Update ./missing to version that includes GPL exemption.

[nvi.git] / ex / ex_cscope.c

/*-
 * Copyright (c) 1994, 1996
 *      Rob Mayoff.  All rights reserved.
 * Copyright (c) 1996
 *      Keith Bostic.  All rights reserved.
 *
 * See the LICENSE file for redistribution information.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "$Id: ex_cscope.c,v 10.19 2001/06/25 15:19:15 skimo Exp $ (Berkeley) $Date: 2001/06/25 15:19:15 $";
#endif /* not lint */

#include <sys/param.h>
#include <sys/types.h>          /* XXX: param.h may not have included types.h */
#include <sys/queue.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>

#include <bitstring.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>

#include "../common/common.h"
#include "pathnames.h"
#include "tag.h"

#define CSCOPE_DBFILE           "cscope.out"
#define CSCOPE_PATHS            "cscope.tpath"

/*
 * 0name        find all uses of name
 * 1name        find definition of name
 * 2name        find all function calls made from name
 * 3name        find callers of name
 * 4string      find text string (cscope 12.9)
 * 4name        find assignments to name (cscope 13.3)
 * 5pattern     change pattern -- NOT USED
 * 6pattern     find pattern
 * 7name        find files with name as substring
 * 8name        find files #including name
 */
#define FINDHELP "\
find c|d|e|f|g|i|s|t buffer|pattern\n\
      c: find callers of name\n\
      d: find all function calls made from name\n\
      e: find pattern\n\
      f: find files with name as substring\n\
      g: find definition of name\n\
      i: find files #including name\n\
      s: find all uses of name\n\
      t: find assignments to name"

static int cscope_add __P((SCR *, EXCMD *, CHAR_T *));
static int cscope_find __P((SCR *, EXCMD*, CHAR_T *));
static int cscope_help __P((SCR *, EXCMD *, CHAR_T *));
static int cscope_kill __P((SCR *, EXCMD *, CHAR_T *));
static int cscope_reset __P((SCR *, EXCMD *, CHAR_T *));

typedef struct _cc {
        char     *name;
        int     (*function) __P((SCR *, EXCMD *, CHAR_T *));
        char     *help_msg;
        char     *usage_msg;
} CC;

static CC const cscope_cmds[] = {
        { "add",   cscope_add,
          "Add a new cscope database", "add file | directory" },
        { "find",  cscope_find,
          "Query the databases for a pattern", FINDHELP },
        { "help",  cscope_help,
          "Show help for cscope commands", "help [command]" },
        { "kill",  cscope_kill,
          "Kill a cscope connection", "kill number" },
        { "reset", cscope_reset,
          "Discard all current cscope connections", "reset" },
        { NULL }
};

static TAGQ     *create_cs_cmd __P((SCR *, char *, size_t *));
static int       csc_help __P((SCR *, char *));
static void      csc_file __P((SCR *,
                    CSC *, char *, char **, size_t *, int *));
static int       get_paths __P((SCR *, CSC *));
static CC const *lookup_ccmd __P((char *));
static int       parse __P((SCR *, CSC *, TAGQ *, int *));
static int       read_prompt __P((SCR *, CSC *));
static int       run_cscope __P((SCR *, CSC *, char *));
static int       start_cscopes __P((SCR *, EXCMD *));
static int       terminate __P((SCR *, CSC *, int));

/*
 * ex_cscope --
 *      Perform an ex cscope.
 *
 * PUBLIC: int ex_cscope __P((SCR *, EXCMD *));
 */
int
ex_cscope(SCR *sp, EXCMD *cmdp)
{
        CC const *ccp;
        EX_PRIVATE *exp;
        int i;
        CHAR_T *cmd;
        CHAR_T *p;
        char *np;
        size_t nlen;

        /* Initialize the default cscope directories. */
        exp = EXP(sp);
        if (!F_ISSET(exp, EXP_CSCINIT) && start_cscopes(sp, cmdp))
                return (1);
        F_SET(exp, EXP_CSCINIT);

        /* Skip leading whitespace. */
        for (p = cmdp->argv[0]->bp, i = cmdp->argv[0]->len; i > 0; --i, ++p)
                if (!isspace(*p))
                        break;
        if (i == 0)
                goto usage;

        /* Skip the command to any arguments. */
        for (cmd = p; i > 0; --i, ++p)
                if (isspace(*p))
                        break;
        if (*p != '\0') {
                *p++ = '\0';
                for (; *p && isspace(*p); ++p);
        }

        INT2CHAR(sp, cmd, STRLEN(cmd) + 1, np, nlen);
        if ((ccp = lookup_ccmd(np)) == NULL) {
usage:          msgq(sp, M_ERR, "309|Use \"cscope help\" for help");
                return (1);
        }

        /* Call the underlying function. */
        return (ccp->function(sp, cmdp, p));
}

/*
 * start_cscopes --
 *      Initialize the cscope package.
 */
static int
start_cscopes(SCR *sp, EXCMD *cmdp)
{
        size_t blen, len;
        char *bp, *cscopes, *p, *t;
        CHAR_T *wp;
        size_t wlen;

        /*
         * EXTENSION #1:
         *
         * If the CSCOPE_DIRS environment variable is set, we treat it as a
         * list of cscope directories that we're using, similar to the tags
         * edit option.
         *
         * XXX
         * This should probably be an edit option, although that implies that
         * we start/stop cscope processes periodically, instead of once when
         * the editor starts.
         */
        if ((cscopes = getenv("CSCOPE_DIRS")) == NULL)
                return (0);
        len = strlen(cscopes);
        GET_SPACE_RET(sp, bp, blen, len);
        memcpy(bp, cscopes, len + 1);

        for (cscopes = t = bp; (p = strsep(&t, "\t :")) != NULL;)
                if (*p != '\0') {
                        CHAR2INT(sp, p, strlen(p) + 1, wp, wlen);
                        (void)cscope_add(sp, cmdp, wp);
                }

        FREE_SPACE(sp, bp, blen);
        return (0);
}

/*
 * cscope_add --
 *      The cscope add command.
 */
static int
cscope_add(SCR *sp, EXCMD *cmdp, CHAR_T *dname)
{
        struct stat sb;
        EX_PRIVATE *exp;
        CSC *csc;
        size_t len;
        int cur_argc;
        char *dbname, path[MAXPATHLEN];
        char *np;
        size_t nlen;

        exp = EXP(sp);

        /*
         *  0 additional args: usage.
         *  1 additional args: matched a file.
         * >1 additional args: object, too many args.
         */
        cur_argc = cmdp->argc;
        if (argv_exp2(sp, cmdp, dname, STRLEN(dname))) {
                return (1);
        }
        if (cmdp->argc == cur_argc) {
                (void)csc_help(sp, "add");
                return (1);
        }
        if (cmdp->argc == cur_argc + 1)
                dname = cmdp->argv[cur_argc]->bp;
        else {
                ex_emsg(sp, np, EXM_FILECOUNT);
                return (1);
        }

        INT2CHAR(sp, dname, STRLEN(dname)+1, np, nlen);

        /*
         * The user can specify a specific file (so they can have multiple
         * Cscope databases in a single directory) or a directory.  If the
         * file doesn't exist, we're done.  If it's a directory, append the
         * standard database file name and try again.  Store the directory
         * name regardless so that we can use it as a base for searches.
         */
        if (stat(np, &sb)) {
                msgq(sp, M_SYSERR, np);
                return (1);
        }
        if (S_ISDIR(sb.st_mode)) {
                (void)snprintf(path, sizeof(path),
                    "%s/%s", np, CSCOPE_DBFILE);
                if (stat(path, &sb)) {
                        msgq(sp, M_SYSERR, path);
                        return (1);
                }
                dbname = CSCOPE_DBFILE;
        } else if ((dbname = strrchr(np, '/')) != NULL)
                *dbname++ = '\0';

        /* Allocate a cscope connection structure and initialize its fields. */
        len = strlen(np);
        CALLOC_RET(sp, csc, CSC *, 1, sizeof(CSC) + len);
        csc->dname = csc->buf;
        csc->dlen = len;
        memcpy(csc->dname, np, len);
        csc->mtime = sb.st_mtime;

        /* Get the search paths for the cscope. */
        if (get_paths(sp, csc))
                goto err;

        /* Start the cscope process. */
        if (run_cscope(sp, csc, dbname))
                goto err;

        /*
         * Add the cscope connection to the screen's list.  From now on, 
         * on error, we have to call terminate, which expects the csc to
         * be on the chain.
         */
        LIST_INSERT_HEAD(&exp->cscq, csc, q);

        /* Read the initial prompt from the cscope to make sure it's okay. */
        if (read_prompt(sp, csc)) {
                terminate(sp, csc, 0);
                return (1);
        }

        return (0);

err:    free(csc);
        return (1);
}

/*
 * get_paths --
 *      Get the directories to search for the files associated with this
 *      cscope database.
 */
static int
get_paths(SCR *sp, CSC *csc)
{
        struct stat sb;
        int fd, nentries;
        size_t len;
        char *p, **pathp, buf[MAXPATHLEN * 2];

        /*
         * EXTENSION #2:
         *
         * If there's a cscope directory with a file named CSCOPE_PATHS, it
         * contains a colon-separated list of paths in which to search for
         * files returned by cscope.
         *
         * XXX
         * These paths are absolute paths, and not relative to the cscope
         * directory.  To fix this, rewrite the each path using the cscope
         * directory as a prefix.
         */
        (void)snprintf(buf, sizeof(buf), "%s/%s", csc->dname, CSCOPE_PATHS);
        if (stat(buf, &sb) == 0) {
                /* Read in the CSCOPE_PATHS file. */
                len = sb.st_size;
                MALLOC_RET(sp, csc->pbuf, char *, len + 1);
                if ((fd = open(buf, O_RDONLY, 0)) < 0 ||
                    read(fd, csc->pbuf, len) != len) {
                         msgq_str(sp, M_SYSERR, buf, "%s");
                         if (fd >= 0)
                                (void)close(fd);
                         return (1);
                }
                (void)close(fd);
                csc->pbuf[len] = '\0';

                /* Count up the entries. */
                for (nentries = 0, p = csc->pbuf; *p != '\0'; ++p)
                        if (p[0] == ':' && p[1] != '\0')
                                ++nentries;

                /* Build an array of pointers to the paths. */
                CALLOC_GOTO(sp,
                    csc->paths, char **, nentries + 1, sizeof(char **));
                for (pathp = csc->paths, p = strtok(csc->pbuf, ":");
                    p != NULL; p = strtok(NULL, ":"))
                        *pathp++ = p;
                return (0);
        }

        /*
         * If the CSCOPE_PATHS file doesn't exist, we look for files
         * relative to the cscope directory.
         */
        if ((csc->pbuf = strdup(csc->dname)) == NULL) {
                msgq(sp, M_SYSERR, NULL);
                return (1);
        }
        CALLOC_GOTO(sp, csc->paths, char **, 2, sizeof(char *));
        csc->paths[0] = csc->pbuf;
        return (0);

alloc_err:
        if (csc->pbuf != NULL) {
                free(csc->pbuf);
                csc->pbuf = NULL;
        }
        return (1);
}

/*
 * run_cscope --
 *      Fork off the cscope process.
 */
static int
run_cscope(SCR *sp, CSC *csc, char *dbname)
{
        int to_cs[2], from_cs[2];
        char cmd[MAXPATHLEN * 2];

        /*
         * Cscope reads from to_cs[0] and writes to from_cs[1]; vi reads from
         * from_cs[0] and writes to to_cs[1].
         */
        to_cs[0] = to_cs[1] = from_cs[0] = from_cs[0] = -1;
        if (pipe(to_cs) < 0 || pipe(from_cs) < 0) {
                msgq(sp, M_SYSERR, "pipe");
                goto err;
        }
        switch (csc->pid = vfork()) {
        case -1:
                msgq(sp, M_SYSERR, "vfork");
err:            if (to_cs[0] != -1)
                        (void)close(to_cs[0]);
                if (to_cs[1] != -1)
                        (void)close(to_cs[1]);
                if (from_cs[0] != -1)
                        (void)close(from_cs[0]);
                if (from_cs[1] != -1)
                        (void)close(from_cs[1]);
                return (1);
        case 0:                         /* child: run cscope. */
                (void)dup2(to_cs[0], STDIN_FILENO);
                (void)dup2(from_cs[1], STDOUT_FILENO);
                (void)dup2(from_cs[1], STDERR_FILENO);

                /* Close unused file descriptors. */
                (void)close(to_cs[1]);
                (void)close(from_cs[0]);

                /* Run the cscope command. */
#define CSCOPE_CMD_FMT          "cd '%s' && exec cscope -dl -f %s"
                (void)snprintf(cmd, sizeof(cmd),
                    CSCOPE_CMD_FMT, csc->dname, dbname);
                (void)execl(_PATH_BSHELL, "sh", "-c", cmd, NULL);
                msgq_str(sp, M_SYSERR, cmd, "execl: %s");
                _exit (127);
                /* NOTREACHED */
        default:                        /* parent. */
                /* Close unused file descriptors. */
                (void)close(to_cs[0]);
                (void)close(from_cs[1]);

                /*
                 * Save the file descriptors for later duplication, and
                 * reopen as streams.
                 */
                csc->to_fd = to_cs[1];
                csc->to_fp = fdopen(to_cs[1], "w");
                csc->from_fd = from_cs[0];
                csc->from_fp = fdopen(from_cs[0], "r");
                break;
        }
        return (0);
}

/*
 * cscope_find --
 *      The cscope find command.
 */
static int
cscope_find(SCR *sp, EXCMD *cmdp, CHAR_T *pattern)
{
        CSC *csc, *csc_next;
        EX_PRIVATE *exp;
        FREF *frp;
        TAGQ *rtqp, *tqp;
        TAG *rtp;
        db_recno_t lno;
        size_t cno, search;
        int force, istmp, matches;
        char *np = NULL;
        size_t nlen;

        exp = EXP(sp);

        /* Check for connections. */
        if (exp->cscq.lh_first == NULL) {
                msgq(sp, M_ERR, "310|No cscope connections running");
                return (1);
        }

        /*
         * Allocate all necessary memory before doing anything hard.  If the
         * tags stack is empty, we'll need the `local context' TAGQ structure
         * later.
         */
        rtp = NULL;
        rtqp = NULL;
        if (exp->tq.cqh_first == (void *)&exp->tq) {
                /* Initialize the `local context' tag queue structure. */
                CALLOC_GOTO(sp, rtqp, TAGQ *, 1, sizeof(TAGQ));
                CIRCLEQ_INIT(&rtqp->tagq);

                /* Initialize and link in its tag structure. */
                CALLOC_GOTO(sp, rtp, TAG *, 1, sizeof(TAG));
                CIRCLEQ_INSERT_HEAD(&rtqp->tagq, rtp, q);
                rtqp->current = rtp; 
        }

        /* Create the cscope command. */
        INT2CHAR(sp, pattern, STRLEN(pattern) + 1, np, nlen);
        np = strdup(np);
        if ((tqp = create_cs_cmd(sp, np, &search)) == NULL)
                goto err;

        /*
         * Stick the current context in a convenient place, we'll lose it
         * when we switch files.
         */
        frp = sp->frp;
        lno = sp->lno;
        cno = sp->cno;
        istmp = F_ISSET(sp->frp, FR_TMPFILE) && !F_ISSET(cmdp, E_NEWSCREEN);

        /* Search all open connections for a match. */
        matches = 0;
        for (csc = exp->cscq.lh_first; csc != NULL; csc = csc_next) {
                /* Copy csc->q.lh_next here in case csc is killed. */
                csc_next = csc->q.le_next;

                /*
                 * Send the command to the cscope program.  (We skip the
                 * first two bytes of the command, because we stored the
                 * search cscope command character and a leading space
                 * there.)
                 */
                (void)fprintf(csc->to_fp, "%d%s\n", search, tqp->tag + 2);
                (void)fflush(csc->to_fp);

                /* Read the output. */
                if (parse(sp, csc, tqp, &matches)) {
                        if (rtqp != NULL)
                                free(rtqp);
                        tagq_free(sp, tqp);
                        return (1);
                }
        }

        if (matches == 0) {
                msgq(sp, M_INFO, "278|No matches for query");
                return (0);
        }

        tqp->current = tqp->tagq.cqh_first;

        /* Try to switch to the first tag. */
        force = FL_ISSET(cmdp->iflags, E_C_FORCE);
        if (F_ISSET(cmdp, E_NEWSCREEN)) {
                if (ex_tag_Nswitch(sp, tqp->current, force))
                        goto err;

                /* Everything else gets done in the new screen. */
                sp = sp->nextdisp;
                exp = EXP(sp);
        } else
                if (ex_tag_nswitch(sp, tqp->current, force))
                        goto err;

        /*
         * If this is the first tag, put a `current location' queue entry
         * in place, so we can pop all the way back to the current mark.
         * Note, it doesn't point to much of anything, it's a placeholder.
         */
        if (exp->tq.cqh_first == (void *)&exp->tq) {
                CIRCLEQ_INSERT_HEAD(&exp->tq, rtqp, q);
        } else
                rtqp = exp->tq.cqh_first;

        /* Link the current TAGQ structure into place. */
        CIRCLEQ_INSERT_HEAD(&exp->tq, tqp, q);

        (void)cscope_search(sp, tqp, tqp->current);

        /*
         * Move the current context from the temporary save area into the
         * right structure.
         *
         * If we were in a temporary file, we don't have a context to which
         * we can return, so just make it be the same as what we're moving
         * to.  It will be a little odd that ^T doesn't change anything, but
         * I don't think it's a big deal.
         */
        if (istmp) {
                rtqp->current->frp = sp->frp;
                rtqp->current->lno = sp->lno;
                rtqp->current->cno = sp->cno;
        } else {
                rtqp->current->frp = frp;
                rtqp->current->lno = lno;
                rtqp->current->cno = cno;
        }

        return (0);

err:
alloc_err:
        if (rtqp != NULL)
                free(rtqp);
        if (rtp != NULL)
                free(rtp);
        if (np != NULL)
                free(np);
        return (1);
}

/*
 * create_cs_cmd --
 *      Build a cscope command, creating and initializing the base TAGQ.
 */
static TAGQ *
create_cs_cmd(SCR *sp, char *pattern, size_t *searchp)
{
        CB *cbp;
        TAGQ *tqp;
        size_t tlen;
        char *p;

        /*
         * Cscope supports a "change pattern" command which we never use,
         * cscope command 5.  Set CSCOPE_QUERIES[5] to " " since the user
         * can't pass " " as the first character of pattern.  That way the
         * user can't ask for pattern 5 so we don't need any special-case
         * code.
         */
#define CSCOPE_QUERIES          "sgdct efi"

        if (pattern == NULL)
                goto usage;

        /* Skip leading blanks, check for command character. */
        for (; isblank(pattern[0]); ++pattern);
        if (pattern[0] == '\0' || !isblank(pattern[1]))
                goto usage;
        for (*searchp = 0, p = CSCOPE_QUERIES;
            *p != '\0' && *p != pattern[0]; ++*searchp, ++p);
        if (*p == '\0') {
                msgq(sp, M_ERR,
                    "311|%s: unknown search type: use one of %s",
                    KEY_NAME(sp, pattern[0]), CSCOPE_QUERIES);
                return (NULL);
        }

        /* Skip <blank> characters to the pattern. */
        for (p = pattern + 1; *p != '\0' && isblank(*p); ++p);
        if (*p == '\0') {
usage:          (void)csc_help(sp, "find");
                return (NULL);
        }

        /* The user can specify the contents of a buffer as the pattern. */
        cbp = NULL;
        if (p[0] == '"' && p[1] != '\0' && p[2] == '\0')
                CBNAME(sp, cbp, p[1]);
        if (cbp != NULL) {
                INT2CHAR(sp, cbp->textq.cqh_first->lb,
                        cbp->textq.cqh_first->len, p, tlen);
        } else
                tlen = strlen(p);

        /* Allocate and initialize the TAGQ structure. */
        CALLOC(sp, tqp, TAGQ *, 1, sizeof(TAGQ) + tlen + 3);
        if (tqp == NULL)
                return (NULL);
        CIRCLEQ_INIT(&tqp->tagq);
        tqp->tag = tqp->buf;
        tqp->tag[0] = pattern[0];
        tqp->tag[1] = ' ';
        tqp->tlen = tlen + 2;
        memcpy(tqp->tag + 2, p, tlen);
        tqp->tag[tlen + 2] = '\0';
        F_SET(tqp, TAG_CSCOPE);

        return (tqp);
}

/*
 * parse --
 *      Parse the cscope output.
 */
static int
parse(SCR *sp, CSC *csc, TAGQ *tqp, int *matchesp)
{
        TAG *tp;
        db_recno_t slno;
        size_t dlen, nlen, slen;
        int ch, i, isolder, nlines;
        char *dname, *name, *search, *p, *t, dummy[2], buf[2048];

        for (;;) {
                if (!fgets(buf, sizeof(buf), csc->from_fp))
                        goto io_err;

                /*
                 * If the database is out of date, or there's some other
                 * problem, cscope will output error messages before the
                 * number-of-lines output.  Display/discard any output
                 * that doesn't match what we want.
                 */
#define CSCOPE_NLINES_FMT       "cscope: %d lines%1[\n]"
                if (sscanf(buf, CSCOPE_NLINES_FMT, &nlines, dummy) == 2)
                        break;
                if ((p = strchr(buf, '\n')) != NULL)
                        *p = '\0';
                msgq(sp, M_ERR, "%s: \"%s\"", csc->dname, buf);
        }

        while (nlines--) {
                if (fgets(buf, sizeof(buf), csc->from_fp) == NULL)
                        goto io_err;

                /* If the line's too long for the buffer, discard it. */
                if ((p = strchr(buf, '\n')) == NULL) {
                        while ((ch = getc(csc->from_fp)) != EOF && ch != '\n');
                        continue;
                }
                *p = '\0';

                /*
                 * The cscope output is in the following format:
                 *
                 *      <filename> <context> <line number> <pattern>
                 *
                 * Figure out how long everything is so we can allocate in one
                 * swell foop, but discard anything that looks wrong.
                 */
                for (p = buf, i = 0;
                    i < 3 && (t = strsep(&p, "\t ")) != NULL; ++i)
                        switch (i) {
                        case 0:                 /* Filename. */
                                name = t;
                                nlen = strlen(name);
                                break;
                        case 1:                 /* Context. */
                                break;
                        case 2:                 /* Line number. */
                                slno = (db_recno_t)atol(t);
                                break;
                        }
                if (i != 3 || p == NULL || t == NULL)
                        continue;

                /* The rest of the string is the search pattern. */
                search = p;
                slen = strlen(p);

                /* Resolve the file name. */
                csc_file(sp, csc, name, &dname, &dlen, &isolder);

                /*
                 * If the file is older than the cscope database, that is,
                 * the database was built since the file was last modified,
                 * or there wasn't a search string, use the line number.
                 */
                if (isolder || strcmp(search, "<unknown>") == 0) {
                        search = NULL;
                        slen = 0;
                }

                /*
                 * Allocate and initialize a tag structure plus the variable
                 * length cscope information that follows it.
                 */
                CALLOC_RET(sp, tp,
                    TAG *, 1, sizeof(TAG) + dlen + 2 + nlen + 1 + slen + 1);
                tp->fname = (char *)tp->buf;
                if (dlen != 0) {
                        memcpy(tp->fname, dname, dlen);
                        tp->fname[dlen] = '/';
                        ++dlen;
                }
                memcpy(tp->fname + dlen, name, nlen + 1);
                tp->fnlen = dlen + nlen;
                tp->slno = slno;
                if (slen != 0) {
                        tp->search = (CHAR_T*)(tp->fname + tp->fnlen + 1);
                        MEMCPYW(tp->search, search, (tp->slen = slen) + 1);
                }
                CIRCLEQ_INSERT_TAIL(&tqp->tagq, tp, q);

                ++*matchesp;
        }

        (void)read_prompt(sp, csc);
        return (0);

io_err: if (feof(csc->from_fp))
                errno = EIO;
        msgq_str(sp, M_SYSERR, "%s", csc->dname);
        terminate(sp, csc, 0);
        return (1);
}

/*
 * csc_file --
 *      Search for the right path to this file.
 */
static void
csc_file(SCR *sp, CSC *csc, char *name, char **dirp, size_t *dlenp, int *isolderp)
{
        struct stat sb;
        char **pp, buf[MAXPATHLEN];

        /*
         * Check for the file in all of the listed paths.  If we don't
         * find it, we simply return it unchanged.  We have to do this
         * now, even though it's expensive, because if the user changes
         * directories, we can't change our minds as to where the file
         * lives.
         */
        for (pp = csc->paths; *pp != NULL; ++pp) {
                (void)snprintf(buf, sizeof(buf), "%s/%s", *pp, name);
                if (stat(buf, &sb) == 0) {
                        *dirp = *pp;
                        *dlenp = strlen(*pp);
                        *isolderp = sb.st_mtime < csc->mtime;
                        return;
                }
        }
        *dlenp = 0;
}

/*
 * cscope_help --
 *      The cscope help command.
 */
static int
cscope_help(SCR *sp, EXCMD *cmdp, CHAR_T *subcmd)
{
        char *np;
        size_t nlen;

        INT2CHAR(sp, subcmd, STRLEN(subcmd) + 1, np, nlen);
        return (csc_help(sp, np));
}

/*
 * csc_help --
 *      Display help/usage messages.
 */
static int
csc_help(SCR *sp, char *cmd)
{
        CC const *ccp;

        if (cmd != NULL && *cmd != '\0')
                if ((ccp = lookup_ccmd(cmd)) == NULL) {
                        ex_printf(sp,
                            "%s doesn't match any cscope command\n", cmd);
                        return (1);
                } else {
                        ex_printf(sp,
                          "Command: %s (%s)\n", ccp->name, ccp->help_msg);
                        ex_printf(sp, "  Usage: %s\n", ccp->usage_msg);
                        return (0);
                }

        ex_printf(sp, "cscope commands:\n");
        for (ccp = cscope_cmds; ccp->name != NULL; ++ccp)
                ex_printf(sp, "  %*s: %s\n", 5, ccp->name, ccp->help_msg);
        return (0);
}

/*
 * cscope_kill --
 *      The cscope kill command.
 */
static int
cscope_kill(SCR *sp, EXCMD *cmdp, CHAR_T *cn)
{
        char *np;
        size_t nlen;

        INT2CHAR(sp, cn, STRLEN(cn) + 1, np, nlen);
        return (terminate(sp, NULL, atoi(np)));
}

/*
 * terminate --
 *      Detach from a cscope process.
 */
static int
terminate(SCR *sp, CSC *csc, int n)
{
        EX_PRIVATE *exp;
        int i, pstat;

        exp = EXP(sp);

        /*
         * We either get a csc structure or a number.  If not provided a
         * csc structure, find the right one.
         */
        if (csc == NULL) {
                if (n < 1)
                        goto badno;
                for (i = 1, csc = exp->cscq.lh_first;
                    csc != NULL; csc = csc->q.le_next, i++)
                        if (i == n)
                                break;
                if (csc == NULL) {
badno:                  msgq(sp, M_ERR, "312|%d: no such cscope session", n);
                        return (1);
                }
        }

        /*
         * XXX
         * Theoretically, we have the only file descriptors to the process,
         * so closing them should let it exit gracefully, deleting temporary
         * files, etc.  The original vi cscope integration sent the cscope
         * connection a SIGTERM signal, so I'm not sure if closing the file
         * descriptors is sufficient.
         */
        if (csc->from_fp != NULL)
                (void)fclose(csc->from_fp);
        if (csc->to_fp != NULL)
                (void)fclose(csc->to_fp);
        (void)waitpid(csc->pid, &pstat, 0);

        /* Discard cscope connection information. */
        LIST_REMOVE(csc, q);
        if (csc->pbuf != NULL)
                free(csc->pbuf);
        if (csc->paths != NULL)
                free(csc->paths);
        free(csc);
        return (0);
}

/*
 * cscope_reset --
 *      The cscope reset command.
 */
static int
cscope_reset(SCR *sp, EXCMD *cmdp, CHAR_T *notusedp)
{
        EX_PRIVATE *exp;

        for (exp = EXP(sp); exp->cscq.lh_first != NULL;) {
                static CHAR_T one[] = {'1', 0};
                if (cscope_kill(sp, cmdp, one))
                        return (1);
        }
        return (0);
}

/*
 * cscope_display --
 *      Display current connections.
 *
 * PUBLIC: int cscope_display __P((SCR *));
 */
int
cscope_display(SCR *sp)
{
        EX_PRIVATE *exp;
        CSC *csc;
        int i;

        exp = EXP(sp);
        if (exp->cscq.lh_first == NULL) {
                ex_printf(sp, "No cscope connections.\n");
                return (0);
        }
        for (i = 1,
            csc = exp->cscq.lh_first; csc != NULL; ++i, csc = csc->q.le_next)
                ex_printf(sp,
                    "%2d %s (process %lu)\n", i, csc->dname, (u_long)csc->pid);
        return (0);
}

/*
 * cscope_search --
 *      Search a file for a cscope entry.
 *
 * PUBLIC: int cscope_search __P((SCR *, TAGQ *, TAG *));
 */
int
cscope_search(SCR *sp, TAGQ *tqp, TAG *tp)
{
        MARK m;

        /* If we don't have a search pattern, use the line number. */
        if (tp->search == NULL) {
                if (!db_exist(sp, tp->slno)) {
                        tag_msg(sp, TAG_BADLNO, tqp->tag);
                        return (1);
                }
                m.lno = tp->slno;
        } else {
                /*
                 * Search for the tag; cheap fallback for C functions
                 * if the name is the same but the arguments have changed.
                 */
                m.lno = 1;
                m.cno = 0;
                if (f_search(sp, &m, &m,
                    tp->search, tp->slen, NULL, SEARCH_CSCOPE | SEARCH_FIRST)) {
                        tag_msg(sp, TAG_SEARCH, tqp->tag);
                        return (1);
                }

                /*
                 * !!!
                 * Historically, tags set the search direction if it wasn't
                 * already set.
                 */
                if (sp->searchdir == NOTSET)
                        sp->searchdir = FORWARD;
        }

        /*
         * !!!
         * Tags move to the first non-blank, NOT the search pattern start.
         */
        sp->lno = m.lno;
        sp->cno = 0;
        (void)nonblank(sp, sp->lno, &sp->cno);
        return (0);
}


/*
 * lookup_ccmd --
 *      Return a pointer to the command structure.
 */
static CC const *
lookup_ccmd(char *name)
{
        CC const *ccp;
        size_t len;

        len = strlen(name);
        for (ccp = cscope_cmds; ccp->name != NULL; ++ccp)
                if (strncmp(name, ccp->name, len) == 0)
                        return (ccp);
        return (NULL);
}

/*
 * read_prompt --
 *      Read a prompt from cscope.
 */
static int
read_prompt(SCR *sp, CSC *csc)
{
        int ch;

#define CSCOPE_PROMPT           ">> "
        for (;;) {
                while ((ch =
                    getc(csc->from_fp)) != EOF && ch != CSCOPE_PROMPT[0]);
                if (ch == EOF) {
                        terminate(sp, csc, 0);
                        return (1);
                }
                if (getc(csc->from_fp) != CSCOPE_PROMPT[1])
                        continue;
                if (getc(csc->from_fp) != CSCOPE_PROMPT[2])
                        continue;
                break;
        }
        return (0);
}