#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <time.h>

int bmh(char *str, char *pattern, int fpos);

int main(void)
{
    char src[16];
    char seek[] = "vasyan";
    int ret = 0;
    int sz = strlen(seek);

    FILE *fp = fopen("test.txt", "r");
    if(fp == NULL) {
        printf("fopen error\n");
        return 1;
    }

    ret = fread(src, sizeof(char), 15, fp);
    src[ret] = '\0';
    int fpos = 0;

    printf("Seek for substring: %s\n", seek);

    while(1){

        ret = bmh(src, seek, fpos);
        if(ret >= 0) {
            fpos += ret;
            break;
        } else {
            fpos += strlen(src) - sz + 1;
        }

        memmove(src, &src[16-sz-1], sz);

        ret = fread(&src[sz], sizeof(char), 15-sz, fp);

        if(ret == 0) {
            ret = -1;
            break;
        }
    }

    if(ret >= 0)
        printf("Substring found at %d\n", fpos);
    else
        printf("Substring not found\n");

    return 0;
}

int bmh(char *str, char *pattern, int fpos)
{
    int shift[256];
    int n = strlen(str);
    int m = strlen(pattern);

    char ch, lastch;

    for(int i=0;i<256;i++)
        shift[i] = m;

    for(int i=0;i<m-1;i++)
        shift[pattern[i]] = m - i - 1;

    lastch = pattern[m - 1];
    for(int i=0;i<=n-m;i+=shift[ch]) {
        ch = str[i+m-1];
        if(ch == lastch) {
            if(memcmp(&str[i], pattern, m-1) == 0)
                return i;
        }
    }

    return -1;
}