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Sample

futures-util 0.3.34: Differentiate futures-util stream stalling in chunks vs ready_chunks, sink feed vs send lazy flushing, forward poll_close semantics, and take_while item loss

Verified sample for cargo futures-util 0.3.34: Differentiate futures-util stream stalling in chunks vs ready_chunks, sink feed vs send lazy flushing, forward…

sha256:8dad9b00522c8ec7137956d2d7912d83e26f8020a34995bffe05df84d036a872

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Execution evidence

The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.

Evidence basis
Signed contract pass
Verification receipts
2
Signing keys that built it
2
Declared environment rust linux x64 rust rust cargo

Verification-run environments

Environment Contract Stages Run
rust 1 · linux alpine/x64 · docker ed25519:d91480838ac982c9 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · cargo@1
2026-08-16
rust 1 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · cargo@1
2026-08-18

Case

HOW
Goal
Differentiate futures-util stream stalling in chunks vs ready_chunks, sink feed vs send lazy flushing, forward poll_close semantics, and take_while item loss
Packages
Symbols
  • futures_util::stream::StreamExt::ready_chunks
  • futures_util::stream::StreamExt::chunks
  • futures_util::stream::StreamExt::forward
  • futures_util::sink::SinkExt::feed
  • futures_util::stream::StreamExt::take_while
  • futures_util::stream::StreamExt::buffered
  • futures_util::stream::StreamExt::buffer_unordered
  • futures_util::select_biased
  • futures_util::stream::FuturesUnordered
  • futures_util::future::Abortable
Environment
rust
Created
2026-08-16T09:31:34Z

Contract

  1. StreamExt::chunks returns Poll::Pending and withholds buffered items when upstream is pending before filling chunk capacity, whereas ready_chunks yields immediately
  2. StreamExt::forward feeds stream items into a sink and closes the sink via poll_close upon stream completion rather than leaving it open with poll_flush
  3. SinkExt::feed buffers items via start_send without triggering poll_flush while send triggers poll_flush on every call
  4. StreamExt::take_while permanently consumes and drops the first item failing predicate from the underlying stream
  5. StreamExt::buffered imposes head-of-line blocking preserving stream order whereas buffer_unordered yields in completion order
  6. select_biased! polls branch futures in top-down order deterministically when multiple branches are ready simultaneously
  7. FuturesUnordered returns Ready(None) when empty but remains reusable when subsequent futures are pushed
  8. Abortable resolves to Err(Aborted) when cancelled before completion but retains completed values intact

Files

  • Cargo.lock
  • Cargo.toml
  • NOTES.md
  • csx.json
  • src/custom_sink.rs
  • src/lib.rs
  • src/step_stream.rs
  • tests/futures_util_traps.rs

Download the source artifact (tar.gz)

Origin Seeder

csx-seed