The C Users' Group Library 1994 August/wc-cdrom-cusersgrouplibrary-1994-08.iso/vol_200/292_03/lksym.c

C/C++ Source or Header | 1990-07-17 | 4KB | 254 lines

/* lksym.c */

/*
 * (C) Copyright 1989,1990
 * All Rights Reserved
 *
 * Alan R. Baldwin
 * 721 Berkeley St.
 * Kent, Ohio  44240
 */

#include <stdio.h>
#include <string.h>
#include <alloc.h>
#include "aslink.h"

/*
 * This routine is called early in the
 * game to set up the symbol hashtable.
 */
VOID
syminit()
{
    register h;
    struct sym **spp;

    spp = &symhash[0];
    while (spp < &symhash[NHASH])
        *spp++ = NULL;
}

/*
 * Find/Create a global symbol entry.
 *
 * S xxxxxx Defnnnn
 *   |      |  |
 *   |      |  `-- sp->s_addr
 *   |      `----- sp->s_type
 *   `------------ sp->s_id
 *
 */
struct sym *
newsym()
{
    register c, i, nglob;
    struct sym *tsp;
    struct sym **s;
    char id[NCPS];

    getid(id, -1);
    tsp = lkpsym(id, 1);
    c = getnb();get();get();
    if (c == 'R') {
        tsp->s_type |= S_REF;
        if (eval())
            fprintf(stderr, "Non zero S_REF\n");
    } else
    if (c == 'D') {
        i = eval();
        if (tsp->s_type & S_DEF && tsp->s_addr != i)
            fprintf(stderr, "Multiple definition of %.8s\n", id);
        tsp->s_type |= S_DEF;
        /*
         * Set value and area extension link.
         */
        tsp->s_addr = i;
        tsp->s_axp = axp;
    } else {
        fprintf(stderr, "Invalid symbol type %c for %.8s\n", c, id);
        exit(1);
    }
    /*
     * Place pointer in header symbol list
     */
    if (headp == NULL) {
        fprintf(stderr, "No header defined\n");
        exit(1);
    }
    nglob = hp->h_nglob;
    s = hp->s_list;
    for (i=0; i < nglob ;++i) {
        if (s[i] == NULL) {
            s[i] = tsp;
            return(tsp);
        }
    }
    fprintf(stderr, "Header symbol list overflow\n");
    exit(1);
}

/*
 * Lookup the name `id' in the hashtable.
 * If it is not found either return a
 * `NULL' (`f' is false) or a
 * pointer to a newly created hash table
 * entry (`f' is true).
 */
struct sym *
lkpsym(id, f)
char *id;
{
    register struct sym *sp;
    register h;

    h = hash(id);
    sp = symhash[h];
    while (sp != NULL) {
        if (symeq(id, sp->s_id))
            return (sp);
        sp = sp->s_sp;
    }
    if (f == 0)
        return (NULL);
    sp = (struct sym *) new (sizeof(struct sym));
    sp->s_sp = symhash[h];
    symhash[h] = sp;
    strncpy(sp->s_id, id, NCPS);
    return (sp);
}

/*
 * Get value of relocated symbol
 */
addr_t
symval(tsp)
register struct sym *tsp;
{
    register addr_t val;

    val = tsp->s_addr;
    if (tsp->s_axp) {
        val += tsp->s_axp->a_addr;
    }
    return(val);
}

/*
 * Check for undefined symbols
 */
VOID
symdef(fp)
FILE *fp;
{
    register struct sym *sp;
    register i;

    for (i=0; i<NHASH; ++i) {
        sp = symhash[i];
        while (sp) {
            if (sp->s_axp == NULL)
                sp->s_axp = areap->a_axp;
            if ((sp->s_type & S_DEF) == 0)
                symmod(fp, sp);
            sp = sp->s_sp;
        }
    }
}

VOID
symmod(fp, tsp)
FILE *fp;
struct sym *tsp;
{
    register i, j;
    struct sym **p;

    if ((hp = headp) != NULL) {
        while(hp) {
        p = hp->s_list;
        for (i=0; i<hp->h_nglob; ++i) {
            if (p[i] == tsp) {
            fprintf(fp, "\n?ASlink-W-Undefined Global %8.8s ", tsp->s_id);
            fprintf(fp, "referenced by module %8.8s\n", hp->m_id);
            }
        }
        hp = hp->h_hp;
        }
    }
}

/*
 * Compare two symbol names.
 */
int
symeq(p1, p2)
register char *p1, *p2;
{
    register n;

    n = NCPS;
    do {

#if    CASE_SENSITIVE
        if (*p1++ != *p2++)
            return (0);
#else
        if (ccase[*p1++] != ccase[*p2++])
            return (0);
#endif

    } while (--n);
    return (1);
}

/*
 * Given a pointer to a symbol name
 * compute and return the hash table
 * bucket.
 * The `sum of all the characters mod
 * table size' algorithm is perhaps
 * not the best.
 */
int
hash(p)
register char *p;
{
    register h, n;

    h = 0;
    n = NCPS;
    do {

#if    CASE_SENSITIVE
        h += *p++;
#else
        h += ccase[*p++];
#endif

    } while (--n);
    return (h&HMASK);
}

/*
 * Allocate and clear a block of space.
 * Leave if there is no space left
 * at all.
 */
VOID *
new(n)
unsigned int n;
{
    register char *p,*q;
    register unsigned int i;

    if ((p = (char *) malloc(n)) == NULL) {
        fprintf(stderr, "Out of space!\n");
        exit(1);
    }
    for (i=0,q=p; i<n; i++) {
        *q++ = 0;
    }
    return (p);
}