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MmapSnapshot

Struct MmapSnapshot 

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pub struct MmapSnapshot { /* private fields */ }
Expand description

File-backed, cross-process seqlock snapshot.

Only the seqlock header and the SnapshotData block are shared; the layout is the #[repr(C)] prefix of SharedSnapshot, so the two are byte-compatible. The seqlock protocol (odd/even sequence, retry on torn reads) is identical across processes — the OS guarantees coherence of MAP_SHARED pages.

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impl MmapSnapshot

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pub const FILE_SIZE: usize

Required file size in bytes for a shared snapshot mapping.

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pub fn write(&self, data: &SnapshotData) -> Result<(), String>

Publish a full SnapshotData under the seqlock.

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pub fn begin_write(&self) -> Result<u64, String>

Begin an in-place write; returns the token for end_write.

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pub fn end_write(&self, expected: u64)

End an in-place write started with begin_write.

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pub unsafe fn data_mut(&self) -> &mut SnapshotData

Exclusive &mut access to the data block while the seqlock is held.

§Safety

Caller must hold the seqlock (begin_write, not yet end_write).

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pub fn read(&self) -> Option<SnapshotData>

Read the snapshot; None after SNAPSHOT_MAX_RETRIES torn reads or while the file is not initialized.

Trait Implementations§

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impl Send for MmapSnapshot

Available on non-WebAssembly only.
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impl Sync for MmapSnapshot

Available on non-WebAssembly only.

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