This crate mainly exists to provide the Soroban [Host] type, which is the implementation of the [Env] interface between guest contract code and the host it runs within.
This crate also re-exports all of the content of the [soroban_env_common] crate for use by host (or contract local-testing) code. Most of the type and module definitions visible here are actually defined in the common crate.
The Host can be configured with or without support for a [vm::Vm],
depending on the "vm" cargo feature. When enabled, the VM is currently a
thin wrapper around the wasmi
interpreter, though other VMs might be supported in the future.
It may seem unusual to configure a contract host without a VM, but this
configuration makes more sense when considering that Soroban supports a
"local testing" configuration where host and guest code are both compiled
natively and linked together for a faster and richer debugging and testing
experience. When testing this way, developers may also wish to enable the
"testutils" feature, which enables an interface on [Host] for registering
other test contracts by ID.
The [Host] type provides some facilities above and beyond just the [Env] trait, including:
- The [budget] module which is responsible for measuring and limiting execution costs in terms of CPU and memory.
- The [storage] module which is responsible for providing an interface between contracts and their durable storage.