contrib/sendmail-8.14/libsm/fread.c

   1 /*
   2  * Copyright (c) 2000-2001 Sendmail, Inc. and its suppliers.
   3  *      All rights reserved.
   4  * Copyright (c) 1990, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Chris Torek.
   9  *
  10  * By using this file, you agree to the terms and conditions set
  11  * forth in the LICENSE file which can be found at the top level of
  12  * the sendmail distribution.
  13  */
  14
  15 #include <sm/gen.h>
  16 SM_RCSID("@(#)$Id: fread.c,v 1.28 2001/09/11 04:04:48 gshapiro Exp $")
  17 #include <string.h>
  18 #include <errno.h>
  19 #include <sm/io.h>
  20 #include <sm/assert.h>
  21 #include "local.h"
  22
  23 /*
  24 **  SM_IO_READ -- read data from the file pointer
  25 **
  26 **      Parameters:
  27 **              fp -- file pointer to read from
  28 **              timeout -- time to complete the read
  29 **              buf -- location to place read data
  30 **              size -- size of each chunk of data
  31 **
  32 **      Returns:
  33 **              Failure: returns 0 (zero) _and_ sets errno
  34 **              Success: returns the number of whole chunks read.
  35 **
  36 **      A read returning 0 (zero) is only an indication of error when errno
  37 **      has been set.
  38 */
  39
  40 size_t
  41 sm_io_read(fp, timeout, buf, size)
  42         SM_FILE_T *fp;
  43         int timeout;
  44         void *buf;
  45         size_t size;
  46 {
  47         register size_t resid = size;
  48         register char *p;
  49         register int r;
  50
  51         SM_REQUIRE_ISA(fp, SmFileMagic);
  52
  53         if (fp->f_read == NULL)
  54         {
  55                 errno = ENODEV;
  56                 return 0;
  57         }
  58
  59         /*
  60         **  The ANSI standard requires a return value of 0 for a count
  61         **  or a size of 0.  Peculiarily, it imposes no such requirements
  62         **  on fwrite; it only requires read to be broken.
  63         */
  64
  65         if (resid == 0)
  66                 return 0;
  67         if (fp->f_r < 0)
  68                 fp->f_r = 0;
  69         p = buf;
  70         while ((int) resid > (r = fp->f_r))
  71         {
  72                 (void) memcpy((void *) p, (void *) fp->f_p, (size_t) r);
  73                 fp->f_p += r;
  74                 /* fp->f_r = 0 ... done in sm_refill */
  75                 p += r;
  76                 resid -= r;
  77                 if ((fp->f_flags & SMNOW) != 0 && r > 0)
  78                 {
  79                         /*
  80                         **  Take whatever we have available. Spend no more time
  81                         **  trying to get all that has been requested.
  82                         **  This is needed on some file types (such as
  83                         **  SASL) that would jam when given extra, untimely
  84                         **  reads.
  85                         */
  86
  87                         fp->f_r -= r;
  88                         return size - resid;
  89                 }
  90                 if (sm_refill(fp, timeout) != 0)
  91                 {
  92                         /* no more input: return partial result */
  93                         return size - resid;
  94                 }
  95         }
  96         (void) memcpy((void *) p, (void *) fp->f_p, resid);
  97         fp->f_r -= resid;
  98         fp->f_p += resid;
  99         return size;
 100 }