LibContext

Git Source

Conventions for working with context as a calling contract. All of this functionality is OPTIONAL but probably useful for the majority of use cases. By building and authenticating onchain, caller provided and signed contexts all in a standard way the overall usability of context is greatly improved for expression authors and readers. Any calling contract that can match the context expectations of an existing expression is one large step closer to compatibility and portability, inheriting network effects of what has already been authored elsewhere.

Functions

base

The base context is the msg.sender and address of the calling contract. As the interpreter itself is called via an external interface and may be statically calling itself, it MAY NOT have any ability to inspect either of these values. Even if this were not the case the calling contract cannot assume the existence of some opcode(s) in the interpreter that inspect the caller, so providing these two values as context is sufficient to decouple the calling contract from the interpreter. It is STRONGLY RECOMMENDED that even if the calling contract has "no context" that it still provides this base to every eval. Calling contracts DO NOT need to call this directly. It is built and merged automatically into the standard context built by build.

function base() internal view returns (uint256[] memory);

Returns

hash

Standard hashing process over a single SignedContextV1. Notably used to hash a list as SignedContextV1[] but could also be used to hash a single SignedContextV1 in isolation. Avoids allocating memory by hashing each struct field in sequence within the memory scratch space.

function hash(SignedContextV1 memory signedContext) internal pure returns (bytes32 hashed);

Parameters

hash

Standard hashing process over a list of signed contexts. Situationally useful if the calling contract wants to record that it has seen a set of signed data then later compare it against some input (e.g. to ensure that many calls of some function all share the same input values). Note that unlike the internals of build, this hashes over the signer and the signature, to ensure that some data cannot be re-signed and used under a different provenance later.

function hash(SignedContextV1[] memory signedContexts) internal pure returns (bytes32 hashed);

Parameters

Returns

build

Builds a standard 2-dimensional context array from base, calling and signed contexts. Note that "columns" of a context array refer to each uint256[] and each item within a uint256[] is a "row".

function build(uint256[][] memory baseContext, SignedContextV1[] memory signedContexts)
    internal
    view
    returns (uint256[][] memory);

Parameters