flags.c

标准c库代码,可以应用于各个系统提供了大量的基本函数

/* No user fns here. Pesch 15apr92 */

/*
 * Copyright (c) 1990 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include <stdio.h>
#include <time.h>
#include <fcntl.h>

#include <errno.h>
#include <sys/types.h>

/*
 * Return the (stdio) flags for a given mode.  Store the flags
 * to be passed to an open() syscall through *optr.
 * Return 0 on error.
 */

int
__sflags (ptr, mode, optr)
     struct _reent *ptr;
     register char *mode;
     int *optr;
{
  register int ret, m, o;

  switch (mode[0])
    {
    case 'r':			/* open for reading */
      ret = __SRD;
      m = O_RDONLY;
      o = 0;
      break;

    case 'w':			/* open for writing */
      ret = __SWR;
      m = O_WRONLY;
      o = O_CREAT | O_TRUNC;
      break;

    case 'a':			/* open for appending */
      ret = __SWR | __SAPP;
      m = O_WRONLY;
      o = O_CREAT | O_APPEND;
      break;
    default:			/* illegal mode */
      ptr->_errno = EINVAL;
      return (0);
    }
  if (mode[1] == '+' || mode[2] == '+')
    {
      ret |= __SRW;
      m = O_RDWR;
    }
  if (mode[1] == 'b' || mode[2] == 'b')
    {
#ifdef O_BINARY
      m |= O_BINARY;
#endif
    }
  else
    {
#ifdef O_TEXT
      m |= O_TEXT;
#endif
    }

  *optr = m | o;
  return ret;
}