feat: streaming refill buffers for WASM state transfer#63
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iduartgomez merged 1 commit intomainfrom Mar 24, 2026
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Instead of allocating the full state size in WASM linear memory upfront, the host now writes data into small 64KB buffers with a [total_len: u32] header. The contract reads via StreamingBuffer, which calls a host import (__frnt__fill_buffer) to refill the buffer when exhausted. This reduces WASM memory usage from O(state_size) to O(64KB) for large contracts. For small states (<64KB), all data fits in one buffer with zero host callbacks. Changes: - Add StreamingBuffer with std::io::Read impl (contract-side) - Add __frnt__fill_buffer host import declaration - Add bytes_read(), reset_pointers(), last_read_ptr(), last_write_ptr() to BufferBuilder - Make compute_ptr public for host-side use - Update wasm_interface to use streaming reads for all contract operations - Add 7 unit tests for StreamingBuffer (non-refill path) - Bump version to 0.3.4
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Summary
StreamingBufferwithstd::io::Readimpl for streaming large state data from host to contract[total_len: u32][data...]header into small 64KB buffers__frnt__fill_bufferhost import to refillChanges
memory/buf.rs:StreamingBuffer,BufferBuilderaccessors (bytes_read,last_read_ptr,last_write_ptr),compute_ptrmade public, host import declaration, 7 unit testsmemory.rs:wasm_interfaceupdated to useStreamingBufferfor all contract operationsTest plan
StreamingBuffer::Read(basic, exact, chunks, empty, EOF, roundtrip)cargo test --features contract,net,testing,tracepasses (matches CI config)