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      1 /* This program takes a command line argument and encodes a message in
      2  * one of MsgType1, MsgType2 or MsgType3.
      3  */
      4 
      5 #include <stdio.h>
      6 #include <string.h>
      7 #include <stdlib.h>
      8 
      9 #include <pb_encode.h>
     10 #include "unionproto.pb.h"
     11 
     12 /* This function is the core of the union encoding process. It handles
     13  * the top-level pb_field_t array manually, in order to encode a correct
     14  * field tag before the message. The pointer to MsgType_fields array is
     15  * used as an unique identifier for the message type.
     16  */
     17 bool encode_unionmessage(pb_ostream_t *stream, const pb_field_t messagetype[], const void *message)
     18 {
     19     const pb_field_t *field;
     20     for (field = UnionMessage_fields; field->tag != 0; field++)
     21     {
     22         if (field->ptr == messagetype)
     23         {
     24             /* This is our field, encode the message using it. */
     25             if (!pb_encode_tag_for_field(stream, field))
     26                 return false;
     27 
     28             return pb_encode_submessage(stream, messagetype, message);
     29         }
     30     }
     31 
     32     /* Didn't find the field for messagetype */
     33     return false;
     34 }
     35 
     36 int main(int argc, char **argv)
     37 {
     38     if (argc != 2)
     39     {
     40         fprintf(stderr, "Usage: %s (1|2|3)\n", argv[0]);
     41         return 1;
     42     }
     43 
     44     uint8_t buffer[512];
     45     pb_ostream_t stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
     46 
     47     bool status = false;
     48     int msgtype = atoi(argv[1]);
     49     if (msgtype == 1)
     50     {
     51         /* Send message of type 1 */
     52         MsgType1 msg = {42};
     53         status = encode_unionmessage(&stream, MsgType1_fields, &msg);
     54     }
     55     else if (msgtype == 2)
     56     {
     57         /* Send message of type 2 */
     58         MsgType2 msg = {true};
     59         status = encode_unionmessage(&stream, MsgType2_fields, &msg);
     60     }
     61     else if (msgtype == 3)
     62     {
     63         /* Send message of type 3 */
     64         MsgType3 msg = {3, 1415};
     65         status = encode_unionmessage(&stream, MsgType3_fields, &msg);
     66     }
     67     else
     68     {
     69         fprintf(stderr, "Unknown message type: %d\n", msgtype);
     70         return 2;
     71     }
     72 
     73     if (!status)
     74     {
     75         fprintf(stderr, "Encoding failed!\n");
     76         return 3;
     77     }
     78     else
     79     {
     80         fwrite(buffer, 1, stream.bytes_written, stdout);
     81         return 0; /* Success */
     82     }
     83 }
     84 
     85 
     86