/*
 * SPDX-License-Identifier: MIT
 * Copyright (c) 2025 Fabio Scotto di Santolo
 */


#include <fcntl.h>
#include <linux/fs.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>

/* get_block - for the file associated with the given fd, returns
 * the physical block mapping to logical_block
 */
int get_block(int fd, int logical_block);

/* get_nr_blocks - returns the number of logical blocks
 * consumed by the file associated with fd
 */
int get_nr_blocks(int fd);

/* print_blocks - for each logical block consumed by the file
 * associated with fd, prints to standard out the tuple
 * "(logical block, physical block)"
 */
void print_blocks(int fd);

int main(int argc, char *argv[])
{
	if (argc < 2) {
		fprintf(stderr, "usage: %s <file>\n", argv[0]);
		return 1;
	}

	int fd = open(argv[1], O_RDONLY);
	if (fd < 0) {
		perror("open");
		return 1;
	}

	print_blocks(fd);
	return 0;
}

int get_block(int fd, int logical_block)
{
	int ret = ioctl(fd, FIBMAP, &logical_block);
	if (ret < 0) {
		perror("ioctl");
		return -1;
	}
	return logical_block;
}

int get_nr_blocks(int fd)
{
	struct stat buf;
	int ret = fstat(fd, &buf);
	if (ret < 0) {
		perror("fstat");
		return -1;
	}
	return buf.st_blocks;
}

void print_blocks(int fd)
{
	int nr_blocks = get_nr_blocks(fd);
	if (nr_blocks < 0) {
		fprintf(stderr, "get_nr_blocks failed!\n");
		return;
	}

	if (nr_blocks == 0) {
		printf("no allocated blocks\n");
		return;
	} else if (nr_blocks == 1) {
		printf("1 block\n");
	} else {
		printf("%d blocks\n\n", nr_blocks);
	}

	for (int i = 0; i < nr_blocks; i++) {
		int phys_block = get_block(fd, i);
		if (phys_block < 0) {
			fprintf(stderr, "get_block failed!\n");
			return;
		}
		if (!phys_block)
			continue;

		printf("(%u, %u) ", i, phys_block);
	}
	putchar('\n');
}