id.c

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/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/
 
#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
#include <cgraph/cghdr.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdlib.h>
#include <util/alloc.h>
 
/* a default ID allocator that works off the shared string lib */
 
typedef struct {
  IDTYPE counter; 
  Agraph_t *g;    
} state_t;
 
static void *idopen(Agraph_t * g, Agdisc_t* disc)
{
    (void)disc;
 
  state_t *s = gv_alloc(sizeof(state_t));
  *s = (state_t){.g = g};
  return s;
}
 
static long idmap(void *state, int objtype, char *str, IDTYPE *id,
                  int createflag)
{
    char *s;
    state_t *st = state;
 
    (void)objtype;
    if (str) {
        if (createflag)
            s = agstrdup(st->g, str);
        else
            s = agstrbind(st->g, str);
        // The scheme of using pointers as the IDs of named objects and odd
        // numbers as the IDs of unnamed objects relies on heap pointers being
        // even, to avoid collisions. So the low bit had better be unset.
        assert((uintptr_t)s % 2 == 0 &&
               "heap pointer with low bit set will collide with anonymous IDs");
        *id = (IDTYPE)(uintptr_t)s;
    } else {
        *id = st->counter * 2 + 1;
        ++st->counter;
    }
    return 1;
}
 
        /* we don't allow users to explicitly set IDs, either */
static long idalloc(void *state, int objtype, IDTYPE request)
{
    (void)state;
    (void)objtype;
    (void)request;
    return 0;
}
 
static void idfree(void *state, int objtype, IDTYPE id)
{
    (void)objtype;
    state_t *st = state;
    if (id % 2 == 0)
        agstrfree(st->g, (char *)(uintptr_t)id);
}
 
static char *idprint(void *state, int objtype, IDTYPE id)
{
    (void)state;
    (void)objtype;
    if (id % 2 == 0)
        return (char *)(uintptr_t)id;
    else
        return NULL;
}
 
static void idregister(void *state, int objtype, void *obj)
{
    (void)state;
    (void)objtype;
    (void)obj;
}
 
Agiddisc_t AgIdDisc = {
    idopen,
    idmap,
    idalloc,
    idfree,
    idprint,
    free,
    idregister
};
 
/* aux functions incl. support for disciplines with anonymous IDs */
 
int agmapnametoid(Agraph_t * g, int objtype, char *str,
          IDTYPE *result, bool createflag) {
    int rv;
 
    if (str && str[0] != LOCALNAMEPREFIX) {
        rv = (int) AGDISC(g, id)->map(AGCLOS(g, id), objtype, str, result,
                                createflag);
        if (rv)
            return rv;
    }
 
    /* either an internal ID, or disc. can't map strings */
    if (str) {
        rv = aginternalmaplookup(g, objtype, str, result);
        if (rv)
            return rv;
    } else
        rv = 0;
 
    if (createflag) {
        /* get a new anonymous ID, and store in the internal map */
        rv = (int) AGDISC(g, id)->map(AGCLOS(g, id), objtype, NULL, result,
                                createflag);
        if (rv && str)
            aginternalmapinsert(g, objtype, str, *result);
    }
    return rv;
}
 
int agallocid(Agraph_t * g, int objtype, IDTYPE request)
{
    return (int) AGDISC(g, id)->alloc(AGCLOS(g, id), objtype, request);
}
 
void agfreeid(Agraph_t * g, int objtype, IDTYPE id)
{
    (void) aginternalmapdelete(g, objtype, id);
    (AGDISC(g, id)->free) (AGCLOS(g, id), objtype, id);
}
 
char *agnameof(void *obj)
{
    Agraph_t *g;
    char *rv;
 
    /* perform internal lookup first */
    g = agraphof(obj);
    rv = aginternalmapprint(g, AGTYPE(obj), AGID(obj));
    if (rv != NULL)
        return rv;
 
    if (AGDISC(g, id)->print) {
        rv = AGDISC(g, id)->print(AGCLOS(g, id), AGTYPE(obj), AGID(obj));
        if (rv != NULL)
            return rv;
    }
    if (AGTYPE(obj) != AGEDGE) {
        static char buf[32];
        snprintf(buf, sizeof(buf), "%c%" PRIu64, LOCALNAMEPREFIX, AGID(obj));
        rv = buf;
    }
    else
        rv = 0;
    return rv;
}
 
/* register a graph object in an external namespace */
void agregister(Agraph_t * g, int objtype, void *obj)
{
        AGDISC(g, id)->idregister(AGCLOS(g, id), objtype, obj);
}