ChDriver.
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LZ4 compression and CityHash checksums, backed by a Rust NIF.
These are the low-level primitives ClickHouse's wire compression is built
on: lz4_compress/1 and lz4_decompress/2 work with raw LZ4 blocks (not
the LZ4 Frame format), and cityhash128/1 computes the checksum
ClickHouse uses to verify each compressed block.
You won't normally call this module directly — ChDriver.Protocol.Block.Compressed
builds the full block envelope on top of it. It's public because the
primitives are useful on their own if you need raw LZ4/CityHash outside
the driver.
Summary
Functions
Computes the 128-bit CityHash v1.0.2 checksum of data, returned as a
16-byte binary already in ClickHouse's on-wire byte order.
Compresses data using raw LZ4 block compression (no frame header).
Decompresses a raw LZ4 block.
Functions
@spec cityhash128(iodata()) :: <<_::128>>
Computes the 128-bit CityHash v1.0.2 checksum of data, returned as a
16-byte binary already in ClickHouse's on-wire byte order.
Compresses data using raw LZ4 block compression (no frame header).
@spec lz4_decompress(iodata(), non_neg_integer()) :: {:ok, binary()} | {:error, String.t()}
Decompresses a raw LZ4 block.
uncompressed_size must be known ahead of time — the raw LZ4 block
format has no length prefix of its own, so the caller has to supply it
(ClickHouse carries it in the block header).