E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 1 | .. This work is licensed under a Creative Commons Attribution 4.0 International License. |
| 2 | .. SPDX-License-Identifier: CC-BY-4.0 |
| 3 | .. CAUTION: this document is generated from source in doc/src/rtd. |
| 4 | .. To make changes edit the source and recompile the document. |
| 5 | .. Do NOT make changes directly to .rst or .md files. |
| 6 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 7 | ============================================================================================ |
| 8 | Man Page: rmr_alloc_msg |
| 9 | ============================================================================================ |
| 10 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 11 | |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 12 | |
| 13 | |
| 14 | RMR LIBRARY FUNCTIONS |
| 15 | ===================== |
| 16 | |
| 17 | |
| 18 | |
| 19 | NAME |
| 20 | ---- |
| 21 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 22 | rmr_alloc_msg |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 23 | |
| 24 | |
| 25 | SYNOPSIS |
| 26 | -------- |
| 27 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 28 | |
| 29 | :: |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 30 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 31 | #include <rmr/rmr.h> |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 32 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 33 | rmr_mbuf_t* rmr_alloc_msg( void* ctx, int size ); |
| 34 | |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 35 | |
| 36 | |
| 37 | DESCRIPTION |
| 38 | ----------- |
| 39 | |
| 40 | The ``rmr_alloc_msg`` function is used to allocate a buffer |
| 41 | which the user programme can write into and then send through |
| 42 | the RMR library. The buffer is allocated such that sending it |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 43 | requires no additional copying out of the buffer. If the |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 44 | value passed in ``size`` is less than or equal to 0, then the |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 45 | *normal maximum size* supplied on the *rmr_init* call will be |
| 46 | used. When *size* is greater than zero, the message allocated |
| 47 | will have at least the indicated number of bytes in the |
| 48 | payload. There is no maximum size imposed by RMR, however the |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 49 | underlying system memory management (e.g. malloc) functions |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 50 | may impose a limit. |
| 51 | |
| 52 | The *ctx* parameter is the void context pointer that was |
| 53 | returned by the *rmr_init* function. |
| 54 | |
| 55 | The pointer to the message buffer returned is a structure |
| 56 | which has some user application visible fields; the structure |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 57 | is described in ``rmr.h,`` and is illustrated below. |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 58 | |
| 59 | |
| 60 | :: |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 61 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 62 | typedef struct { |
| 63 | int state; |
| 64 | int mtype; |
| 65 | int len; |
| 66 | unsigned char* payload; |
| 67 | unsigned char* xaction; |
| 68 | int sub_id; |
| 69 | int tp_state; |
| 70 | } rmr_mbuf_t; |
| 71 | |
| 72 | |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 73 | Where: |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 74 | |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 75 | .. list-table:: |
| 76 | :widths: auto |
| 77 | :header-rows: 0 |
| 78 | :class: borderless |
| 79 | |
| 80 | * - **state** |
| 81 | - |
| 82 | Is the current buffer state. Following a call to |
| 83 | ``rmr_send_msg`` the state indicates whether the buffer was |
| 84 | successfully sent which determines exactly what the payload |
| 85 | points to. If the send failed, the payload referenced by the |
| 86 | buffer is the message that failed to send (allowing the |
| 87 | application to attempt a retransmission). When the state is |
| 88 | ``RMR_OK`` the buffer represents an empty buffer that the |
| 89 | application may fill in in preparation to send. |
| 90 | |
| 91 | * - **mtype** |
| 92 | - |
| 93 | When sending a message, the application is expected to set |
| 94 | this field to the appropriate message type value (as |
| 95 | determined by the user programme). Upon send this value |
| 96 | determines how the RMR library will route the message. For a |
| 97 | buffer which has been received, this field will contain the |
| 98 | message type that was set by the sending application. |
| 99 | |
| 100 | * - **len** |
| 101 | - |
| 102 | The application using a buffer to send a message is expected |
| 103 | to set the length value to the actual number of bytes that it |
| 104 | placed into the message. This is likely less than the total |
| 105 | number of bytes that the message can carry. For a message |
| 106 | buffer that is passed to the application as the result of a |
| 107 | receive call, this will be the value that the sending |
| 108 | application supplied and should indicate the number of bytes |
| 109 | in the payload which are valid. |
| 110 | |
| 111 | * - **payload** |
| 112 | - |
| 113 | The payload is a pointer to the actual received data. The |
| 114 | user programme may read and write from/to the memory |
| 115 | referenced by the payload up until the point in time that the |
| 116 | buffer is used on a ``rmr_send, rmr_call`` or |
| 117 | ``rmr_reply`` function call. Once the buffer has been passed |
| 118 | back to a RMR library function the user programme should |
| 119 | **NOT** make use of the payload pointer. |
| 120 | |
| 121 | * - **xaction** |
| 122 | - |
| 123 | The *xaction* field is a pointer to a fixed sized area in the |
| 124 | message into which the user may write a transaction ID. The |
| 125 | ID is optional with the exception of when the user |
| 126 | application uses the ``rmr_call`` function to send a message |
| 127 | and wait for the reply; the underlying RMR processing expects |
| 128 | that the matching reply message will also contain the same |
| 129 | data in the *xaction* field. |
| 130 | |
| 131 | * - **sub_id** |
| 132 | - |
| 133 | This value is the subscription ID. It, in combination with |
| 134 | the message type is used by rmr to determine the target |
| 135 | endpoint when sending a message. If the application to |
| 136 | application protocol does not warrant the use of a |
| 137 | subscription ID, the RMR constant RMR_VOID_SUBID should be |
| 138 | placed in this field. When an application is forwarding or |
| 139 | returning a buffer to the sender, it is the application's |
| 140 | responsibility to set/reset this value. |
| 141 | |
| 142 | * - **tp_state** |
| 143 | - |
| 144 | For C applications making use of RMR, the state of a |
| 145 | transport based failure will often be available via |
| 146 | ``errno.`` However, some wrapper environments may not have |
| 147 | direct access to the C-lib ``errno`` value. RMR send and |
| 148 | receive operations will place the current value of |
| 149 | ``errno`` into this field which should make it available to |
| 150 | wrapper functions. User applications are strongly cautioned |
| 151 | against relying on the value of errno as some transport |
| 152 | mechanisms may not set this value on all calls. This value |
| 153 | should also be ignored any time the message status is |
| 154 | ``RMR_OK.`` |
| 155 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 156 | |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 157 | |
| 158 | |
| 159 | RETURN VALUE |
| 160 | ------------ |
| 161 | |
| 162 | The function returns a pointer to a ``rmr_mbuf`` structure, |
| 163 | or NULL on error. |
| 164 | |
| 165 | |
| 166 | ERRORS |
| 167 | ------ |
| 168 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 169 | |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 170 | .. list-table:: |
| 171 | :widths: auto |
| 172 | :header-rows: 0 |
| 173 | :class: borderless |
| 174 | |
| 175 | * - **ENOMEM** |
| 176 | - |
| 177 | Unable to allocate memory. |
| 178 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 179 | |
E. Scott Daniels | a3a121c | 2020-05-06 09:07:08 -0400 | [diff] [blame^] | 180 | |
| 181 | |
| 182 | SEE ALSO |
| 183 | -------- |
| 184 | |
E. Scott Daniels | 117030c | 2020-04-10 17:17:02 -0400 | [diff] [blame] | 185 | rmr_tralloc_msg(3), rmr_call(3), rmr_free_msg(3), |
| 186 | rmr_init(3), rmr_init_trace(3), rmr_get_trace(3), |
| 187 | rmr_get_trlen(3), rmr_payload_size(3), rmr_send_msg(3), |
| 188 | rmr_rcv_msg(3), rmr_rcv_specific(3), rmr_rts_msg(3), |
| 189 | rmr_ready(3), rmr_fib(3), rmr_has_str(3), rmr_tokenise(3), |
| 190 | rmr_mk_ring(3), rmr_ring_free(3), rmr_set_trace(3) |