/*      $OpenBSD: regerror.c,v 1.15 2020/12/30 08:56:38 tb Exp $ */
/*-
 * Copyright (c) 1992, 1993, 1994 Henry Spencer.
 * Copyright (c) 1992, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Henry Spencer.
 *
 * 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.
 *
 *      @(#)regerror.c  8.4 (Berkeley) 3/20/94
 */

#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <stdlib.h>
#include <regex.h>

#include "utils.h"

static const char *regatoi(const regex_t *, char *, int);

static const struct rerr {
        int code;
        const char *name;
        const char *explain;
} rerrs[] = {
        { REG_NOMATCH,  "REG_NOMATCH",  "regexec() failed to match" },
        { REG_BADPAT,   "REG_BADPAT",   "invalid regular expression" },
        { REG_ECOLLATE, "REG_ECOLLATE", "invalid collating element" },
        { REG_ECTYPE,   "REG_ECTYPE",   "invalid character class" },
        { REG_EESCAPE,  "REG_EESCAPE",  "trailing backslash (\\)" },
        { REG_ESUBREG,  "REG_ESUBREG",  "invalid backreference number" },
        { REG_EBRACK,   "REG_EBRACK",   "brackets ([ ]) not balanced" },
        { REG_EPAREN,   "REG_EPAREN",   "parentheses not balanced" },
        { REG_EBRACE,   "REG_EBRACE",   "braces not balanced" },
        { REG_BADBR,    "REG_BADBR",    "invalid repetition count(s)" },
        { REG_ERANGE,   "REG_ERANGE",   "invalid character range" },
        { REG_ESPACE,   "REG_ESPACE",   "out of memory" },
        { REG_BADRPT,   "REG_BADRPT",   "repetition-operator operand invalid" },
        { REG_EMPTY,    "REG_EMPTY",    "empty (sub)expression" },
        { REG_ASSERT,   "REG_ASSERT",   "\"can't happen\" -- you found a bug" },
        { REG_INVARG,   "REG_INVARG",   "invalid argument to regex routine" },
        { 0,            "",             "*** unknown regexp error code ***" }
};

/*
 - regerror - the interface to error numbers
 = extern size_t regerror(int, const regex_t *, char *, size_t);
 */
size_t
regerror(int errcode, const regex_t *preg, char *errbuf, size_t errbuf_size)
{
        const struct rerr *r;
        size_t len;
        int target = errcode &~ REG_ITOA;
        const char *s;
        char convbuf[50];

        if (errcode == REG_ATOI)
                s = regatoi(preg, convbuf, sizeof convbuf);
        else {
                for (r = rerrs; r->code != 0; r++)
                        if (r->code == target)
                                break;
        
                if (errcode&REG_ITOA) {
                        if (r->code != 0) {
                                assert(strlen(r->name) < sizeof(convbuf));
                                (void) strlcpy(convbuf, r->name, sizeof convbuf);
                        } else
                                (void)snprintf(convbuf, sizeof convbuf,
                                    "REG_0x%x", target);
                        s = convbuf;
                } else
                        s = r->explain;
        }

        if (errbuf_size != 0)
                len = strlcpy(errbuf, s, errbuf_size);
        else
                len = strlen(s);

        return len + 1;
}

/*
 - regatoi - internal routine to implement REG_ATOI
 */
static const char *
regatoi(const regex_t *preg, char *localbuf, int localbufsize)
{
        const struct rerr *r;

        for (r = rerrs; r->code != 0; r++)
                if (strcmp(r->name, preg->re_endp) == 0)
                        break;
        if (r->code == 0)
                return("0");

        (void)snprintf(localbuf, localbufsize, "%d", r->code);
        return(localbuf);
}