Download
This task consists of retrieving Compact Blocks from the server and sending them downstream to the other tasks.
Lightwalletd offers a streaming interface that allows us to retrieve a range of blocks without blocking.
The start height is our latest synchronization height + 1. The end height is the latest block. The range can potentially be very large, but we don’t buffer more than a chunk of blocks and therefore can process large ranges.
Block Chunks
Warp Sync does not process blocks individually but as a sub ranges of the whole synchronization range.
When we receive a block, we filter out the transactions that have too many outputs/actions (Spam Filter) by clearing their output EPK and CIPHERTEXT.
We need to keep the CMU. They are needed for the Witness update.
The library queries the device available memory and adjusts the maximum number of outputs per chunk with a cap of 200 000 outputs.
The outputs are counted before the spam filter.
Otherwise, we could have an extremly high number of outputs to process in the “Update Witness” stage.
Once a chunk is full, we send it down through the pipeline to the next processing stage.
Download continues asynchronously in parallel with block chunk processing.