/*      $NetBSD: str.c,v 1.30 2018/05/26 11:20:30 leot Exp $    */

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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>
#ifndef lint
#if 0
static char sccsid[] = "@(#)str.c       8.2 (Berkeley) 4/28/95";
#endif
__RCSID("$NetBSD: str.c,v 1.30 2018/05/26 11:20:30 leot Exp $");
#endif /* not lint */

#include <sys/types.h>

#include <err.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <assert.h>

#include "extern.h"

struct str {
        enum { STRING1, STRING2 } which;
        enum { EOS, INFINITE, NORMAL, RANGE, SEQUENCE, SET } state;
        int cnt;                        /* character count */
        int lastch;                     /* last character */
        int equiv[2];                   /* equivalence set */
        int *set;                       /* set of characters */
        const char *str;                /* user's string */
};

static int backslash(STR *);
static int bracket(STR *);
static int c_class(const void *, const void *);
static int *genclass(const char *, size_t);
static void genequiv(STR *);
static int genrange(STR *);
static void genseq(STR *);

STR *
str_create(int whichstring, const char *txt)
{
        STR *s;

        s = malloc(sizeof(*s));
        if (s == NULL) {
                err(1, "Out of memory");
        }

        s->which = whichstring == 2 ? STRING2 : STRING1;
        s->state = NORMAL;
        s->cnt = 0;
        s->lastch = OOBCH;
        s->equiv[0] = 0;
        s->equiv[1] = OOBCH;
        s->set = NULL;
        s->str = txt;

        return s;
}

void
str_destroy(STR *s)
{
        if (s->set != NULL && s->set != s->equiv) {
                free(s->set);
        }
        free(s);
}

int
next(STR *s, int *ret)
{
        int ch;

        switch (s->state) {
        case EOS:
                *ret = s->lastch;
                return 0;
        case INFINITE:
                *ret = s->lastch;
                return 1;
        case NORMAL:
                ch = (unsigned char)s->str[0];
                switch (ch) {
                case '\0':
                        s->state = EOS;
                        *ret = s->lastch;
                        return 0;
                case '\\':
                        s->lastch = backslash(s);
                        break;
                case '[':
                        if (bracket(s)) {
                                return next(s, ret);
                        }
                        /* FALLTHROUGH */
                default:
                        ++s->str;
                        s->lastch = ch;
                        break;
                }

                /* We can start a range at any time. */
                if (s->str[0] == '-' && genrange(s)) {
                        return next(s, ret);
                }
                *ret = s->lastch;
                return 1;
        case RANGE:
                if (s->cnt == 0) {
                        s->state = NORMAL;
                        return next(s, ret);
                }
                s->cnt--;
                ++s->lastch;
                *ret = s->lastch;
                return 1;
        case SEQUENCE:
                if (s->cnt == 0) {
                        s->state = NORMAL;
                        return next(s, ret);
                }
                s->cnt--;
                *ret = s->lastch;
                return 1;
        case SET:
                s->lastch = s->set[s->cnt++];
                if (s->lastch == OOBCH) {
                        s->state = NORMAL;
                        if (s->set != s->equiv) {
                                free(s->set);
                        }
                        s->set = NULL;
                        return next(s, ret);
                }
                *ret = s->lastch;
                return 1;
        }
        /* NOTREACHED */
        assert(0);
        *ret = s->lastch;
        return 0;
}

static int
bracket(STR *s)
{
        const char *p;
        int *q;

        switch (s->str[1]) {
        case ':':                               /* "[:class:]" */
                if ((p = strstr(s->str + 2, ":]")) == NULL)
                        return 0;
                s->str += 2;
                q = genclass(s->str, p - s->str);
                s->state = SET;
                s->set = q;
                s->cnt = 0;
                s->str = p + 2;
                return 1;
        case '=':                               /* "[=equiv=]" */
                if ((p = strstr(s->str + 2, "=]")) == NULL)
                        return 0;
                s->str += 2;
                genequiv(s);
                s->str = p + 2;
                return 1;
        default:                                /* "[\###*n]" or "[#*n]" */
                if ((p = strpbrk(s->str + 2, "*]")) == NULL)
                        return 0;
                if (p[0] != '*' || strchr(p, ']') == NULL)
                        return 0;
                s->str += 1;
                genseq(s);
                return 1;
        }
        /* NOTREACHED */
}

typedef struct {
        const char *name;
        int (*func)(int);
} CLASS;

static const CLASS classes[] = {
        { "alnum",  isalnum  },
        { "alpha",  isalpha  },
        { "blank",  isblank  },
        { "cntrl",  iscntrl  },
        { "digit",  isdigit  },
        { "graph",  isgraph  },
        { "lower",  islower  },
        { "print",  isprint  },
        { "punct",  ispunct  },
        { "space",  isspace  },
        { "upper",  isupper  },
        { "xdigit", isxdigit },
};

typedef struct {
        const char *name;
        size_t len;
} CLASSKEY;

static int *
genclass(const char *class, size_t len)
{
        int ch;
        const CLASS *cp;
        CLASSKEY key;
        int *p;
        unsigned pos, num;

        /* Find the class */
        key.name = class;
        key.len = len;
        cp = bsearch(&key, classes, __arraycount(classes), sizeof(classes[0]),
                     c_class);
        if (cp == NULL) {
                errx(1, "unknown class %.*s", (int)len, class);
        }

        /*
         * Figure out what characters are in the class
         */

        num = NCHARS + 1;
        p = malloc(num * sizeof(*p));
        if (p == NULL) {
                err(1, "malloc");
        }

        pos = 0;
        for (ch = 0; ch < NCHARS; ch++) {
                if (cp->func(ch)) {
                        p[pos++] = ch;
                }
        }

        p[pos++] = OOBCH;
        for (; pos < num; pos++) {
                p[pos] = 0;
        }

        return p;
}

static int
c_class(const void *av, const void *bv)
{
        const CLASSKEY *a = av;
        const CLASS *b = bv;
        size_t blen;
        int r;

        blen = strlen(b->name);
        r = strncmp(a->name, b->name, a->len);
        if (r != 0) {
                return r;
        }
        if (a->len < blen) {
                /* someone gave us a prefix of the right name */
                return -1;
        }
        assert(a-> len == blen);
        return 0;
}

/*
 * English doesn't have any equivalence classes, so for now
 * we just syntax check and grab the character.
 */
static void
genequiv(STR *s)
{
        int ch;

        ch = (unsigned char)s->str[0];
        if (ch == '\\') {
                s->equiv[0] = backslash(s);
        } else {
                s->equiv[0] = ch;
                s->str++;
        }
        if (s->str[0] != '=') {
                errx(1, "Misplaced equivalence equals sign");
        }
        s->str++;
        if (s->str[0] != ']') {
                errx(1, "Misplaced equivalence right bracket");
        }
        s->str++;

        s->cnt = 0;
        s->state = SET;
        s->set = s->equiv;
}

static int
genrange(STR *s)
{
        int stopval;
        const char *savestart;

        savestart = s->str++;
        stopval = s->str[0] == '\\' ? backslash(s) : (unsigned char)*s->str++;
        if (stopval < (unsigned char)s->lastch) {
                s->str = savestart;
                return 0;
        }
        s->cnt = stopval - s->lastch + 1;
        s->state = RANGE;
        --s->lastch;
        return 1;
}

static void
genseq(STR *s)
{
        char *ep;

        if (s->which == STRING1) {
                errx(1, "Sequences only valid in string2");
        }

        if (*s->str == '\\') {
                s->lastch = backslash(s);
        } else {
                s->lastch = (unsigned char)*s->str++;
        }
        if (*s->str != '*') {
                errx(1, "Misplaced sequence asterisk");
        }

        s->str++;
        switch (s->str[0]) {
        case '\\':
                s->cnt = backslash(s);
                break;
        case ']':
                s->cnt = 0;
                ++s->str;
                break;
        default:
                if (isdigit((unsigned char)s->str[0])) {
                        s->cnt = strtol(s->str, &ep, 0);
                        if (*ep == ']') {
                                s->str = ep + 1;
                                break;
                        }
                }
                errx(1, "illegal sequence count");
                /* NOTREACHED */
        }

        s->state = s->cnt ? SEQUENCE : INFINITE;
}

/*
 * Translate \??? into a character.  Up to 3 octal digits, if no digits either
 * an escape code or a literal character.
 */
static int
backslash(STR *s)
{
        int ch, cnt, val;

        cnt = val = 0;
        for (;;) {
                /* Consume the character we're already on. */
                s->str++;

                /* Look at the next character. */
                ch = (unsigned char)s->str[0];
                if (!isascii(ch) || !isdigit(ch)) {
                        break;
                }
                val = val * 8 + ch - '0';
                if (++cnt == 3) {
                        /* Enough digits; consume this one and stop */
                        ++s->str;
                        break;
                }
        }
        if (cnt) {
                /* We saw digits, so return their value */
                if (val >= OOBCH)
                        errx(1, "Invalid octal character value");
                return val;
        }
        if (ch == '\0') {
                /* \<end> -> \ */
                s->state = EOS;
                return '\\';
        }

        /* Consume the escaped character */
        s->str++;

        switch (ch) {
        case 'a':                       /* escape characters */
                return '\7';
        case 'b':
                return '\b';
        case 'e':
                return '\033';
        case 'f':
                return '\f';
        case 'n':
                return '\n';
        case 'r':
                return '\r';
        case 't':
                return '\t';
        case 'v':
                return '\13';
        default:                        /* \q -> q */
                return ch;
        }
}