/*      $NetBSD: open_memstream.c,v 1.2 2024/01/23 15:32:54 christos Exp $      */

/*-
 * Copyright (c) 2013 Advanced Computing Technologies LLC
 * Written by: John H. Baldwin <jhb@FreeBSD.org>
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 0
__FBSDID("$FreeBSD: head/lib/libc/stdio/open_memstream.c 247411 2013-02-27 19:50:46Z jhb $");
#endif
__RCSID("$NetBSD: open_memstream.c,v 1.2 2024/01/23 15:32:54 christos Exp $");

#include "namespace.h"
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>

#define OFF_MAX LLONG_MAX

struct memstream {
        char **bufp;
        size_t *sizep;
        size_t len;
        size_t offset;
};

static __inline size_t
off_t_to_size_t(off_t off)
{
        if (off < 0 || off >= SSIZE_MAX)
                return SSIZE_MAX - 1;
        return (size_t)off;
}

static int
memstream_grow(struct memstream *ms, off_t newoff)
{
        char *buf;
        size_t newsize;

        newsize = off_t_to_size_t(newoff);
        if (newsize > ms->len) {
                buf = realloc(*ms->bufp, newsize + 1);
                if (buf != NULL) {
#ifdef DEBUG
                        fprintf(stderr, "MS: %p growing from %zd to %zd\n",
                            ms, ms->len, newsize);
#endif
                        memset(buf + ms->len + 1, 0, newsize - ms->len);
                        *ms->bufp = buf;
                        ms->len = newsize;
                        return (1);
                }
                return (0);
        }
        return (1);
}

static void
memstream_update(struct memstream *ms)
{

        *ms->sizep = ms->len < ms->offset ? ms->len : ms->offset;
}

static ssize_t
memstream_write(void *cookie, const void *buf, size_t len)
{
        struct memstream *ms;
        size_t tocopy;
        off_t more;

        ms = cookie;
        more = ms->offset;
        more += len;
        if (!memstream_grow(ms, more))
                return (-1);
        tocopy = ms->len - ms->offset;
        if (len < tocopy)
                tocopy = len;
        memcpy(*ms->bufp + ms->offset, buf, tocopy);
        ms->offset += tocopy;
        memstream_update(ms);
#ifdef DEBUG
        fprintf(stderr, "MS: write(%p, %zu) = %zu\n", ms, len, tocopy);
#endif
        return (ssize_t)tocopy;
}

static off_t
memstream_seek(void *cookie, off_t pos, int whence)
{
        struct memstream *ms;
#ifdef DEBUG
        size_t old;
#endif

        ms = cookie;
#ifdef DEBUG
        old = ms->offset;
#endif
        switch (whence) {
        case SEEK_SET:
                /* _fseeko() checks for negative offsets. */
                assert(pos >= 0);
                ms->offset = off_t_to_size_t(pos);
                break;
        case SEEK_CUR:
                /* This is only called by _ftello(). */
                assert(pos == 0);
                break;
        case SEEK_END:
                if (pos < 0) {
                        if (pos + (ssize_t)ms->len < 0) {
#ifdef DEBUG
                                fprintf(stderr,
                                    "MS: bad SEEK_END: pos %jd, len %zu\n",
                                    (intmax_t)pos, ms->len);
#endif
                                errno = EINVAL;
                                return (-1);
                        }
                } else {
                        if (OFF_MAX - (ssize_t)ms->len < pos) {
#ifdef DEBUG
                                fprintf(stderr,
                                    "MS: bad SEEK_END: pos %jd, len %zu\n",
                                    (intmax_t)pos, ms->len);
#endif
                                errno = EOVERFLOW;
                                return (-1);
                        }
                }
                ms->offset = off_t_to_size_t(ms->len + pos);
                break;
        }
        memstream_update(ms);
#ifdef DEBUG
        fprintf(stderr, "MS: seek(%p, %jd, %d) %zu -> %zu\n", ms,
            (intmax_t)pos, whence, old, ms->offset);
#endif
        return (ms->offset);
}

static int
memstream_close(void *cookie)
{

        free(cookie);
        return (0);
}

FILE *
open_memstream(char **bufp, size_t *sizep)
{
        struct memstream *ms;
        int save_errno;
        FILE *fp;

        if (bufp == NULL || sizep == NULL) {
                errno = EINVAL;
                return (NULL);
        }
        *bufp = calloc(1, 1);
        if (*bufp == NULL)
                return (NULL);
        ms = malloc(sizeof(*ms));
        if (ms == NULL) {
                save_errno = errno;
                free(*bufp);
                *bufp = NULL;
                errno = save_errno;
                return (NULL);
        }
        ms->bufp = bufp;
        ms->sizep = sizep;
        ms->len = 0;
        ms->offset = 0;
        memstream_update(ms);
        fp = funopen2(ms, NULL, memstream_write, memstream_seek,
            NULL, memstream_close);
        if (fp == NULL) {
                save_errno = errno;
                free(ms);
                free(*bufp);
                *bufp = NULL;
                errno = save_errno;
                return (NULL);
        }
        fwide(fp, -1);
        return (fp);
}