Add ByteBuffer serialization to Filter interface and implementations - #1

Adds writeTo(ByteBuffer) and static readFrom(ByteBuffer) methods to enable filter persistence. Each filter writes a version byte (starting at 1) followed by its data members.

Implementation Coverage

Fully implemented (13 filters):

• Bloom filters: Bloom, BlockedBloom, CountingBloom
• Xor filters: Xor8, Xor16, XorBinaryFuse8/16/32, XorPlus8
• Cuckoo filters: Cuckoo8/16, CuckooPlus8/16

Stub implementations (5 filters):

• GolombCompressedSet - requires BitBuffer/MonotoneList serialization
• SuccinctCounting* variants - require BitField/Select serialization

Stubs throw UnsupportedOperationException with TODO comments.

Example Usage

// Serialize
Xor8 filter = Xor8.construct(keys);
ByteBuffer buffer = ByteBuffer.allocate(bufferSize);
filter.writeTo(buffer);

// Deserialize
buffer.flip();
Xor8 restored = Xor8.readFrom(buffer);

Implementation Details

• Rank9 helper extended with ByteBuffer support for XorPlus8
• Private constructors added for deserialization where needed
• Test suite uses generic method to eliminate repetition across filter types
• Version checking ensures compatibility on deserialization

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.