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fread.c

/*
 * Copyright (c) 2000-2001 Sendmail, Inc. and its suppliers.
 *      All rights reserved.
 * Copyright (c) 1990, 1993
 *    The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the sendmail distribution.
 */

#include <sm/gen.h>
SM_RCSID("@(#)$Id: fread.c,v 1.28 2001/09/11 04:04:48 gshapiro Exp $")
#include <string.h>
#include <errno.h>
#include <sm/io.h>
#include <sm/assert.h>
#include "local.h"

/*
**  SM_IO_READ -- read data from the file pointer
**
**    Parameters:
**          fp -- file pointer to read from
**          timeout -- time to complete the read
**          buf -- location to place read data
**          size -- size of each chunk of data
**
**    Returns:
**          Failure: returns 0 (zero) _and_ sets errno
**          Success: returns the number of whole chunks read.
**
**    A read returning 0 (zero) is only an indication of error when errno
**    has been set.
*/

size_t
sm_io_read(fp, timeout, buf, size)
      SM_FILE_T *fp;
      int timeout;
      void *buf;
      size_t size;
{
      register size_t resid = size;
      register char *p;
      register int r;

      SM_REQUIRE_ISA(fp, SmFileMagic);

      if (fp->f_read == NULL)
      {
            errno = ENODEV;
            return 0;
      }

      /*
      **  The ANSI standard requires a return value of 0 for a count
      **  or a size of 0.  Peculiarily, it imposes no such requirements
      **  on fwrite; it only requires read to be broken.
      */

      if (resid == 0)
            return 0;
      if (fp->f_r < 0)
            fp->f_r = 0;
      p = buf;
      while ((int) resid > (r = fp->f_r))
      {
            (void) memcpy((void *) p, (void *) fp->f_p, (size_t) r);
            fp->f_p += r;
            /* fp->f_r = 0 ... done in sm_refill */
            p += r;
            resid -= r;
            if ((fp->f_flags & SMNOW) != 0 && r > 0)
            {
                  /*
                  **  Take whatever we have available. Spend no more time
                  **  trying to get all that has been requested.
                  **  This is needed on some file types (such as
                  **  SASL) that would jam when given extra, untimely
                  **  reads.
                  */

                  fp->f_r -= r;
                  return size - resid;
            }
            if (sm_refill(fp, timeout) != 0)
            {
                  /* no more input: return partial result */
                  return size - resid;
            }
      }
      (void) memcpy((void *) p, (void *) fp->f_p, resid);
      fp->f_r -= resid;
      fp->f_p += resid;
      return size;
}

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