usr/src/cmd/sendmail/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 #pragma ident   "%Z%%M% %I%     %E% SMI"
  16
  17 #include <sm/gen.h>
  18 SM_RCSID("@(#)$Id: fread.c,v 1.26 2001/02/28 20:54:03 ca Exp $")
  19 #include <string.h>
  20 #include <errno.h>
  21 #include <sm/io.h>
  22 #include <sm/assert.h>
  23 #include "local.h"
  24
  25 /*
  26 **  SM_IO_READ -- read data from the file pointer
  27 **
  28 **      Parameters:
  29 **              fp -- file pointer to read from
  30 **              timeout -- time to complete the read
  31 **              buf -- location to place read data
  32 **              size -- size of each chunk of data
  33 **
  34 **      Returns:
  35 **              Failure: returns 0 (zero) _and_ sets errno
  36 **              Success: returns the number of whole chunks read.
  37 **
  38 **      A read returning 0 (zero) is only an indication of error when errno
  39 **      has been set.
  40 */
  41
  42 size_t
  43 sm_io_read(fp, timeout, buf, size)
  44         SM_FILE_T *fp;
  45         int timeout;
  46         void *buf;
  47         size_t size;
  48 {
  49         register size_t resid = size;
  50         register char *p;
  51         register int r;
  52
  53         SM_REQUIRE_ISA(fp, SmFileMagic);
  54
  55         if (fp->f_read == NULL)
  56         {
  57                 errno = ENODEV;
  58                 return 0;
  59         }
  60
  61         /*
  62         **  The ANSI standard requires a return value of 0 for a count
  63         **  or a size of 0.  Peculiarily, it imposes no such requirements
  64         **  on fwrite; it only requires read to be broken.
  65         */
  66
  67         if (resid == 0)
  68                 return 0;
  69         if (fp->f_r < 0)
  70                 fp->f_r = 0;
  71         p = buf;
  72         while ((int) resid > (r = fp->f_r))
  73         {
  74                 (void) memcpy((void *) p, (void *) fp->f_p, (size_t) r);
  75                 fp->f_p += r;
  76                 /* fp->f_r = 0 ... done in sm_refill */
  77                 p += r;
  78                 resid -= r;
  79                 if ((fp->f_flags & SMNOW) != 0 && r > 0)
  80                 {
  81                         /*
  82                         **  Take whatever we have available. Spend no more time
  83                         **  trying to get all that has been requested.
  84                         **  This is needed on some file types (such as
  85                         **  SASL) that would jam when given extra, untimely
  86                         **  reads.
  87                         */
  88
  89                         fp->f_r -= r;
  90                         return size - resid;
  91                 }
  92                 if (sm_refill(fp, timeout) != 0)
  93                 {
  94                         /* no more input: return partial result */
  95                         return size - resid;
  96                 }
  97         }
  98         (void) memcpy((void *) p, (void *) fp->f_p, resid);
  99         fp->f_r -= resid;
 100         fp->f_p += resid;
 101         return size;
 102 }