Attribute Macro pallet_revive_proc_macro::define_env

#[define_env]

Defines a host functions set that can be imported by contract wasm code.

NB: Be advised that all functions defined by this macro will panic if called with unexpected arguments.

It’s up to you as the user of this macro to check signatures of wasm code to be executed and reject the code if any imported function has a mismatched signature.

Example

#[define_env]
pub mod some_env {
	fn foo(ctx: _, memory: _, key_ptr: u32, value_ptr: u32, value_len: u32) -> Result<(), TrapReason> {
		ctx.some_host_fn(KeyType::Fix, key_ptr, value_ptr, value_len).map(|_| ())
	}
}

This example will expand to the foo() defined in the wasm module named seal0. This is because the module seal0 is the default when no module is specified.

To define a host function in seal2 and seal3 modules, it should be annotated with the appropriate attribute as follows:

Example

#[define_env]
pub mod some_env {
	#[version(2)]
	fn foo(ctx: _, memory: _, key_ptr: u32, value_ptr: u32, value_len: u32) -> Result<ReturnErrorCode, TrapReason> {
		ctx.some_host_fn(KeyType::Fix, key_ptr, value_ptr, value_len).map(|_| ())
	}

	#[version(3)]
	#[unstable]
	fn bar(ctx: _, memory: _, key_ptr: u32, value_ptr: u32, value_len: u32) -> Result<u32, TrapReason> {
		ctx.some_host_fn(KeyType::Fix, key_ptr, value_ptr, value_len).map(|_| ())
	}
}

The function bar is additionally annotated with unstable which removes it from the stable interface. Check out the README to learn about unstable functions.

In this example, the following host functions will be generated by the macro:

• foo() in module seal1,
• seal_foo() in module seal1,
• bar() in module seal42.

Only following return types are allowed for the host functions defined with the macro:

• Result<(), TrapReason>,
• Result<ReturnErrorCode, TrapReason>,
• Result<u32, TrapReason>.
• Result<u64, TrapReason>.

The macro expands to pub struct Env declaration, with the following traits implementations:

• pallet_revive::wasm::Environment<Runtime<E>> where E: Ext
• pallet_revive::wasm::Environment<()>

The implementation on () can be used in places where no Ext exists, yet. This is useful when only checking whether a code can be instantiated without actually executing any code.

To build up these docs, run:

cargo doc