//! Generic array are commonly used as a return value for hash digests, so

//! it's a good idea to allow to hexlify them easily. This module implements

//! `std::fmt::LowerHex` and `std::fmt::UpperHex` traits.

//!

//! Example:

//!

//! ```rust

//! # #[macro_use]

//! # extern crate generic_array;

//! # extern crate typenum;

//! # fn main() {

//! let array = arr![u8; 10, 20, 30];

//! assert_eq!(format!("{:x}", array), "0a141e");

//! # }

//! ```

//!

use core::{fmt, str, ops::Add, cmp::min};

use typenum::*;

use crate::{ArrayLength, GenericArray};

static LOWER_CHARS: &'static [u8] = b"0123456789abcdef";

static UPPER_CHARS: &'static [u8] = b"0123456789ABCDEF";

impl<T: ArrayLength<u8>> fmt::LowerHex for GenericArray<u8, T>

where

    T: Add<T>,

    <T as Add<T>>::Output: ArrayLength<u8>,

{

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        let max_digits = f.precision().unwrap_or_else(|| self.len() * 2);

        let max_hex = (max_digits >> 1) + (max_digits & 1);

        if T::USIZE < 1024 {

            // For small arrays use a stack allocated

            // buffer of 2x number of bytes

            let mut res = GenericArray::<u8, Sum<T, T>>::default();

            self.iter().take(max_hex).enumerate().for_each(|(i, c)| {

                res[i * 2] = LOWER_CHARS[(c >> 4) as usize];

                res[i * 2 + 1] = LOWER_CHARS[(c & 0xF) as usize];

            });

            f.write_str(unsafe { str::from_utf8_unchecked(&res[..max_digits]) })?;

        } else {

            // For large array use chunks of up to 1024 bytes (2048 hex chars)

            let mut buf = [0u8; 2048];

            let mut digits_left = max_digits;

            for chunk in self[..max_hex].chunks(1024) {

                chunk.iter().enumerate().for_each(|(i, c)| {

                    buf[i * 2] = LOWER_CHARS[(c >> 4) as usize];

                    buf[i * 2 + 1] = LOWER_CHARS[(c & 0xF) as usize];

                });

                let n = min(chunk.len() * 2, digits_left);

                f.write_str(unsafe { str::from_utf8_unchecked(&buf[..n]) })?;

                digits_left -= n;

            }

        }

        Ok(())

    }

}

impl<T: ArrayLength<u8>> fmt::UpperHex for GenericArray<u8, T>

where

    T: Add<T>,

    <T as Add<T>>::Output: ArrayLength<u8>,

{

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        let max_digits = f.precision().unwrap_or_else(|| self.len() * 2);

        let max_hex = (max_digits >> 1) + (max_digits & 1);

        if T::USIZE < 1024 {

            // For small arrays use a stack allocated

            // buffer of 2x number of bytes

            let mut res = GenericArray::<u8, Sum<T, T>>::default();

            self.iter().take(max_hex).enumerate().for_each(|(i, c)| {

                res[i * 2] = UPPER_CHARS[(c >> 4) as usize];

                res[i * 2 + 1] = UPPER_CHARS[(c & 0xF) as usize];

            });

            f.write_str(unsafe { str::from_utf8_unchecked(&res[..max_digits]) })?;

        } else {

            // For large array use chunks of up to 1024 bytes (2048 hex chars)

            let mut buf = [0u8; 2048];

            let mut digits_left = max_digits;

            for chunk in self[..max_hex].chunks(1024) {

                chunk.iter().enumerate().for_each(|(i, c)| {

                    buf[i * 2] = UPPER_CHARS[(c >> 4) as usize];

                    buf[i * 2 + 1] = UPPER_CHARS[(c & 0xF) as usize];

                });

                let n = min(chunk.len() * 2, digits_left);

                f.write_str(unsafe { str::from_utf8_unchecked(&buf[..n]) })?;

                digits_left -= n;

            }

        }

        Ok(())

    }

}