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Documentation / @etherfold/core / cursorSyncedThrough

Function: cursorSyncedThrough() ​

cursorSyncedThrough<ABI>(lastSync, blockNumber): LastSync<ABI>

Defined in: packages/core/src/internal/engine/utils.ts:779

The cursor that describes a fold SYNCED THROUGH blockNumber, and the one rule for narrowing a cursor anywhere in this system.

A cursor is not a label, it is a claim that can be resumed from, so every cursor that is PUBLISHED or PERSISTED has to be true on its own. Narrowing one is therefore not "copy it and lower lastToBlock": the unconfirmed window is the set of blocks already folded, and the engine treats the top of it as the boundary above which events are NEW. A window reaching ABOVE lastToBlock makes the blocks in between invisible -- they are neither below the resume point nor above the window, so nothing ever delivers them, and the loss is silent and permanent.

What is truncated, and what deliberately is not ​

  • lastToBlock becomes blockNumber, which is the point: it is what getFromBlock resumes from.
  • unconfirmedBlocks is cut to the ones at or below it. They are ascending, so this is a prefix, and it has to be one.
  • latestBlock is NOT truncated. It is the chain tip that was observed, not progress through it, and lowering it would widen the re-fetch window for no reason.
  • context is not touched: it is the identity the core validates, and it is the same identity whichever block of the stream this is.

It lives HERE, in the engine, because two layers need the identical rule and a second implementation is a divergence waiting to happen: the batch loop in promiseToFeed narrows a cursor per BATCH, and applyEventStream narrows one per BLOCK (@etherfold/processor-entities re-exports this as syncedThrough). The last unit of a stream needs no narrowing at all and gets the lastSync itself, so the common case costs nothing.

Type Parameters ​

ABI ​

ABI extends Abi

Parameters ​

lastSync ​

LastSync<ABI>

blockNumber ​

number

Returns ​

LastSync<ABI>