Module hdk::hdk

source ·
Expand description

The interface between the host and guest is implemented as an HdkT trait.

The set_hdk function globally sets a RefCell to track the current HDK implementation. When the mock feature is set then this will default to an HDK that always errors, else a WASM host is assumed to exist. The mockall crate (in prelude with mock feature) can be used to generate compatible mocks for unit testing. See mocking examples in the test WASMs crate, such as agent_info.


  • Used as a placeholder before any other Hdk is registered. Generally only useful for testing but technically can be set any time.
  • The HDK implemented as externs provided by the host.



  • When mocking is enabled the mockall crate automatically builds a MockHdkT for us.


  • At any time the global HDK can be set to a different hdk. Generally this is only useful during rust unit testing. When executing wasm without the mock feature, the host will be assumed.