50 lines
2.1 KiB
Markdown
50 lines
2.1 KiB
Markdown
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# Box Patterns (dev guide; docs-only)
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Status: design notes to standardize reusable Box idioms. No runtime/spec change during the feature‑pause.
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## OwnershipBox / LeaseBox
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- Intent: make ownership vs borrowing explicit for resource Boxes.
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- Rules
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- OwnershipBox owns the underlying handle; calls `fini()` on drop.
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- LeaseBox references an owned Box without taking responsibility to `fini()`.
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- Upgrading a lease to ownership must be explicit (and validated).
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- Smells avoided: double-close, leaked handles, implicit transfer.
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## CancelTokenBox / DeadlineBox
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- Intent: structured cancellation and time limits across waiting APIs.
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- Rules
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- Token can be passed to blocking APIs (Channel/Select/Waiter) to abort waits.
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- DeadlineBox wraps an absolute time; APIs accept either `token` or `deadline`.
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- Cancellation is idempotent; multiple cancel calls are safe.
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- Effects
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- Waiting ops return promptly with a well-typed cancel/timeout indicator.
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## CapabilityBox
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- Intent: define minimal authority (I/O, net, thread, fs) explicitly.
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- Rules
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- Boxes that access external capabilities must declare the capability dependency.
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- Tests can substitute Noop/Mock capability Boxes.
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- Effects
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- Principle of least privilege; easier sandboxing and auditing.
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## AffinityBox
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- Intent: encode thread/runtime affinity constraints.
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- Rules
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- Annotate Boxes that must be used on their creator thread or via Actor mailbox.
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- Violations produce early, explicit errors (not UB).
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- Effects
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- Predictable behavior across concurrency boundaries.
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## ObservableBox
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- Intent: unify tracing/metrics hooks.
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- Rules
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- Emit JSONL events with `ts`, `box_id`, `op`, `ok`, and domain-specific fields.
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- Allow opt-in (`NYASH_*_TRACE=1`) and keep logs stable for tooling.
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- Effects
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- Cross-cutting visibility with one schema; simpler troubleshooting.
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## Composition Tips
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- Separate hot/cold paths: ThinBox (hot) vs RichBox (full) to avoid overhead on the critical path.
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- Prefer immutable handles + message passing across threads (Actor) to avoid races.
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- Keep `birth/fini` idempotent; document post-fini behavior (no-op vs error).
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