Frame data structure

crates/derive/src/lib.rs

@@ -13,6 +13,11 @@
 
 extern crate alloc;
 
+pub mod params;
 pub mod stages;
 pub mod traits;
 pub mod types;
+
+/// The derivation pipeline is responsible for deriving L2 inputs from L1 data.
+#[derive(Debug, Clone, Copy)]
+pub struct DerivationPipeline;

crates/derive/src/params.rs

@@ -0,0 +1,22 @@
+//! This module contains the parameters and identifying types for the derivation pipeline.
+
+/// Count the tagging info as 200 in terms of buffer size.
+pub const FRAME_OVERHEAD: u64 = 200;
+
+/// The version of the derivation pipeline.
+pub const DERIVATION_VERSION_0: u8 = 0;
+
+/// [MAX_SPAN_BATCH_BYTES] is the maximum amount of bytes that will be needed
+/// to decode every span batch field. This value cannot be larger than
+/// MaxRLPBytesPerChannel because single batch cannot be larger than channel size.
+pub const MAX_SPAN_BATCH_BYTES: u64 = MAX_RLP_BYTES_PER_CHANNEL;
+
+/// [MAX_RLP_BYTES_PER_CHANNEL] is the maximum amount of bytes that will be read from
+/// a channel. This limit is set when decoding the RLP.
+pub const MAX_RLP_BYTES_PER_CHANNEL: u64 = 10_000_000;
+
+/// [CHANNEL_ID_LENGTH] is the length of the channel ID.
+pub const CHANNEL_ID_LENGTH: usize = 16;
+
+/// [ChannelID] is an opaque identifier for a channel.
+pub type ChannelID = [u8; CHANNEL_ID_LENGTH];

crates/derive/src/stages/frame_queue.rs

@@ -1 +1,17 @@
+//! This module contains the [FrameQueue] stage of the derivation pipeline.
 
+use super::l1_retrieval::L1Retrieval;
+use crate::traits::{ChainProvider, DataAvailabilityProvider};
+use alloc::collections::VecDeque;
+use alloy_primitives::Bytes;
+
+pub struct FrameQueue<T, DAP, CP>
+where
+    DAP: DataAvailabilityProvider,
+    CP: ChainProvider,
+{
+    /// The previous stage in the pipeline.
+    pub prev: L1Retrieval<T, DAP, CP>,
+    /// The current frame queue.
+    queue: VecDeque<Bytes>,
+}

crates/derive/src/types/frame.rs

@@ -0,0 +1,153 @@
+//! This module contains the [Frame] type used within the derivation pipeline.
+
+use crate::params::{ChannelID, DERIVATION_VERSION_0};
+use alloc::vec::Vec;
+use anyhow::{anyhow, bail, Result};
+
+/// Frames cannot be larger than 1MB.
+/// Data transactions that carry frames are generally not larger than 128 KB due to L1 network conditions,
+/// but we leave space to grow larger anyway (gas limit allows for more data).
+const MAX_FRAME_LEN: usize = 1000;
+
+/// A channel frame is a segment of a channel's data.
+///
+/// *Encoding*
+/// frame = `channel_id ++ frame_number ++ frame_data_length ++ frame_data ++ is_last`
+/// * channel_id        = bytes16
+/// * frame_number      = uint16
+/// * frame_data_length = uint32
+/// * frame_data        = bytes
+/// * is_last           = bool
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Frame {
+    /// The unique idetifier for the frame.
+    pub id: ChannelID,
+    /// The number of the frame.
+    pub number: u16,
+    /// The data within the frame.
+    pub data: Vec<u8>,
+    /// Whether or not the frame is the last in the sequence.
+    pub is_last: bool,
+}
+
+impl Frame {
+    /// Encode the frame into a byte vector.
+    pub fn encode(&self) -> Vec<u8> {
+        let mut encoded = Vec::with_capacity(16 + 2 + 4 + self.data.len() + 1);
+        encoded.extend_from_slice(&self.id);
+        encoded.extend_from_slice(&self.number.to_be_bytes());
+        encoded.extend_from_slice(&(self.data.len() as u32).to_be_bytes());
+        encoded.extend_from_slice(&self.data);
+        encoded.push(self.is_last as u8);
+        encoded
+    }
+
+    /// Decode a frame from a byte vector.
+    pub fn decode(encoded: &[u8]) -> Result<(usize, Self)> {
+        const BASE_FRAME_LEN: usize = 16 + 2 + 4 + 1;
+
+        if encoded.len() < BASE_FRAME_LEN {
+            bail!("Frame too short to decode");
+        }
+
+        let id = encoded[..16]
+            .try_into()
+            .map_err(|e| anyhow!("Error: {e}"))?;
+        let number = u16::from_be_bytes(
+            encoded[16..18]
+                .try_into()
+                .map_err(|e| anyhow!("Error: {e}"))?,
+        );
+        let data_len = u32::from_be_bytes(
+            encoded[18..22]
+                .try_into()
+                .map_err(|e| anyhow!("Error: {e}"))?,
+        ) as usize;
+        let data = encoded[22..22 + data_len].to_vec();
+        let is_last = encoded[22 + data_len] != 0;
+        Ok((
+            BASE_FRAME_LEN + data_len,
+            Self {
+                id,
+                number,
+                data,
+                is_last,
+            },
+        ))
+    }
+
+    /// ParseFrames parse the on chain serialization of frame(s) in an L1 transaction. Currently only version 0 of the
+    /// serialization format is supported. All frames must be parsed without error and there must not be any left over
+    /// data and there must be at least one frame.
+    ///
+    /// Frames are stored in L1 transactions with the following format:
+    /// * `data = DerivationVersion0 ++ Frame(s)`
+    /// Where there is one or more frames concatenated together.
+    fn parse_frames(encoded: &[u8]) -> Result<Vec<Self>> {
+        if encoded.is_empty() {
+            bail!("No frames to parse");
+        }
+        if encoded[0] != DERIVATION_VERSION_0 {
+            bail!("Unsupported derivation version");
+        }
+
+        let data = &encoded[1..];
+        let mut frames = Vec::new();
+        let mut offset = 0;
+        while offset < data.len() {
+            let (frame_length, frame) = Self::decode(&data[offset..])?;
+            frames.push(frame);
+            offset += frame_length;
+        }
+
+        if offset != data.len() {
+            bail!("Frame data length mismatch");
+        }
+        if frames.is_empty() {
+            bail!("No frames decoded");
+        }
+
+        Ok(frames)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    extern crate std;
+
+    use super::*;
+
+    #[test]
+    fn test_encode_frame_roundtrip() {
+        let frame = Frame {
+            id: [1; 16],
+            number: 0,
+            data: std::vec![],
+            is_last: true,
+        };
+
+        let (_, frame_decoded) = Frame::decode(&frame.encode()).unwrap();
+        assert_eq!(frame, frame_decoded);
+    }
+
+    #[test]
+    fn test_decode_many() {
+        let frame = Frame {
+            id: [1; 16],
+            number: 0,
+            data: std::vec![],
+            is_last: true,
+        };
+        let mut bytes = Vec::new();
+        bytes.extend_from_slice(&[DERIVATION_VERSION_0]);
+        (0..5).for_each(|_| {
+            bytes.extend_from_slice(&frame.encode());
+        });
+
+        let frames = Frame::parse_frames(bytes.as_slice()).unwrap();
+        assert_eq!(frames.len(), 5);
+        (0..5).for_each(|i| {
+            assert_eq!(frames[i], frame);
+        });
+    }
+}

crates/derive/src/types/mod.rs

@@ -29,3 +29,6 @@ pub use eips::{
 
 mod genesis;
 pub use genesis::Genesis;
+
+mod frame;
+pub use frame::Frame;

crates/derive/src/types/system_config.rs

@@ -68,15 +68,16 @@ impl SystemConfig {
                 continue;
             }
 
-            for log in receipt.logs.iter() {
+            receipt.logs.iter().try_for_each(|log| {
                 let topics = log.topics();
                 if log.address == rollup_config.l1_system_config_address
                     && !topics.is_empty()
                     && topics[0] == CONFIG_UPDATE_TOPIC
                 {
                     self.process_config_update_log(log, rollup_config, l1_time)?;
                 }
-            }
+                Ok(())
+            })?;
         }
         Ok(())
     }