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use error::*;
const BASE: u64 = 0x20;
pub fn decode<T: AsRef<str>>(input: T) -> Result<u64> {
let input = input.as_ref();
match input.len() {
0 => Err(Error::new(
Kind::EmptyString,
"Encoded input string is empty.",
)),
n if n > 13 => Err(Error::new(Kind::OutOfRange, "Encoded value is too large")),
_ => {
let mut place = BASE.pow(input.len() as u32 - 1);
let mut n = 0;
for (idx, u) in input.bytes().enumerate() {
let digit = to_normal_digit(idx, u)?;
n += u64::from(digit).wrapping_mul(place);
place /= BASE;
}
Ok(n)
}
}
}
fn to_normal_digit(idx: usize, u: u8) -> Result<u8> {
static VALUE_MAPPING: [i8; 256] = [
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15,
16, 17, 1, 18, 19, 1, 20, 21, 0, 22, 23, 24, 25, 26, -2, 27, 28, 29, 30, 31, -1, -1, -1,
-1, -1, -1, 10, 11, 12, 13, 14, 15, 16, 17, 1, 18, 19, 1, 20, 21, 0, 22, 23, 24, 25, 26,
-2, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1,
];
unsafe {
match *VALUE_MAPPING.get_unchecked(u as usize) {
-1 => Err(Error::new(
Kind::InvalidDigit(idx, u),
"Invalid encoded digit.",
)),
-2 => Err(Error::new(
Kind::CheckDigitUnsupported(idx, u),
"Check digits not currently supported.",
)),
result => Ok(result as u8),
}
}
}
#[cfg(test)]
mod tests {
use decoding::decode;
use error::*;
#[test]
fn zero_length_strings_fail() {
let input = "";
let expected = Err(Error::new(Kind::EmptyString, "Don't care"));
let actual = decode(input);
assert_eq!(expected, actual);
}
#[test]
fn long_strings_fail() {
let input = "12345678910121";
let expected = Err(Error::new(Kind::OutOfRange, "Don't care"));
let actual = decode(input);
assert_eq!(expected, actual);
}
#[test]
fn invalid_bytes_fail() {
let input = "fZZ!2";
let expected = Err(Error::new(Kind::InvalidDigit(3, 33), "Don't care"));
let actual = decode(input);
assert_eq!(expected, actual);
}
#[test]
fn zero_becomes_zero() {
let input = "0";
let expected = Ok(0);
let actual = decode(input);
assert_eq!(expected, actual);
}
#[test]
fn large_values_become_large_values() {
assert_eq!(Ok(65535), decode("1zzz"));
assert_eq!(Ok(65535), decode("1ZZZ"));
}
#[test]
fn map_to_0() {
assert_eq!(Ok(0), decode("O"));
assert_eq!(Ok(0), decode("o"));
}
#[test]
fn map_to_1() {
assert_eq!(Ok(1), decode("I"));
assert_eq!(Ok(1), decode("i"));
assert_eq!(Ok(1), decode("L"));
assert_eq!(Ok(1), decode("l"));
}
#[test]
fn z_equals_31() {
assert_eq!(Ok(31), decode("z"));
assert_eq!(Ok(31), decode("Z"));
}
#[test]
fn q_equals_23() {
assert_eq!(Ok(23), decode("q"));
assert_eq!(Ok(23), decode("Q"));
}
#[test]
fn four_z_q_works() {
assert_eq!(Ok(5111), decode("4zq"));
assert_eq!(Ok(5111), decode("4ZQ"));
}
#[test]
fn max_value_works() {
assert_eq!(Ok(18446744073709551615), decode("fzzzzzzzzzzzz"));
}
#[test]
fn u_produces_an_error_instead_of_a_crash() {
assert!(decode("iVuv").is_err());
assert!(decode("iVUv").is_err());
}
}