/*

 * Copyright (c) Christos Zoulas 2017.

 * 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 immediately at the beginning of the file, without modification,

 *    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 "file.h"

#ifndef lint

FILE_RCSID("@(#)$File: buffer.c,v 1.14 2025/05/28 19:22:22 christos Exp $")

#endif  /* lint */

#include "magic.h"

#include <unistd.h>

#include <string.h>

#include <stdlib.h>

#include <sys/stat.h>

void

buffer_init(struct buffer *b, int fd, const struct stat *st, const void *data,

    size_t len)

{

  b->fd = fd;

  if (st)

    memcpy(&b->st, st, sizeof(b->st));

  else if (b->fd == -1 || fstat(b->fd, &b->st) == -1)

    memset(&b->st, 0, sizeof(b->st));

  b->fbuf = data;

  b->flen = len;

  b->eoff = 0;

  b->ebuf = NULL;

  b->elen = 0;

}

void

buffer_fini(struct buffer *b)

{

  free(b->ebuf);

  b->ebuf = NULL;

  b->elen = 0;

}

int

buffer_fill(const struct buffer *bb)

{

  struct buffer *b = CCAST(struct buffer *, bb);

  if (b->elen != 0)

    return b->elen == FILE_BADSIZE ? -1 : 0;

  // Nothing to refill, everything is in memory

  if (b->fd == -1)

    return 0;

  if (!S_ISREG(b->st.st_mode))

    goto out;

  b->elen = CAST(size_t, b->st.st_size) < b->flen ?

      CAST(size_t, b->st.st_size) : b->flen;

  if (b->elen == 0) {

    free(b->ebuf);

    b->ebuf = NULL;

    return 0;

  }

  if ((b->ebuf = malloc(b->elen)) == NULL)

    goto out;

  b->eoff = b->st.st_size - b->elen;

  if (pread(b->fd, b->ebuf, b->elen, b->eoff) == -1) {

    free(b->ebuf);

    b->ebuf = NULL;

    goto out;

  }

  return 0;

out:

  b->elen = FILE_BADSIZE;

  return -1;

}