when end a "temporary file" edit session, turn on the FR_IGNORE bit

[nvi.git] / ex / ex_subst.c

/*-
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "$Id: ex_subst.c,v 8.25 1993/12/17 16:22:38 bostic Exp $ (Berkeley) $Date: 1993/12/17 16:22:38 $";
#endif /* not lint */

#include <sys/types.h>

#include <ctype.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

#include "vi.h"
#include "excmd.h"

#define SUB_FIRST       0x01            /* The 'r' flag isn't reasonable. */
#define SUB_MUSTSETR    0x02            /* The 'r' flag is required. */

static int              checkmatchsize __P((SCR *, regex_t *));
static inline int       regsub __P((SCR *,
                            char *, char **, size_t *, size_t *));
static int              substitute __P((SCR *, EXF *,
                            EXCMDARG *, char *, regex_t *, u_int));
/*
 * ex_substitute --
 *      [line [,line]] s[ubstitute] [[/;]pat[/;]/repl[/;] [cgr] [count] [#lp]]
 *
 *      Substitute on lines matching a pattern.
 */
int
ex_substitute(sp, ep, cmdp)
        SCR *sp;
        EXF *ep;
        EXCMDARG *cmdp;
{
        regex_t *re, lre;
        size_t blen, len;
        u_int flags;
        int delim, eval, reflags, replaced;
        char *bp, *ptrn, *rep, *p, *t;

        /*
         * Skip leading white space.
         *
         * !!!
         * Historic vi allowed any non-alphanumeric to serve as the
         * substitution command delimiter.
         *
         * !!!
         * If the arguments are empty, it's the same as &, i.e. we
         * repeat the last substitution.
         */
        for (p = cmdp->argv[0]->bp,
            len = cmdp->argv[0]->len; len > 0; --len, ++p) {
                if (!isblank(*p))
                        break;
        }
        if (len == 0)
                return (ex_subagain(sp, ep, cmdp));
        delim = *p++;
        if (isalnum(delim))
                return (substitute(sp, ep,
                    cmdp, p, &sp->subre, SUB_MUSTSETR));

        /*
         * Get the pattern string, toss escaped characters.
         *
         * !!!
         * Historic vi accepted any of the following forms:
         *
         *      :s/abc/def/             change "abc" to "def"
         *      :s/abc/def              change "abc" to "def"
         *      :s/abc/                 delete "abc"
         *      :s/abc                  delete "abc"
         *
         * QUOTING NOTE:
         *
         * Only toss an escape character if it escapes a delimiter.
         * This means that "s/A/\\\\f" replaces "A" with "\\f".  It
         * would be nice to be more regular, i.e. for each layer of
         * escaping a single escape character is removed, but that's
         * not how the historic vi worked.
         */
        for (ptrn = t = p;;) {
                if (p[0] == '\0' || p[0] == delim) {
                        if (p[0] == delim)
                                ++p;
                        /*
                         * !!!
                         * Nul terminate the pattern string -- it's passed
                         * to regcomp which doesn't understand anything else.
                         */
                        *t = '\0';
                        break;
                }
                if (p[0] == '\\' && p[1] == delim)
                        ++p;
                *t++ = *p++;
        }

        /* If the pattern string is empty, use the last one. */
        if (*ptrn == NULL) {
                if (!F_ISSET(sp, S_SUBRE_SET)) {
                        msgq(sp, M_ERR,
                            "No previous regular expression.");
                        return (1);
                }
                re = &sp->subre;
                flags = 0;
        } else {
                /* Set RE flags. */
                reflags = 0;
                if (O_ISSET(sp, O_EXTENDED))
                        reflags |= REG_EXTENDED;
                if (O_ISSET(sp, O_IGNORECASE))
                        reflags |= REG_ICASE;

                /* Convert vi-style RE's to POSIX 1003.2 RE's. */
                if (re_conv(sp, &ptrn, &replaced))
                        return (1);

                /* Compile the RE. */
                eval = regcomp(&lre, (char *)ptrn, reflags);

                /* Free up any allocated memory. */
                if (replaced)
                        FREE_SPACE(sp, ptrn, 0);

                if (eval) {
                        re_error(sp, eval, &lre);
                        return (1);
                }

                /*
                 * Set saved RE.
                 *
                 * !!!
                 * Historic practice is that substitutes set the search
                 * direction as well as both substitute and search RE's.
                 */
                sp->searchdir = FORWARD;
                sp->sre = lre;
                F_SET(sp, S_SRE_SET);
                sp->subre = lre;
                F_SET(sp, S_SUBRE_SET);

                re = &lre;
                flags = SUB_FIRST;
        }

        /*
         * Get the replacement string.
         *
         * The special character ~ (\~ if O_MAGIC not set) inserts the
         * previous replacement string into this replacement string.
         *
         * The special character & (\& if O_MAGIC not set) matches the
         * entire RE.  No handling of & is required here, it's done by
         * regsub().
         *
         * QUOTING NOTE:
         *
         * Only toss an escape character if it escapes a delimiter or
         * if O_MAGIC is set and it escapes a tilde.
         */
        if (*p == '\0') {
                if (sp->repl != NULL)
                        FREE(sp->repl, sp->repl_len);
                sp->repl = NULL;
                sp->repl_len = 0;
        } else {
                /*
                 * Count ~'s to figure out how much space we need.  We could
                 * special case nonexistent last patterns or whether or not
                 * O_MAGIC is set, but it's probably not worth the effort.
                 */
                for (rep = p, len = 0;
                    p[0] != '\0' && p[0] != delim; ++p, ++len)
                        if (p[0] == '~')
                                len += sp->repl_len;
                GET_SPACE_RET(sp, bp, blen, len);
                for (t = bp, len = 0, p = rep;;) {
                        if (p[0] == '\0' || p[0] == delim) {
                                if (p[0] == delim)
                                        ++p;
                                break;
                        }
                        if (p[0] == '\\') {
                                if (p[1] == delim)
                                        ++p;
                                else if (p[1] == '~') {
                                        ++p;
                                        if (!O_ISSET(sp, O_MAGIC))
                                                goto tilde;
                                }
                        } else if (p[0] == '~' && O_ISSET(sp, O_MAGIC)) {
tilde:                          ++p;
                                memmove(t, sp->repl, sp->repl_len);
                                t += sp->repl_len;
                                len += sp->repl_len;
                                continue;
                        }
                        *t++ = *p++;
                        ++len;
                }
                if (sp->repl != NULL)
                        FREE(sp->repl, sp->repl_len);
                if ((sp->repl = malloc(len)) == NULL) {
                        msgq(sp, M_SYSERR, NULL);
                        FREE_SPACE(sp, bp, blen);
                        return (1);
                }
                memmove(sp->repl, bp, len);
                sp->repl_len = len;
                FREE_SPACE(sp, bp, blen);
        }

        if (checkmatchsize(sp, &sp->subre))
                return (1);
        return (substitute(sp, ep, cmdp, p, re, flags));
}

/*
 * ex_subagain --
 *      [line [,line]] & [cgr] [count] [#lp]]
 *
 *      Substitute using the last substitute RE and replacement pattern.
 */
int
ex_subagain(sp, ep, cmdp)
        SCR *sp;
        EXF *ep;
        EXCMDARG *cmdp;
{
        if (!F_ISSET(sp, S_SUBRE_SET)) {
                msgq(sp, M_ERR, "No previous regular expression.");
                return (1);
        }
        return (substitute(sp, ep, cmdp, cmdp->argv[0]->bp, &sp->subre, 0));
}

/*
 * ex_subtilde --
 *      [line [,line]] ~ [cgr] [count] [#lp]]
 *
 *      Substitute using the last RE and last substitute replacement pattern.
 */
int
ex_subtilde(sp, ep, cmdp)
        SCR *sp;
        EXF *ep;
        EXCMDARG *cmdp;
{
        if (!F_ISSET(sp, S_SRE_SET)) {
                msgq(sp, M_ERR, "No previous regular expression.");
                return (1);
        }
        return (substitute(sp, ep, cmdp, cmdp->argv[0]->bp, &sp->sre, 0));
}

/* 
 * The nasty part of the substitution is what happens when the replacement
 * string contains newlines.  It's a bit tricky -- consider the information
 * that has to be retained for "s/f\(o\)o/^M\1^M\1/".  The solution here is
 * to build a set of newline offets which we use to break the line up later,
 * when the replacement is done.  Don't change it unless you're pretty damned
 * confident.
 */
#define NEEDNEWLINE(sp) {                                               \
        if (sp->newl_len == sp->newl_cnt) {                             \
                sp->newl_len += 25;                                     \
                REALLOC(sp, sp->newl, size_t *,                         \
                    sp->newl_len * sizeof(size_t));                     \
                if (sp->newl == NULL) {                                 \
                        sp->newl_len = 0;                               \
                        return (1);                                     \
                }                                                       \
        }                                                               \
}

#define BUILD(sp, l, len) {                                             \
        if (lbclen + (len) > lblen) {                                   \
                lblen += MAX(lbclen + (len), 256);                      \
                REALLOC(sp, lb, char *, lblen);                         \
                if (lb == NULL) {                                       \
                        lbclen = 0;                                     \
                        return (1);                                     \
                }                                                       \
        }                                                               \
        memmove(lb + lbclen, l, len);                                   \
        lbclen += len;                                                  \
}

#define NEEDSP(sp, len, pnt) {                                          \
        if (lbclen + (len) > lblen) {                                   \
                lblen += MAX(lbclen + (len), 256);                      \
                REALLOC(sp, lb, char *, lblen);                         \
                if (lb == NULL) {                                       \
                        lbclen = 0;                                     \
                        return (1);                                     \
                }                                                       \
                pnt = lb + lbclen;                                      \
        }                                                               \
}

/*
 * substitute --
 *      Do the substitution.  This stuff is *really* tricky.  There are
 *      lots of special cases, and general nastiness.  Don't mess with it
 *      unless you're pretty confident.
 */
static int
substitute(sp, ep, cmdp, s, re, flags)
        SCR *sp;
        EXF *ep;
        EXCMDARG *cmdp;
        char *s;
        regex_t *re;
        u_int flags;
{
        MARK from, to;
        recno_t elno, lno, lastline;
        size_t blen, cnt, last, lbclen, lblen, len, offset;
        int do_eol_match, eflags, empty_ok, eval, linechanged, quit;
        int cflag, gflag, lflag, nflag, pflag, rflag;
        char *bp, *lb;

        /*
         * Historic vi permitted the '#', 'l' and 'p' options in vi mode, but
         * it only displayed the last change.  I'd disallow them, but they are
         * useful in combination with the [v]global commands.  In the current
         * model the problem is combining them with the 'c' flag -- the screen
         * would have to flip back and forth between the confirm screen and the
         * ex print screen, which would be pretty awful.  We do display all
         * changes, though, for what that's worth.
         *
         * !!!
         * Historic vi was fairly strict about the order of "options", the
         * count, and "flags".  I'm somewhat fuzzy on the difference between
         * options and flags, anyway, so this is a simpler approach, and we
         * just take it them in whatever order the user gives them.  (The ex
         * usage statement doesn't reflect this.)
         */
        cflag = gflag = lflag = nflag = pflag = rflag = 0;
        for (lno = OOBLNO; *s != '\0'; ++s)
                switch (*s) {
                case ' ':
                case '\t':
                        break;
                case '0': case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                        if (lno != OOBLNO)
                                goto usage;
                        errno = 0;
                        lno = strtoul(s, &s, 10);
                        if (errno == ERANGE) {
                                if (lno == LONG_MAX)
                                        msgq(sp, M_ERR, "Count overflow.");
                                else if (lno == LONG_MIN)
                                        msgq(sp, M_ERR, "Count underflow.");
                                else
                                        msgq(sp, M_SYSERR, NULL);
                                return (1);
                        }
                        /*
                         * In historic vi, the count was inclusive from the
                         * second address.
                         */
                        cmdp->addr1.lno = cmdp->addr2.lno;
                        cmdp->addr2.lno += lno - 1;
                        break;
                case '#':
                        nflag = 1;
                        break;
                case 'c':
                        cflag = 1;
                        break;
                case 'g':
                        gflag = 1;
                        break;
                case 'l':
                        lflag = 1;
                        break;
                case 'p':
                        pflag = 1;
                        break;
                case 'r':
                        if (LF_ISSET(SUB_FIRST)) {
                                msgq(sp, M_ERR,
                    "Regular expression specified; r flag meaningless.");
                                return (1);
                        }
                        if (!F_ISSET(sp, S_SUBRE_SET)) {
                                msgq(sp, M_ERR,
                                    "No previous regular expression.");
                                return (1);
                        }
                        rflag = 1;
                        break;
                default:
                        goto usage;
                }

        if (*s != '\0' || !rflag && LF_ISSET(SUB_MUSTSETR)) {
usage:          msgq(sp, M_ERR, "Usage: %s", cmdp->cmd->usage);
                return (1);
        }

        if (IN_VI_MODE(sp) && cflag && (lflag || nflag || pflag)) {
                msgq(sp, M_ERR,
        "The #, l and p flags may not be combined with the c flag in vi mode.");
                return (1);
        }

        /* Get some space. */
        GET_SPACE_RET(sp, bp, blen, 512);

        /*
         * lb:          build buffer pointer.
         * lbclen:      current length of built buffer.
         * lblen;       length of build buffer.
         */
        lb = NULL;
        lbclen = lblen = 0;

        /*
         * Since multiple changes can happen in a line, we only increment
         * the change count on the first change to a line.
         */
        lastline = OOBLNO;

        /* For each line... */
        for (quit = 0, lno = cmdp->addr1.lno,
            elno = cmdp->addr2.lno; !quit && lno <= elno; ++lno) {

                /* Get the line. */
                if ((s = file_gline(sp, ep, lno, &len)) == NULL) {
                        GETLINE_ERR(sp, lno);
                        return (1);
                }

                /*
                 * Make a local copy if doing confirmation -- when calling
                 * the confirm routine we're likely to lose our cached copy.
                 */
                if (cflag) {
                        ADD_SPACE_RET(sp, bp, blen, len)
                        memmove(bp, s, len);
                        s = bp;
                }

                /* Reset the buffer pointer. */
                lbclen = 0;

                /* Reset empty match flag. */
                empty_ok = 1;

                /*
                 * We don't want to have to do a setline if the line didn't
                 * change -- keep track of whether or not this line changed.
                 */
                linechanged = 0;

                /* New line, do EOL match. */
                do_eol_match = 1;

                /* It's not nul terminated, but we pretend it is. */
                eflags = REG_STARTEND;

                /* The search area is from 's' to the end of the line. */
nextmatch:      sp->match[0].rm_so = 0;
                sp->match[0].rm_eo = len;

                /* Get the next match. */
skipmatch:      eval = regexec(re,
                    (char *)s, re->re_nsub + 1, sp->match, eflags);

                /*
                 * There wasn't a match -- if there was an error, deal with
                 * it.  If there was a previous match in this line, resolve
                 * the changes into the database.  Otherwise, just move on.
                 */
                if (eval == REG_NOMATCH) {
                        if (linechanged)
                                goto endmatch;
                        continue;
                }
                if (eval != 0) {
                        re_error(sp, eval, re);
                        goto ret1;
                }

                /*
                 * !!!
                 * It's possible to match 0-length strings -- for example, the
                 * command s;a*;X;, when matched against the string "aabb" will
                 * result in "XbXbX", i.e. the matches are "aa", the space
                 * between the b's and the space between the b's and the end of
                 * the string.  There is a similar space between the beginning
                 * of the string and the a's.  The rule that we use (because vi
                 * historically used it) is that any 0-length match, occurring
                 * immediately after a match, is ignored.  Otherwise, the above
                 * example would have resulted in "XXbXbX".  Another example is
                 * incorrectly using " *" to replace groups of spaces with one
                 * space.
                 *
                 * The way we do this is that if we just had a successful match,
                 * the starting offset does not skip characters, and the match
                 * is empty, ignore the match and move forward.  If there's no
                 * more characters in the string, we were attempting to match
                 * after the last character, so quit.
                 */
                if (!empty_ok && sp->match[0].rm_so == sp->match[0].rm_eo) {
                        empty_ok = 1;

                        /*
                         * Can't get here if !gflag or !linechanged, so just
                         * test cflag.  Same logic also guarantees that offset
                         * has been initialized.
                         */
                        if (cflag) {
                                if (sp->match[0].rm_so == offset) {
                                        if (len == offset)
                                                goto endmatch;
                                        BUILD(sp, s, 1)
                                        ++s;
                                        --len;
                                        sp->match[0].rm_eo = len;
                                        goto skipmatch;
                                }
                        } else
                                if (sp->match[0].rm_so == 0) {
                                        if (!len)
                                                goto endmatch;
                                        BUILD(sp, s, 1)
                                        ++s;
                                        --len;
                                        goto nextmatch;
                                }
                }

                /* Confirm change. */
                if (cflag) {
                        /*
                         * Set the cursor position for confirmation.  Note,
                         * if we matched on a '$', the cursor may be past
                         * the end of line.
                         *
                         * XXX
                         * May want to "fix" this in the confirm routine;
                         * the confirm routine may be able to display a
                         * cursor past EOL.
                         */
                        from.lno = lno;
                        from.cno = sp->match[0].rm_so;
                        to.lno = lno;
                        to.cno = sp->match[0].rm_eo;
                        if (len != 0) {
                                if (to.cno >= len)
                                        to.cno = len - 1;
                                if (from.cno >= len)
                                        from.cno = len - 1;
                        }

                        switch (sp->s_confirm(sp, ep, &from, &to)) {
                        case CONF_YES:
                                break;
                        case CONF_NO:
                                /*
                                 * Copy the bytes before the match and the
                                 * bytes in the match into the build buffer.
                                 */
                                BUILD(sp, s, sp->match[0].rm_eo);
                                goto skip;
                        case CONF_QUIT:
                                /* Set the quit flag. */
                                quit = 1;

                                /* If interruptible, pass the info back. */
                                if (F_ISSET(sp, S_INTERRUPTIBLE))
                                        F_SET(sp, S_INTERRUPTED);
                                
                                /*
                                 * If any changes, resolve them, otherwise
                                 * return to the main loop.
                                 */
                                if (linechanged)
                                        goto endmatch;
                                continue;
                        }
                }

                /* Copy the bytes before the match into the build buffer. */
                BUILD(sp, s, sp->match[0].rm_so);

                /*
                 * Update the cursor to the start of the change.
                 *
                 * !!!
                 * Historic vi just put the cursor on the first non-blank
                 * of the last line changed.  This might be better.
                 */
                if (!cflag)
                        sp->cno = sp->match[0].rm_so;

                /* Substitute the matching bytes. */
                if (regsub(sp, s, &lb, &lbclen, &lblen))
                        goto ret1;

                /* Set the change flag so we know this line was modified. */
                linechanged = 1;

                /* Move the pointers past the matched bytes. */
skip:           s += sp->match[0].rm_eo;
                len -= sp->match[0].rm_eo;

                /* Got a match, turn off empty patterns. */
                empty_ok = 0;

                /* Only the first search matches anchored expression. */
                eflags |= REG_NOTBOL;

                /*
                 * If doing a global change with confirmation, we have to
                 * update the screen.  The basic idea is to store the line
                 * so the screen update routines can find it, but start at
                 * the old offset.
                 */
                if (linechanged && cflag && gflag) {
                        /* Save offset. */
                        offset = lbclen;
                        
                        /* Copy the suffix. */
                        if (len)
                                BUILD(sp, s, len)

                        /* Store inserted lines, adjusting the build buffer. */
                        last = 0;
                        if (sp->newl_cnt) {
                                for (cnt = 0; cnt < sp->newl_cnt;
                                    ++cnt, ++lno, ++elno, ++lastline) {
                                        if (file_iline(sp, ep, lno,
                                            lb + last, sp->newl[cnt] - last))
                                                goto ret1;
                                        last = sp->newl[cnt] + 1;
                                        ++sp->rptlines[L_ADDED];
                                }
                                lbclen -= last;
                                offset -= last;

                                sp->newl_cnt = 0;
                        }

                        /* Store and retrieve the line. */
                        if (file_sline(sp, ep, lno, lb + last, lbclen))
                                goto ret1;
                        if ((s = file_gline(sp, ep, lno, &len)) == NULL) {
                                GETLINE_ERR(sp, lno);
                                goto ret1;
                        }
                        ADD_SPACE_RET(sp, bp, blen, len)
                        memmove(bp, s, len);
                        s = bp;

                        /* Restart the build. */
                        lbclen = 0;

                        /* Update changed line counter. */
                        if (lastline != lno) {
                                ++sp->rptlines[L_CHANGED];
                                lastline = lno;
                        }

                        /*
                         * Do a test for the after the string match.  Set
                         * REG_NOTEOL so the '$' pattern only matches once.
                         */
                        if (!do_eol_match)
                                goto endmatch;

                        if (offset == len) {
                                do_eol_match = 0;
                                eflags |= REG_NOTEOL;
                        }

                        /* Start in the middle of the line. */
                        sp->match[0].rm_so = offset;
                        sp->match[0].rm_eo = len;

                        goto skipmatch;
                }

                /*
                 * If it's a global:
                 * Do a test for the after the string match.  Set
                 * REG_NOTEOL so the '$' pattern only matches once.
                 */
                if (gflag && do_eol_match) {
                        if (!len) {
                                do_eol_match = 0;
                                eflags |= REG_NOTEOL;
                        }
                        goto nextmatch;
                        
                }

                /* Copy any remaining bytes into the build buffer. */
endmatch:       if (len)
                        BUILD(sp, s, len)

                /* Store inserted lines, adjusting the build buffer. */
                last = 0;
                if (sp->newl_cnt) {
                        for (cnt = 0; cnt < sp->newl_cnt;
                            ++cnt, ++lno, ++elno, ++lastline) {
                                if (file_iline(sp, ep,
                                    lno, lb + last, sp->newl[cnt] - last))
                                        goto ret1;
                                last = sp->newl[cnt] + 1;
                                ++sp->rptlines[L_ADDED];
                        }
                        lbclen -= last;

                        sp->newl_cnt = 0;
                        linechanged = 1;
                }

                /* Store the changed line. */
                if (linechanged)
                        if (file_sline(sp, ep, lno, lb + last, lbclen))
                                goto ret1;

                /* Update changed line counter. */
                if (lastline != lno) {
                        ++sp->rptlines[L_CHANGED];
                        lastline = lno;
                }

                /* Display as necessary. */
                if (lflag || nflag || pflag) {
                        from.lno = to.lno = lno;
                        from.cno = to.cno = 0;
                        if (lflag)
                                ex_print(sp, ep, &from, &to, E_F_LIST);
                        if (nflag)
                                ex_print(sp, ep, &from, &to, E_F_HASH);
                        if (pflag)
                                ex_print(sp, ep, &from, &to, E_F_PRINT);
                }
        }

        /*
         * Cursor moves to last line changed, unless doing confirm,
         * in which case don't move it.
         */
        if (!cflag && lastline != OOBLNO)
                sp->lno = lastline;

        /*
         * Note if nothing found.  Else, if nothing displayed to the
         * screen, put something up.
         */
        if (sp->rptlines[L_CHANGED] == 0 && !F_ISSET(sp, S_GLOBAL))
                msgq(sp, M_INFO, "No match found.");
        else if (!lflag && !nflag && !pflag)
                F_SET(sp, S_AUTOPRINT);

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

ret1:   FREE_SPACE(sp, bp, blen);
        return (1);
}

/*
 * regsub --
 *      Do the substitution for a regular expression.
 */
static inline int
regsub(sp, ip, lbp, lbclenp, lblenp)
        SCR *sp;
        char *ip;                       /* Input line. */
        char **lbp;
        size_t *lbclenp, *lblenp;
{
        enum { C_NOTSET, C_LOWER, C_ONELOWER, C_ONEUPPER, C_UPPER } conv;
        size_t lbclen, lblen;           /* Local copies. */
        size_t mlen;                    /* Match length. */
        size_t rpl;                     /* Remaining replacement length. */
        char *rp;                       /* Replacement pointer. */
        int ch;
        int no;                         /* Match replacement offset. */
        char *p, *t;                    /* Buffer pointers. */
        char *lb;                       /* Local copies. */

        lb = *lbp;                      /* Get local copies. */
        lbclen = *lbclenp;
        lblen = *lblenp;

        /*
         * QUOTING NOTE:
         *
         * There are some special sequences that vi provides in the
         * replacement patterns.
         *       & string the RE matched (\& if nomagic set)
         *      \# n-th regular subexpression   
         *      \E end \U, \L conversion
         *      \e end \U, \L conversion
         *      \l convert the next character to lower-case
         *      \L convert to lower-case, until \E, \e, or end of replacement
         *      \u convert the next character to upper-case
         *      \U convert to upper-case, until \E, \e, or end of replacement
         *
         * Otherwise, since this is the lowest level of replacement, discard
         * all escape characters.  This (hopefully) follows historic practice.
         */
#define ADDCH(ch) {                                                     \
        u_int __value;                                                  \
        __value = term_key_val(sp, ch);                                 \
        if (__value == K_CR || __value == K_NL) {                       \
                NEEDNEWLINE(sp);                                        \
                sp->newl[sp->newl_cnt++] = lbclen;                      \
        } else if (conv != C_NOTSET) {                                  \
                switch (conv) {                                         \
                case C_ONELOWER:                                        \
                        conv = C_NOTSET;                                \
                        /* FALLTHROUGH */                               \
                case C_LOWER:                                           \
                        if (isupper(ch))                                \
                                ch = tolower(ch);                       \
                        break;                                          \
                case C_ONEUPPER:                                        \
                        conv = C_NOTSET;                                \
                        /* FALLTHROUGH */                               \
                case C_UPPER:                                           \
                        if (islower(ch))                                \
                                ch = toupper(ch);                       \
                        break;                                          \
                default:                                                \
                        abort();                                        \
                }                                                       \
        }                                                               \
        NEEDSP(sp, 1, p);                                               \
        *p++ = ch;                                                      \
        ++lbclen;                                                       \
}
        conv = C_NOTSET;
        for (rp = sp->repl, rpl = sp->repl_len, p = lb + lbclen; rpl--;) {
                switch (ch = *rp++) {
                case '&':
                        if (O_ISSET(sp, O_MAGIC)) {
                                no = 0;
                                goto subzero;
                        }
                        break;
                case '\\':
                        if (rpl == 0)
                                break;
                        --rpl;
                        switch (ch = *rp) {
                        case '&':
                                if (!O_ISSET(sp, O_MAGIC)) {
                                        ++rp;
                                        no = 0;
                                        goto subzero;
                                }
                                break;
                        case '0': case '1': case '2': case '3': case '4':
                        case '5': case '6': case '7': case '8': case '9':
                                no = *rp++ - '0';
subzero:                        if (sp->match[no].rm_so == -1 ||
                                    sp->match[no].rm_eo == -1)
                                        continue;
                                mlen =
                                    sp->match[no].rm_eo - sp->match[no].rm_so;
                                for (t = ip + sp->match[no].rm_so; mlen--; ++t)
                                        ADDCH(*t);
                                continue;
                        case 'e':
                        case 'E':
                                ++rp;
                                conv = C_NOTSET;
                                continue;
                        case 'l':
                                ++rp;
                                conv = C_ONELOWER;
                                continue;
                        case 'L':
                                ++rp;
                                conv = C_LOWER;
                                continue;
                        case 'u':
                                ++rp;
                                conv = C_ONEUPPER;
                                continue;
                        case 'U':
                                ++rp;
                                conv = C_UPPER;
                                continue;
                        default:
                                ++rp;
                                break;
                        }
                }
                ADDCH(ch);
        }

        *lbp = lb;                      /* Update caller's information. */
        *lbclenp = lbclen;
        *lblenp = lblen;
        return (0);
}

static int
checkmatchsize(sp, re)
        SCR *sp;
        regex_t *re;
{
        /* Build nsub array as necessary. */
        if (sp->matchsize < re->re_nsub + 1) {
                sp->matchsize = re->re_nsub + 1;
                REALLOC(sp, sp->match,
                    regmatch_t *, sp->matchsize * sizeof(regmatch_t));
                if (sp->match == NULL) {
                        sp->matchsize = 0;
                        return (1);
                }
        }
        return (0);
}