CIGI API Version 2.7.1 
CIGI API : Users' Guide
Using the API : IG Response Message Packets

IG Response Message Packets

The IG response message packet was introduced in CIGI version 2, and is used to notify the Host of a condition in the IG that may be of value to the user. IG response messages are only sent from the IG to the host when the ig_mode field in the IG control packet is set to IG_CONTROL_IG_MODE_DEBUG.

Message Size

This packet contains a message of variable length and its size is limited by the value of CIGI_MAX_PACKET_SIZE, declared in the cigi_icd.h header file. The entire size of the packet must not exceed the value indicated by CIGI_MAX_PACKET_SIZE. Thus, the length of the actual message is lmited to this value minus the size of the other fields in the packet, defined as CIGI_IG_RESPONSE_MESSAGE_BASE_SIZE.

Max message size = CIGI_MAX_PACKET_SIZE - CIGI_IG_RESPONSE_MESSAGE_BASE_SIZE

The total message size is determined by the number of characters (1 byte each) in the message, including a terminating NULL character. This maximum message size is defined as IG_RESPONSE_MAX_MESSAGE_LEN.

Setting the Message String

The message string contained in the IG response message packet should be set through the API, in order to ensure that the packet_size is set correctly and to check the message size. The following API function is used for this purpose. 

/* Sets the message field in a CIGI_IG_RESPONSE_MESSAGE packet */

int CigiSetIGResponseString( 
    CIGI_IG_RESPONSE_MESSAGE *igResponse, 
    const char *message
);

Sending the Message

The IG response message is added to the outgoing message buffer and sent like any other ougoing message, using the following function. 

/* Adds a CIGI_IG_RESPONSE_MESSAGE packet to the 
 * outgoing message buffer */

int CigiAddPacketIGResponseMessage( 
    const int sessionid, 
    const CIGI_IG_RESPONSE_MESSAGE* packet
);

Although the CIGI_IG_RESPONSE_MESSAGE structure definition contains a buffer to hold a message of size up to the value of IG_RESPONSE_MAX_MESSAGE_LEN, only the bytes that actually contain part of the message string are sent when the outgoing message is sent.

Note: The size of the packet sent will be padded if necessary, so that the total number of bytes sent (including the terminating NULL character) will end on a 32-bit word boundary. This is done to ensure that if any packets follow the IG response message will start on a word boundary in the outgoing message buffer.

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