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PR_Writev
=========
Writes data to a socket from multiple buffers.
Syntax
------
.. code::
#include <prio.h>
PRInt32 PR_Writev(
PRFileDesc *fd,
PRIOVec *iov,
PRInt32 size,
PRIntervalTime timeout);
#define PR_MAX_IOVECTOR_SIZE 16
Parameters
~~~~~~~~~~
The function has the following parameters:
``fd``
A pointer to a :ref:`PRFileDesc` object for a socket.
``iov``
An array of ``PRIOVec`` structures that describe the buffers to write
from.
``size``
Number of ``PRIOVec`` structures in the ``iov`` array. The value of
this parameter must not be greater than ``PR_MAX_IOVECTOR_SIZE``. If
it is, the function will fail and the error will be set to
``PR_BUFFER_OVERFLOW_ERROR``.
``timeout``
A value of type :ref:`PRIntervalTime` describing the time limit for
completion of the entire write operation.
Returns
~~~~~~~
One of the following values:
- A positive number indicates the number of bytes successfully written.
- The value -1 indicates that the operation failed. The reason for the
failure can be obtained by calling :ref:`PR_GetError`.
Description
-----------
The thread calling :ref:`PR_Writev` blocks until all the data is written or
the write operation fails. Therefore, the return value is equal to
either the sum of all the buffer lengths (on success) or -1 (on
failure). Note that if :ref:`PR_Writev` returns -1, part of the data may
have been written before an error occurred. If the timeout parameter is
not ``PR_INTERVAL_NO_TIMEOUT`` and all the data cannot be written in the
specified interval, :ref:`PR_Writev` returns -1 with the error code
``PR_IO_TIMEOUT_ERROR``.
This is the type definition for ``PRIOVec``:
.. code::
typedef struct PRIOVec {
char *iov_base;
int iov_len;
} PRIOVec;
The ``PRIOVec`` structure has the following fields:
``iov_base``
A pointer to the beginning of the buffer.
``iov_len``
The size of the buffer.