/*	$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 <bsd/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 <assert.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.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;
  }
}
