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Encode refs according to the spec #189

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Oct 11, 2024
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Encode refs according to the spec #189

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35 changes: 27 additions & 8 deletions icechunk/src/refs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,13 +8,15 @@ use thiserror::Error;
use crate::{format::SnapshotId, Storage, StorageError};

fn crock_encode_int(n: u64) -> String {
base32::encode(base32::Alphabet::Crockford, &n.to_be_bytes())
// skip the first 3 bytes (zeroes)
base32::encode(base32::Alphabet::Crockford, &n.to_be_bytes()[3..=7])
}

fn crock_decode_int(data: &str) -> Option<u64> {
let bytes = base32::decode(base32::Alphabet::Crockford, data)?;
let bytes = bytes.try_into().ok()?;
Some(u64::from_be_bytes(bytes))
// re insert the first 3 bytes removed during encoding
let mut bytes = vec![0, 0, 0];
bytes.extend(base32::decode(base32::Alphabet::Crockford, data)?);
Some(u64::from_be_bytes(bytes.as_slice().try_into().ok()?))
}

#[derive(Debug, Error)]
Expand Down Expand Up @@ -70,14 +72,16 @@ impl Ref {
pub struct BranchVersion(pub u64);

impl BranchVersion {
const MAX_VERSION_NUMBER: u64 = 1099511627775;
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Do you really think 10 trillion is enough?!? 😆

I would love for someone to use icechunk so heavily that they hit this limit.

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they'll get a Rust panic too!


fn decode(version: &str) -> RefResult<Self> {
let n = crock_decode_int(version)
.ok_or(RefError::InvalidBranchVersion(version.to_string()))?;
Ok(BranchVersion(u64::MAX - n))
Ok(BranchVersion(BranchVersion::MAX_VERSION_NUMBER - n))
}

fn encode(&self) -> String {
crock_encode_int(u64::MAX - self.0)
crock_encode_int(BranchVersion::MAX_VERSION_NUMBER - self.0)
}

fn to_path(&self, branch_name: &str) -> RefResult<String> {
Expand Down Expand Up @@ -281,9 +285,24 @@ mod tests {

#[tokio::test]
async fn test_branch_version_encoding() -> Result<(), Box<dyn std::error::Error>> {
let targets = (0..10u64).chain(once(u64::MAX));
let targets = (0..10u64).chain(once(BranchVersion::MAX_VERSION_NUMBER));
let encodings = [
"ZZZZZZZZ", "ZZZZZZZY", "ZZZZZZZX", "ZZZZZZZW", "ZZZZZZZV",
// no U
"ZZZZZZZT", "ZZZZZZZS", "ZZZZZZZR", "ZZZZZZZQ", "ZZZZZZZP",
];

for n in targets {
let round = BranchVersion::decode(BranchVersion(n).encode().as_str())?;
let encoded = BranchVersion(n).encode();

if n < 100 {
assert_eq!(encoded, encodings[n as usize]);
}
if n == BranchVersion::MAX_VERSION_NUMBER {
assert_eq!(encoded, "00000000");
}

let round = BranchVersion::decode(encoded.as_str())?;
assert_eq!(round, BranchVersion(n));
}
Ok(())
Expand Down