// SPDX-License-Identifier: GPL-2.0
#include <linux/unistd.h>
#include <linux/bpf.h>

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>

#include <bpf/bpf.h>
#include "bpf_util.h"

#define MAX_INDEX 64
#define MAX_STARS 38

static void stars(char *str, long val, long max, int width)
{
        int i;

        for (i = 0; i < (width * val / max) - 1 && i < width - 1; i++)
                str[i] = '*';
        if (val > max)
                str[i - 1] = '+';
        str[i] = '\0';
}

int main(int argc, char **argv)
{
        unsigned int nr_cpus = bpf_num_possible_cpus();
        const char *map_filename = "/sys/fs/bpf/tc/globals/lwt_len_hist_map";
        uint64_t values[nr_cpus], sum, max_value = 0, data[MAX_INDEX] = {};
        uint64_t key = 0, next_key, max_key = 0;
        char starstr[MAX_STARS];
        int i, map_fd;

        map_fd = bpf_obj_get(map_filename);
        if (map_fd < 0) {
                fprintf(stderr, "bpf_obj_get(%s): %s(%d)\n",
                        map_filename, strerror(errno), errno);
                return -1;
        }

        while (bpf_map_get_next_key(map_fd, &key, &next_key) == 0) {
                if (next_key >= MAX_INDEX) {
                        fprintf(stderr, "Key %lu out of bounds\n", next_key);
                        continue;
                }

                bpf_map_lookup_elem(map_fd, &next_key, values);

                sum = 0;
                for (i = 0; i < nr_cpus; i++)
                        sum += values[i];

                data[next_key] = sum;
                if (sum && next_key > max_key)
                        max_key = next_key;

                if (sum > max_value)
                        max_value = sum;

                key = next_key;
        }

        for (i = 1; i <= max_key + 1; i++) {
                stars(starstr, data[i - 1], max_value, MAX_STARS);
                printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
                       (1l << i) >> 1, (1l << i) - 1, data[i - 1],
                       MAX_STARS, starstr);
        }

        close(map_fd);

        return 0;
}