feat: add std::io::Write impl for BufferMut#62
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iduartgomez merged 4 commits intomainfrom Mar 23, 2026
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Enables bincode::serialize_into to write directly into WASM linear memory buffers, eliminating the intermediate Vec<u8> allocation that was previously needed when serializing data across the FFI boundary.
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- Remove 3 unnecessary WrappedState .clone() calls in contract.rs; write() only needs AsRef<[u8]>, no ownership transfer required - Add init_buf_with_capacity() to allocate WASM buffers by size without needing the data upfront - Use bincode::serialize_into to write RelatedContracts and UpdateData directly into WASM memory, eliminating intermediate Vec allocations - Fix pre-existing clippy warnings in test code (wildcard_enum_match_arm, assertions_on_constants) Depends on freenet/freenet-stdlib#62 for the std::io::Write impl on BufferMut.
4 tasks
Tests cover basic write, exact fill, partial write when near full, error on full buffer, empty slice, write_all, write_all overflow, and bincode::serialize_into integration. Uses host-memory buffers (no WASM runtime needed).
The from_raw_parts call in from_raw_builder's trace block panics when start_ptr is null (even with size=0) on newer Rust versions. Skip the trace logging when the linear memory pointer is null, which happens in host-memory buffer tests.
Includes std::io::Write impl for BufferMut, enabling direct serialization into WASM linear memory buffers.
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Summary
impl std::io::Write for BufferMutinmemory/buf.rsbincode::serialize_intoto write directly into WASM linear memory buffers, eliminating the intermediateVec<u8>allocation previously needed when serializing data across the FFI boundaryContext
Part of the state copying improvement initiative. The host currently serializes
RelatedContractsandUpdateDatato a tempVec<u8>, then copies that Vec into WASM memory — a double copy. With thisWriteimpl, freenet-core can usebincode::serialize_into(&mut buf)to write directly into the WASM buffer.Test plan
cargo testpassescargo clippy --all-targetsclean