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// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// 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.
//! Hex binary-to-text encoding
pub use self::FromHexError::*;
use std::fmt;
use std::error;
/// A trait for converting a value to hexadecimal encoding
pub trait ToHex {
/// Converts the value of `self` to a hex value, returning the owned
/// string.
fn to_hex(&self) -> String;
}
const CHARS: &'static [u8] = b"0123456789abcdef";
impl ToHex for [u8] {
/// Turn a vector of `u8` bytes into a hexadecimal string.
fn to_hex(&self) -> String {
let mut v = Vec::with_capacity(self.len() * 2);
for &byte in self {
v.push(CHARS[(byte >> 4) as usize]);
v.push(CHARS[(byte & 0xf) as usize]);
}
unsafe { String::from_utf8_unchecked(v) }
}
}
/// A trait for converting hexadecimal encoded values
pub trait FromHex {
/// Converts the value of `self`, interpreted as hexadecimal encoded data,
/// into an owned vector of bytes, returning the vector.
fn from_hex(&self) -> Result<Vec<u8>, FromHexError>;
}
/// Errors that can occur when decoding a hex encoded string
#[derive(Copy, Clone, Debug)]
pub enum FromHexError {
/// The input contained a character not part of the hex format
InvalidHexCharacter(char, usize),
/// The input had an invalid length
InvalidHexLength,
}
impl fmt::Display for FromHexError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
InvalidHexCharacter(ch, idx) => {
write!(f, "Invalid character '{}' at position {}", ch, idx)
}
InvalidHexLength => write!(f, "Invalid input length"),
}
}
}
impl error::Error for FromHexError {
fn description(&self) -> &str {
match *self {
InvalidHexCharacter(..) => "invalid character",
InvalidHexLength => "invalid length",
}
}
}
impl FromHex for str {
/// Convert any hexadecimal encoded string (literal, `@`, `&`, or `~`)
/// to the byte values it encodes.
///
/// You can use the `String::from_utf8` function to turn a
/// `Vec<u8>` into a string with characters corresponding to those values.
///
fn from_hex(&self) -> Result<Vec<u8>, FromHexError> {
// This may be an overestimate if there is any whitespace
let mut b = Vec::with_capacity(self.len() / 2);
let mut modulus = 0;
let mut buf = 0;
for (idx, byte) in self.bytes().enumerate() {
buf <<= 4;
match byte {
b'A'...b'F' => buf |= byte - b'A' + 10,
b'a'...b'f' => buf |= byte - b'a' + 10,
b'0'...b'9' => buf |= byte - b'0',
b' ' | b'\r' | b'\n' | b'\t' => {
buf >>= 4;
continue;
}
_ => {
let ch = self[idx..].chars().next().unwrap();
return Err(InvalidHexCharacter(ch, idx));
}
}
modulus += 1;
if modulus == 2 {
modulus = 0;
b.push(buf);
}
}
match modulus {
0 => Ok(b.into_iter().collect()),
_ => Err(InvalidHexLength),
}
}
}
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