Pack repeated fields with Nanopb library

main.c

#include <pb_decode.h>
#include <pb_encode.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>

#include "Test.pb.h"

bool str_encode(pb_ostream_t *stream, const pb_field_t *field,
                void *const *arg) {
    const char *str = *arg;

    if (!pb_encode_tag_for_field(stream, field)) {
        return false;
    }

    return pb_encode_string(stream, (unsigned char *)str, strlen(str));
}

struct repeated {
    void **repeated_f;
    int index;
    size_t max_size;
};

bool req_encode(pb_ostream_t *stream, const pb_field_t *field,
                void *const *arg) {
    struct repeated *req = *arg;
    while (req->index < req->max_size) {
        SearchRequest *sreq = ((SearchRequest **)req->repeated_f)[req->index];
        printf("%s: Try to encode: %s\n", __func__, sreq->query.arg);
        ++req->index;

        if (!pb_encode_tag(stream, PB_WT_STRING, field->tag)) {
            return false;
        }

        if (!pb_encode_submessage(stream, SearchRequest_fields, sreq)) {
            return false;
        }
    }

    return true;
}

int main(void) {
    const char *str1 = "Hello";
    const char *str2 = "World";
    unsigned char buffer[128];
    size_t message_length;
    bool status;
    Result result_msg = Result_init_default;
    pb_ostream_t stream = pb_ostream_from_buffer(buffer, sizeof buffer);
    SearchRequest first = {
        .query = {.funcs = {.encode = str_encode}, .arg = str1}};
    SearchRequest second = {
        .query = {.funcs = {.encode = str_encode}, .arg = str2}};
    SearchRequest *requests[] = {&first, &second};
    struct repeated r1 = {.repeated_f = requests, .index = 0, .max_size = 2};

    result_msg.requests.funcs.encode = req_encode;
    result_msg.requests.arg = &r1;
    status = pb_encode(&stream, Result_fields, &result_msg);
    message_length = stream.bytes_written;

    if (!status) {
        printf("Encoding failed: %s\n", PB_GET_ERROR(&stream));
        return -1;
    }

    printf("Success: %zu written\n", message_length);
    for (size_t i = 0; i < message_length; ++i) {
        printf("%02hhx", buffer[i]);
    }
    puts("");

    return 0;
}

Test.proto

syntax = "proto3";

message SearchRequest {
  string query = 1;
}

message Result {
  repeated SearchRequest requests = 1;
}

@ssevans87 would you tell whether snippet above was helpful?

@vpetrigo Hello. I can tell, the snippet above was very helpful for me.
due to your example I was able to pack and unpack something more complex. Thanks!

Thanks a lot for the snippet!!! it was very helpful for me.