1 /* This program reads a message from stdin, detects its type and decodes it.
2 */
3
4 #include <stdio.h>
5 #include <string.h>
6 #include <stdlib.h>
7
8 #include <pb_decode.h>
9 #include <pb_common.h>
10 #include "unionproto.pb.h"
11
12 /* This function reads manually the first tag from the stream and finds the
13 * corresponding message type. It doesn't yet decode the actual message.
14 *
15 * Returns a pointer to the MsgType_fields array, as an identifier for the
16 * message type. Returns null if the tag is of unknown type or an error occurs.
17 */
decode_unionmessage_type(pb_istream_t * stream)18 const pb_msgdesc_t* decode_unionmessage_type(pb_istream_t *stream)
19 {
20 pb_wire_type_t wire_type;
21 uint32_t tag;
22 bool eof;
23
24 while (pb_decode_tag(stream, &wire_type, &tag, &eof))
25 {
26 if (wire_type == PB_WT_STRING)
27 {
28 pb_field_iter_t iter;
29 if (pb_field_iter_begin(&iter, UnionMessage_fields, NULL) &&
30 pb_field_iter_find(&iter, tag))
31 {
32 /* Found our field. */
33 return iter.submsg_desc;
34 }
35 }
36
37 /* Wasn't our field.. */
38 pb_skip_field(stream, wire_type);
39 }
40
41 return NULL;
42 }
43
decode_unionmessage_contents(pb_istream_t * stream,const pb_msgdesc_t * messagetype,void * dest_struct)44 bool decode_unionmessage_contents(pb_istream_t *stream, const pb_msgdesc_t *messagetype, void *dest_struct)
45 {
46 pb_istream_t substream;
47 bool status;
48 if (!pb_make_string_substream(stream, &substream))
49 return false;
50
51 status = pb_decode(&substream, messagetype, dest_struct);
52 pb_close_string_substream(stream, &substream);
53 return status;
54 }
55
main()56 int main()
57 {
58 /* Read the data into buffer */
59 uint8_t buffer[512];
60 size_t count = fread(buffer, 1, sizeof(buffer), stdin);
61 pb_istream_t stream = pb_istream_from_buffer(buffer, count);
62
63 const pb_msgdesc_t *type = decode_unionmessage_type(&stream);
64 bool status = false;
65
66 if (type == MsgType1_fields)
67 {
68 MsgType1 msg = {};
69 status = decode_unionmessage_contents(&stream, MsgType1_fields, &msg);
70 printf("Got MsgType1: %d\n", msg.value);
71 }
72 else if (type == MsgType2_fields)
73 {
74 MsgType2 msg = {};
75 status = decode_unionmessage_contents(&stream, MsgType2_fields, &msg);
76 printf("Got MsgType2: %s\n", msg.value ? "true" : "false");
77 }
78 else if (type == MsgType3_fields)
79 {
80 MsgType3 msg = {};
81 status = decode_unionmessage_contents(&stream, MsgType3_fields, &msg);
82 printf("Got MsgType3: %d %d\n", msg.value1, msg.value2);
83 }
84
85 if (!status)
86 {
87 printf("Decode failed: %s\n", PB_GET_ERROR(&stream));
88 return 1;
89 }
90
91 return 0;
92 }
93
94
95
96
