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Merged
skel84 merged 3 commits into from
Mar 26, 2026
Merged

refactor: extract shared wal frame codec #133

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eaccb5b
refactor: extract shared wal frame codec
skel84 Mar 26, 2026
7192eb0
fix: address wal frame review feedback
skel84 Mar 26, 2026
55ebbbf
test: harden wal frame edge coverage
skel84 Mar 26, 2026
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11 changes: 10 additions & 1 deletion Cargo.lock
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1 change: 1 addition & 0 deletions Cargo.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
[workspace]
members = [
"crates/allocdb-retire-queue",
"crates/allocdb-wal-frame",
"crates/allocdb-bench",
"crates/allocdb-core",
"crates/allocdb-node",
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2 changes: 1 addition & 1 deletion crates/allocdb-core/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ rust-version.workspace = true

[dependencies]
allocdb-retire-queue = { path = "../allocdb-retire-queue" }
crc32c = "0.6.8"
allocdb-wal-frame = { path = "../allocdb-wal-frame" }
log = "0.4.28"

[lints]
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187 changes: 28 additions & 159 deletions crates/allocdb-core/src/wal.rs
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Original file line number Diff line number Diff line change
@@ -1,30 +1,15 @@
use crate::ids::{Lsn, Slot};
use allocdb_wal_frame::{RawFrame, WalFormat, scan_frames_with};

const MAGIC: u32 = 0x4144_424c;
const VERSION: u16 = 1;
const HEADER_LEN: usize = 31;
pub use allocdb_wal_frame::{DecodeError, RecordType, ScanStopReason};

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum RecordType {
ClientCommand = 1,
InternalCommand = 2,
SnapshotMarker = 3,
}

impl RecordType {
fn encode(self) -> u8 {
self as u8
}
const FORMAT: WalFormat = WalFormat {
magic: 0x4144_424c,
checksum_start: 8,
};

fn decode(value: u8) -> Result<Self, DecodeError> {
match value {
1 => Ok(Self::ClientCommand),
2 => Ok(Self::InternalCommand),
3 => Ok(Self::SnapshotMarker),
_ => Err(DecodeError::InvalidRecordType(value)),
}
}
}
#[cfg(test)]
const HEADER_LEN: usize = allocdb_wal_frame::HEADER_LEN;

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Frame {
Expand All @@ -34,30 +19,13 @@ pub struct Frame {
pub payload: Vec<u8>,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum DecodeError {
BufferTooShort,
InvalidMagic(u32),
InvalidVersion(u16),
InvalidRecordType(u8),
InvalidChecksum,
PayloadTooLarge,
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ScanResult {
pub frames: Vec<Frame>,
pub valid_up_to: usize,
pub stop_reason: ScanStopReason,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum ScanStopReason {
CleanEof,
TornTail { offset: usize },
Corruption { offset: usize, error: DecodeError },
}

impl Frame {
/// Encodes one WAL frame using explicit little-endian fields and a CRC32C checksum.
///
Expand All @@ -66,21 +34,13 @@ impl Frame {
/// Panics if the payload length does not fit into `u32`.
#[must_use]
pub fn encode(&self) -> Vec<u8> {
let payload_len =
u32::try_from(self.payload.len()).expect("payload length must fit in u32 for WAL");
let mut bytes = Vec::with_capacity(HEADER_LEN + self.payload.len());
bytes.extend_from_slice(&MAGIC.to_le_bytes());
bytes.extend_from_slice(&VERSION.to_le_bytes());
bytes.extend_from_slice(&self.lsn.get().to_le_bytes());
bytes.extend_from_slice(&self.request_slot.get().to_le_bytes());
bytes.push(self.record_type.encode());
bytes.extend_from_slice(&payload_len.to_le_bytes());
bytes.extend_from_slice(&0u32.to_le_bytes());
bytes.extend_from_slice(&self.payload);

let checksum = crc32c::crc32c(&bytes[8..]);
bytes[27..31].copy_from_slice(&checksum.to_le_bytes());
bytes
RawFrame::encode_parts(
FORMAT,
self.lsn.get(),
self.request_slot.get(),
self.record_type,
&self.payload,
)
}

/// Decodes one complete WAL frame.
Expand All @@ -94,50 +54,7 @@ impl Frame {
///
/// Panics only if the implementation's fixed header layout assumptions are violated.
pub fn decode(bytes: &[u8]) -> Result<Self, DecodeError> {
if bytes.len() < HEADER_LEN {
return Err(DecodeError::BufferTooShort);
}

let magic = u32::from_le_bytes(bytes[0..4].try_into().expect("slice has exact size"));
if magic != MAGIC {
return Err(DecodeError::InvalidMagic(magic));
}

let version = u16::from_le_bytes(bytes[4..6].try_into().expect("slice has exact size"));
if version != VERSION {
return Err(DecodeError::InvalidVersion(version));
}

let lsn = Lsn(u64::from_le_bytes(
bytes[6..14].try_into().expect("slice has exact size"),
));
let request_slot = Slot(u64::from_le_bytes(
bytes[14..22].try_into().expect("slice has exact size"),
));
let record_type = RecordType::decode(bytes[22])?;
let payload_len =
u32::from_le_bytes(bytes[23..27].try_into().expect("slice has exact size"));
let payload_len = usize::try_from(payload_len).expect("u32 payload must fit usize");
let frame_len = HEADER_LEN + payload_len;
if bytes.len() < frame_len {
return Err(DecodeError::BufferTooShort);
}

let stored_checksum =
u32::from_le_bytes(bytes[27..31].try_into().expect("slice has exact size"));
let mut checksum_bytes = bytes[..frame_len].to_vec();
checksum_bytes[27..31].copy_from_slice(&0u32.to_le_bytes());
let computed_checksum = crc32c::crc32c(&checksum_bytes[8..]);
if stored_checksum != computed_checksum {
return Err(DecodeError::InvalidChecksum);
}

Ok(Self {
lsn,
request_slot,
record_type,
payload: bytes[31..frame_len].to_vec(),
})
Ok(Self::from_raw(RawFrame::decode_with(bytes, FORMAT)?))
}

/// Returns the full frame length implied by the encoded payload length field.
Expand All @@ -150,75 +67,27 @@ impl Frame {
///
/// Panics only if the implementation's fixed header layout assumptions are violated.
pub fn encoded_len(bytes: &[u8]) -> Result<usize, DecodeError> {
if bytes.len() < HEADER_LEN {
return Err(DecodeError::BufferTooShort);
}

let magic = u32::from_le_bytes(bytes[0..4].try_into().expect("slice has exact size"));
if magic != MAGIC {
return Err(DecodeError::InvalidMagic(magic));
}
RawFrame::encoded_len_with(bytes, FORMAT)
}

let version = u16::from_le_bytes(bytes[4..6].try_into().expect("slice has exact size"));
if version != VERSION {
return Err(DecodeError::InvalidVersion(version));
fn from_raw(frame: RawFrame) -> Self {
Self {
lsn: Lsn(frame.lsn),
request_slot: Slot(frame.request_slot),
record_type: frame.record_type,
payload: frame.payload,
}

let record_type = bytes[22];
let _ = RecordType::decode(record_type)?;
let payload_len =
u32::from_le_bytes(bytes[23..27].try_into().expect("slice has exact size"));
let payload_len = usize::try_from(payload_len).map_err(|_| DecodeError::PayloadTooLarge)?;
Ok(HEADER_LEN + payload_len)
}
}

/// Scans a WAL buffer and stops at the first torn or invalid frame boundary.
#[must_use]
pub fn scan_frames(bytes: &[u8]) -> ScanResult {
let mut frames = Vec::new();
let mut offset = 0usize;
let mut stop_reason = ScanStopReason::CleanEof;

while offset < bytes.len() {
let remaining = &bytes[offset..];
let frame_len = match Frame::encoded_len(remaining) {
Ok(frame_len) => frame_len,
Err(DecodeError::BufferTooShort) => {
stop_reason = ScanStopReason::TornTail { offset };
break;
}
Err(error) => {
stop_reason = ScanStopReason::Corruption { offset, error };
break;
}
};

if remaining.len() < frame_len {
stop_reason = ScanStopReason::TornTail { offset };
break;
}

match Frame::decode(&remaining[..frame_len]) {
Ok(frame) => {
frames.push(frame);
offset += frame_len;
}
Err(DecodeError::BufferTooShort) => {
stop_reason = ScanStopReason::TornTail { offset };
break;
}
Err(error) => {
stop_reason = ScanStopReason::Corruption { offset, error };
break;
}
}
}

let scanned = scan_frames_with(bytes, FORMAT);
ScanResult {
frames,
valid_up_to: offset,
stop_reason,
frames: scanned.frames.into_iter().map(Frame::from_raw).collect(),
valid_up_to: scanned.valid_up_to,
stop_reason: scanned.stop_reason,
}
}

Expand Down
11 changes: 11 additions & 0 deletions crates/allocdb-wal-frame/Cargo.toml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
[package]
name = "allocdb-wal-frame"
version.workspace = true
edition.workspace = true
rust-version.workspace = true

[dependencies]
crc32c = "0.6.8"

[lints]
workspace = true
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