2 ==================================================================================
3 Copyright (c) 2019 Nokia
4 Copyright (c) 2018-2019 AT&T Intellectual Property.
6 Licensed under the Apache License, Version 2.0 (the "License");
7 you may not use this file except in compliance with the License.
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10 http://www.apache.org/licenses/LICENSE-2.0
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13 distributed under the License is distributed on an "AS IS" BASIS,
14 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 See the License for the specific language governing permissions and
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17 ==================================================================================
20 Mnemonic rmr_alloc_msg.xfm
21 Abstract The manual page for the rmr_alloc_msg function.
22 Author E. Scott Daniels
26 .** if formatting with tfm, the roff.im will cause roff output to be generated
27 .** if formatting with pfm, then pretty postscript will be generated
30 .im &{lib}/generic_ps.im
32 .gv e OUTPUT_RST use_rst
42 &h1(RMR Library Functions)
51 rmr_mbuf_t* rmr_alloc_msg( void* a, int size );
56 The &cw(rmr_alloc_msg) function is used to allocate a buffer which the user
57 programme can write into and then send through the RMR library.
58 The buffer is allocated such that sending it requires no additional copying
60 If the value passed in &cw(size) is 0, then the default size supplied on the
61 &ital(rmr_init) call will be used.
62 The &ital(a) parameter is the void context pointer that was returned by
63 the &ital(rmr_init) function.
66 The pointer to the message buffer returned is a structure which has some
67 user application visible fields; the structure is described in &cw(rmr.h,)
68 and is illustrated below.
76 unsigned char* payload;
82 &beg_dlist(.75i : ^&bold_font )
83 &ditem(state ) Is the current buffer state. Following a call to &cw(rmr_send_msg)
84 the state indicates whether the buffer was successfully sent which determines
85 exactly what the payload points to. If the send failed, the payload referenced
86 by the buffer is the message that failed to send (allowing the application to
87 attempt a retransmission).
88 When the state is &cw(RMR_OK) the buffer represents an empty buffer that the application
89 may fill in in preparation to send.
92 &ditem(mtype ) When sending a message, the application is expected to set this field
93 to the appropriate message type value (as determined by the user programme). Upon send
94 this value determines how the RMR library will route the message.
95 For a buffer which has been received, this field will contain the message type that was
96 set by the sending application.
99 &ditem(len ) The application using a buffer to send a message is expected to set the
100 length value to the actual number of bytes that it placed into the message. This
101 is likely less than the total number of bytes that the message can carry.
102 For a message buffer that is passed to the application as the result of a receive
103 call, this will be the value that the sending application supplied and should
104 indicate the number of bytes in the payload which are valid.
107 &ditem(payload ) The payload is a pointer to the actual received data. The
108 user programme may read and write from/to the memory referenced by the payload
109 up until the point in time that the buffer is used on a &cw(rmr_send, rmr_call)
110 or &cw(rmr_reply) function call.
111 Once the buffer has been passed back to a RMR library function the user programme
112 should &bold(NOT) make use of the payload pointer.
116 &ditem(a ) The &ital(a) field is a pointer to a fixed sized area in
117 the message into which the user may write a transaction ID.
118 The ID is optional with the exception of when the user application uses the &cw(rmr_call)
119 function to send a message and wait for the reply; the underlying RMR processing
120 expects that the matching reply message will also contain the same data in the
125 The function returns a pointer to a &cw(rmr_mbuf) structure, or NULL on error.
128 &beg_dlist(.75i : ^&bold_font )
129 &di(ENOMEM) Unable to allocate memory.