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|
//! 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(())
}
}
|
