// 2>/dev/null; set -e; X=${0%.c} ; [ "$X" -nt "$0" ] || gcc -s -o "$X" -D_FILE_OFFSET_BITS=64 -Wall -O3 "$0" && hide "$X"; exec "$X" "$@"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <libgen.h>

// Yeah ... I really need a C library like libb.
// Use ccan and contribute to ccan.

size_t bs = 4096;

#define check_need_nl() if (need_nl) { fprintf(stderr, "\n"); need_nl = 0; }
int main(int argc, char **argv)
{
	if (argc != 2 || argv[1][0] == '-') {
		char *prog = basename(strdup(argv[0]));
		fprintf(stderr, "usage: %s badfile\n", prog);
		exit(1);
	}

	char *file = argv[1];

	int fd = open(file, O_RDWR);
	if (fd == -1) { perror("open"); exit(1); }

	struct stat st;
	if (fstat(fd, &st) == -1) { perror("fstat"); exit(1); }
	off_t size = st.st_size;

	char buf[bs];
	char zero[bs];
	memset(zero, 0, bs);

	int mod = 0;
	off_t pos = 0;
	int perc, perc0 = -1;
	int need_nl = 0;
	for(;;) {
		perc = (int)(100*pos/size);
		if (perc != perc0) {
			fprintf(stderr, "\r%d%% ", perc);
			perc0 = perc;
			need_nl = 1;
		}
		if (pos+bs > size) { bs = size - pos; }
		size_t len = read(fd, buf, bs);
		if (len == 0) break;
		if (len == -1) {
			if (errno != EIO) { check_need_nl(); perror("read"); exit(1); }
			check_need_nl();
			fprintf(stderr, "bad block at offset %jd, overwriting with %zd byte zero block\n", (intmax_t)pos, bs);
			if (lseek(fd, pos, SEEK_SET) == -1) { check_need_nl(); perror("lseek"); exit(1); }
			if (write(fd, zero, bs) == -1) { check_need_nl(); perror("write"); exit(1); }
			mod = 1;
			len = bs;
		}
		if (len != bs) {
			check_need_nl();
			fprintf(stderr, "read did not return expected number of bytes: %zd vs %zd at %jd - quitting\n", len, bs, (intmax_t)pos);
		}
		pos += len;
	}
	check_need_nl();
	if (mod && fsync(fd) == -1) { perror("fsync"); exit(1); }
	exit(0);
}