In addition to the structures that define the connect and I/O functions, you pass a resmgr_attr_t structure to resmgr_attach() to specify the attributes of the resource manager.
The resmgr_attr_t structure is defined as follows:
typedef struct _resmgr_attr { unsigned flags; unsigned nparts_max; size_t msg_max_size; int (*other_func)(resmgr_context_t *, void *msg); unsigned reserved[4]; } resmgr_attr_t;
The members include:
If necessary, your resource manager can determine that a message came from a client of a different endian-ness by checking to see if the _NTO_MI_ENDIAN_DIFF bit is set in the flags member of the _msg_info structure that's included in the resmgr_context_t structure that's passed to the handler functions.
These members will be important when you start writing your own handler functions.
If you specify a value of zero for nparts_max, the resource manager library will bump the value to the minimum usable by the library itself. Why would you want to set the size of the IOV array? As we'll see in the Getting the resource manager library to do the reply section of the Handling Read and Write Messages chapter, you can tell the resource manager library to do our replying for us. We may want to give it an IOV array that points to N buffers containing the reply data. But, since we'll ask the library to do the reply for us, we need to use its IOV array, which of course would need to be big enough to point to our N buffers.
If the resource manager library gets an I/O message that it doesn't know how to handle, it'll call the routine specified by the other_func member, if non-NULL. (If it's NULL, the resource manager library will return an ENOSYS to the client, effectively stating that it doesn't know what this message means.)
You might specify a non-NULL value for other_func in the case where you've specified some form of custom messaging between clients and your resource manager, although the recommended approach for this is the devctl() function call (client) and the _IO_DEVCTL message handler (server) or a MsgSend*() function call (client) and the _IO_MSG message handler (server).
For non-I/O message types, you should use the message_attach() function, which attaches a message range for the dispatch handle. When a message with a type in that range is received, the dispatch_block() function calls a user-supplied function that's responsible for doing any specific work, such as replying to the client.