/* read for MMIXware.   Copyright (C) 2001 Hans-Peter Nilsson   Permission to use, copy, modify, and distribute this software is   freely granted, provided that the above copyright notice, this notice   and the following disclaimer are preserved with no changes.   THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR   IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR   PURPOSE.  */#include <_ansi.h>#include <sys/types.h>#include <sys/stat.h>#include "sys/syscall.h"#include <errno.h>int_read (int file,       char *ptr,       size_t len){  long ret;  if ((unsigned int) file >= 32 || _MMIX_allocated_filehandle[file] == 0)    {      errno = EBADF;      return -1;    }  if (isatty(file))    {      ret = TRAP3f (SYS_Fgets, file, ptr, len);      if (ret == -1)        return 0;      return ret;    }  ret = TRAP3f (SYS_Fread, file, ptr, len);  /* Map the return codes:     -1-len: an error.  We return -1.     0: success.  We return len.     n-len: end-of-file after n chars read.  We return n. */  if (ret == 0)    return len;  if (ret == -1 - (long) len)    {      /* We don't know the nature of the failure, so this is an	 approximation.  */      errno = EIO;      return -1;    }  return ret + len;}