nlen - needed;
        !            56:                }
        !            57:                else {  /* Combine blocks, using all of both. */
        !            58:                        mp->blksize = nlen = realsize(nlen);
        !            59:                        mp = bumpp(mp, nlen);
        !            60:                        __a_count--;
        !            61:                }
        !            62:                if (nmp == __a_scanp)
        !            63:                        __a_scanp = mp;
        !            64:                return cp;
        !            65:        }
        !            66: 
        !            67:        /* Otherwise, malloc new arena, copy current to it, free current. */
        !            68:        if ((mp = (MBLOCK *)malloc(size)) == NULL)
        !            69:                return NULL;
        !            70:        memcpy(mp, cp, len - sizeof(unsigned));
        !            71:        free(cp);
        !            72:        return((char *)mp);
        !            73: }

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