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33 lines
1.4 KiB
Markdown
33 lines
1.4 KiB
Markdown
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# Message Segmentation
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Split large payloads into Waku-sized segments with optional Reed–Solomon parity for robust reconstruction. Inbound segmented messages are reassembled and persisted until complete.
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## Features
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- **Segmentation**: Outbound payloads over the configured size are split into segments; smaller payloads pass through unchanged.
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- **Reconstruction**: Inbound segments can be processed out of order and reassembled into the original message.
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- **Erasure coding**: Adds parity segments at 12.5% of data segments (≤ SegmentsReedsolomonMaxCount), enabling recovery with ~87.5% of segments.
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- **Persistence**: Segments and completion state are stored (SQLite) and survive restarts.
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- **API simplicity**: Main parameter is the maximum segment size; inject your persistence object.
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## Essential API
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- **Types**: `SegmentationHander`, `Chunk`, `Message`
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- **Outbound**: `segmentMessage(handler, chunk: Chunk): Result[seq[Chunk], string]`
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- **Inbound**: `handleSegmentationLayer(handler, message: var Message): Result[void, string]`
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- **Helpers**: `isParityMessage(segment: SegmentMessage): bool`
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- **Parameters**: `segmentSize` (bytes); provide `SegmentationPersistence` instance
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Notes
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- Parity rate is 12.5% (`SegmentsParityRate = 0.125`).
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## Wire format
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Segments are protobuf-encoded (`segment_message.proto`):
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## Tests
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See `tests/test_segmentation.nim` for examples covering in-order/out-of-order and parity recovery paths.
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