libbruteforce 4.0.1

/*
MIT License

Copyright (c) 2022 Philipp Schuster

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
//! This module describes all structures and functions related with "indices".
//! Indices is the representation of a possible combination in our cracking
//! process. The indices array has the length of the maximum crack size.
//! The indices describe the index inside the alphabet. Whats special here
//! is that indices start at -1. -1 means that the current guesses are not
//! that long. E.g. means [-1, -1, -1, 2] that we so far just tried combinations
//! with one digit. Once a index goes from -1 to 0 it never goes back.

/// Initializes the array with -1 in each field and returns it.
/// Array is created on the heap.
///
/// The array represents the indices of the symbols in the current
/// iteration trying to crack the password.
///
/// Example: If our alphabet is Σ={a,b,c}, our maximum password
/// length is 5 and our current attempt is `,,a,c,b` then the
/// indices will be `-1,-1,0,2,1`. Values will never ever
/// go back to "-1" once been at 0 because we can't have empty
/// slots inside a word (they shall be marked with a space in
/// the alphabet).
pub fn indices_create(max_length: u32, min_length: u32) -> Box<[isize]> {
    if min_length > max_length {
        panic!("max_length must be >= min_length")
    }
    // -1 means no symbol yet
    let mut slice = vec![-1; max_length as usize].into_boxed_slice();
    for i in 0..min_length {
        let index = (max_length - 1 - i) as usize;
        slice[index] = 0; // from -1 to 0
    }
    slice
}

/// Transforms the indices array into a string using the alphabet.
/// Empty slots will be skipped. They contain the empty word.
#[inline] // small but notable performance gain
pub fn indices_to_string(buf: &mut String, alphabet: &[char], indices: &[isize]) {
    // clear keeps the capacity
    buf.clear();
    indices
        .iter()
        // skip empty fields. -1 means nothing (the empty word ""), not " "
        .filter(|index| **index != -1)
        .map(|index| alphabet[*index as usize])
        .for_each(|char| buf.push(char))
}

/// Increments the indices array by a given number.
/// Returns Ok() on next number or Err() on final
/// overflow (=done).
#[inline]
pub fn indices_increment_by(
    alphabet: &[char],
    indices: &mut [isize],
    add_value: usize,
) -> Result<(), &'static str> {
    if add_value == 0 {
        // Nothing to do
        return Ok(());
    }

    // The carry from the last iteration; in the first iteration the carry
    // is the add_value; in each further iteration its the actual carry
    let mut carry = add_value;

    // we go from left to right => reverse
    for index in (0..indices.len()).rev() {
        if carry == 0 {
            // done, no more carry to bring to the next position
            break;
        }

        // the current index at this position in the indices array
        let current_value = indices[index];
        // new value; possibly overflowed its range
        let mut new_value = current_value + carry as isize;

        // out of bounds? modulo!
        if new_value >= alphabet.len() as isize {
            // carry for next position/next iteration
            carry = new_value as usize / alphabet.len();
            new_value %= alphabet.len() as isize;
        } else {
            carry = 0;
        }

        indices[index] = new_value;
    }

    if carry == 0 {
        Ok(())
    } else {
        // at the end its not the original state or the maximum value but some
        // invalid value
        Err("Overflow detected! Data/state is now invalid and no longer reliable!")
    }
}

#[cfg(test)]
mod tests {
    use crate::symbols::combination_count;

    use super::*;

    #[test]
    fn test_create_indices_arr() {
        let arr = indices_create(3, 0);
        assert_eq!(arr[0], -1);
        assert_eq!(arr[1], -1);
        assert_eq!(arr[2], -1);

        let arr = indices_create(3, 2);
        // expected: [-1; 0; 0]
        assert_eq!(arr[0], -1);
        assert_eq!(arr[1], 0);
        assert_eq!(arr[2], 0);

        let arr = indices_create(3, 3);
        // expected: [-1; 0; 0]
        assert_eq!(arr[0], 0);
        assert_eq!(arr[1], 0);
        assert_eq!(arr[2], 0);
    }

    #[test]
    #[should_panic]
    fn test_create_indices_arr_panic() {
        indices_create(0, 1);
    }

    #[test]
    fn test_get_word_as_string_1() {
        let alphabet: Box<[char]> = Box::from(['a', 'b', 'c']);
        let mut arr = indices_create(5, 0);
        arr[2] = 1;
        arr[3] = 2;
        arr[4] = 0;
        let mut str_buf = String::new();
        indices_to_string(&mut str_buf, &alphabet, &arr);
        assert_eq!(str_buf, "bca", "Strings should equal")
    }

    #[test]
    fn test_get_word_as_string_2() {
        let alphabet: Box<[char]> = Box::from(['a', 'b', 'c']);
        let mut arr = indices_create(5, 0);
        arr[0] = 1;
        arr[1] = 1;
        arr[2] = 1;
        arr[3] = 2;
        arr[4] = 0;
        let mut str_buf = String::new();
        indices_to_string(&mut str_buf, &alphabet, &arr);
        assert_eq!(str_buf, "bbbca", "Strings should equal")
    }

    #[test]
    fn test_increment_indices_array_add1_overflow() {
        let alphabet: Box<[char]> = Box::from(['0', '1']);
        let mut arr = indices_create(5, 0);
        arr[3] = 1;
        arr[4] = 1;
        indices_increment_by(&alphabet, &mut arr, 1).unwrap();
        assert_eq!(arr[0], -1, "after '11' comes '000'");
        assert_eq!(arr[1], -1, "after '11' comes '000'");
        assert_eq!(arr[2], 0, "after '11' comes '000'");
        assert_eq!(arr[3], 0, "after '11' comes '000'");
        assert_eq!(arr[4], 0, "after '11' comes '000'");
    }

    #[test]
    fn test_increment_indices_array_add1() {
        let alphabet: Box<[char]> = Box::from(['a', 'b', 'c', 'd', 'e', 'f']);
        let mut arr = indices_create(5, 0);
        arr[2] = 3;
        arr[3] = 5;
        arr[4] = 5;
        indices_increment_by(&alphabet, &mut arr, 1).unwrap();
        assert_eq!(arr[2], 4, "after 'ffd' comes 'ffe'");
        assert_eq!(arr[3], 0, "after 'ffd' comes 'ffe'");
        assert_eq!(arr[4], 0, "after 'ffd' comes 'ffe'");
    }

    #[test]
    fn test_increment_indices_array_add1_initial() {
        let alphabet: Box<[char]> = Box::from(['a', 'b']);
        let mut arr = indices_create(5, 0);
        indices_increment_by(&alphabet, &mut arr, 1).unwrap();
        assert_eq!(arr[4], 0, "after () comes 'a'");
    }

    #[test]
    fn test_increment_indices_array_total_overflow() {
        let alphabet: Box<[char]> = Box::from(['a', 'b', 'c', 'd', 'e', 'f']);
        let mut arr = indices_create(3, 0);
        arr[0] = 5;
        arr[1] = 5;
        arr[2] = 5;
        assert!(
            indices_increment_by(&alphabet, &mut arr, 1).is_err(),
            "fff with length 3 should not be incrementable!"
        )
    }

    #[test]
    fn test_increment_indices_to_upper_bound() {
        let len = 3;
        let alphabet: Box<[char]> = Box::from(['a', 'b', 'c']);
        let mut indices = indices_create(len, 0);
        // should make -1 -1 -1 to 2 2 2
        // minus one because we are already at the first element (-1, -1, -1)
        let steps = combination_count(&alphabet, len, 0) - 1;
        indices_increment_by(&alphabet, &mut indices, steps).unwrap();
        for i in 0..len {
            assert_eq!(indices[i as usize], (alphabet.len() - 1) as isize)
        }
    }
}