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/*
* writev() - POSIX 1003.1 - Read a Vector
*
* OpenGroup URL:
*
* http://www.opengroup.org/onlinepubs/009695399/functions/writev.html
*
* COPYRIGHT (c) 1989-2011.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <sys/types.h>
#include <sys/uio.h>
#include <rtems/libio_.h>
#include <rtems/seterr.h>
ssize_t writev(
int fd,
const struct iovec *iov,
int iovcnt
)
{
ssize_t total;
int v;
int bytes;
rtems_libio_t *iop;
ssize_t old;
bool all_zeros;
rtems_libio_check_fd( fd );
iop = rtems_libio_iop( fd );
rtems_libio_check_is_open( iop );
rtems_libio_check_permissions_with_error( iop, LIBIO_FLAGS_WRITE, EBADF );
/*
* Argument validation on IO vector
*/
if ( !iov )
rtems_set_errno_and_return_minus_one( EINVAL );
if ( iovcnt <= 0 )
rtems_set_errno_and_return_minus_one( EINVAL );
if ( iovcnt > IOV_MAX )
rtems_set_errno_and_return_minus_one( EINVAL );
/*
* OpenGroup says that you are supposed to return EINVAL if the
* sum of the iov_len values in the iov array would overflow a
* ssize_t.
*
* Also we would like to ensure that no IO is performed if there
* are obvious errors in the iovec. So this extra loop ensures
* that we do not do anything if there is an argument error.
*
* In addition,the OpenGroup specification says that if all the
* iov_len entries are zero, then the call has no effect. So
* this loop does that check as well and sets "all-zero" appropriately.
* The variable "all_zero" is used as an early exit point before
* entering the write loop.
*/
all_zeros = true;
for ( old=0, total=0, v=0 ; v < iovcnt ; v++ ) {
/*
* iov[v].iov_len cannot be less than 0 because size_t is unsigned.
* So we only check for zero.
*/
if ( iov[v].iov_base == 0 )
rtems_set_errno_and_return_minus_one( EINVAL );
if ( iov[v].iov_len )
all_zeros = false;
/* check for wrap */
old = total;
total += iov[v].iov_len;
if ( total < old || total > SSIZE_MAX )
rtems_set_errno_and_return_minus_one( EINVAL );
}
/*
* A writev with all zeros is supposed to have no effect per OpenGroup.
*/
if ( all_zeros == true ) {
return 0;
}
/*
* Now process the writev().
*/
for ( total=0, v=0 ; v < iovcnt ; v++ ) {
/* all zero lengths has no effect */
if ( iov[v].iov_len == 0 )
continue;
bytes = (*iop->pathinfo.handlers->write_h)(
iop,
iov[v].iov_base,
iov[v].iov_len
);
if ( bytes < 0 )
return -1;
if ( bytes > 0 ) {
iop->offset += bytes;
total += bytes;
}
if (bytes != iov[ v ].iov_len)
break;
}
return total;
}
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