/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1992 Diomidis Spinellis.
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Diomidis Spinellis of Imperial College, University of London.
 *
 * 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/cdefs.h>

#include <sys/types.h>
#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <regex.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>

#include "defs.h"
#include "extern.h"

#define LHSZ    128
#define LHMASK  (LHSZ - 1)
static struct labhash {
        struct  labhash *lh_next;
        u_int   lh_hash;
        struct  s_command *lh_cmd;
        int     lh_ref;
} *labels[LHSZ];

static char      *compile_addr(char *, struct s_addr *);
static char      *compile_ccl(char **, char *);
static char      *compile_delimited(char *, char *, int);
static char      *compile_flags(char *, struct s_subst *);
static regex_t   *compile_re(char *, int);
static char      *compile_subst(char *, struct s_subst *);
static char      *compile_text(void);
static char      *compile_tr(char *, struct s_tr **);
static struct s_command
                **compile_stream(struct s_command **);
static char      *duptoeol(char *, const char *);
static void       enterlabel(struct s_command *);
static struct s_command
                 *findlabel(char *);
static void       fixuplabel(struct s_command *, struct s_command *);
static void       uselabel(void);

/*
 * Command specification.  This is used to drive the command parser.
 */
struct s_format {
        char code;                              /* Command code */
        int naddr;                              /* Number of address args */
        enum e_args args;                       /* Argument type */
};

static struct s_format cmd_fmts[] = {
        {'{', 2, GROUP},
        {'}', 0, ENDGROUP},
        {'a', 1, TEXT},
        {'b', 2, BRANCH},
        {'c', 2, TEXT},
        {'d', 2, EMPTY},
        {'D', 2, EMPTY},
        {'g', 2, EMPTY},
        {'G', 2, EMPTY},
        {'h', 2, EMPTY},
        {'H', 2, EMPTY},
        {'i', 1, TEXT},
        {'l', 2, EMPTY},
        {'n', 2, EMPTY},
        {'N', 2, EMPTY},
        {'p', 2, EMPTY},
        {'P', 2, EMPTY},
        {'q', 1, EMPTY},
        {'r', 1, RFILE},
        {'s', 2, SUBST},
        {'t', 2, BRANCH},
        {'w', 2, WFILE},
        {'x', 2, EMPTY},
        {'y', 2, TR},
        {'!', 2, NONSEL},
        {':', 0, LABEL},
        {'#', 0, COMMENT},
        {'=', 1, EMPTY},
        {'\0', 0, COMMENT},
};

/* The compiled program. */
struct s_command *prog;

/*
 * Compile the program into prog.
 * Initialise appends.
 */
void
compile(void)
{
        *compile_stream(&prog) = NULL;
        fixuplabel(prog, NULL);
        uselabel();
        if (appendnum == 0)
                appends = NULL;
        else if ((appends = malloc(sizeof(struct s_appends) * appendnum)) ==
            NULL)
                err(1, "malloc");
        if ((match = malloc((maxnsub + 1) * sizeof(regmatch_t))) == NULL)
                err(1, "malloc");
}

#define EATSPACE() do {                                                 \
        if (p)                                                          \
                while (*p && isspace((unsigned char)*p))                \
                        p++;                                            \
        } while (0)

static struct s_command **
compile_stream(struct s_command **link)
{
        char *p;
        static char lbuf[_POSIX2_LINE_MAX + 1]; /* To save stack */
        struct s_command *cmd, *cmd2, *stack;
        struct s_format *fp;
        char re[_POSIX2_LINE_MAX + 1];
        int naddr;                              /* Number of addresses */

        stack = NULL;
        for (;;) {
                if ((p = cu_fgets(lbuf, sizeof(lbuf), NULL)) == NULL) {
                        if (stack != NULL)
                                errx(1, "%lu: %s: unexpected EOF (pending }'s)",
                                                        linenum, fname);
                        return (link);
                }

semicolon:      EATSPACE();
                if (p) {
                        if (*p == '#' || *p == '\0')
                                continue;
                        else if (*p == ';') {
                                p++;
                                goto semicolon;
                        }
                }
                if ((*link = cmd = malloc(sizeof(struct s_command))) == NULL)
                        err(1, "malloc");
                link = &cmd->next;
                cmd->startline = cmd->nonsel = 0;
                /* First parse the addresses */
                naddr = 0;

/* Valid characters to start an address */
#define addrchar(c)     (strchr("0123456789/\\$", (c)))
                if (addrchar(*p)) {
                        naddr++;
                        if ((cmd->a1 = malloc(sizeof(struct s_addr))) == NULL)
                                err(1, "malloc");
                        p = compile_addr(p, cmd->a1);
                        EATSPACE();                             /* EXTENSION */
                        if (*p == ',') {
                                p++;
                                EATSPACE();                     /* EXTENSION */
                                naddr++;
                                if ((cmd->a2 = malloc(sizeof(struct s_addr)))
                                    == NULL)
                                        err(1, "malloc");
                                p = compile_addr(p, cmd->a2);
                                EATSPACE();
                        } else
                                cmd->a2 = NULL;
                } else
                        cmd->a1 = cmd->a2 = NULL;

nonsel:         /* Now parse the command */
                if (!*p)
                        errx(1, "%lu: %s: command expected", linenum, fname);
                cmd->code = *p;
                for (fp = cmd_fmts; fp->code; fp++)
                        if (fp->code == *p)
                                break;
                if (!fp->code)
                        errx(1, "%lu: %s: invalid command code %c", linenum, fname, *p);
                if (naddr > fp->naddr)
                        errx(1,
                                "%lu: %s: command %c expects up to %d address(es), found %d",
                                linenum, fname, *p, fp->naddr, naddr);
                switch (fp->args) {
                case NONSEL:                    /* ! */
                        p++;
                        EATSPACE();
                        cmd->nonsel = 1;
                        goto nonsel;
                case GROUP:                     /* { */
                        p++;
                        EATSPACE();
                        cmd->next = stack;
                        stack = cmd;
                        link = &cmd->u.c;
                        if (*p)
                                goto semicolon;
                        break;
                case ENDGROUP:
                        /*
                         * Short-circuit command processing, since end of
                         * group is really just a noop.
                         */
                        cmd->nonsel = 1;
                        if (stack == NULL)
                                errx(1, "%lu: %s: unexpected }", linenum, fname);
                        cmd2 = stack;
                        stack = cmd2->next;
                        cmd2->next = cmd;
                        /*FALLTHROUGH*/
                case EMPTY:             /* d D g G h H l n N p P q x = \0 */
                        p++;
                        EATSPACE();
                        if (*p == ';') {
                                p++;
                                link = &cmd->next;
                                goto semicolon;
                        }
                        if (*p)
                                errx(1, "%lu: %s: extra characters at the end of %c command",
                                                linenum, fname, cmd->code);
                        break;
                case TEXT:                      /* a c i */
                        p++;
                        EATSPACE();
                        if (*p != '\\')
                                errx(1,
"%lu: %s: command %c expects \\ followed by text", linenum, fname, cmd->code);
                        p++;
                        EATSPACE();
                        if (*p)
                                errx(1,
                                "%lu: %s: extra characters after \\ at the end of %c command",
                                linenum, fname, cmd->code);
                        cmd->t = compile_text();
                        break;
                case COMMENT:                   /* \0 # */
                        break;
                case WFILE:                     /* w */
                        p++;
                        EATSPACE();
                        if (*p == '\0')
                                errx(1, "%lu: %s: filename expected", linenum, fname);
                        cmd->t = duptoeol(p, "w command");
                        if (aflag)
                                cmd->u.fd = -1;
                        else if ((cmd->u.fd = open(p,
                            O_WRONLY|O_APPEND|O_CREAT|O_TRUNC,
                            DEFFILEMODE)) == -1)
                                err(1, "%s", p);
                        break;
                case RFILE:                     /* r */
                        p++;
                        EATSPACE();
                        if (*p == '\0')
                                errx(1, "%lu: %s: filename expected", linenum, fname);
                        else
                                cmd->t = duptoeol(p, "read command");
                        break;
                case BRANCH:                    /* b t */
                        p++;
                        EATSPACE();
                        if (*p == '\0')
                                cmd->t = NULL;
                        else
                                cmd->t = duptoeol(p, "branch");
                        break;
                case LABEL:                     /* : */
                        p++;
                        EATSPACE();
                        cmd->t = duptoeol(p, "label");
                        if (strlen(p) == 0)
                                errx(1, "%lu: %s: empty label", linenum, fname);
                        enterlabel(cmd);
                        break;
                case SUBST:                     /* s */
                        p++;
                        if (*p == '\0' || *p == '\\')
                                errx(1,
"%lu: %s: substitute pattern can not be delimited by newline or backslash",
                                        linenum, fname);
                        if ((cmd->u.s = calloc(1, sizeof(struct s_subst))) == NULL)
                                err(1, "malloc");
                        p = compile_delimited(p, re, 0);
                        if (p == NULL)
                                errx(1,
                                "%lu: %s: unterminated substitute pattern", linenum, fname);

                        /* Compile RE with no case sensitivity temporarily */
                        if (*re == '\0')
                                cmd->u.s->re = NULL;
                        else
                                cmd->u.s->re = compile_re(re, 0);
                        --p;
                        p = compile_subst(p, cmd->u.s);
                        p = compile_flags(p, cmd->u.s);

                        /* Recompile RE with case sensitivity from "I" flag if any */
                        if (*re == '\0')
                                cmd->u.s->re = NULL;
                        else
                                cmd->u.s->re = compile_re(re, cmd->u.s->icase);
                        EATSPACE();
                        if (*p == ';') {
                                p++;
                                link = &cmd->next;
                                goto semicolon;
                        }
                        break;
                case TR:                        /* y */
                        p++;
                        p = compile_tr(p, &cmd->u.y);
                        EATSPACE();
                        if (*p == ';') {
                                p++;
                                link = &cmd->next;
                                goto semicolon;
                        }
                        if (*p)
                                errx(1,
"%lu: %s: extra text at the end of a transform command", linenum, fname);
                        break;
                }
        }
}

static int
hex2char(const char *in, char *out, int len)
{
        long ord;
        char *endptr, hexbuf[3];

        hexbuf[0] = in[0];
        hexbuf[1] = len > 1 ? in[1] : '\0';
        hexbuf[2] = '\0';

        errno = 0;
        ord = strtol(hexbuf, &endptr, 16);
        if (*endptr != '\0' || errno != 0)
                return (ERANGE);
        *out = (char)ord;
        return (0);
}

static bool
hexdigit(char c)
{
        int lc;

        lc = tolower(c);
        return isdigit(lc) || (lc >= 'a' && lc <= 'f');
}

static bool
dohex(const char *in, char *out, int *len)
{
        int tmplen;

        if (!hexdigit(in[0]))
                return (false);
        tmplen = 1;
        if (hexdigit(in[1]))
                ++tmplen;
        if (hex2char(in, out, tmplen) == 0) {
                *len = tmplen;
                return (true);
        }

        return (false);
}

/*
 * Get a delimited string.  P points to the delimiter of the string; d points
 * to a buffer area.  Newline and delimiter escapes are processed; other
 * escapes are ignored.
 *
 * Returns a pointer to the first character after the final delimiter or NULL
 * in the case of a non-terminated string.  The character array d is filled
 * with the processed string.
 */
static char *
compile_delimited(char *p, char *d, int is_tr)
{
        int hexlen;
        char c;

        c = *p++;
        if (c == '\0')
                return (NULL);
        else if (c == '\\')
                errx(1, "%lu: %s: \\ can not be used as a string delimiter",
                                linenum, fname);
        else if (c == '\n')
                errx(1, "%lu: %s: newline can not be used as a string delimiter",
                                linenum, fname);
        while (*p) {
                if (*p == '[' && *p != c) {
                        if (!is_tr) {
                                if ((d = compile_ccl(&p, d)) == NULL) {
                                        errx(1,
                                            "%lu: %s: unbalanced brackets ([])",
                                            linenum, fname);
                                }
                                continue;
                        }
                } else if (*p == '\\' && p[1] == '[') {
                        if (is_tr)
                                p++;
                        else
                                *d++ = *p++;
                } else if (*p == '\\' && p[1] == c) {
                        p++;
                } else if (*p == '\\' &&
                    (p[1] == 'n' || p[1] == 'r' || p[1] == 't')) {
                        switch (p[1]) {
                        case 'n':
                                *d++ = '\n';
                                break;
                        case 'r':
                                *d++ = '\r';
                                break;
                        case 't':
                                *d++ = '\t';
                                break;
                        }
                        p += 2;
                        continue;
                } else if (*p == '\\' && p[1] == 'x') {
                        if (dohex(&p[2], d, &hexlen)) {
                                ++d;
                                p += hexlen + 2;
                                continue;
                        }
                } else if (*p == '\\' && p[1] == '\\') {
                        if (is_tr)
                                p++;
                        else
                                *d++ = *p++;
                } else if (*p == c) {
                        *d = '\0';
                        return (p + 1);
                }
                *d++ = *p++;
        }
        return (NULL);
}


/* compile_ccl: expand a POSIX character class */
static char *
compile_ccl(char **sp, char *t)
{
        int c, d, hexlen;
        char *s = *sp;

        *t++ = *s++;
        if (*s == '^')
                *t++ = *s++;
        if (*s == ']')
                *t++ = *s++;
        for (; *s && (*t = *s) != ']'; s++, t++) {
                if (*s == '[' && ((d = *(s+1)) == '.' || d == ':' || d == '=')) {
                        *++t = *++s, t++, s++;
                        for (c = *s; (*t = *s) != ']' || c != d; s++, t++)
                                if ((c = *s) == '\0')
                                        return NULL;
                } else if (*s == '\\') {
                        switch (s[1]) {
                        case 'n':
                                *t = '\n';
                                s++;
                                break;
                        case 'r':
                                *t = '\r';
                                s++;
                                break;
                        case 't':
                                *t = '\t';
                                s++;
                                break;
                        case 'x':
                                if (dohex(&s[2], t, &hexlen))
                                        s += hexlen + 1;
                                break;
                        }
                }
        }
        return (*s == ']') ? *sp = ++s, ++t : NULL;
}

/*
 * Compiles the regular expression in RE and returns a pointer to the compiled
 * regular expression.
 * Cflags are passed to regcomp.
 */
static regex_t *
compile_re(char *re, int case_insensitive)
{
        regex_t *rep;
        int eval, flags;


        flags = rflags;
        if (case_insensitive)
                flags |= REG_ICASE;
        if ((rep = malloc(sizeof(regex_t))) == NULL)
                err(1, "malloc");
        if ((eval = regcomp(rep, re, flags)) != 0)
                errx(1, "%lu: %s: RE error: %s",
                                linenum, fname, strregerror(eval, rep));
        if (maxnsub < rep->re_nsub)
                maxnsub = rep->re_nsub;
        return (rep);
}

/*
 * Compile the substitution string of a regular expression and set res to
 * point to a saved copy of it.  Nsub is the number of parenthesized regular
 * expressions.
 */
static char *
compile_subst(char *p, struct s_subst *s)
{
        static char lbuf[_POSIX2_LINE_MAX + 1];
        int asize, hexlen, size;
        u_char ref;
        char c, *text, *op, *sp;
        int more = 1, sawesc = 0;

        c = *p++;                       /* Terminator character */
        if (c == '\0')
                return (NULL);

        s->maxbref = 0;
        s->linenum = linenum;
        asize = 2 * _POSIX2_LINE_MAX + 1;
        if ((text = malloc(asize)) == NULL)
                err(1, "malloc");
        size = 0;
        do {
                op = sp = text + size;
                for (; *p; p++) {
                        if (*p == '\\' || sawesc) {
                                /*
                                 * If this is a continuation from the last
                                 * buffer, we won't have a character to
                                 * skip over.
                                 */
                                if (sawesc)
                                        sawesc = 0;
                                else
                                        p++;

                                if (*p == '\0') {
                                        /*
                                         * This escaped character is continued
                                         * in the next part of the line.  Note
                                         * this fact, then cause the loop to
                                         * exit w/ normal EOL case and reenter
                                         * above with the new buffer.
                                         */
                                        sawesc = 1;
                                        p--;
                                        continue;
                                } else if (strchr("123456789", *p) != NULL) {
                                        *sp++ = '\\';
                                        ref = *p - '0';
                                        if (s->re != NULL &&
                                            ref > s->re->re_nsub)
                                                errx(1, "%lu: %s: \\%c not defined in the RE",
                                                                linenum, fname, *p);
                                        if (s->maxbref < ref)
                                                s->maxbref = ref;
                                } else {
                                        switch (*p) {
                                        case '&':
                                        case '\\':
                                                *sp++ = '\\';
                                                break;
                                        case 'n':
                                                *p = '\n';
                                                break;
                                        case 'r':
                                                *p = '\r';
                                                break;
                                        case 't':
                                                *p = '\t';
                                                break;
                                        case 'x':
#define ADVANCE_N(s, n)                                 \
        do {                                            \
                char *adv = (s);                        \
                while (*(adv + (n) - 1) != '\0') {      \
                        *adv = *(adv + (n));            \
                        ++adv;                          \
                }                                       \
                *adv = '\0';                            \
        } while (0);
                                                if (dohex(&p[1], p, &hexlen)) {
                                                        ADVANCE_N(p + 1,
                                                            hexlen);
                                                }
                                                break;
                                        }
                                }
                        } else if (*p == c) {
                                if (*++p == '\0' && more) {
                                        if (cu_fgets(lbuf, sizeof(lbuf), &more))
                                                p = lbuf;
                                }
                                *sp++ = '\0';
                                size += sp - op;
                                if ((s->new = realloc(text, size)) == NULL)
                                        err(1, "realloc");
                                return (p);
                        } else if (*p == '\n') {
                                errx(1,
"%lu: %s: unescaped newline inside substitute pattern", linenum, fname);
                                /* NOTREACHED */
                        }
                        *sp++ = *p;
                }
                size += sp - op;
                if (asize - size < _POSIX2_LINE_MAX + 1) {
                        asize *= 2;
                        if ((text = realloc(text, asize)) == NULL)
                                err(1, "realloc");
                }
        } while (cu_fgets(p = lbuf, sizeof(lbuf), &more) != NULL);
        errx(1, "%lu: %s: unterminated substitute in regular expression",
                        linenum, fname);
        /* NOTREACHED */
}

/*
 * Compile the flags of the s command
 */
static char *
compile_flags(char *p, struct s_subst *s)
{
        int gn;                 /* True if we have seen g or n */
        unsigned long nval;
        char wfile[_POSIX2_LINE_MAX + 1], *q, *eq;

        s->n = 1;                               /* Default */
        s->p = 0;
        s->wfile = NULL;
        s->wfd = -1;
        s->icase = 0;
        for (gn = 0;;) {
                EATSPACE();                     /* EXTENSION */
                switch (*p) {
                case 'g':
                        if (gn)
                                errx(1,
"%lu: %s: more than one number or 'g' in substitute flags", linenum, fname);
                        gn = 1;
                        s->n = 0;
                        break;
                case '\0':
                case '\n':
                case ';':
                        return (p);
                case 'p':
                        s->p = 1;
                        break;
                case 'i':
                case 'I':
                        s->icase = 1;
                        break;
                case '1': case '2': case '3':
                case '4': case '5': case '6':
                case '7': case '8': case '9':
                        if (gn)
                                errx(1,
"%lu: %s: more than one number or 'g' in substitute flags", linenum, fname);
                        gn = 1;
                        errno = 0;
                        nval = strtol(p, &p, 10);
                        if (errno == ERANGE || nval > INT_MAX)
                                errx(1,
"%lu: %s: overflow in the 'N' substitute flag", linenum, fname);
                        s->n = nval;
                        p--;
                        break;
                case 'w':
                        p++;
#ifdef HISTORIC_PRACTICE
                        if (*p != ' ') {
                                warnx("%lu: %s: space missing before w wfile", linenum, fname);
                                return (p);
                        }
#endif
                        EATSPACE();
                        q = wfile;
                        eq = wfile + sizeof(wfile) - 1;
                        while (*p) {
                                if (*p == '\n')
                                        break;
                                if (q >= eq)
                                        err(1, "wfile too long");
                                *q++ = *p++;
                        }
                        *q = '\0';
                        if (q == wfile)
                                errx(1, "%lu: %s: no wfile specified", linenum, fname);
                        s->wfile = strdup(wfile);
                        if (!aflag && (s->wfd = open(wfile,
                            O_WRONLY|O_APPEND|O_CREAT|O_TRUNC,
                            DEFFILEMODE)) == -1)
                                err(1, "%s", wfile);
                        return (p);
                default:
                        errx(1, "%lu: %s: bad flag in substitute command: '%c'",
                                        linenum, fname, *p);
                        break;
                }
                p++;
        }
}

/*
 * Compile a translation set of strings into a lookup table.
 */
static char *
compile_tr(char *p, struct s_tr **py)
{
        struct s_tr *y;
        int i;
        const char *op, *np;
        char old[_POSIX2_LINE_MAX + 1];
        char new[_POSIX2_LINE_MAX + 1];
        size_t oclen, oldlen, nclen, newlen;
        mbstate_t mbs1, mbs2;

        if ((*py = y = malloc(sizeof(*y))) == NULL)
                err(1, NULL);
        y->multis = NULL;
        y->nmultis = 0;

        if (*p == '\0' || *p == '\\')
                errx(1,
        "%lu: %s: transform pattern can not be delimited by newline or backslash",
                        linenum, fname);
        p = compile_delimited(p, old, 1);
        if (p == NULL)
                errx(1, "%lu: %s: unterminated transform source string",
                                linenum, fname);
        p = compile_delimited(p - 1, new, 1);
        if (p == NULL)
                errx(1, "%lu: %s: unterminated transform target string",
                                linenum, fname);
        EATSPACE();
        op = old;
        oldlen = mbsrtowcs(NULL, &op, 0, NULL);
        if (oldlen == (size_t)-1)
                err(1, NULL);
        np = new;
        newlen = mbsrtowcs(NULL, &np, 0, NULL);
        if (newlen == (size_t)-1)
                err(1, NULL);
        if (newlen != oldlen)
                errx(1, "%lu: %s: transform strings are not the same length",
                                linenum, fname);
        if (MB_CUR_MAX == 1) {
                /*
                 * The single-byte encoding case is easy: generate a
                 * lookup table.
                 */
                for (i = 0; i <= UCHAR_MAX; i++)
                        y->bytetab[i] = (char)i;
                for (; *op; op++, np++)
                        y->bytetab[(u_char)*op] = *np;
        } else {
                /*
                 * Multi-byte encoding case: generate a lookup table as
                 * above, but only for single-byte characters. The first
                 * bytes of multi-byte characters have their lookup table
                 * entries set to 0, which causes do_tr() to search through
                 * an auxiliary vector of multi-byte mappings.
                 */
                memset(&mbs1, 0, sizeof(mbs1));
                memset(&mbs2, 0, sizeof(mbs2));
                for (i = 0; i <= UCHAR_MAX; i++)
                        y->bytetab[i] = (btowc(i) != WEOF) ? i : 0;
                while (*op != '\0') {
                        oclen = mbrlen(op, MB_LEN_MAX, &mbs1);
                        if (oclen == (size_t)-1 || oclen == (size_t)-2)
                                errc(1, EILSEQ, NULL);
                        nclen = mbrlen(np, MB_LEN_MAX, &mbs2);
                        if (nclen == (size_t)-1 || nclen == (size_t)-2)
                                errc(1, EILSEQ, NULL);
                        if (oclen == 1 && nclen == 1)
                                y->bytetab[(u_char)*op] = *np;
                        else {
                                y->bytetab[(u_char)*op] = 0;
                                y->multis = realloc(y->multis,
                                    (y->nmultis + 1) * sizeof(*y->multis));
                                if (y->multis == NULL)
                                        err(1, NULL);
                                i = y->nmultis++;
                                y->multis[i].fromlen = oclen;
                                memcpy(y->multis[i].from, op, oclen);
                                y->multis[i].tolen = nclen;
                                memcpy(y->multis[i].to, np, nclen);
                        }
                        op += oclen;
                        np += nclen;
                }
        }
        return (p);
}

/*
 * Compile the text following an a, c, or i command.
 */
static char *
compile_text(void)
{
        int asize, esc_nl, size;
        char *text, *p, *op, *s;
        char lbuf[_POSIX2_LINE_MAX + 1];

        asize = 2 * _POSIX2_LINE_MAX + 1;
        if ((text = malloc(asize)) == NULL)
                err(1, "malloc");
        size = 0;
        while (cu_fgets(lbuf, sizeof(lbuf), NULL) != NULL) {
                op = s = text + size;
                p = lbuf;
#ifdef LEGACY_BSDSED_COMPAT
                EATSPACE();
#endif
                for (esc_nl = 0; *p != '\0'; p++) {
                        if (*p == '\\' && p[1] != '\0' && *++p == '\n')
                                esc_nl = 1;
                        *s++ = *p;
                }
                size += s - op;
                if (!esc_nl) {
                        *s = '\0';
                        break;
                }
                if (asize - size < _POSIX2_LINE_MAX + 1) {
                        asize *= 2;
                        if ((text = realloc(text, asize)) == NULL)
                                err(1, "realloc");
                }
        }
        text[size] = '\0';
        if ((p = realloc(text, size + 1)) == NULL)
                err(1, "realloc");
        return (p);
}

/*
 * Get an address and return a pointer to the first character after
 * it.  Fill the structure pointed to according to the address.
 */
static char *
compile_addr(char *p, struct s_addr *a)
{
        char *end, re[_POSIX2_LINE_MAX + 1];
        int icase;

        icase = 0;

        a->type = 0;
        switch (*p) {
        case '\\':                              /* Context address */
                ++p;
                /* FALLTHROUGH */
        case '/':                               /* Context address */
                p = compile_delimited(p, re, 0);
                if (p == NULL)
                        errx(1, "%lu: %s: unterminated regular expression", linenum, fname);
                /* Check for case insensitive regexp flag */
                if (*p == 'I') {
                        icase = 1;
                        p++;
                }
                if (*re == '\0')
                        a->u.r = NULL;
                else
                        a->u.r = compile_re(re, icase);
                a->type = AT_RE;
                return (p);

        case '$':                               /* Last line */
                a->type = AT_LAST;
                return (p + 1);

        case '+':                               /* Relative line number */
                a->type = AT_RELLINE;
                p++;
                /* FALLTHROUGH */
                                                /* Line number */
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
                if (a->type == 0)
                        a->type = AT_LINE;
                a->u.l = strtol(p, &end, 10);
                return (end);
        default:
                errx(1, "%lu: %s: expected context address", linenum, fname);
                return (NULL);
        }
}

/*
 * duptoeol --
 *      Return a copy of all the characters up to \n or \0.
 */
static char *
duptoeol(char *s, const char *ctype)
{
        size_t len;
        int ws;
        char *p, *start;

        ws = 0;
        for (start = s; *s != '\0' && *s != '\n'; ++s)
                ws = isspace((unsigned char)*s);
        *s = '\0';
        if (ws)
                warnx("%lu: %s: whitespace after %s", linenum, fname, ctype);
        len = s - start + 1;
        if ((p = malloc(len)) == NULL)
                err(1, "malloc");
        return (memmove(p, start, len));
}

/*
 * Convert goto label names to addresses, and count a and r commands, in
 * the given subset of the script.  Free the memory used by labels in b
 * and t commands (but not by :).
 *
 * TODO: Remove } nodes
 */
static void
fixuplabel(struct s_command *cp, struct s_command *end)
{

        for (; cp != end; cp = cp->next)
                switch (cp->code) {
                case 'a':
                case 'r':
                        appendnum++;
                        break;
                case 'b':
                case 't':
                        /* Resolve branch target. */
                        if (cp->t == NULL) {
                                cp->u.c = NULL;
                                break;
                        }
                        if ((cp->u.c = findlabel(cp->t)) == NULL)
                                errx(1, "%lu: %s: undefined label '%s'", linenum, fname, cp->t);
                        free(cp->t);
                        break;
                case '{':
                        /* Do interior commands. */
                        fixuplabel(cp->u.c, cp->next);
                        break;
                }
}

/*
 * Associate the given command label for later lookup.
 */
static void
enterlabel(struct s_command *cp)
{
        struct labhash **lhp, *lh;
        u_char *p;
        u_int h, c;

        for (h = 0, p = (u_char *)cp->t; (c = *p) != 0; p++)
                h = (h << 5) + h + c;
        lhp = &labels[h & LHMASK];
        for (lh = *lhp; lh != NULL; lh = lh->lh_next)
                if (lh->lh_hash == h && strcmp(cp->t, lh->lh_cmd->t) == 0)
                        errx(1, "%lu: %s: duplicate label '%s'", linenum, fname, cp->t);
        if ((lh = malloc(sizeof *lh)) == NULL)
                err(1, "malloc");
        lh->lh_next = *lhp;
        lh->lh_hash = h;
        lh->lh_cmd = cp;
        lh->lh_ref = 0;
        *lhp = lh;
}

/*
 * Find the label contained in the command l in the command linked
 * list cp.  L is excluded from the search.  Return NULL if not found.
 */
static struct s_command *
findlabel(char *name)
{
        struct labhash *lh;
        u_char *p;
        u_int h, c;

        for (h = 0, p = (u_char *)name; (c = *p) != 0; p++)
                h = (h << 5) + h + c;
        for (lh = labels[h & LHMASK]; lh != NULL; lh = lh->lh_next) {
                if (lh->lh_hash == h && strcmp(name, lh->lh_cmd->t) == 0) {
                        lh->lh_ref = 1;
                        return (lh->lh_cmd);
                }
        }
        return (NULL);
}

/*
 * Warn about any unused labels.  As a side effect, release the label hash
 * table space.
 */
static void
uselabel(void)
{
        struct labhash *lh, *next;
        int i;

        for (i = 0; i < LHSZ; i++) {
                for (lh = labels[i]; lh != NULL; lh = next) {
                        next = lh->lh_next;
                        if (!lh->lh_ref)
                                warnx("%lu: %s: unused label '%s'",
                                    linenum, fname, lh->lh_cmd->t);
                        free(lh);
                }
        }
}