sync

[bitrig.git] / bin / pax / pat_rep.c

/*      $OpenBSD: pat_rep.c,v 1.32 2012/12/04 02:24:45 deraadt Exp $    */
/*      $NetBSD: pat_rep.c,v 1.4 1995/03/21 09:07:33 cgd Exp $  */

/*-
 * Copyright (c) 1992 Keith Muller.
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Keith Muller of the University of California, San Diego.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <regex.h>
#include "pax.h"
#include "pat_rep.h"
#include "extern.h"

/*
 * routines to handle pattern matching, name modification (regular expression
 * substitution and interactive renames), and destination name modification for
 * copy (-rw). Both file name and link names are adjusted as required in these
 * routines.
 */

#define MAXSUBEXP       10              /* max subexpressions, DO NOT CHANGE */
static PATTERN *pathead = NULL;         /* file pattern match list head */
static PATTERN *pattail = NULL;         /* file pattern match list tail */
static REPLACE *rephead = NULL;         /* replacement string list head */
static REPLACE *reptail = NULL;         /* replacement string list tail */

static int rep_name(char *, size_t, int *, int);
static int tty_rename(ARCHD *);
static int fix_path(char *, int *, char *, int);
static int fn_match(char *, char *, char **);
static char * range_match(char *, int);
static int resub(regex_t *, regmatch_t *, char *, char *, char *, char *);

/*
 * rep_add()
 *      parses the -s replacement string; compiles the regular expression
 *      and stores the compiled value and it's replacement string together in
 *      replacement string list. Input to this function is of the form:
 *              /old/new/pg
 *      The first char in the string specifies the delimiter used by this
 *      replacement string. "Old" is a regular expression in "ed" format which
 *      is compiled by regcomp() and is applied to filenames. "new" is the
 *      substitution string; p and g are options flags for printing and global
 *      replacement (over the single filename)
 * Return:
 *      0 if a proper replacement string and regular expression was added to
 *      the list of replacement patterns; -1 otherwise.
 */

int
rep_add(char *str)
{
        char *pt1;
        char *pt2;
        REPLACE *rep;
        int res;
        char rebuf[BUFSIZ];

        /*
         * throw out the bad parameters
         */
        if ((str == NULL) || (*str == '\0')) {
                paxwarn(1, "Empty replacement string");
                return(-1);
        }

        /*
         * first character in the string specifies what the delimiter is for
         * this expression
         */
        for (pt1 = str+1; *pt1; pt1++) {
                if (*pt1 == '\\') {
                        pt1++;
                        continue;
                }
                if (*pt1 == *str)
                        break;
        }
        if (*pt1 == '\0') {
                paxwarn(1, "Invalid replacement string %s", str);
                return(-1);
        }

        /*
         * allocate space for the node that handles this replacement pattern
         * and split out the regular expression and try to compile it
         */
        if ((rep = (REPLACE *)malloc(sizeof(REPLACE))) == NULL) {
                paxwarn(1, "Unable to allocate memory for replacement string");
                return(-1);
        }

        *pt1 = '\0';
        if ((res = regcomp(&(rep->rcmp), str+1, 0)) != 0) {
                regerror(res, &(rep->rcmp), rebuf, sizeof(rebuf));
                paxwarn(1, "%s while compiling regular expression %s", rebuf, str);
                (void)free((char *)rep);
                return(-1);
        }

        /*
         * put the delimiter back in case we need an error message and
         * locate the delimiter at the end of the replacement string
         * we then point the node at the new substitution string
         */
        *pt1++ = *str;
        for (pt2 = pt1; *pt2; pt2++) {
                if (*pt2 == '\\') {
                        pt2++;
                        continue;
                }
                if (*pt2 == *str)
                        break;
        }
        if (*pt2 == '\0') {
                regfree(&(rep->rcmp));
                (void)free((char *)rep);
                paxwarn(1, "Invalid replacement string %s", str);
                return(-1);
        }

        *pt2 = '\0';
        rep->nstr = pt1;
        pt1 = pt2++;
        rep->flgs = 0;

        /*
         * set the options if any
         */
        while (*pt2 != '\0') {
                switch (*pt2) {
                case 'g':
                case 'G':
                        rep->flgs  |= GLOB;
                        break;
                case 'p':
                case 'P':
                        rep->flgs  |= PRNT;
                        break;
                default:
                        regfree(&(rep->rcmp));
                        (void)free((char *)rep);
                        *pt1 = *str;
                        paxwarn(1, "Invalid replacement string option %s", str);
                        return(-1);
                }
                ++pt2;
        }

        /*
         * all done, link it in at the end
         */
        rep->fow = NULL;
        if (rephead == NULL) {
                reptail = rephead = rep;
                return(0);
        }
        reptail->fow = rep;
        reptail = rep;
        return(0);
}

/*
 * pat_add()
 *      add a pattern match to the pattern match list. Pattern matches are used
 *      to select which archive members are extracted. (They appear as
 *      arguments to pax in the list and read modes). If no patterns are
 *      supplied to pax, all members in the archive will be selected (and the
 *      pattern match list is empty).
 * Return:
 *      0 if the pattern was added to the list, -1 otherwise
 */

int
pat_add(char *str, char *chdname)
{
        PATTERN *pt;

        /*
         * throw out the junk
         */
        if ((str == NULL) || (*str == '\0')) {
                paxwarn(1, "Empty pattern string");
                return(-1);
        }

        /*
         * allocate space for the pattern and store the pattern. the pattern is
         * part of argv so do not bother to copy it, just point at it. Add the
         * node to the end of the pattern list
         */
        if ((pt = (PATTERN *)malloc(sizeof(PATTERN))) == NULL) {
                paxwarn(1, "Unable to allocate memory for pattern string");
                return(-1);
        }

        pt->pstr = str;
        pt->pend = NULL;
        pt->plen = strlen(str);
        pt->fow = NULL;
        pt->flgs = 0;
        pt->chdname = chdname;

        if (pathead == NULL) {
                pattail = pathead = pt;
                return(0);
        }
        pattail->fow = pt;
        pattail = pt;
        return(0);
}

/*
 * pat_chk()
 *      complain if any the user supplied pattern did not result in a match to
 *      a selected archive member.
 */

void
pat_chk(void)
{
        PATTERN *pt;
        int wban = 0;

        /*
         * walk down the list checking the flags to make sure MTCH was set,
         * if not complain
         */
        for (pt = pathead; pt != NULL; pt = pt->fow) {
                if (pt->flgs & MTCH)
                        continue;
                if (!wban) {
                        paxwarn(1, "WARNING! These patterns were not matched:");
                        ++wban;
                }
                (void)fprintf(stderr, "%s\n", pt->pstr);
        }
}

/*
 * pat_sel()
 *      the archive member which matches a pattern was selected. Mark the
 *      pattern as having selected an archive member. arcn->pat points at the
 *      pattern that was matched. arcn->pat is set in pat_match()
 *
 *      NOTE: When the -c option is used, we are called when there was no match
 *      by pat_match() (that means we did match before the inverted sense of
 *      the logic). Now this seems really strange at first, but with -c we
 *      need to keep track of those patterns that cause an archive member to NOT
 *      be selected (it found an archive member with a specified pattern)
 * Return:
 *      0 if the pattern pointed at by arcn->pat was tagged as creating a
 *      match, -1 otherwise.
 */

int
pat_sel(ARCHD *arcn)
{
        PATTERN *pt;
        PATTERN **ppt;
        int len;

        /*
         * if no patterns just return
         */
        if ((pathead == NULL) || ((pt = arcn->pat) == NULL))
                return(0);

        /*
         * when we are NOT limited to a single match per pattern mark the
         * pattern and return
         */
        if (!nflag) {
                pt->flgs |= MTCH;
                return(0);
        }

        /*
         * we reach this point only when we allow a single selected match per
         * pattern, if the pattern matches a directory and we do not have -d
         * (dflag) we are done with this pattern. We may also be handed a file
         * in the subtree of a directory. in that case when we are operating
         * with -d, this pattern was already selected and we are done
         */
        if (pt->flgs & DIR_MTCH)
                return(0);

        if (!dflag && ((pt->pend != NULL) || (arcn->type == PAX_DIR))) {
                /*
                 * ok we matched a directory and we are allowing
                 * subtree matches but because of the -n only its children will
                 * match. This is tagged as a DIR_MTCH type.
                 * WATCH IT, the code assumes that pt->pend points
                 * into arcn->name and arcn->name has not been modified.
                 * If not we will have a big mess. Yup this is another kludge
                 */

                /*
                 * if this was a prefix match, remove trailing part of path
                 * so we can copy it. Future matches will be exact prefix match
                 */
                if (pt->pend != NULL)
                        *pt->pend = '\0';

                if ((pt->pstr = strdup(arcn->name)) == NULL) {
                        paxwarn(1, "Pattern select out of memory");
                        if (pt->pend != NULL)
                                *pt->pend = '/';
                        pt->pend = NULL;
                        return(-1);
                }

                /*
                 * put the trailing / back in the source string
                 */
                if (pt->pend != NULL) {
                        *pt->pend = '/';
                        pt->pend = NULL;
                }
                pt->plen = strlen(pt->pstr);

                /*
                 * strip off any trailing /, this should really never happen
                 */
                len = pt->plen - 1;
                if (*(pt->pstr + len) == '/') {
                        *(pt->pstr + len) = '\0';
                        pt->plen = len;
                }
                pt->flgs = DIR_MTCH | MTCH;
                arcn->pat = pt;
                return(0);
        }

        /*
         * we are then done with this pattern, so we delete it from the list
         * because it can never be used for another match.
         * Seems kind of strange to do for a -c, but the pax spec is really
         * vague on the interaction of -c, -n and -d. We assume that when -c
         * and the pattern rejects a member (i.e. it matched it) it is done.
         * In effect we place the order of the flags as having -c last.
         */
        pt = pathead;
        ppt = &pathead;
        while ((pt != NULL) && (pt != arcn->pat)) {
                ppt = &(pt->fow);
                pt = pt->fow;
        }

        if (pt == NULL) {
                /*
                 * should never happen....
                 */
                paxwarn(1, "Pattern list inconsistent");
                return(-1);
        }
        *ppt = pt->fow;
        (void)free((char *)pt);
        arcn->pat = NULL;
        return(0);
}

/*
 * pat_match()
 *      see if this archive member matches any supplied pattern, if a match
 *      is found, arcn->pat is set to point at the potential pattern. Later if
 *      this archive member is "selected" we process and mark the pattern as
 *      one which matched a selected archive member (see pat_sel())
 * Return:
 *      0 if this archive member should be processed, 1 if it should be
 *      skipped and -1 if we are done with all patterns (and pax should quit
 *      looking for more members)
 */

int
pat_match(ARCHD *arcn)
{
        PATTERN *pt;

        arcn->pat = NULL;

        /*
         * if there are no more patterns and we have -n (and not -c) we are
         * done. otherwise with no patterns to match, matches all
         */
        if (pathead == NULL) {
                if (nflag && !cflag)
                        return(-1);
                return(0);
        }

        /*
         * have to search down the list one at a time looking for a match.
         */
        pt = pathead;
        while (pt != NULL) {
                /*
                 * check for a file name match unless we have DIR_MTCH set in
                 * this pattern then we want a prefix match
                 */
                if (pt->flgs & DIR_MTCH) {
                        /*
                         * this pattern was matched before to a directory
                         * as we must have -n set for this (but not -d). We can
                         * only match CHILDREN of that directory so we must use
                         * an exact prefix match (no wildcards).
                         */
                        if ((arcn->name[pt->plen] == '/') &&
                            (strncmp(pt->pstr, arcn->name, pt->plen) == 0))
                                break;
                } else if (fn_match(pt->pstr, arcn->name, &pt->pend) == 0)
                        break;
                pt = pt->fow;
        }

        /*
         * return the result, remember that cflag (-c) inverts the sense of a
         * match
         */
        if (pt == NULL)
                return(cflag ? 0 : 1);

        /*
         * we had a match, now when we invert the sense (-c) we reject this
         * member. However we have to tag the pattern a being successful, (in a
         * match, not in selecting a archive member) so we call pat_sel() here.
         */
        arcn->pat = pt;
        if (!cflag)
                return(0);

        if (pat_sel(arcn) < 0)
                return(-1);
        arcn->pat = NULL;
        return(1);
}

/*
 * fn_match()
 * Return:
 *      0 if this archive member should be processed, 1 if it should be
 *      skipped and -1 if we are done with all patterns (and pax should quit
 *      looking for more members)
 *      Note: *pend may be changed to show where the prefix ends.
 */

static int
fn_match(char *pattern, char *string, char **pend)
{
        char c;
        char test;

        *pend = NULL;
        for (;;) {
                switch (c = *pattern++) {
                case '\0':
                        /*
                         * Ok we found an exact match
                         */
                        if (*string == '\0')
                                return(0);

                        /*
                         * Check if it is a prefix match
                         */
                        if ((dflag == 1) || (*string != '/'))
                                return(-1);

                        /*
                         * It is a prefix match, remember where the trailing
                         * / is located
                         */
                        *pend = string;
                        return(0);
                case '?':
                        if ((test = *string++) == '\0')
                                return (-1);
                        break;
                case '*':
                        c = *pattern;
                        /*
                         * Collapse multiple *'s.
                         */
                        while (c == '*')
                                c = *++pattern;

                        /*
                         * Optimized hack for pattern with a * at the end
                         */
                        if (c == '\0')
                                return (0);

                        /*
                         * General case, use recursion.
                         */
                        while ((test = *string) != '\0') {
                                if (!fn_match(pattern, string, pend))
                                        return (0);
                                ++string;
                        }
                        return (-1);
                case '[':
                        /*
                         * range match
                         */
                        if (((test = *string++) == '\0') ||
                            ((pattern = range_match(pattern, test)) == NULL))
                                return (-1);
                        break;
                case '\\':
                default:
                        if (c != *string++)
                                return (-1);
                        break;
                }
        }
        /* NOTREACHED */
}

static char *
range_match(char *pattern, int test)
{
        char c;
        char c2;
        int negate;
        int ok = 0;

        if ((negate = (*pattern == '!')) != 0)
                ++pattern;

        while ((c = *pattern++) != ']') {
                /*
                 * Illegal pattern
                 */
                if (c == '\0')
                        return (NULL);

                if ((*pattern == '-') && ((c2 = pattern[1]) != '\0') &&
                    (c2 != ']')) {
                        if ((c <= test) && (test <= c2))
                                ok = 1;
                        pattern += 2;
                } else if (c == test)
                        ok = 1;
        }
        return (ok == negate ? NULL : pattern);
}

/*
 * mod_name()
 *      modify a selected file name. first attempt to apply replacement string
 *      expressions, then apply interactive file rename. We apply replacement
 *      string expressions to both filenames and file links (if we didn't the
 *      links would point to the wrong place, and we could never be able to
 *      move an archive that has a file link in it). When we rename files
 *      interactively, we store that mapping (old name to user input name) so
 *      if we spot any file links to the old file name in the future, we will
 *      know exactly how to fix the file link.
 * Return:
 *      0 continue to  process file, 1 skip this file, -1 pax is finished
 */

int
mod_name(ARCHD *arcn)
{
        int res = 0;

        /*
         * Strip off leading '/' if appropriate.
         * Currently, this option is only set for the tar format.
         */
        while (rmleadslash && arcn->name[0] == '/') {
                if (arcn->name[1] == '\0') {
                        arcn->name[0] = '.';
                } else {
                        (void)memmove(arcn->name, &arcn->name[1],
                            strlen(arcn->name));
                        arcn->nlen--;
                }
                if (rmleadslash < 2) {
                        rmleadslash = 2;
                        paxwarn(0, "Removing leading / from absolute path names in the archive");
                }
        }
        while (rmleadslash && arcn->ln_name[0] == '/' &&
            (arcn->type == PAX_HLK || arcn->type == PAX_HRG)) {
                if (arcn->ln_name[1] == '\0') {
                        arcn->ln_name[0] = '.';
                } else {
                        (void)memmove(arcn->ln_name, &arcn->ln_name[1],
                            strlen(arcn->ln_name));
                        arcn->ln_nlen--;
                }
                if (rmleadslash < 2) {
                        rmleadslash = 2;
                        paxwarn(0, "Removing leading / from absolute path names in the archive");
                }
        }

        /*
         * IMPORTANT: We have a problem. what do we do with symlinks?
         * Modifying a hard link name makes sense, as we know the file it
         * points at should have been seen already in the archive (and if it
         * wasn't seen because of a read error or a bad archive, we lose
         * anyway). But there are no such requirements for symlinks. On one
         * hand the symlink that refers to a file in the archive will have to
         * be modified to so it will still work at its new location in the
         * file system. On the other hand a symlink that points elsewhere (and
         * should continue to do so) should not be modified. There is clearly
         * no perfect solution here. So we handle them like hardlinks. Clearly
         * a replacement made by the interactive rename mapping is very likely
         * to be correct since it applies to a single file and is an exact
         * match. The regular expression replacements are a little harder to
         * justify though. We claim that the symlink name is only likely
         * to be replaced when it points within the file tree being moved and
         * in that case it should be modified. what we really need to do is to
         * call an oracle here. :)
         */
        if (rephead != NULL) {
                /*
                 * we have replacement strings, modify the name and the link
                 * name if any.
                 */
                if ((res = rep_name(arcn->name, sizeof(arcn->name), &(arcn->nlen), 1)) != 0)
                        return(res);

                if (((arcn->type == PAX_SLK) || (arcn->type == PAX_HLK) ||
                    (arcn->type == PAX_HRG)) &&
                    ((res = rep_name(arcn->ln_name, sizeof(arcn->ln_name), &(arcn->ln_nlen), 0)) != 0))
                        return(res);
        }

        if (iflag) {
                /*
                 * perform interactive file rename, then map the link if any
                 */
                if ((res = tty_rename(arcn)) != 0)
                        return(res);
                if ((arcn->type == PAX_SLK) || (arcn->type == PAX_HLK) ||
                    (arcn->type == PAX_HRG))
                        sub_name(arcn->ln_name, &(arcn->ln_nlen), sizeof(arcn->ln_name));
        }
        return(res);
}

/*
 * tty_rename()
 *      Prompt the user for a replacement file name. A "." keeps the old name,
 *      a empty line skips the file, and an EOF on reading the tty, will cause
 *      pax to stop processing and exit. Otherwise the file name input, replaces
 *      the old one.
 * Return:
 *      0 process this file, 1 skip this file, -1 we need to exit pax
 */

static int
tty_rename(ARCHD *arcn)
{
        char tmpname[PAXPATHLEN+2];
        int res;

        /*
         * prompt user for the replacement name for a file, keep trying until
         * we get some reasonable input. Archives may have more than one file
         * on them with the same name (from updates etc). We print verbose info
         * on the file so the user knows what is up.
         */
        tty_prnt("\nATTENTION: %s interactive file rename operation.\n", argv0);

        for (;;) {
                ls_tty(arcn);
                tty_prnt("Input new name, or a \".\" to keep the old name, ");
                tty_prnt("or a \"return\" to skip this file.\n");
                tty_prnt("Input > ");
                if (tty_read(tmpname, sizeof(tmpname)) < 0)
                        return(-1);
                if (strcmp(tmpname, "..") == 0) {
                        tty_prnt("Try again, illegal file name: ..\n");
                        continue;
                }
                if (strlen(tmpname) > PAXPATHLEN) {
                        tty_prnt("Try again, file name too long\n");
                        continue;
                }
                break;
        }

        /*
         * empty file name, skips this file. a "." leaves it alone
         */
        if (tmpname[0] == '\0') {
                tty_prnt("Skipping file.\n");
                return(1);
        }
        if ((tmpname[0] == '.') && (tmpname[1] == '\0')) {
                tty_prnt("Processing continues, name unchanged.\n");
                return(0);
        }

        /*
         * ok the name changed. We may run into links that point at this
         * file later. we have to remember where the user sent the file
         * in order to repair any links.
         */
        tty_prnt("Processing continues, name changed to: %s\n", tmpname);
        res = add_name(arcn->name, arcn->nlen, tmpname);
        arcn->nlen = strlcpy(arcn->name, tmpname, sizeof(arcn->name));
        if (arcn->nlen >= sizeof(arcn->name))
                arcn->nlen = sizeof(arcn->name) - 1; /* XXX truncate? */
        if (res < 0)
                return(-1);
        return(0);
}

/*
 * set_dest()
 *      fix up the file name and the link name (if any) so this file will land
 *      in the destination directory (used during copy() -rw).
 * Return:
 *      0 if ok, -1 if failure (name too long)
 */

int
set_dest(ARCHD *arcn, char *dest_dir, int dir_len)
{
        if (fix_path(arcn->name, &(arcn->nlen), dest_dir, dir_len) < 0)
                return(-1);

        /*
         * It is really hard to deal with symlinks here, we cannot be sure
         * if the name they point was moved (or will be moved). It is best to
         * leave them alone.
         */
        if ((arcn->type != PAX_HLK) && (arcn->type != PAX_HRG))
                return(0);

        if (fix_path(arcn->ln_name, &(arcn->ln_nlen), dest_dir, dir_len) < 0)
                return(-1);
        return(0);
}

/*
 * fix_path
 *      concatenate dir_name and or_name and store the result in or_name (if
 *      it fits). This is one ugly function.
 * Return:
 *      0 if ok, -1 if the final name is too long
 */

static int
fix_path(char *or_name, int *or_len, char *dir_name, int dir_len)
{
        char *src;
        char *dest;
        char *start;
        int len;

        /*
         * we shift the or_name to the right enough to tack in the dir_name
         * at the front. We make sure we have enough space for it all before
         * we start. since dest always ends in a slash, we skip of or_name
         * if it also starts with one.
         */
        start = or_name;
        src = start + *or_len;
        dest = src + dir_len;
        if (*start == '/') {
                ++start;
                --dest;
        }
        if ((len = dest - or_name) > PAXPATHLEN) {
                paxwarn(1, "File name %s/%s, too long", dir_name, start);
                return(-1);
        }
        *or_len = len;

        /*
         * enough space, shift
         */
        while (src >= start)
                *dest-- = *src--;
        src = dir_name + dir_len - 1;

        /*
         * splice in the destination directory name
         */
        while (src >= dir_name)
                *dest-- = *src--;

        *(or_name + len) = '\0';
        return(0);
}

/*
 * rep_name()
 *      walk down the list of replacement strings applying each one in order.
 *      when we find one with a successful substitution, we modify the name
 *      as specified. if required, we print the results. if the resulting name
 *      is empty, we will skip this archive member. We use the regexp(3)
 *      routines (regexp() ought to win a prize as having the most cryptic
 *      library function manual page).
 *      --Parameters--
 *      name is the file name we are going to apply the regular expressions to
 *      (and may be modified)
 *      nsize is the size of the name buffer.
 *      nlen is the length of this name (and is modified to hold the length of
 *      the final string).
 *      prnt is a flag that says whether to print the final result.
 * Return:
 *      0 if substitution was successful, 1 if we are to skip the file (the name
 *      ended up empty)
 */

static int
rep_name(char *name, size_t nsize, int *nlen, int prnt)
{
        REPLACE *pt;
        char *inpt;
        char *outpt;
        char *endpt;
        char *rpt;
        int found = 0;
        int res;
        regmatch_t pm[MAXSUBEXP];
        char nname[PAXPATHLEN+1];       /* final result of all replacements */
        char buf1[PAXPATHLEN+1];        /* where we work on the name */

        /*
         * copy the name into buf1, where we will work on it. We need to keep
         * the orig string around so we can print out the result of the final
         * replacement. We build up the final result in nname. inpt points at
         * the string we apply the regular expression to. prnt is used to
         * suppress printing when we handle replacements on the link field
         * (the user already saw that substitution go by)
         */
        pt = rephead;
        (void)strlcpy(buf1, name, sizeof(buf1));
        inpt = buf1;
        outpt = nname;
        endpt = outpt + PAXPATHLEN;

        /*
         * try each replacement string in order
         */
        while (pt != NULL) {
                do {
                        char *oinpt = inpt;
                        /*
                         * check for a successful substitution, if not go to
                         * the next pattern, or cleanup if we were global
                         */
                        if (regexec(&(pt->rcmp), inpt, MAXSUBEXP, pm, 0) != 0)
                                break;

                        /*
                         * ok we found one. We have three parts, the prefix
                         * which did not match, the section that did and the
                         * tail (that also did not match). Copy the prefix to
                         * the final output buffer (watching to make sure we
                         * do not create a string too long).
                         */
                        found = 1;
                        rpt = inpt + pm[0].rm_so;

                        while ((inpt < rpt) && (outpt < endpt))
                                *outpt++ = *inpt++;
                        if (outpt == endpt)
                                break;

                        /*
                         * for the second part (which matched the regular
                         * expression) apply the substitution using the
                         * replacement string and place it the prefix in the
                         * final output. If we have problems, skip it.
                         */
                        if ((res = resub(&(pt->rcmp),pm,pt->nstr,oinpt,outpt,endpt))
                            < 0) {
                                if (prnt)
                                        paxwarn(1, "Replacement name error %s",
                                            name);
                                return(1);
                        }
                        outpt += res;

                        /*
                         * we set up to look again starting at the first
                         * character in the tail (of the input string right
                         * after the last character matched by the regular
                         * expression (inpt always points at the first char in
                         * the string to process). If we are not doing a global
                         * substitution, we will use inpt to copy the tail to
                         * the final result. Make sure we do not overrun the
                         * output buffer
                         */
                        inpt += pm[0].rm_eo - pm[0].rm_so;

                        if ((outpt == endpt) || (*inpt == '\0'))
                                break;

                        /*
                         * if the user wants global we keep trying to
                         * substitute until it fails, then we are done.
                         */
                } while (pt->flgs & GLOB);

                if (found)
                        break;

                /*
                 * a successful substitution did NOT occur, try the next one
                 */
                pt = pt->fow;
        }

        if (found) {
                /*
                 * we had a substitution, copy the last tail piece (if there is
                 * room) to the final result
                 */
                while ((outpt < endpt) && (*inpt != '\0'))
                        *outpt++ = *inpt++;

                *outpt = '\0';
                if ((outpt == endpt) && (*inpt != '\0')) {
                        if (prnt)
                                paxwarn(1,"Replacement name too long %s >> %s",
                                    name, nname);
                        return(1);
                }

                /*
                 * inform the user of the result if wanted
                 */
                if (prnt && (pt->flgs & PRNT)) {
                        if (*nname == '\0')
                                (void)fprintf(stderr,"%s >> <empty string>\n",
                                    name);
                        else
                                (void)fprintf(stderr,"%s >> %s\n", name, nname);
                }

                /*
                 * if empty inform the caller this file is to be skipped
                 * otherwise copy the new name over the orig name and return
                 */
                if (*nname == '\0')
                        return(1);
                *nlen = strlcpy(name, nname, nsize);
        }
        return(0);
}

/*
 * resub()
 *      apply the replacement to the matched expression. expand out the old
 *      style ed(1) subexpression expansion.
 * Return:
 *      -1 if error, or the number of characters added to the destination.
 */

static int
resub(regex_t *rp, regmatch_t *pm, char *src, char *inpt, char *dest,
        char *destend)
{
        char *spt;
        char *dpt;
        char c;
        regmatch_t *pmpt;
        int len;
        int subexcnt;

        spt =  src;
        dpt = dest;
        subexcnt = rp->re_nsub;
        while ((dpt < destend) && ((c = *spt++) != '\0')) {
                /*
                 * see if we just have an ordinary replacement character
                 * or we refer to a subexpression.
                 */
                if (c == '&') {
                        pmpt = pm;
                } else if ((c == '\\') && (*spt >= '0') && (*spt <= '9')) {
                        /*
                         * make sure there is a subexpression as specified
                         */
                        if ((len = *spt++ - '0') > subexcnt)
                                return(-1);
                        pmpt = pm + len;
                } else {
                        /*
                         * Ordinary character, just copy it
                         */
                        if ((c == '\\') && (*spt != '\0'))
                                c = *spt++;
                        *dpt++ = c;
                        continue;
                }

                /*
                 * continue if the subexpression is bogus
                 */
                if ((pmpt->rm_so < 0) || (pmpt->rm_eo < 0) ||
                    ((len = pmpt->rm_eo - pmpt->rm_so) <= 0))
                        continue;

                /*
                 * copy the subexpression to the destination.
                 * fail if we run out of space or the match string is damaged
                 */
                if (len > (destend - dpt))
                        return (-1);
                strncpy(dpt, inpt + pmpt->rm_so, len);
                dpt += len;
        }
        return(dpt - dest);
}