MsgInfo(), MsgInfo_r()

Get additional information about a message

Synopsis:

#include <sys/neutrino.h>

int MsgInfo( int rcvid,
             struct _msg_info* info );

int MsgInfo_r( int rcvid,
               struct _msg_info* info );

Library:

libc

Description:

The MsgInfo() and MsgInfo_r() functions are identical except in the way they indicate errors. See the Returns section for details.

These kernel calls store additional information on a received message into info. The rcvid argument is the return value from MsgReceive*().

The parameters returned in the info have at least the following members:

Member	Description
`uint32_t` nd	The node descriptor of the client machine as viewed by the server.
`uint32_t` srcnd	The node descriptor of the server as viewed by the client.
`pid_t` pid	The process ID of the sending thread.
`int32_t` tid	The thread ID of the sending thread.
`int32_t` chid	The channel ID the message was received on.
`int32_t` scoid	The server connection ID.
`int32_t` coid	The client connection ID.
`int32_t` msglen	The number of bytes received.
`int32_t` srcmsglen	The length of the source message, in bytes, as sent by MsgSend(). This may be greater than the value in msglen. This member is only valid if _NTO_CHF_SENDER_LEN was set in the flags* argument to ChannelCreate() for the channel that transmitted the message.
`int16_t` priority	The priority of the sending thread.
`int16_t` flags	The client has an unblock pending _NTO_MI_UNBLOCK_REQ (i.e. a timeout on the send occurred or a signal was delivered and _NTO_CHF_UNBLOCK is set on the channel).

The info->msglen and info->srcmsglen members are valid only until the next MsgRead*() / MsgWrite*() call!

If msglen is less than srcmsglen, and also less than the receive buffer size, it's a network transaction that requires more reading of data with MsgRead*().

Blocking states

This call doesn't block.

Node descriptor

The node descriptor datatype is a magic cookie.

To:	Use this function:
Compare two nd objects	ND_NODE_CMP()
Convert a nd to text	netmgr_ndtostr()
Convert text to a nd	netmgr_strtond()

Returns:

The only difference between these functions is the way they indicate errors:

MsgInfo(): If an error occurs, -1 is returned and errno is set. Any other value returned indicates success.
MsgInfo_r(): EOK is returned on success. This function does NOT set errno. If an error occurs, any value in the Errors section may be returned.

Errors:

EFAULT: A fault occurred when the kernel tried to access the buffers provided.
ESRCH: The thread indicated by rcvid doesn't exist.

Classification:

QNX 6

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes