给我写一个kafka生产者代码，读取txt文件，以json格式发送到kafka集群

好的，以下是一个简单的Kafka生产者代码，用于读取txt文件并将其以JSON格式发送到Kafka集群：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <librdkafka/rdkafka.h>

#define MAX_LINE_LEN 1024

int main(int argc, char **argv) {
    if (argc != 4) {
        fprintf(stderr, "Usage: %s <broker> <topic> <filename>\n", argv[]);
        return 1;
    }

    char *broker = argv[1];
    char *topic = argv[2];
    char *filename = argv[3];

    rd_kafka_t *rk;
    rd_kafka_conf_t *conf;
    char errstr[512];

    conf = rd_kafka_conf_new();
    if (rd_kafka_conf_set(conf, "bootstrap.servers", broker, errstr, sizeof(errstr)) != RD_KAFKA_CONF_OK) {
        fprintf(stderr, "Failed to set broker: %s\n", errstr);
        return 1;
    }

    rk = rd_kafka_new(RD_KAFKA_PRODUCER, conf, errstr, sizeof(errstr));
    if (!rk) {
        fprintf(stderr, "Failed to create producer: %s\n", errstr);
        return 1;
    }

    FILE *fp = fopen(filename, "r");
    if (!fp) {
        fprintf(stderr, "Failed to open file: %s\n", filename);
        return 1;
    }

    char line[MAX_LINE_LEN];
    while (fgets(line, MAX_LINE_LEN, fp)) {
        char *json = "{\"message\": \"%s\"}";
        char *msg = malloc(strlen(json) + strlen(line) + 1);
        sprintf(msg, json, line);

        rd_kafka_produce(
            rk,
            RD_KAFKA_PARTITION_UA,
            RD_KAFKA_MSG_F_COPY,
            msg,
            strlen(msg),
            NULL,
            ,
            NULL
        );

        rd_kafka_poll(rk, );
        free(msg);
    }

    fclose(fp);
    rd_kafka_flush(rk, 10000);
    rd_kafka_destroy(rk);
    return ;
}

请注意，此代码仅用于演示目的，实际使用时需要进行适当的错误处理和参数验证。