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

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use std::fmt::Write;
use std::num::ParseIntError;

/// A simple trait allowing something to be converted into a hex
/// string.
pub trait ToHexString {
    fn to_hex_string(&self) -> String;
}

/// A simple trait allowing something to be converted from a hex
/// string.
pub trait FromHexString {
    type Error;

    fn from_hex_string(&self) -> Result<Vec<u8>, Self::Error>;
}

/// A default implementation for byte slices.
impl ToHexString for [u8] {
    fn to_hex_string(&self) -> String {
        let size = 2 + (2 * self.len());
        let mut hexstr = String::with_capacity(size);
        // Prepend "0x"
        write!(hexstr, "0x").unwrap();
        // Write each byte
        for b in self {
            write!(hexstr, "{:02x}", b).unwrap();
        }
        // Done
        hexstr
    }
}

/// A default implementation for string slices
impl FromHexString for str {
    type Error = ParseIntError;
    //
    fn from_hex_string(&self) -> Result<Vec<u8>, Self::Error> {
        let mut bytes: Vec<u8> = Vec::new();
        // Remove prepended "0x" (only if present)
        let slice = if self.len() > 2 && &self[0..2] == "0x" {
            &self[2..]
        } else {
            &self
        };
        // Parse contents of string
        for i in (0..slice.len()).step_by(2) {
            // Pull out the byte
            let byte = u8::from_str_radix(&slice[i..i + 2], 16)?;
            // Push it!
            bytes.push(byte);
        }
        //
        Ok(bytes)
    }
}