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pub fn decode(values: &[u8]) -> (u64, usize) {
let mut result = 0;
let mut shift = 0;
let mut consumed = 0;
for byte in values {
consumed += 1;
if shift == 63 && *byte > 1 {
panic!()
};
result |= u64::from(byte & 0b01111111) << shift;
if byte & 0b10000000 == 0 {
break;
}
shift += 7;
}
(result, consumed)
}
pub fn encode(mut value: u64, container: &mut [u8]) -> usize {
let mut consumed = 0;
let mut iter = container.iter_mut();
loop {
let mut byte = (value as u8) & !128;
value >>= 7;
if value != 0 {
byte |= 128;
}
*iter.next().unwrap() = byte;
consumed += 1;
if value == 0 {
break;
}
}
consumed
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn decode_1() {
let data = vec![0xe5, 0x8e, 0x26, 0xDE, 0xAD, 0xBE, 0xEF];
let (value, len) = decode(&data);
assert_eq!(value, 624_485);
assert_eq!(len, 3);
}
#[test]
fn decode_2() {
let data = vec![0b00010000, 0b00000001, 0b00000011, 0b00000011];
let (value, len) = decode(&data);
assert_eq!(value, 16);
assert_eq!(len, 1);
}
#[test]
fn round_trip() {
let original = 123124234u64;
let mut container = [0u8; 10];
let encoded_len = encode(original, &mut container);
let (value, len) = decode(&container);
assert_eq!(value, original);
assert_eq!(len, encoded_len);
}
#[test]
fn min_value() {
let original = u64::MIN;
let mut container = [0u8; 10];
let encoded_len = encode(original, &mut container);
let (value, len) = decode(&container);
assert_eq!(value, original);
assert_eq!(len, encoded_len);
}
#[test]
fn max_value() {
let original = u64::MAX;
let mut container = [0u8; 10];
let encoded_len = encode(original, &mut container);
let (value, len) = decode(&container);
assert_eq!(value, original);
assert_eq!(len, encoded_len);
}
}