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Import functions

The #[marine] macro can also wrap a Rust extern block. In this case, all functions declared in it are considered imported functions. If there are imported functions in some module, say, module A, then

  • There should be another module, module B, that exports the same functions. The name of module B is indicated in the link macro (see examples below)
  • Module B should be loaded into Marine by the moment the loading of module A starts. Module A cannot be loaded if at least one imported function is absent in Marine.

Function import requirements​

  • wrap an extern block with the function(s) to be imported with the #[marine] macro
  • all function(s) arguments must be of the mtype type
  • the return type of the function(s) must be mtype

Examples​

See the examples below of wrapped extern block usage:

rust
#[marine]
pub struct TestRecord {
    pub field_0: i32,
    pub field_1: Vec<Vec<u8>>,
}
// wrap the extern block with the marine macro to expose the function
// as an import to the Marine VM
#[marine]
#[link(wasm_import_module = "some_module")]
extern "C" {
    pub fn foo(arg: Vec<Vec<Vec<Vec<TestRecord>>>>, arg_2: String) -> Vec<Vec<Vec<Vec<TestRecord>>>>;
}
rust
#[marine]
pub struct TestRecord {
    pub field_0: i32,
    pub field_1: Vec<Vec<u8>>,
}
// wrap the extern block with the marine macro to expose the function
// as an import to the Marine VM
#[marine]
#[link(wasm_import_module = "some_module")]
extern "C" {
    pub fn foo(arg: Vec<Vec<Vec<Vec<TestRecord>>>>, arg_2: String) -> Vec<Vec<Vec<Vec<TestRecord>>>>;
}