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Nanaloveyuki
75 lines
1.8 KiB
Markdown
75 lines
1.8 KiB
Markdown
---
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name: runtime-sink-file-reopen-truncate
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group: api
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category: runtime
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update-time: 20260613
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description: Reopen the file sink behind a RuntimeSink in truncate mode.
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key-word:
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- runtime
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- sink
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- file
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- public
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---
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## Runtime-sink-file-reopen-truncate
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Reopen the file sink behind a `RuntimeSink` in truncate mode. This helper is the explicit truncate-oriented direct recovery or reset shortcut.
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### Interface
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```moonbit
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pub fn RuntimeSink::file_reopen_truncate(self : RuntimeSink) -> Bool {
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```
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#### input
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- `self : RuntimeSink` - Runtime sink whose file sink should be reopened in truncate mode.
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#### output
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- `Bool` - Whether reopen succeeded.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- Plain `File` runtime variants reopen in truncate mode.
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- `QueuedFile` runtime variants forward reopen behavior to the wrapped inner file sink.
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- This helper is a specialized shortcut for a common reset-style reopen mode.
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- Non-file runtime variants return `false`.
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### How to Use
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Here are some specific examples provided.
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#### When Need A Fresh Output File
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When a runtime file should be reopened from an empty state:
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```moonbit
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ignore(sink.file_reopen_truncate())
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```
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In this example, reopen behavior truncates the file before future writes continue.
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#### When Want An Explicit Truncate Shortcut
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When code should make destructive reopen intent obvious:
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```moonbit
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let ok = sink.file_reopen_truncate()
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```
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In this example, the call site expresses reset-style reopen behavior directly.
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### Error Case
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e.g.:
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- If the runtime sink is not file-backed, the method returns `false`.
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- If callers want to preserve existing file content, `file_reopen_append()` is the correct API.
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### Notes
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1. Use this helper when starting from a fresh file is intentional.
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2. Truncate-mode reopen is a stronger action than generic reopen recovery.
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