refill.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 The 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 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include <stdio.h>
#include "local.h"
#include <stdlib.h>

static int
lflush (fp)
     FILE *fp;
{
  if ((fp->_flags & (__SLBF | __SWR)) == __SLBF | __SWR)
    return fflush (fp);
  return 0;
}

/*
 * Refill a stdio buffer.
 * Return EOF on eof or error, 0 otherwise.
 */

int
_DEFUN (__srefill, (fp),
	register FILE * fp)
{
  /* make sure stdio is set up */

  CHECK_INIT (fp);

  fp->_r = 0;			/* largely a convenience for callers */

  /* SysV does not make this test; take it out for compatibility */
  if (fp->_flags & __SEOF)
    return EOF;

  /* if not already reading, have to be reading and writing */
  if ((fp->_flags & __SRD) == 0)
    {
      if ((fp->_flags & __SRW) == 0)
	return EOF;
      /* switch to reading */
      if (fp->_flags & __SWR)
	{
	  if (fflush (fp))
	    return EOF;
	  fp->_flags &= ~__SWR;
	  fp->_w = 0;
	  fp->_lbfsize = 0;
	}
      fp->_flags |= __SRD;
    }
  else
    {
      /*
       * We were reading.  If there is an ungetc buffer,
       * we must have been reading from that.  Drop it,
       * restoring the previous buffer (if any).  If there
       * is anything in that buffer, return.
       */
      if (HASUB (fp))
	{
	  FREEUB (fp);
	  if ((fp->_r = fp->_ur) != 0)
	    {
	      fp->_p = fp->_up;
	      return 0;
	    }
	}
    }

  if (fp->_bf._base == NULL)
    __smakebuf (fp);

  /*
   * Before reading from a line buffered or unbuffered file,
   * flush all line buffered output files, per the ANSI C
   * standard.
   */

  if (fp->_flags & (__SLBF | __SNBF))
    (void) _fwalk (fp->_data, lflush);
  fp->_p = fp->_bf._base;
  fp->_r = (*fp->_read) (fp->_cookie, (char *) fp->_p, fp->_bf._size);
  fp->_flags &= ~__SMOD;	/* buffer contents are again pristine */
  if (fp->_r <= 0)
    {
      if (fp->_r == 0)
	fp->_flags |= __SEOF;
      else
	{
	  fp->_r = 0;
	  fp->_flags |= __SERR;
	}
      return EOF;
    }
  return 0;
}