/*
 * replace_data v1.3   (c) 1998,2004 by van Hauser / THC <vh@thc.org>
 * http://www.thc.org
 *
 * searchs for data on a blockdevice
 */
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define NEEDLE_SIZE 1024
#define BUFSIZE 65536

FILE *f;
char needle[NEEDLE_SIZE];
char *thumb;
unsigned long add_count = 0;
off_t count = 0;
unsigned int son;
char *prog;

void help() {
    printf("Syntax: %s [-i] blockdevice searchstring replacestring\n", prog);
    printf("[-i] ignore case\n");
    exit(1);
}                        

void clean_string (char *buf) {
    unsigned int i = son;
    char *c_ptr = buf + son - 1;
    do {    
        c_ptr++; i++;
        if ( (*c_ptr < 32) || (*c_ptr > 126) || (i > 60) ) {
            *c_ptr = '\0';
        }
    } while (*c_ptr != '\0');
}

void search_and_replace (char *buf, unsigned long bufsize, unsigned long readsize) {
    unsigned int i = 0;
    char *c_ptr = buf;
    long where;
    while (bufsize >= (son + i)) {
        if (strncmp(c_ptr, needle, son) == 0) {
            if (bufsize == readsize)
              where = (long) (c_ptr - buf) - (long) readsize;
            else
              where = -1 * ((long) readsize + son - 1 - (long)(c_ptr - buf));
            fseek(f, where, SEEK_CUR);
            fwrite(thumb, son, 1, f);
            fseek(f, -where, SEEK_CUR);
            if (sizeof(count) < 8)
 	      printf("found at %lu, replaced\n", (unsigned long) (count + add_count + i));
 	    else
 	      printf("found at %llu, replaced\n", (unsigned long long) (count + add_count + i));
        }
        c_ptr++; i++;
    }
}

int main (int argc, char *argv[]) {
    char dev[100];
    struct stat st;
    unsigned long loop = 0, read_error = 0;
    size_t reat, reat_old = 0;
    unsigned int jump_size, ignore = 0, i = 1;
    char buf[BUFSIZE];
    char tmpbuf[(NEEDLE_SIZE - 1)*2];
    
    prog = argv[0];
    if ((argc < 4) || (argc >5)) {
	help(1);
    }
    if (argc == 5) {
	if (strncmp(argv[i++], "-i", 2) != 0) {
	    help();
	}
	ignore++;
    }
    strncpy(dev, argv[i++], sizeof(dev) - 1);
    strncpy(needle, argv[i++], sizeof(needle) - 1);
    thumb = argv[argc - 1];
    if (strlen(thumb) != strlen(needle)) {
        printf("Error: searchstring and replacestring need to have the same length\n");
        exit(1);
    }
    if (lstat(dev, &st) != 0) {
        perror("Can't access blockdevice");
        exit(1);
    }
    if ((st.st_mode & S_IFBLK) != S_IFBLK) {
        printf("Warning: %s is not a block device\n", dev);
    }
    if ((f = fopen(dev, "r+")) == NULL) {
        perror("Can't open blockdevice for reading and writing");
	exit(1);
    }

    jump_size = strlen(needle) - 1;
    son = strlen(needle);
    if (ignore) {
        for (i=0; i<son; i++) {
             needle[i] = tolower(needle[i]);
        }
    }
    do {
        loop++;
        jump_size = son - 1;
        reat = fread(&buf, 1, BUFSIZE, f);
        if (reat != BUFSIZE) {
            read_error++;
	    if (reat <= strlen (needle) -1) {
                jump_size = (unsigned int) (reat % BUFSIZE);
            }
        }
        if (reat > 0) {
          if (ignore) {
            for (i=0; i<reat; i++) {
                buf[i] = tolower(buf[i]);
            }
          }
          if (loop > 1) {
            add_count = (unsigned long) (BUFSIZE + 1 - son);
            memcpy(tmpbuf + son - 1, buf, jump_size);
	    search_and_replace(tmpbuf, son - 1 + jump_size, reat);
            count = count + reat_old;
            add_count = 0;
          }
	  search_and_replace(buf, reat, reat);
	  memcpy(tmpbuf, buf + reat - son + 1, son - 1);
	  reat_old = reat;
	}
    } while ((feof(f) == 0) && (read_error == 0));
    fclose(f);
    exit(0);
}