/*      $NetBSD: pread.c,v 1.8 2019/09/13 02:19:46 manu Exp $    */

/*
* Copyright (c) 1996
*      Matthias Drochner.  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 ``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 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.
*
*/

/* read into destination in flat addr space */

#include <lib/libsa/stand.h>

#include "libi386.h"

#ifdef SAVE_MEMORY
#define BUFSIZE (1*1024)
#else
#define BUFSIZE (4*1024)
#endif

static char     *buf;

ssize_t
pread(int fd, void *dest, size_t size)
{
       size_t             rsize;

       if (!buf)
               buf = alloc(BUFSIZE);

       rsize = size;
       while (rsize > 0) {
               size_t count;
               ssize_t got;

               count = (rsize < BUFSIZE ? rsize : BUFSIZE);

               got = read(fd, buf, count);
               if (got < 0)
                       return -1;

               /* put to physical space */
               vpbcopy(buf, dest, got);

               dest += got;
               rsize -= got;
               if (got < count)
                       break;  /* EOF */
       }
       return size - rsize;
}