generic_array/
hex.rs

1//! Generic array are commonly used as a return value for hash digests, so
2//! it's a good idea to allow to hexlify them easily. This module implements
3//! `std::fmt::LowerHex` and `std::fmt::UpperHex` traits.
4//!
5//! Example:
6//!
7//! ```rust
8//! # #[macro_use]
9//! # extern crate generic_array;
10//! # extern crate typenum;
11//! # fn main() {
12//! let array = arr![u8; 10, 20, 30];
13//! assert_eq!(format!("{:x}", array), "0a141e");
14//! # }
15//! ```
16//!
17
18use core::{fmt, str, ops::Add, cmp::min};
19
20use typenum::*;
21
22use crate::{ArrayLength, GenericArray};
23
24static LOWER_CHARS: &'static [u8] = b"0123456789abcdef";
25static UPPER_CHARS: &'static [u8] = b"0123456789ABCDEF";
26
27impl<T: ArrayLength<u8>> fmt::LowerHex for GenericArray<u8, T>
28where
29    T: Add<T>,
30    <T as Add<T>>::Output: ArrayLength<u8>,
31{
32    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
33        let max_digits = f.precision().unwrap_or_else(|| self.len() * 2);
34        let max_hex = (max_digits >> 1) + (max_digits & 1);
35
36        if T::USIZE < 1024 {
37            // For small arrays use a stack allocated
38            // buffer of 2x number of bytes
39            let mut res = GenericArray::<u8, Sum<T, T>>::default();
40
41            self.iter().take(max_hex).enumerate().for_each(|(i, c)| {
42                res[i * 2] = LOWER_CHARS[(c >> 4) as usize];
43                res[i * 2 + 1] = LOWER_CHARS[(c & 0xF) as usize];
44            });
45
46            f.write_str(unsafe { str::from_utf8_unchecked(&res[..max_digits]) })?;
47        } else {
48            // For large array use chunks of up to 1024 bytes (2048 hex chars)
49            let mut buf = [0u8; 2048];
50            let mut digits_left = max_digits;
51
52            for chunk in self[..max_hex].chunks(1024) {
53                chunk.iter().enumerate().for_each(|(i, c)| {
54                    buf[i * 2] = LOWER_CHARS[(c >> 4) as usize];
55                    buf[i * 2 + 1] = LOWER_CHARS[(c & 0xF) as usize];
56                });
57
58                let n = min(chunk.len() * 2, digits_left);
59                f.write_str(unsafe { str::from_utf8_unchecked(&buf[..n]) })?;
60                digits_left -= n;
61            }
62        }
63        Ok(())
64    }
65}
66
67impl<T: ArrayLength<u8>> fmt::UpperHex for GenericArray<u8, T>
68where
69    T: Add<T>,
70    <T as Add<T>>::Output: ArrayLength<u8>,
71{
72    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
73        let max_digits = f.precision().unwrap_or_else(|| self.len() * 2);
74        let max_hex = (max_digits >> 1) + (max_digits & 1);
75
76        if T::USIZE < 1024 {
77            // For small arrays use a stack allocated
78            // buffer of 2x number of bytes
79            let mut res = GenericArray::<u8, Sum<T, T>>::default();
80
81            self.iter().take(max_hex).enumerate().for_each(|(i, c)| {
82                res[i * 2] = UPPER_CHARS[(c >> 4) as usize];
83                res[i * 2 + 1] = UPPER_CHARS[(c & 0xF) as usize];
84            });
85
86            f.write_str(unsafe { str::from_utf8_unchecked(&res[..max_digits]) })?;
87        } else {
88            // For large array use chunks of up to 1024 bytes (2048 hex chars)
89            let mut buf = [0u8; 2048];
90            let mut digits_left = max_digits;
91
92            for chunk in self[..max_hex].chunks(1024) {
93                chunk.iter().enumerate().for_each(|(i, c)| {
94                    buf[i * 2] = UPPER_CHARS[(c >> 4) as usize];
95                    buf[i * 2 + 1] = UPPER_CHARS[(c & 0xF) as usize];
96                });
97
98                let n = min(chunk.len() * 2, digits_left);
99                f.write_str(unsafe { str::from_utf8_unchecked(&buf[..n]) })?;
100                digits_left -= n;
101            }
102        }
103        Ok(())
104    }
105}
generic_array/hex.rs

generic_array/
hex.rs
