1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
// Copyright 2020 Parity Technologies
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! General bytes-related utilities.
//!
//! Includes a pretty-printer for bytes, in the form of `ToPretty` and `PrettySlice`
//! as

#![cfg_attr(not(feature = "std"), no_std)]

#[cfg(not(feature = "std"))]
extern crate alloc;

#[cfg(not(feature = "std"))]
use alloc::{format, string::String, vec::Vec};
use core::{cmp::min, fmt, ops};

/// Slice pretty print helper
pub struct PrettySlice<'a>(&'a [u8]);

impl<'a> fmt::Debug for PrettySlice<'a> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		for i in 0..self.0.len() {
			if i > 0 {
				write!(f, "·{:02x}", self.0[i])?;
			} else {
				write!(f, "{:02x}", self.0[i])?;
			}
		}
		Ok(())
	}
}

impl<'a> fmt::Display for PrettySlice<'a> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		for i in 0..self.0.len() {
			write!(f, "{:02x}", self.0[i])?;
		}
		Ok(())
	}
}

/// Trait to allow a type to be pretty-printed in `format!`, where unoverridable
/// defaults cannot otherwise be avoided.
pub trait ToPretty {
	/// Convert a type into a derivative form in order to make `format!` print it prettily.
	fn pretty(&self) -> PrettySlice<'_>;
	/// Express the object as a hex string.
	fn to_hex(&self) -> String {
		format!("{}", self.pretty())
	}
}

impl<T: AsRef<[u8]>> ToPretty for T {
	fn pretty(&self) -> PrettySlice<'_> {
		PrettySlice(self.as_ref())
	}
}

/// A byte collection reference that can either be a slice or a vector
pub enum BytesRef<'a> {
	/// This is a reference to a vector
	Flexible(&'a mut Bytes),
	/// This is a reference to a slice
	Fixed(&'a mut [u8]),
}

impl<'a> BytesRef<'a> {
	/// Writes given `input` to this `BytesRef` starting at `offset`.
	/// Returns number of bytes written to the ref.
	/// NOTE can return number greater then `input.len()` in case flexible vector had to be extended.
	pub fn write(&mut self, offset: usize, input: &[u8]) -> usize {
		match *self {
			BytesRef::Flexible(ref mut data) => {
				let data_len = data.len();
				let wrote = input.len() + if data_len > offset { 0 } else { offset - data_len };

				data.resize(offset, 0);
				data.extend_from_slice(input);
				wrote
			}
			BytesRef::Fixed(ref mut data) if offset < data.len() => {
				let max = min(data.len() - offset, input.len());
				data[offset..(max + offset)].copy_from_slice(&input[..max]);
				max
			}
			_ => 0,
		}
	}
}

impl<'a> ops::Deref for BytesRef<'a> {
	type Target = [u8];

	fn deref(&self) -> &[u8] {
		match *self {
			BytesRef::Flexible(ref bytes) => bytes,
			BytesRef::Fixed(ref bytes) => bytes,
		}
	}
}

impl<'a> ops::DerefMut for BytesRef<'a> {
	fn deref_mut(&mut self) -> &mut [u8] {
		match *self {
			BytesRef::Flexible(ref mut bytes) => bytes,
			BytesRef::Fixed(ref mut bytes) => bytes,
		}
	}
}

/// Vector of bytes.
pub type Bytes = Vec<u8>;

#[cfg(test)]
mod tests {
	use super::BytesRef;
	#[cfg(not(feature = "std"))]
	use alloc::vec;

	#[test]
	fn should_write_bytes_to_fixed_bytesref() {
		// given
		let mut data1 = vec![0, 0, 0];
		let mut data2 = vec![0, 0, 0];
		let (res1, res2) = {
			let mut bytes1 = BytesRef::Fixed(&mut data1[..]);
			let mut bytes2 = BytesRef::Fixed(&mut data2[1..2]);

			// when
			let res1 = bytes1.write(1, &[1, 1, 1]);
			let res2 = bytes2.write(3, &[1, 1, 1]);
			(res1, res2)
		};

		// then
		assert_eq!(&data1, &[0, 1, 1]);
		assert_eq!(res1, 2);

		assert_eq!(&data2, &[0, 0, 0]);
		assert_eq!(res2, 0);
	}

	#[test]
	fn should_write_bytes_to_flexible_bytesref() {
		// given
		let mut data1 = vec![0, 0, 0];
		let mut data2 = vec![0, 0, 0];
		let mut data3 = vec![0, 0, 0];
		let (res1, res2, res3) = {
			let mut bytes1 = BytesRef::Flexible(&mut data1);
			let mut bytes2 = BytesRef::Flexible(&mut data2);
			let mut bytes3 = BytesRef::Flexible(&mut data3);

			// when
			let res1 = bytes1.write(1, &[1, 1, 1]);
			let res2 = bytes2.write(3, &[1, 1, 1]);
			let res3 = bytes3.write(5, &[1, 1, 1]);
			(res1, res2, res3)
		};

		// then
		assert_eq!(&data1, &[0, 1, 1, 1]);
		assert_eq!(res1, 3);

		assert_eq!(&data2, &[0, 0, 0, 1, 1, 1]);
		assert_eq!(res2, 3);

		assert_eq!(&data3, &[0, 0, 0, 0, 0, 1, 1, 1]);
		assert_eq!(res3, 5);
	}
}