MsgReceivePulsev(), MsgReceivePulsev_r()

Receive a pulse on a channel

Synopsis:

#include <sys/neutrino.h>

int MsgReceivePulsev( int chid,
                      const iov_t * piov,
                      int parts,
                      struct _msg_info * info );

int MsgReceivePulsev_r( int chid,
                        const iov_t * piov,
                        int parts,
                        struct _msg_info * info );

Arguments:

chid

The ID of a channel that you established by calling ChannelCreate().

piov

An array of buffers where the function can store the received data.

parts

The number of elements in the array.

info

The function doesn't update this structure, so you typically pass NULL for this argument.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The MsgReceivePulsev() and MsgReceivePulsev_r() kernel calls wait for a pulse to arrive on the channel identified by chid and places the received data in the array of buffers pointed to by piov.

These functions are identical, except in the way they indicate errors; see the Returns section for details.

The number of bytes transferred is the minimum of that specified by both the sender and the receiver. The received data isn't allowed to overflow the receive buffer area provided.

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The first buffer of the IOV (input/output vector) must be big enough to contain a pulse. If it isn't, the functions indicate an error of EFAULT.

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If a pulse is waiting on the channel when you call MsgReceivePulsev(), the calling thread doesn't block, and the pulse is immediately copied. If a pulse isn't waiting, the calling thread enters the RECEIVE-blocked state until a pulse arrives.

If multiple pulses are sent to a channel without a thread waiting to receive them, the pulses are queued in priority order.

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The thread's effective priority might change when it receives a pulse. For more information, see “Priority inheritance and messages” in the Interprocess Communication (IPC) chapter of the System Architecture guide.

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On success, MsgReceivePulsev() and MsgReceivePulsev_r() return 0 to indicate that they received a pulse. When a pulse is received:

• the kernel space allocated to hold it is immediately released
• the IOV's first buffer contains a pulse message of type _pulse.

Blocking states

Returns:

The only difference between MsgReceivePulsev() and MsgReceivePulsev_r() is the way they indicate errors. On success, they both return 0.

If an error occurs:

• MsgReceivePulsev() returns -1 and sets errno.
• MsgReceivePulsev_r() returns the negative of a value from the Errors section. This function doesn't set errno.

Errors:

EFAULT

A fault occurred when the kernel tried to access the buffers provided. Because the OS accesses the sender's buffers only when MsgReceivePulsev() is called, a fault could occur in the sender if the sender's buffers are invalid. If a fault occurs when accessing the sender buffers (only) they'll receive an EFAULT and MsgReceivePulsev() won't unblock.

EINTR

The call was interrupted by a signal.

EOVERFLOW

The sum of the IOV lengths exceeds INT_MAX.

ESRCH

The channel indicated by chid doesn't exist.

ETIMEDOUT

A kernel timeout unblocked the call. See TimerTimeout().

Classification:

QNX Neutrino

See also:

MsgDeliverEvent(), MsgReceive(), MsgReceivePulse(), MsgReceivev(), MsgSendPulse(), _pulse, TimerTimeout()