// Copyright Purdea Andrei
// released under the GNU GPL (v2 or later)

#include <stdio.h>
#include <sys/ioctl.h>
#include <linux/fs.h>
#include <errno.h>
#include <sys/time.h>
#include <fcntl.h>

int main(int argc, char ** argv) {
    int i;
    if (argc!=2) {
        printf("Usage: %s /dev/sdX\n", argv[0]);
        printf("WARNING! This Is Destructive!!!!\n");
        return -1;
    }
    int fd = open(argv[1], O_WRONLY);
    if (fd<0) {
        perror("ERROR: Can't open device file");
        return -2;
    }
    for (i=0;i<3;i++) {
        printf("THIS IS VERY DESTRUCTIVE!!!\n");
        printf("\033[31mTHIS IS VERY DESTRUCTIVE!!!\033(B\033[m\n");
    }
    printf("YOU ARE ABOUT TO OVERWRITE DATA ON %s\n", argv[1]);
    printf("Are you absolutely sure that you want to do this? (y/n) ");
    char resp;
    scanf("%c", &resp);
    if (resp!='y') return -100;
    
    // The first 4 GiB is going to be discarded.
    // First a 2GiB segment is discarded
    // then a 1GiB segment is discarded
    // then an 512 MiB segment is discarded, and so on...
    // the last segment discarded is an 512 byte segment.
    
    // before allt this the last 512 bytes of the file will be discarded (this time is not measured)
    __uint64_t range[2] = { ((1L << (32 - 9)) - 1) << 9, 1L << 9 };
    // ^^ the default values point to the last sector
    // this is done because the absolute first discard in a series of discards is sometimes slower.
    if (ioctl(fd, BLKDISCARD, &range)==-1) {
        perror("ERROR: can't send BLKDISCARD ioctl");
        return -3;
    }
    
    printf("  offset (sectors) ,    count (sectors) ,    time (microseconds)\n");
    printf("-------------------,--------------------,------------------------\n");
    
    range[0] = 0;
    range[1] = 1L << 31;
    struct timeval start, stop, result;
    
    for (i=31;i>=9;i--) { // go from 512-byte blocks, to 2 GiB
        gettimeofday(&start, NULL);
        if (ioctl(fd, BLKDISCARD, &range)==-1) {
            perror("ERROR: can't send BLKDISCARD ioctl");
            return -3;
        }
        gettimeofday(&stop, NULL);
        timersub(&stop, &start, &result);
        printf("     %8d      ,      %8d      ,      %7d\n", range[0]>>9, range[1]>>9, result.tv_sec * 1000000 + result.tv_usec);
        range[0] = range[0] + range[1];
        range[1] >>= 1;
    }
    return 0;

}