Polkadot Parachain

placeholder //TODO Write content :) (https://github.com/paritytech/polkadot/issues/159)

lib.rs:

Defines primitive types for creating or validating a parachain.

When compiled with standard library support, this crate exports a wasm module that can be used to validate parachain WASM.

Parachain WASM

Polkadot parachain WASM is in the form of a module which imports a memory instance and exports a function validate_block.

validate accepts as input two i32 values, representing a pointer/length pair respectively, that encodes ValidationParams.

validate returns an u64 which is a pointer to an u8 array and its length. The data in the array is expected to be a SCALE encoded ValidationResult.

ASCII-diagram demonstrating the return data format:

[pointer][length]
  32bit   32bit
        ^~~ returned pointer & length

The wasm-api (enabled only when std feature is not enabled and wasm-api feature is enabled) provides utilities for setting up a parachain WASM module in Rust.