Getting Events Data
fn ws_get_data(event_id i32, payload_ptr i32, payload_size i32) -> i32
Please check out the Hello World! section to learn how to create a basic WASM module that can be executed in W3bstream
When a W3bstream event matches a Project event strategy, the respective applet's handler is called and the event ID is passed as an argument.
Inside an applet, you can access the event's payload using the
ws_get_data W3bstream function. It is exported by the W3bstream WebAssembly VM and must be imported into your applet before it can be used:Go
Rust
C++
Typescript
// go:wasm-module env
// export ws_get_data
func _ws_get_data(rid, ptr, size uint32) int32
// You may refer to https://github.com/machinefi/w3bstream/blob/main/_examples/wasm_common_go/imports.go#L38, or use the `GetDataByRID` defined in wasm_common_go to fetch event's payload.
#[link(wasm_import_module = "env")]
extern "C" {
fn ws_get_data(event_id: i32, payload_ptr: i32, payload_size: i32) -> i32
}
// A C++ example is coming soon
// Typescript support is coming soon
The example below shows how to obtain the event payload and log it to the console:
Go
Rust
C++
Typescript
// go:wasm-module env
// export ws_log
func _ws_log(logLevel, ptr, size uint32) int32
// go:wasm-module env
// export ws_get_data
func _ws_get_data(rid, ptr, size uint32) int32
//export start handler
func _start(event_id uint32) int32 {
message, err := common.GetEventData(event_id)
Log(fmt.Sprintf("Event id %v payload: `%s`", event_is, string(message)))
return 0
}
func BytesToPointer(v []byte) (addr, size uint32) {
ptr := &v[0]
pptr := uintptr(unsafe.Pointer(ptr))
return uint32(pptr), uint32(len(v))
}
func StringToPointer(v string) (addr, size uint32) {
return BytesToPointer([]byte(v))
}
func Log(message string) {
ptr, size := StringToPointer(message)
_ = _ws_log(3, ptr, size) // logInfoLevel = 3
}
#[link(wasm_import_module = "env")]
extern "C" {
fn ws_log(log_level: i32, ptr: *const u8, size: i32) -> i32;
fn ws_get_data(event_id: i32, payload_ptr: i32, payload_size: i32) -> i32
}
#[no_mangle]
// This handler will be matched by the default Project event strategy in W3bstream
pub extern "C" fn start(event_id: i32) -> i32 {
log_info(
&format!("Start handler called with event_id: {}", event_id));
let payload = get_data_as_str(event_id).unwrap();
log_info(&format!("event data as string: {}", payload));
return 0;
}
// Returns the event payload as a string
fn get_data_as_str(event_id: i32) -> Option<String> {
let data_ptr = &mut (0 as i32) as *const _ as *const *mut u8;
let data_size = &(0 as i32);
match unsafe { ws_get_data(event_id, data_ptr, data_size) } {
0 => Some(unsafe { String::from_raw_parts(*data_ptr, *data_size as _, *data_size as _) }),
_ => None,
}
}
// Logs an info message string to the W3bstream console
fn log_info(str: &str) {
unsafe { ws_log(3, str.as_bytes().as_ptr(), str.len() as _) };
}
// A C++ example is coming soon
// Typescript support is coming soon
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