Add transaction and RLP decoding to the state library by chfast · Pull Request #1581 · ipsilon/evmone

chfast · 2026-07-07T07:22:28Z

Add state::decode_transaction, the inverse of the existing RLP encoder: it
decodes a legacy or EIP-2718 typed transaction from its network serialization
into a state::Transaction, rejecting malformed input (exception-free, returns
std::nullopt). Covered by state_rlp unit tests.

codecov · 2026-07-07T07:24:58Z

Codecov Report

❌ Patch coverage is 99.82332% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 97.48%. Comparing base (0b7069a) to head (78d9fb4).

Files with missing lines	Patch %	Lines
test/unittests/state_rlp_decode_test.cpp	99.75%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1581      +/-   ##
==========================================
+ Coverage   97.40%   97.48%   +0.08%     
==========================================
  Files         166      170       +4     
  Lines       14810    15376     +566     
  Branches     3412     3591     +179     
==========================================
+ Hits        14425    14990     +565     
  Misses        281      281              
- Partials      104      105       +1

Flag	Coverage Δ
eest-develop	`89.41% <ø> (ø)`
eest-develop-gmp	`25.02% <0.00%> (-0.96%)`	⬇️
eest-legacy	`16.75% <0.00%> (-0.65%)`	⬇️
eest-libsecp256k1	`27.15% <0.00%> (-1.04%)`	⬇️
eest-stable	`89.37% <ø> (ø)`
evmone-unittests	`93.07% <99.82%> (+0.31%)`	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
core	`96.03% <100.00%> (+0.13%)`	⬆️
tooling	`90.36% <ø> (ø)`
tests	`99.80% <99.75%> (-0.01%)`	⬇️

Files with missing lines	Coverage Δ
test/state/rlp_decode.cpp	`100.00% <100.00%> (ø)`
test/state/rlp_decode.hpp	`100.00% <100.00%> (ø)`
test/state/transaction.cpp	`100.00% <100.00%> (ø)`
test/state/transaction.hpp	`100.00% <ø> (ø)`
test/unittests/state_rlp_decode_test.cpp	`99.75% <99.75%> (ø)`

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Copilot

Pull request overview

This PR adds exception-free transaction decoding to the test/state library by implementing state::decode_transaction() (legacy + EIP-2718 typed envelopes) and introducing supporting RLP decoding primitives, with unit tests validating round-trips and malformed-input rejection.

Changes:

Add state::decode_transaction(bytes_view) -> std::optional<Transaction> and its implementation for legacy/EIP-2718 typed transactions.
Introduce test/state/rlp_decode.{hpp,cpp} with overflow-safe/canonical RLP header decoding and basic decode helpers.
Extend state_rlp unit tests with transaction decode round-trips and regression cases for malformed RLP / invalid transaction encodings.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/unittests/state_rlp_test.cpp	Adds unit tests for transaction decoding and RLP regression cases.
test/state/transaction.hpp	Declares `decode_transaction()` API and documents behavior.
test/state/transaction.cpp	Implements transaction decoding logic for legacy + typed transactions.
test/state/rlp_decode.hpp	Adds header-only RLP decoding primitives (templated decoders).
test/state/rlp_decode.cpp	Implements RLP header decoding and byte/address decoding.
test/state/CMakeLists.txt	Wires new decoder sources into the `test/state` target.

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Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

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Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (2)

test/state/transaction.hpp:93

The public decode_transaction() declaration doesn’t document that legacy transactions are normalized (legacy v is converted to y_parity 0/1 and chain_id is extracted). This is important because rlp_encode() for legacy writes tx.v verbatim, so callers might assume decode_transaction() is a strict inverse and attempt to re-encode the decoded legacy transaction, producing different / invalid bytes.

/// Decodes a transaction from its complete serialization @p data.
///
/// Handles the legacy RLP list and the EIP-2718 typed envelope (type byte followed by an RLP list).
[[nodiscard]] std::optional<Transaction> decode_transaction(bytes_view data) noexcept;

test/state/rlp_decode.cpp:97

decode_header() narrows list_len (uint64_t) into Header::payload_length (uint32_t) without a range check. With very large inputs this can truncate the declared payload length and break list-boundary enforcement. Rejecting list_len > UINT32_MAX avoids silent truncation.

        input.remove_prefix(1 + len_of_list_len);
        out = {static_cast<uint32_t>(list_len), true};  // Fits: list_len < input_len < 4 GiB.
        return true;

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Comments suppressed due to low confidence (1)

test/state/rlp_decode.cpp:40

decode_long_header() relies on an assert() to ensure payload_len fits into Header::payload_length (uint32_t). In release builds the assert is compiled out, so a crafted RLP header with payload_len > UINT32_MAX would silently truncate during the static_cast<uint32_t>, potentially causing incorrect parsing/acceptance of malformed inputs. Add a runtime check and reject oversized payload lengths instead of asserting.

    input.remove_prefix(1 + len_of_len);
    assert(payload_len <= std::numeric_limits<uint32_t>::max());  // Inputs stay well below 4 GiB.
    out = {static_cast<uint32_t>(payload_len), IsList};
    return true;

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Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (2)

test/state/transaction.cpp:156

decode_transaction() constructs Transaction tx;, which default-initializes and leaves several fields indeterminate (sender, max_gas_price, max_priority_gas_price, max_blob_gas_price, value, r, s, etc.). On successful decode these can remain unread/unused today, but the returned Transaction may carry uninitialized data (and reading it is UB). Value-initialize the transaction to guarantee zeroed scalars and a zero sender when it is not recovered by the decoder.

    Transaction tx;

test/state/rlp_decode.hpp:57

take_list_payload() claims that rejecting a non-list item leaves from advanced past its header, but that’s not true for the single-byte form where decode_header() leaves from unchanged. Tighten the comment to avoid implying stronger advancement guarantees than the implementation provides.

/// Reads an RLP list header, advances @p from past the list, and returns its bounded payload.
/// Rejecting a non-list item leaves @p from advanced past its header.

+/// Decodes an EIP-7702 authorization.
+/// A malformed tuple leaves @p from past it and @p to partially assigned.
+///
+/// Declared here (not file-local) so the generic rlp::decode(std::vector<T>&) finds it by ADL.
+[[nodiscard]] bool decode(bytes_view& from, Authorization& to) noexcept;


+/// Decodes the RLP header, advancing @p input past it. Returns false on malformed input.
+/// On success the payload fits the advanced input: out.payload_length <= input.size().
+/// The only decoder that leaves @p input unchanged on failure.
+[[nodiscard]] bool decode_header(bytes_view& input, Header& out) noexcept;


Copilot

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

The state library can encode a transaction but not decode one: t8n and the state tests assemble transactions from JSON fields, so the serialized form a fixture carries is never parsed and never checked. Add state::decode_transaction(), the inverse of the existing RLP encoder. It takes a legacy RLP list or an EIP-2718 typed envelope and returns std::nullopt on malformed input, without throwing. The RLP primitives it needs are new. rlp_decode.{hpp,cpp} decodes a header and enforces canonicality (no leading-zero lengths or integers, the long form only above 55 bytes, a single byte below 0x80 unwrapped), bounds a scalar by the destination width, requires an exact width for addresses and hashes, and provides generic list, pair and vector decoders. The access list and the EIP-7702 authorization list go through the vector decoder, the latter via an ADL-visible decode(Authorization&). Decoding is not a strict inverse of the encoder: the legacy wire v is normalized into (chain_id, y_parity), so re-encoding a decoded legacy transaction need not reproduce its bytes, and v=35/36 collapses onto the pre-EIP-155 v=27/28 form. The declaration says so and a TODO records the fix. The unit tests give both new files 100% line and MC/DC coverage (clang source-based); the only regions left uncovered are the failure path of the payload-length assert, which cannot be reached. Co-authored-by: rodiazet <radek.zagorowicz@gmail.com>

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chfast requested a review from Copilot July 7, 2026 07:35

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chfast force-pushed the state/decode-transaction branch 3 times, most recently from 72d44f2 to dcc7adb Compare July 7, 2026 10:23

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Comment thread test/state/transaction.cpp

chfast force-pushed the state/decode-transaction branch from dcc7adb to dd6bed2 Compare July 7, 2026 10:30

chfast changed the title ~~test: Add transaction decoding to the state library~~ Add transaction decoding to the state library Jul 7, 2026

chfast force-pushed the state/decode-transaction branch 3 times, most recently from 3060cb0 to aaeddfc Compare July 7, 2026 15:42

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chfast force-pushed the state/decode-transaction branch from 98cdda2 to b0183cb Compare July 24, 2026 17:31

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chfast force-pushed the state/decode-transaction branch from e0b35fa to 23c3b92 Compare July 26, 2026 19:21

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chfast changed the title ~~Add transaction decoding to the state library~~ Add transaction and RLP decoding to the state library Jul 26, 2026

chfast force-pushed the state/decode-transaction branch from 1175942 to 66fe20d Compare July 26, 2026 21:01

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chfast merged commit 7686df8 into master Jul 26, 2026
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chfast deleted the state/decode-transaction branch July 26, 2026 21:41

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Add transaction and RLP decoding to the state library - #1581

Add transaction and RLP decoding to the state library#1581
chfast merged 1 commit into
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chfast commented Jul 7, 2026

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