bcomps.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
 *************************************************************************/
 
 
/*
 * Generate biconnected components
 *
 * Written by Emden Gansner
 */
#include "config.h"
 
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <getopt.h>
 
#include <stdlib.h>
#include <cgraph/agxbuf.h>
#include <cgraph/alloc.h>
#include <cgraph/cgraph.h>
#include <cgraph/exit.h>
#include <cgraph/gv_math.h>
#include <cgraph/ingraphs.h>
#include <cgraph/stack.h>
#include <cgraph/unreachable.h>
 
typedef struct {
    Agrec_t h;
    Agraph_t *next;
} Agraphinfo_t;
 
typedef struct {
    Agrec_t h;
} Agedgeinfo_t;
 
typedef struct {
    Agrec_t h;
    int low;
    int val;
    int isCut;
} Agnodeinfo_t;
 
#define Low(n)  (((Agnodeinfo_t*)(n->base.data))->low)
#define Cut(n)  (((Agnodeinfo_t*)(n->base.data))->isCut)
#define N(n)  (((Agnodeinfo_t*)(n->base.data))->val)
#define NEXTBLK(g)  (((Agraphinfo_t*)(g->base.data))->next)
 
char **Files;
int verbose;
int silent;
char *outfile = 0;
char *path = 0;
char *suffix = 0;
int external;                   /* emit blocks as root graphs */
int doTree;                     /* emit block-cutpoint tree */
 
typedef struct {
    int count;
    int nComp;
    gv_stack_t stk;
    Agraph_t *blks;
} bcstate;
 
static char *blockName(agxbuf *xb, char *gname, int d) {
    if (*gname == '%') /* anonymous graph */
        agxbprint(xb, "_%s_bcc_%d", gname, d);
    else
        agxbprint(xb, "%s_bcc_%d", gname, d);
    return agxbuse(xb);
}
 
/* getName:
 * Generate name for output using input template.
 * Has form path_<g>_<i>.suffix, for ith write for the gth graph.
 * If isTree, use path_<g>_t.suffix.
 * If sufcnt is zero and graph 0, use outfile
 */
static char *getName(int ng, int nb)
{
    agxbuf name = {0};
 
    if (ng == 0 && nb == 0)
        agxbput(&name, outfile);
    else {
        if (suffix) {
            if (nb < 0)
                agxbprint(&name, "%s_%d_T.%s", path, ng, suffix);
            else
                agxbprint(&name, "%s_%d_%d.%s", path, ng, nb, suffix);
        } else {
            if (nb < 0)
                agxbprint(&name, "%s_%d_T", path, ng);
            else
                agxbprint(&name, "%s_%d_%d", path, ng, nb);
        }
    }
    return agxbdisown(&name);
}
 
static void gwrite(Agraph_t * g, int ng, int nb)
{
    FILE *outf;
    char *name;
 
    if (silent)
        return;
    if (!outfile) {
        agwrite(g, stdout);
        fflush(stdout);
    } else {
        name = getName(ng, nb);
        outf = fopen(name, "w");
        if (!outf) {
            fprintf(stderr, "Could not open %s for writing\n", name);
            perror("bcomps");
            free(name);
            graphviz_exit(1);
        }
        free(name);
        agwrite(g, outf);
        fclose(outf);
    }
}
 
static Agraph_t *mkBlock(Agraph_t * g, bcstate * stp)
{
    Agraph_t *sg;
 
    stp->nComp++;
    agxbuf xb = {0};
    sg = agsubg(g, blockName(&xb, agnameof(g), stp->nComp), 1);
    agxbfree(&xb);
    agbindrec(sg, "info", sizeof(Agraphinfo_t), true);
    NEXTBLK(sg) = stp->blks;
    stp->blks = sg;
    return sg;
}
 
static void
dfs(Agraph_t * g, Agnode_t * u, bcstate * stp, Agnode_t * parent)
{
    Agnode_t *v;
    Agedge_t *e;
    Agedge_t *ep;
    Agraph_t *sg;
 
    stp->count++;
    Low(u) = N(u) = stp->count;
    for (e = agfstedge(g, u); e; e = agnxtedge(g, e, u)) {
        if ((v = aghead(e)) == u)
            v = agtail(e);
        if (v == u)
            continue;
        if (N(v) == 0) {
            stack_push(&stp->stk, e);
            dfs(g, v, stp, u);
            Low(u) = imin(Low(u), Low(v));
            if (Low(v) >= N(u)) {       /* u is an articulation point */
                Cut(u) = 1;
                sg = mkBlock(g, stp);
                do {
                    ep = stack_pop(&stp->stk);
                    agsubnode(sg, aghead(ep), 1);
                    agsubnode(sg, agtail(ep), 1);
                } while (ep != e);
            }
        } else if (parent != v) {
            Low(u) = imin(Low(u), N(v));
            if (N(v) < N(u))
                stack_push(&stp->stk, e);
        }
    }
}
 
static void addCutPts(Agraph_t * tree, Agraph_t * blk)
{
    Agnode_t *n;
    Agnode_t *bn;
    Agnode_t *cn;
 
    bn = agnode(tree, agnameof(blk), 1);
    for (n = agfstnode(blk); n; n = agnxtnode(blk, n)) {
        if (Cut(n)) {
            cn = agnode(tree, agnameof(n), 1);
            agedge(tree, bn, cn, 0, 1);
        }
    }
}
 
static int process(Agraph_t * g, int gcnt)
{
    Agnode_t *n;
    bcstate state;
    Agraph_t *blk;
    Agraph_t *tree;
    int bcnt;
 
    aginit(g, AGNODE, "info", sizeof(Agnodeinfo_t), true);
    aginit(g, AGEDGE, "info", sizeof(Agedgeinfo_t), true);
    aginit(g, AGRAPH, "info", sizeof(Agraphinfo_t), true);
 
    state.count = 0;
    state.nComp = 0;
    state.stk = (gv_stack_t){0};
    state.blks = 0;
 
    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
        if (N(n) == 0)
            dfs(g, n, &state, 0);
    }
    for (blk = state.blks; blk; blk = NEXTBLK(blk)) {
        (void)graphviz_node_induce(blk, g);
    }
    if (external) {
        bcnt = 0;
        for (blk = state.blks; blk; blk = NEXTBLK(blk)) {
            gwrite(blk, gcnt, bcnt++);
        }
    } else
        gwrite(g, gcnt, 0);
    if (doTree) {
        tree = agopen("blkcut_tree", Agstrictundirected, 0);
        for (blk = state.blks; blk; blk = NEXTBLK(blk))
            addCutPts(tree, blk);
        gwrite(tree, gcnt, -1);
        agclose(tree);
    }
    if (verbose) {
        int cuts = 0;
        bcnt = 0;
        for (blk = state.blks; blk; blk = NEXTBLK(blk))
            bcnt++;
        for (n = agfstnode(g); n; n = agnxtnode(g, n))
            if (Cut(n))
                cuts++;
        fprintf(stderr, "%s: %d blocks %d cutpoints\n", agnameof(g), bcnt,
                cuts);
    }
    stack_reset(&state.stk);
    if (state.blks && NEXTBLK(state.blks))
        return 1;               /* >= 2 blocks */
    else
        return 0;
}
 
static char *useString =
    "Usage: bcomps [-stvx?] [-o<out template>] <files>\n\
  -o - output file template\n\
  -s - don't print components\n\
  -t - emit block-cutpoint tree\n\
  -v - verbose\n\
  -x - external\n\
  -? - print usage\n\
If no files are specified, stdin is used\n";
 
static void usage(int v)
{
    printf("%s",useString);
    graphviz_exit(v);
}
 
static void split(char *name)
{
    char *sfx = 0;
 
    sfx = strrchr(name, '.');
    if (sfx) {
        size_t size = (size_t)(sfx - name);
        suffix = sfx + 1;
        path = gv_strndup(name, size);
    } else {
        path = name;
    }
}
 
static void init(int argc, char *argv[])
{
    int c;
 
    opterr = 0;
    while ((c = getopt(argc, argv, ":o:xstv?")) != -1) {
        switch (c) {
        case 'o':
            outfile = optarg;
            split(outfile);
            break;
        case 's':
            verbose = 1;
            silent = 1;
            break;
        case 'v':
            verbose = 1;
            break;
        case 't':
            doTree = 1;
            break;
        case 'x':
            external = 1;
            break;
        case ':':
            fprintf(stderr, "bcomps: option -%c missing argument - ignored\n", optopt);
            break;
        case '?':
            if (optopt == '\0' || optopt == '?')
                usage(0);
            else {
                fprintf(stderr,
                        "bcomps: option -%c unrecognized\n", optopt);
                usage(1);
            }
            break;
        default:
            UNREACHABLE();
        }
    }
    argv += optind;
    argc -= optind;
 
    if (argc > 0)
        Files = argv;
}
 
int main(int argc, char *argv[])
{
    Agraph_t *g;
    ingraph_state ig;
    int r = 0;
    int gcnt = 0;
 
    init(argc, argv);
    newIngraph(&ig, Files);
 
    while ((g = nextGraph(&ig)) != 0) {
        r |= process(g, gcnt);
        agclose(g);
        gcnt++;
    }
 
    graphviz_exit(r);
}