/*
 * User-space helper to sort the output of /sys/kernel/debug/page_owner
 *
 * Example use:
 * cat /sys/kernel/debug/page_owner > page_owner_full.txt
 * grep -v ^PFN page_owner_full.txt > page_owner.txt
 * ./sort page_owner.txt sorted_page_owner.txt
*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

struct block_list {
        char *txt;
        int len;
        int num;
};


static struct block_list *list;
static int list_size;
static int max_size;

struct block_list *block_head;

int read_block(char *buf, int buf_size, FILE *fin)
{
        char *curr = buf, *const buf_end = buf + buf_size;

        while (buf_end - curr > 1 && fgets(curr, buf_end - curr, fin)) {
                if (*curr == '\n') /* empty line */
                        return curr - buf;
                curr += strlen(curr);
        }

        return -1; /* EOF or no space left in buf. */
}

static int compare_txt(const void *p1, const void *p2)
{
        const struct block_list *l1 = p1, *l2 = p2;

        return strcmp(l1->txt, l2->txt);
}

static int compare_num(const void *p1, const void *p2)
{
        const struct block_list *l1 = p1, *l2 = p2;

        return l2->num - l1->num;
}

static void add_list(char *buf, int len)
{
        if (list_size != 0 &&
            len == list[list_size-1].len &&
            memcmp(buf, list[list_size-1].txt, len) == 0) {
                list[list_size-1].num++;
                return;
        }
        if (list_size == max_size) {
                printf("max_size too small??\n");
                exit(1);
        }
        list[list_size].txt = malloc(len+1);
        list[list_size].len = len;
        list[list_size].num = 1;
        memcpy(list[list_size].txt, buf, len);
        list[list_size].txt[len] = 0;
        list_size++;
        if (list_size % 1000 == 0) {
                printf("loaded %d\r", list_size);
                fflush(stdout);
        }
}

#define BUF_SIZE        (128 * 1024)

int main(int argc, char **argv)
{
        FILE *fin, *fout;
        char *buf;
        int ret, i, count;
        struct block_list *list2;
        struct stat st;

        if (argc < 3) {
                printf("Usage: ./program <input> <output>\n");
                perror("open: ");
                exit(1);
        }

        fin = fopen(argv[1], "r");
        fout = fopen(argv[2], "w");
        if (!fin || !fout) {
                printf("Usage: ./program <input> <output>\n");
                perror("open: ");
                exit(1);
        }

        fstat(fileno(fin), &st);
        max_size = st.st_size / 100; /* hack ... */

        list = malloc(max_size * sizeof(*list));
        buf = malloc(BUF_SIZE);
        if (!list || !buf) {
                printf("Out of memory\n");
                exit(1);
        }

        for ( ; ; ) {
                ret = read_block(buf, BUF_SIZE, fin);
                if (ret < 0)
                        break;

                add_list(buf, ret);
        }

        printf("loaded %d\n", list_size);

        printf("sorting ....\n");

        qsort(list, list_size, sizeof(list[0]), compare_txt);

        list2 = malloc(sizeof(*list) * list_size);

        printf("culling\n");

        for (i = count = 0; i < list_size; i++) {
                if (count == 0 ||
                    strcmp(list2[count-1].txt, list[i].txt) != 0) {
                        list2[count++] = list[i];
                } else {
                        list2[count-1].num += list[i].num;
                }
        }

        qsort(list2, count, sizeof(list[0]), compare_num);

        for (i = 0; i < count; i++)
                fprintf(fout, "%d times:\n%s\n", list2[i].num, list2[i].txt);

        return 0;
}