feat: correctly handle boundary codec headers (#284)

* feat: correctly handle boundary codec headers

* test: add etherscan url

Author: greged93

crates/codec/src/decoding/batch_header.rs

@@ -0,0 +1,44 @@
+use crate::{
+    decoding::{v0::BatchHeaderV0, v1::BatchHeaderV1, v3::BatchHeaderV3, v7::BatchHeaderV7},
+    DecodingError,
+};
+
+/// The batch header.
+pub enum BatchHeader {
+    /// The batch header for V0.
+    V0(BatchHeaderV0),
+    /// The batch header for V1.
+    V1(BatchHeaderV1),
+    /// The batch header for V3.
+    V3(BatchHeaderV3),
+    /// The batch header for V7.
+    V7(BatchHeaderV7),
+}
+
+impl BatchHeader {
+    /// Returns the total number of L1 messages popped after the batch, if the version supports it.
+    pub fn total_l1_message_popped(&self) -> Option<u64> {
+        match self {
+            BatchHeader::V0(header) => Some(header.total_l1_message_popped),
+            BatchHeader::V1(header) => Some(header.total_l1_message_popped),
+            BatchHeader::V3(header) => Some(header.total_l1_message_popped),
+            BatchHeader::V7(_) => None,
+        }
+    }
+
+    /// Tries to read from the input buffer into the appropriate batch header version.
+    /// Returns [`DecodingError::Eof`] if the buffer is empty or does not contain enough bytes for
+    /// the specific version.
+    pub fn try_from_buf(buf: &mut &[u8]) -> Result<Self, DecodingError> {
+        if buf.is_empty() {
+            return Err(DecodingError::Eof);
+        }
+        let version = buf[0];
+
+        match version {
+            0 => Ok(BatchHeader::V0(BatchHeaderV0::try_from_buf(buf)?)),
+            1..=2 => Ok(BatchHeader::V1(BatchHeaderV1::try_from_buf(buf)?)),
+            3.. => Ok(BatchHeader::V3(BatchHeaderV3::try_from_buf(buf)?)),
+        }
+    }
+}

crates/codec/src/decoding/mod.rs

@@ -3,6 +3,9 @@
 /// Batch related structures.
 pub mod batch;
 
+/// Batch header related structures.
+pub mod batch_header;
+
 /// Blob related helpers.
 pub mod blob;
 

crates/codec/src/decoding/v0/mod.rs

@@ -7,7 +7,9 @@ pub(crate) use block_context::BlockContextV0;
 mod block_context;
 
 use crate::{
-    decoding::{batch::Batch, payload::PayloadData, transaction::Transaction},
+    decoding::{
+        batch::Batch, batch_header::BatchHeader, payload::PayloadData, transaction::Transaction,
+    },
     error::DecodingError,
     L2Block,
 };
@@ -58,8 +60,8 @@ pub fn decode_v0(calldata: &[u8]) -> Result<Batch, DecodingError> {
 
     // decode the parent batch header.
     let raw_parent_header = call.parent_batch_header().ok_or(DecodingError::MissingParentHeader)?;
-    let parent_header = BatchHeaderV0::try_from_buf(&mut (&*raw_parent_header))?;
-    let l1_message_start_index = parent_header.total_l1_message_popped;
+    let parent_header = BatchHeader::try_from_buf(&mut (&*raw_parent_header))?;
+    let l1_message_start_index = parent_header.total_l1_message_popped().expect("exists for v0");
 
     let payload = PayloadData {
         blocks: l2_blocks,

crates/codec/src/decoding/v1/mod.rs

@@ -3,9 +3,7 @@ pub mod zstd;
 use crate::{
     check_buf_len,
     decoding::{
-        batch::Batch,
-        blob::BlobSliceIter,
-        v1::{decode_v1_chunk, BatchHeaderV1},
+        batch::Batch, batch_header::BatchHeader, blob::BlobSliceIter, v1::decode_v1_chunk,
         v2::zstd::decompress_blob_data,
     },
     error::DecodingError,
@@ -32,8 +30,8 @@ pub fn decode_v2(calldata: &[u8], blob: &[u8]) -> Result<Batch, DecodingError> {
 
     // decode the parent batch header.
     let raw_parent_header = call.parent_batch_header().ok_or(DecodingError::MissingParentHeader)?;
-    let parent_header = BatchHeaderV1::try_from_buf(&mut (&*raw_parent_header))?;
-    let l1_message_start_index = parent_header.total_l1_message_popped;
+    let parent_header = BatchHeader::try_from_buf(&mut (&*raw_parent_header))?;
+    let l1_message_start_index = parent_header.total_l1_message_popped().expect("exists for v2");
 
     // get blob iterator and collect, skipping unused bytes.
     let compressed_heap_blob = BlobSliceIter::from_blob_slice(blob).copied().collect::<Vec<_>>();

crates/codec/src/decoding/v2/mod.rs

@@ -1,8 +1,8 @@
 use crate::{
     check_buf_len,
     decoding::{
-        batch::Batch, blob::BlobSliceIter, v1::decode_v1_chunk, v2::zstd::decompress_blob_data,
-        v3::BatchHeaderV3,
+        batch::Batch, batch_header::BatchHeader, blob::BlobSliceIter, v1::decode_v1_chunk,
+        v2::zstd::decompress_blob_data,
     },
     error::DecodingError,
     from_be_bytes_slice_and_advance_buf,
@@ -20,8 +20,8 @@ pub fn decode_v4(calldata: &[u8], blob: &[u8]) -> Result<Batch, DecodingError> {
 
     // decode the parent batch header.
     let raw_parent_header = call.parent_batch_header().ok_or(DecodingError::MissingParentHeader)?;
-    let parent_header = BatchHeaderV3::try_from_buf(&mut (&*raw_parent_header))?;
-    let l1_message_start_index = parent_header.total_l1_message_popped;
+    let parent_header = BatchHeader::try_from_buf(&mut (&*raw_parent_header))?;
+    let l1_message_start_index = parent_header.total_l1_message_popped().expect("exists for v4");
 
     // get blob iterator and collect, skipping unused bytes.
     let mut heap_blob = BlobSliceIter::from_blob_slice(blob).copied().collect::<Vec<_>>();