Looking for portable sort

[BRIAN OLENDER]

Subj: Looking for portable sort algorithm
 
*-*-*-*-* Message continued from prior message *-*-*-*-*
 
void hsort(void *, size_t, size_t, comp_t);
 
void
hsort (void *base,                  /* pointer to the array base */
       size_t nel,                  /* number of elements */
       size_t width,                /* size of elements */
       comp_t comp)                 /* comparison function */
{
    char *i, *j, *l, *ir, *temp;
 
    if (nel < 2)
        return;                 /* if not at least two elements *
 
    if (!(temp = (char *)malloc(width)))
        return;                 /* memory allocation error */
 
    ir = (char *)base + (nel - 1) * width;  /* last element */
    l = (char *)base + (nel >> 1) * width;  /* middle element + 1 */
 
    for (;;) {
        if (l <= base) {                    /* selection phase */
            memcpy(temp, ir, width);        /* make room here */
            memcpy(ir, base, width);        /* select top of heap */
            ir -= width;
            if (ir <= base) {
                memcpy(base, temp, width);  /* smallest element */
                free(temp);
                return;
            }
        }
 
        else {                              /* heap creation phase */
            l -= width;
            memcpy(temp, l, width);         /* element to be sifted */
        }
                                    
        /* sift down element in temp to its proper level */
        j = l;                      
        while (i = j, (j += (j - base + width)) <= ir) {
            if (j < ir && (*comp)(j, j + width) < 0)
                j += width;
 
            if ((*comp)(j, temp) < 0)
                break;
 
            memcpy(i, j, width);   /* demote element in temp */
        }
        memcpy(i, temp, width);     /* this is temp's level */
    }
}
 
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