The World of Computer Software/World_Of_Computer_Software-02-385-Vol-1of3.iso/s/stex2-18.zip/SeeTeX/libtex/search.c

C/C++ Source or Header | 1990-07-10 | 5KB | 181 lines

/*
 * Copyright (c) 1987, 1989 University of Maryland
 * Department of Computer Science.  All rights reserved.
 * Permission to copy for any purpose is hereby granted
 * so long as this copyright notice remains intact.
 */

#ifndef lint
static char rcsid[] = "$Header: /usr/src/local/tex/local/mctex/lib/RCS/search.c,v 3.1 89/08/22 21:58:14 chris Exp $";
#endif

/*
 * Key search routines (for a 32 bit key)
 *
 * SCreate initializes the search control area.
 *
 * SSearch returns the address of the data area (if found or created)
 * or a null pointer (if not).  The last argument controls the disposition
 * in various cases, and is a ``value-result'' parameter.
 *
 * SEnumerate calls the given function on each data object within the
 * search table.  Note that no ordering is specified (though currently
 * it runs in increasing-key-value sequence).
 */

#include "types.h"
#include "search.h"

#if vax || mc68000 || ns32000 || pyr
#define    HARD_ALIGNMENT    4
#else
#define    HARD_ALIGNMENT    16    /* should suffice for most everyone */
#endif

static int DOffset;        /* part of alignment code */

char    *malloc(), *realloc();

struct search *
SCreate(dsize)
    register unsigned int dsize;
{
    register struct search *s;

    if ((s = (struct search *) malloc(sizeof *s)) == 0)
        return (0);

    if (DOffset == 0) {
#ifndef HARD_ALIGNMENT
        DOffset = sizeof(i32);
#else
        DOffset = (sizeof(i32) + HARD_ALIGNMENT - 1) &
            ~(HARD_ALIGNMENT - 1);
#endif
    }
    dsize += DOffset;    /* tack on space for keys */

#ifdef HARD_ALIGNMENT
    /*
     * For machines with strict alignment constraints, it may be
     * necessary to align the data at a multiple of some positive power
     * of two.  In general, it would suffice to make dsize a power of
     * two, but this could be very space-wasteful, so instead we align it
     * to HARD_ALIGNMENT.  64 bit machines might ``#define HARD_ALIGNMENT
     * 8'', for example.  N.B.:  we assume that HARD_ALIGNMENT is a power
     * of two.
     */

    dsize = (dsize + HARD_ALIGNMENT - 1) & ~(HARD_ALIGNMENT - 1);
#endif

    s->s_dsize = dsize;    /* save data object size */
    s->s_space = 10;    /* initially, room for 10 objects */
    s->s_n = 0;        /* and none in the table */
    if ((s->s_data = malloc(s->s_space * dsize)) == 0) {
        free((char *)s);
        return (0);
    }
    return (s);
}

/*
 * We actually use a binary search right now - this may change.
 */
char *
SSearch(s, key, disp)
    register struct search *s;
    register i32 key;
    int *disp;
{
    register char *keyaddr;
    int itemstomove;

    *disp &= S_CREATE | S_EXCL;    /* clear return codes */
    if (s->s_n) {        /* look for the key */
        register int h, l, m;

        h = s->s_n - 1;
        l = 0;
        while (l <= h) {
            m = (l + h) >> 1;
            keyaddr = s->s_data + m * s->s_dsize;
            if (*(i32 *) keyaddr > key)
                h = m - 1;
            else if (*(i32 *) keyaddr < key)
                l = m + 1;
            else {    /* found it, now what? */
                if (*disp & S_EXCL) {
                    *disp |= S_COLL;
                    return (0);    /* collision */
                }
                *disp |= S_FOUND;
                return (keyaddr + DOffset);
            }
        }
        keyaddr = s->s_data + l * s->s_dsize;
    } else
        keyaddr = s->s_data;

    /* keyaddr is now where the key should have been found, if anywhere */
    if ((*disp & S_CREATE) == 0)
        return (0);    /* not found */

    /* avoid using realloc so as to retain old data if out of memory */
    if (s->s_space <= 0) {    /* must expand; double it */
        register char *new;

        if ((new = malloc((s->s_n << 1) * s->s_dsize)) == 0) {
            *disp |= S_ERROR;    /* no space */
            return (0);
        }
        keyaddr = (keyaddr - s->s_data) + new;    /* relocate */
        bcopy(s->s_data, new, s->s_n * s->s_dsize);
        free(s->s_data);
        s->s_data = new;
        s->s_space = s->s_n;
    }
    /* now move any keyed data that is beyond keyaddr down */
    itemstomove = s->s_n - (keyaddr - s->s_data) / s->s_dsize;
    if (itemstomove) {
#ifndef BLOCK_COPY
        register char *from, *to;

        from = s->s_data + s->s_n * s->s_dsize;
        to = from + s->s_dsize;
        while (from > keyaddr)
            *--to = *--from;
#else
        BLOCK_COPY(keyaddr, keyaddr + s->s_dsize,
            itemstomove * s->s_dsize);
#endif
    }
    *disp |= S_NEW;
    s->s_n++;
    s->s_space--;
    *(i32 *) keyaddr = key;
    keyaddr += DOffset;    /* now actually dataaddr */
    /* the bzero is just a frill... */
    bzero(keyaddr, s->s_dsize - DOffset);
    return (keyaddr);
}

/*
 * Call function `f' for each element in the search table `s'.
 */
void
SEnumerate(s, f)
    register struct search *s;
    register void (*f)();
{
    register int n;
    register char *p;

    n = s->s_n;
    p = s->s_data;
    while (--n >= 0) {
        (*f)(p + DOffset, *(i32 *)p);
        p += s->s_dsize;
    }
}