fn hash()

in crypto/src/hash/rescue/rp62_248/mod.rs [95:151]
31 lines of code
6 McCabe index (conditional complexity)

    fn hash(bytes: &[u8]) -> Self::Digest {
        // compute the number of elements required to represent the string; we will be processing
        // the string in 7-byte chunks, thus the number of elements will be equal to the number
        // of such chunks (including a potential partial chunk at the end).
        let num_elements = if bytes.len() % 7 == 0 {
            bytes.len() / 7
        } else {
            bytes.len() / 7 + 1
        };

        // initialize state to all zeros, except for the last element of the capacity part, which
        // is set to the number of elements to be hashed. this is done so that adding zero elements
        // at the end of the list always results in a different hash.
        let mut state = [BaseElement::ZERO; STATE_WIDTH];
        state[STATE_WIDTH - 1] = BaseElement::new(num_elements as u64);

        // break the string into 7-byte chunks, convert each chunk into a field element, and
        // absorb the element into the rate portion of the state. we use 7-byte chunks because
        // every 7-byte chunk is guaranteed to map to some field element.
        let mut i = 0;
        let mut buf = [0_u8; 8];
        for chunk in bytes.chunks(7) {
            if i < num_elements - 1 {
                buf[..7].copy_from_slice(chunk);
            } else {
                // if we are dealing with the last chunk, it may be smaller than 7 bytes long, so
                // we need to handle it slightly differently. we also append a byte with value 1
                // to the end of the string; this pads the string in such a way that adding
                // trailing zeros results in different hash
                let chunk_len = chunk.len();
                buf = [0_u8; 8];
                buf[..chunk_len].copy_from_slice(chunk);
                buf[chunk_len] = 1;
            }

            // convert the bytes into a field element and absorb it into the rate portion of the
            // state; if the rate is filled up, apply the Rescue permutation and start absorbing
            // again from zero index.
            state[i] += BaseElement::new(u64::from_le_bytes(buf));
            i += 1;
            if i % RATE_WIDTH == 0 {
                apply_permutation(&mut state);
                i = 0;
            }
        }

        // if we absorbed some elements but didn't apply a permutation to them (would happen when
        // the number of elements is not a multiple of RATE_WIDTH), apply the Rescue permutation.
        // we don't need to apply any extra padding because we injected total number of elements
        // in the input list into the capacity portion of the state during initialization.
        if i > 0 {
            apply_permutation(&mut state);
        }

        // return the first 4 elements of the state as hash result
        ElementDigest::new(state[..DIGEST_SIZE].try_into().unwrap())
    }