/*      $NetBSD: regsub.c,v 1.4 2024/01/23 15:32:54 christos Exp $      */

/*-
 * Copyright (c) 2015 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Christos Zoulas.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: regsub.c,v 1.4 2024/01/23 15:32:54 christos Exp $");
#endif

#include <sys/param.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <regex.h>

struct str {
        char *s_ptr;
        size_t s_max;
        size_t s_len;
        int s_fixed;
};

#define REINCR  64

static int
addspace(struct str *s, size_t len)
{
        void *v;

        if (s->s_max - s->s_len > len)
                return 0;

        if (s->s_fixed)
                return -1;

        s->s_max += len + REINCR;

        v = realloc(s->s_ptr, s->s_max);
        if (v == NULL)
                return -1;
        s->s_ptr = v;

        return 0;
}

static void
addchar(struct str *s, int c)
{
        if (addspace(s, 1) == -1)
                s->s_len++;
        else
                s->s_ptr[s->s_len++] = c;
        if (c == 0) {
                --s->s_len;
                s->s_ptr[s->s_max - 1] = c;     
        }
}

static void
addnstr(struct str *s, const char *buf, size_t len)
{
        if (addspace(s, len) != -1)
                memcpy(s->s_ptr + s->s_len, buf, len);
        s->s_len += len;
}

static int
initstr(struct str *s, char *buf, size_t len)
{
        s->s_max = len;
        s->s_ptr = buf == NULL ? malloc(len) : buf;
        s->s_fixed = buf != NULL;
        s->s_len = 0;
        return s->s_ptr == NULL ? -1 : 0;
}

static ssize_t
regsub1(char **buf, size_t len, const char *sub,
    const regmatch_t *rm, const char *str)
{
        ssize_t i;
        char c; 
        struct str s;

        if (initstr(&s, *buf, len) == -1)
                return -1;

        while ((c = *sub++) != '\0') {

                switch (c) {
                case '&':
                        i = 0;
                        break;
                case '\\':
                        if (isdigit((unsigned char)*sub))
                                i = *sub++ - '0';
                        else
                                i = -1;
                        break;
                default:
                        i = -1;
                        break;
                }

                if (i == -1) {
                        if (c == '\\' && (*sub == '\\' || *sub == '&'))
                                c = *sub++;
                        addchar(&s, c);
                } else if (rm[i].rm_so != -1 && rm[i].rm_eo != -1) {
                        size_t l = (size_t)(rm[i].rm_eo - rm[i].rm_so);
                        addnstr(&s, str + (size_t)rm[i].rm_so, l);
                }
        }

        addchar(&s, '\0');
        if (!s.s_fixed) {
                if (s.s_len >= s.s_max) {
                        free(s.s_ptr);
                        return -1;
                }
                *buf = s.s_ptr;
        }
        return s.s_len;
}

ssize_t
regnsub(char *buf, size_t len, const char *sub, const regmatch_t *rm,
    const char *str)
{
        return regsub1(&buf, len, sub, rm, str);
}

ssize_t
regasub(char **buf, const char *sub, const regmatch_t *rm, const char *str)
{
        *buf = NULL;
        return regsub1(buf, REINCR, sub, rm, str);
}