callback

Cross-module function call bindings Allows passing function references between WASM modules via the host. The host stores (exec_env, table_index) pairs and invokes them on demand.

AssemblyScript

// @ts-ignore
@external("callback", "callback_register")
export declare function callbackRegister(tableIdx: u32): u32;


// @ts-ignore
@external("callback", "callback_invoke")
export declare function callbackInvoke(handle: u32, argsPtr: u32, nArgs: u32): u32;


// @ts-ignore
@external("callback", "callback_unregister")
export declare function callbackUnregister(handle: u32): void;

Zig

pub extern "callback" fn callback_register(table_idx: u32) u32;

pub extern "callback" fn callback_invoke(handle: u32, args_ptr: u32, n_args: u32) u32;

pub extern "callback" fn callback_unregister(handle: u32) void;

Rust

#[link(wasm_import_module = "callback")]
extern "C" { 
  #[link_name = "callback_register"]
  fn unsafe_callback_register(table_idx: u32) -> u32;

  #[link_name = "callback_invoke"]
  fn unsafe_callback_invoke(handle: u32, args_ptr: u32, n_args: u32) -> u32;

  #[link_name = "callback_unregister"]
  fn unsafe_callback_unregister(handle: u32);
}

pub fn callback_register(table_idx: u32) -> u32 {
  unsafe {
    return unsafe_callback_register(table_idx);
  }
}


pub fn callback_invoke(handle: u32, args_ptr: u32, n_args: u32) -> u32 {
  unsafe {
    return unsafe_callback_invoke(handle, args_ptr, n_args);
  }
}


pub fn callback_unregister(handle: u32) {
  unsafe {
    unsafe_callback_unregister(handle);
  }
}

TinyGo

package callback




//go:wasmimport callback callback_register
func CallbackRegister(TableIdx uint32) uint32;

//go:wasmimport callback callback_invoke
func CallbackInvoke(Handle uint32, ArgsPtr uint32, NArgs uint32) uint32;

//go:wasmimport callback callback_unregister
func CallbackUnregister(Handle uint32);

C

__attribute__((import_module("callback")))
__attribute__((import_name("callback_register")))
extern unsigned int callback_register(unsigned int table_idx);


__attribute__((import_module("callback")))
__attribute__((import_name("callback_invoke")))
extern unsigned int callback_invoke(unsigned int handle, unsigned int args_ptr, unsigned int n_args);


__attribute__((import_module("callback")))
__attribute__((import_name("callback_unregister")))
extern void callback_unregister(unsigned int handle);

C++

extern "C" {
  __attribute__((import_module("callback")))
  __attribute__((import_name("callback_register")))
  extern unsigned int callback_register(unsigned int table_idx);

  __attribute__((import_module("callback")))
  __attribute__((import_name("callback_invoke")))
  extern unsigned int callback_invoke(unsigned int handle, unsigned int args_ptr, unsigned int n_args);

  __attribute__((import_module("callback")))
  __attribute__((import_name("callback_unregister")))
  extern void callback_unregister(unsigned int handle);
}