Documentation

This documentation is for js-polo v0.1.4.

What is js-polo?

js-polo is a JS/TS implementation of the POLO encoding and object serialization scheme. POLO stands for Prefix Ordered Lookup Offsets.

It is intended for use in projects that prioritize deterministic serialization, minimal wire sizes and serialization safety. POLO follows a very strict specification that is optimized for partial decoding and differential messaging. This implementation is compliant with the POLO Specification that describes both the encoding (wire) format as well as implementation guidelines for several languages.

Features

Deterministic Serialization

POLO’s strict specification is intended to create the same serialized wire for an object regardless of implementation. This is critical for cryptographic security with operations such as hashing which is used to guarantee data consistency and tamper proofing.

High Wire Efficiency

POLO has a highly optimized wire format allows messages to be relatively small, even surpassing Protocol Buffers occassionaly. This is mainly because it supports a larger type based wire tagging that allows some information (especially metadata) to be passed around inferentially and thus reducing the total amount of information actually present in the wire.

This is augmented by the fact that POLO supports Atomic Encoding, because of which simple objects such as integers & strings can be encoded without needing to be wrapped within a larger (structural) message.

Partial Encoding/Decoding Constructs

The POLO wire format prefixes all metadata for the wire in the front, this metadata includes the wire type information as well as the offset position of the data. This kind of lookup based offset tags allows us to directly access the data for a particular field order. This capability is currently supported using the Document and Raw constructs.

The Document construct is used to create a string indexed collection of Raw object and it collapses into a special form of the POLO wire called the document-encoded wire with the WireDoc wire type. It’s unique in that it preserves the field name (string index) for the data unlike regular POLO encoding and is similar to encoding schemes like JSON or YAML and consequently consumes more wire space.

The Raw construct is useful for capturing the wire data for a specific field in the struct. It can also be used to define a structure that ‘skips’ the unrequired fields by capturing their raw wire instead of decoding them.

Partial encodign/decoding capabilities for this implementation are unfinished can be extended to support field order based access/write for regular POLO encoded wires in the future.

Differential Messaging (Coming Soon)

POLO’s partially encoding and field order based indexing (and string based indexing for document encoded wires) allows the possibility for messaging that only allows the transmission of the difference between two states, this is useful for any version managment system where the same data is incrementally updated and transmitted, the ability to index the difference and only transmit the difference can result in massive reduction in the wire sizes for these use cases that often re-transmit already available information.