use crate::errors::{Error, Result};
const B64_CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const B64: [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,
62,
-1,
-1,
-1,
63,
52,
53,
54,
55,
56,
57,
58,
59,
60,
61,
-1,
-1,
-1,
-1,
-1,
-1,
-1,
0,
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,
-1,
-1,
-1,
-1,
-1,
-1,
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,
-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,
-1,
];
pub fn parse_vlq_segment(segment: &str) -> Result<Vec<i64>> {
let mut rv = vec![];
let mut cur = 0;
let mut shift = 0;
for c in segment.bytes() {
let enc = i64::from(B64[c as usize]);
let val = enc & 0b11111;
let cont = enc >> 5;
cur += val.checked_shl(shift).ok_or(Error::VlqOverflow)?;
shift += 5;
if cont == 0 {
let sign = cur & 1;
cur >>= 1;
if sign != 0 {
cur = -cur;
}
rv.push(cur);
cur = 0;
shift = 0;
}
}
if cur != 0 || shift != 0 {
Err(Error::VlqLeftover)
} else if rv.is_empty() {
Err(Error::VlqNoValues)
} else {
Ok(rv)
}
}
pub fn generate_vlq_segment(nums: &[i64]) -> Result<String> {
let mut rv = String::new();
for &num in nums {
encode_vlq(&mut rv, num);
}
Ok(rv)
}
pub(crate) fn encode_vlq(out: &mut String, num: i64) {
let mut num = if num < 0 { ((-num) << 1) + 1 } else { num << 1 };
loop {
let mut digit = num & 0b11111;
num >>= 5;
if num > 0 {
digit |= 1 << 5;
}
out.push(B64_CHARS[digit as usize] as char);
if num == 0 {
break;
}
}
}
#[test]
fn test_vlq_decode() {
let rv = parse_vlq_segment("AAAA").unwrap();
assert_eq!(rv, vec![0, 0, 0, 0]);
let rv = parse_vlq_segment("GAAIA").unwrap();
assert_eq!(rv, vec![3, 0, 0, 4, 0]);
}
#[test]
fn test_vlq_encode() {
let rv = generate_vlq_segment(&[0, 0, 0, 0]).unwrap();
assert_eq!(rv.as_str(), "AAAA");
let rv = generate_vlq_segment(&[3, 0, 0, 4, 0]).unwrap();
assert_eq!(rv.as_str(), "GAAIA");
}
#[test]
fn test_overflow() {
match parse_vlq_segment("00000000000000") {
Err(Error::VlqOverflow) => {}
e => {
panic!("Unexpeted result: {:?}", e);
}
}
}