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#[derive(Debug)]
pub enum HexDecodeError {
InvalidByteCount,
InvalidHexCharacter,
}
fn hex_char_byte_to_value(c : u8) -> Result<u8, HexDecodeError> {
if !c.is_ascii_hexdigit() {
return Err(HexDecodeError::InvalidHexCharacter);
}
Ok( (c as char).to_digit(16).unwrap() as u8)
}
fn byte_to_hex_char(b : u8) -> char {
assert!(b <= 15);
match b {
digit if digit < 10 => ('0' as u8 + digit) as char,
letter => ('a' as u8 + letter - 10) as char
}
}
fn append_byte_hex_to_string(byte : u8, string : &mut String) {
let high = (byte & 0xF0) >> 4;
let low = byte & 0x0F;
string.push(byte_to_hex_char(high));
string.push(byte_to_hex_char(low));
}
pub fn decode_hex<T : AsRef<[u8]>>(string : T) -> Result<Vec<u8>, HexDecodeError> {
let chars = string.as_ref();
if chars.len() % 2 != 0 {
return Err(HexDecodeError::InvalidByteCount);
}
let mut data = Vec::new();
let mut index = 0;
let mut first_digit : u8 = 0;
for c in chars.iter() {
if index % 2 != 0 {
let second_digit = hex_char_byte_to_value(*c)?;
let value = first_digit * 16 + second_digit;
data.push(value);
}else {
first_digit = hex_char_byte_to_value(*c)?;
}
index += 1;
}
Ok(data)
}
pub fn encode_hex<T : AsRef<[u8]>>(data : T) -> String {
let mut string = String::new();
let data_ref = data.as_ref();
for b in data_ref.iter() {
append_byte_hex_to_string(*b, &mut string);
}
string
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn decode_zero_bytes_test() {
let string = "";
let data = decode_hex(string).unwrap();
assert_eq!(0, data.len());
}
#[test]
fn decode_one_byte_test() {
let string = "ff";
let data = decode_hex(string).unwrap();
assert_eq!(1, data.len());
assert_eq!(0xff, data[0]);
}
#[test]
fn decode_multiple_bytes_test() {
let string = "ffaabbccdd1122";
let data = decode_hex(string).unwrap();
assert_eq!(7, data.len());
assert_eq!(&[0xff, 0xaa, 0xbb, 0xcc, 0xdd, 0x11, 0x22], data.as_slice());
}
#[test]
fn decode_invalid_character_test() {
let string = "ffaabz";
match decode_hex(string) {
Err(HexDecodeError::InvalidHexCharacter) => {}
_ => panic!("Invalid result returned"),
}
}
#[test]
fn decode_invalid_character_length() {
let string = "ffaab";
match decode_hex(string) {
Err(HexDecodeError::InvalidByteCount) => {}
_ => panic!("Invalid result returned"),
}
}
#[test]
fn encode_zero_bytes() {
let data: &[u8; 0] = &[];
let string = encode_hex(&data);
assert_eq!(string, "");
}
#[test]
fn encode_one_byte() {
let data: &[u8; 1] = &[0xa1];
let string = encode_hex(&data);
assert_eq!(string, "a1");
}
#[test]
fn encode_multiple_bytes() {
let data: &[u8; 5] = &[0xaa, 0xbb, 0xcc, 0xdd, 0xee];
let string = encode_hex(&data);
assert_eq!(string, "aabbccddee");
}
}
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