.if false
==================================================================================
- Copyright (c) 2019 Nokia
+ Copyright (c) 2019 Nokia
Copyright (c) 2018-2019 AT&T Intellectual Property.
Licensed under the Apache License, Version 2.0 (the "License");
&uindent
&h2(DESCRIPTION)
-The &cw(rmr_alloc_msg) function is used to allocate a buffer which the user
+The &cw(rmr_alloc_msg) function is used to allocate a buffer which the user
programme can write into and then send through the RMR library.
The buffer is allocated such that sending it requires no additional copying
-out of the buffer.
+out of the buffer.
If the value passed in &cw(size) is 0, then the default size supplied on the
-&ital(rmr_init) call will be used.
+&ital(rmr_init) call will be used.
The &ital(ctx) parameter is the void context pointer that was returned by
the &ital(rmr_init) function.
&space
-The pointer to the message buffer returned is a structure which has some
+The pointer to the message buffer returned is a structure which has some
user application visible fields; the structure is described in &cw(rmr.h,)
and is illustrated below.
int len;
unsigned char* payload;
unsigned char* xaction;
+ int sub_id;
+ int tp_state;
} rmr_mbuf_t;
&ex_end
&space
&beg_dlist(.75i : ^&bold_font )
-&ditem(state ) Is the current buffer state. Following a call to &cw(rmr_send_msg)
+&ditem(state) Is the current buffer state. Following a call to &cw(rmr_send_msg)
the state indicates whether the buffer was successfully sent which determines
exactly what the payload points to. If the send failed, the payload referenced
-by the buffer is the message that failed to send (allowing the application to
-attempt a retransmission).
+by the buffer is the message that failed to send (allowing the application to
+attempt a retransmission).
When the state is &cw(RMR_OK) the buffer represents an empty buffer that the application
may fill in in preparation to send.
&half_space
-&ditem(mtype ) When sending a message, the application is expected to set this field
+&ditem(mtype) When sending a message, the application is expected to set this field
to the appropriate message type value (as determined by the user programme). Upon send
this value determines how the RMR library will route the message.
For a buffer which has been received, this field will contain the message type that was
-set by the sending application.
+set by the sending application.
&half_space
-&ditem(len ) The application using a buffer to send a message is expected to set the
+&ditem(len) The application using a buffer to send a message is expected to set the
length value to the actual number of bytes that it placed into the message. This
is likely less than the total number of bytes that the message can carry.
For a message buffer that is passed to the application as the result of a receive
-call, this will be the value that the sending application supplied and should
+call, this will be the value that the sending application supplied and should
indicate the number of bytes in the payload which are valid.
&half_space
-&ditem(payload ) The payload is a pointer to the actual received data. The
+&ditem(payload) The payload is a pointer to the actual received data. The
user programme may read and write from/to the memory referenced by the payload
up until the point in time that the buffer is used on a &cw(rmr_send, rmr_call)
-or &cw(rmr_reply) function call.
+or &cw(rmr_reply) function call.
Once the buffer has been passed back to a RMR library function the user programme
should &bold(NOT) make use of the payload pointer.
&half_space
-&ditem(xaction) The &ital(xaction) field is a pointer to a fixed sized area in
-the message into which the user may write a transaction ID.
+&ditem(xaction) The &ital(xaction) field is a pointer to a fixed sized area in
+the message into which the user may write a transaction ID.
The ID is optional with the exception of when the user application uses the &cw(rmr_call)
function to send a message and wait for the reply; the underlying RMR processing
expects that the matching reply message will also contain the same data in the
&ital(xaction) field.
&end_dlist
+&half_space
+&ditem(sub_id)
+This value is the subscription ID. It, in combination with the message type is used
+by rmr to determine the target endpoint when sending a message.
+If the application to application protocol does not warrant the use of a subscription
+ID, the RMR constant RMR_VOID_SUBID should be placed in this field.
+When an application is forwarding or returning a buffer to the sender, it is the
+application's responsibility to set/reset this value.
+
+&half_space
+&ditem(tp_state)
+For C applications making use of RMR, the state of a transport based failure will
+often be available via &cw(errno.)
+However, some wrapper environments may not have direct access to the C-lib &cw(errno)
+value.
+RMR send and receive operations will place the current value of &cw(errno) into this
+field which should make it available to wrapper functions.
+User applications are strongly cautioned against relying on the value of errno as
+some transport mechanisms may not set this value on all calls.
+This value should also be ignored any time the message status is &cw(RMR_OK.)
+
&h2(RETURN VALUE)
The function returns a pointer to a &cw(rmr_mbuf) structure, or NULL on error.
Code Review / ric-plt / lib / rmr.git / blobdiff