source: rtems/cpukit/libcsupport/src/writev.c @ 98b785e

4.115
Last change on this file since 98b785e was 18daff9, checked in by Ralf Corsepius <ralf.corsepius@…>, on 11/29/09 at 13:35:32

Whitespace removal.

  • Property mode set to 100644
File size: 3.0 KB
Line 
1/*
2 *  writev() - POSIX 1003.1 - Read a Vector
3 *
4 *  OpenGroup URL:
5 *
6 *  http://www.opengroup.org/onlinepubs/009695399/functions/writev.html
7 *
8 *  COPYRIGHT (c) 1989-2007.
9 *  On-Line Applications Research Corporation (OAR).
10 *
11 *  The license and distribution terms for this file may be
12 *  found in the file LICENSE in this distribution or at
13 *  http://www.rtems.com/license/LICENSE.
14 *
15 *  $Id$
16 */
17
18#if HAVE_CONFIG_H
19#include "config.h"
20#endif
21
22#include <sys/types.h>
23#include <sys/uio.h>
24
25#include <rtems/libio_.h>
26#include <rtems/seterr.h>
27
28ssize_t writev(
29  int                 fd,
30  const struct iovec *iov,
31  int                 iovcnt
32)
33{
34  ssize_t        total;
35  int            v;
36  int            bytes;
37  rtems_libio_t *iop;
38  ssize_t        old;
39  bool           all_zeros;
40
41  rtems_libio_check_fd( fd );
42  iop = rtems_libio_iop( fd );
43  rtems_libio_check_is_open( iop );
44  rtems_libio_check_permissions( iop, LIBIO_FLAGS_WRITE );
45
46  /*
47   *  Argument validation on IO vector
48   */
49  if ( !iov )
50    rtems_set_errno_and_return_minus_one( EINVAL );
51
52  if ( iovcnt <= 0 )
53    rtems_set_errno_and_return_minus_one( EINVAL );
54
55  if ( iovcnt > IOV_MAX )
56    rtems_set_errno_and_return_minus_one( EINVAL );
57
58  if ( !iop->handlers->write_h )
59    rtems_set_errno_and_return_minus_one( ENOTSUP );
60
61  /*
62   *  OpenGroup says that you are supposed to return EINVAL if the
63   *  sum of the iov_len values in the iov array would overflow a
64   *  ssize_t.
65   *
66   *  Also we would like to ensure that no IO is performed if there
67   *  are obvious errors in the iovec.  So this extra loop ensures
68   *  that we do not do anything if there is an argument error.
69   *
70   *  In addition,the OpenGroup specification says that if all the
71   *  iov_len entries are zero, then the call has no effect.  So
72   *  this loop does that check as well and sets "all-zero" appropriately.
73   *  The variable "all_zero" is used as an early exit point before
74   *  entering the write loop.
75   */
76  all_zeros = true;
77  for ( old=0, total=0, v=0 ; v < iovcnt ; v++ ) {
78
79    if ( !iov[v].iov_base )
80      rtems_set_errno_and_return_minus_one( EINVAL );
81
82    if ( iov[v].iov_len < 0 )
83      rtems_set_errno_and_return_minus_one( EINVAL );
84
85    if ( iov[v].iov_len )
86      all_zeros = false;
87
88    /* check for wrap */
89    old    = total;
90    total += iov[v].iov_len;
91    if ( total < old || total > SSIZE_MAX )
92      rtems_set_errno_and_return_minus_one( EINVAL );
93  }
94
95  /*
96   * A writev with all zeros is supposed to have no effect per OpenGroup.
97   */
98  if ( all_zeros == true ) {
99    return 0;
100  }
101
102  /*
103   *  Now process the writev().
104   */
105  for ( total=0, v=0 ; v < iovcnt ; v++ ) {
106    /* all zero lengths has no effect */
107    if ( iov[v].iov_len == 0 )
108      continue;
109
110    bytes = (*iop->handlers->write_h)( iop, iov[v].iov_base, iov[v].iov_len );
111
112    if ( bytes < 0 )
113      return -1;
114
115    if ( bytes > 0 ) {
116      iop->offset += bytes;
117      total       += bytes;
118    }
119
120    if (bytes != iov[ v ].iov_len)
121      break;
122  }
123
124  return total;
125}
126
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