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-rw-r--r--libs/nanopb/examples/using_union_messages/encode.c85
1 files changed, 85 insertions, 0 deletions
diff --git a/libs/nanopb/examples/using_union_messages/encode.c b/libs/nanopb/examples/using_union_messages/encode.c
new file mode 100644
index 00000000..e124bf91
--- /dev/null
+++ b/libs/nanopb/examples/using_union_messages/encode.c
@@ -0,0 +1,85 @@
+/* This program takes a command line argument and encodes a message in
+ * one of MsgType1, MsgType2 or MsgType3.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <pb_encode.h>
+#include "unionproto.pb.h"
+
+/* This function is the core of the union encoding process. It handles
+ * the top-level pb_field_t array manually, in order to encode a correct
+ * field tag before the message. The pointer to MsgType_fields array is
+ * used as an unique identifier for the message type.
+ */
+bool encode_unionmessage(pb_ostream_t *stream, const pb_field_t messagetype[], const void *message)
+{
+ const pb_field_t *field;
+ for (field = UnionMessage_fields; field->tag != 0; field++)
+ {
+ if (field->ptr == messagetype)
+ {
+ /* This is our field, encode the message using it. */
+ if (!pb_encode_tag_for_field(stream, field))
+ return false;
+
+ return pb_encode_submessage(stream, messagetype, message);
+ }
+ }
+
+ /* Didn't find the field for messagetype */
+ return false;
+}
+
+int main(int argc, char **argv)
+{
+ if (argc != 2)
+ {
+ fprintf(stderr, "Usage: %s (1|2|3)\n", argv[0]);
+ return 1;
+ }
+
+ uint8_t buffer[512];
+ pb_ostream_t stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
+
+ bool status = false;
+ int msgtype = atoi(argv[1]);
+ if (msgtype == 1)
+ {
+ /* Send message of type 1 */
+ MsgType1 msg = {42};
+ status = encode_unionmessage(&stream, MsgType1_fields, &msg);
+ }
+ else if (msgtype == 2)
+ {
+ /* Send message of type 2 */
+ MsgType2 msg = {true};
+ status = encode_unionmessage(&stream, MsgType2_fields, &msg);
+ }
+ else if (msgtype == 3)
+ {
+ /* Send message of type 3 */
+ MsgType3 msg = {3, 1415};
+ status = encode_unionmessage(&stream, MsgType3_fields, &msg);
+ }
+ else
+ {
+ fprintf(stderr, "Unknown message type: %d\n", msgtype);
+ return 2;
+ }
+
+ if (!status)
+ {
+ fprintf(stderr, "Encoding failed!\n");
+ return 3;
+ }
+ else
+ {
+ fwrite(buffer, 1, stream.bytes_written, stdout);
+ return 0; /* Success */
+ }
+}
+
+