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Hello World!

Notice: W3bstream is under development.
The current documentation refers to W3bstream 1.0.0-rc2

Supported languages

SDKs to build W3bstream applets are available for the following languages:

Event handlers

When creating an applet for W3bstream, you must export at least one function inside the resulting WASM module, to serve as an event handler in W3bstream.
This handler can then be linked to a W3bstream event by configuring a strategy in the project's event strategies configuration.
💡 Learn more
Default event handler
When deploying an applet to a W3bstream project, W3bstream creates a default event strategy that connects any W3bstream event to a default _start() handler function with the following signature:
AssemblyScript
export function start(rid: i32): i32
Go
//export start
func _start(event_id uint32) int32
Rust
#[no_mangle]
pub extern "C" fn start(event_id: i32) -> i32
C++
#EMSCRIPTEN_KEEPALIVE uint32_t _start(uint32_t event_id)

The W3bstream Console

W3bstream provides a text console for applets to output text to, which can be accessed through the Log function of the SDK:
AssemblyScript
Golang
import { Log } from "../../assembly/index";
...
Log("Some text");
​
import "github.com/machinefi/w3bstream-wasm-golang-sdk/log"
...
log.Log("Some text");
​

Your first W3bstream "Hello World!"

Creating a “Hello World!” example for W3bstream is now very simple:
AssemblyScript
Go

Get the project ready

Let's start with creating a new folder for the project
mkdir helloworld && cd helloworld
Initialize the project with npm
npm init -y
Install the AssemblyScript compiler
npm install --save-dev assemblyscript
Scaffold a new AssemblyScript project:
npx asinit .
Add the W3bstream AssemblyScript SDK package:
npm install @w3bstream/wasm-sdk
edit the scripts field in package.json and replace it with the following:
"scripts": {
"asbuild:release": "asc assembly/index.ts --use abort=assembly/index/abort --target release",
},
​

Create helloworld.ts

Edit assembly/index.ts, paste the following code and save it:
import { Log } from "@w3bstream/wasm-sdk";
// Export alloc() is needed for w3bstream vm
export { alloc } from "@w3bstream/wasm-sdk";
​
export function start(rid: i32): i32 {
Log("Hello World!");
return 0;
}
​
// The abort method will be exposed inside w3bstream
// in a later release. For now, you can use it to log errors:
export function abort(
message: string | null,
fileName: string | null,
lineNumber: u32,
columnNumber: u32
): void {
if (message == null) message = "unknown error";
if (fileName == null) fileName = "unknown file";
Log("ABORT: " + message
+ " at " + fileName
+ ":" + lineNumber.toString()
+ ":" + columnNumber.toString());
}

​

Build the WASM module

Finally, build the wasm module with:
npm run asbuild
At the end of the building process, the W3bstream module can be found in build/release.wasm

Get the project ready

Let's start with creating a new folder for the project
mkdir helloworld && cd helloworld
Initialize the project with go mod
go mod init helloworld
​

Create helloworld.go

create helloworld.go with the current code and save it:o
package main
​
import "github.com/machinefi/w3bstream-wasm-golang-sdk/log"
​
// main is required for TinyGo to compile to WASM
func main() {}
​
//export start
func _start(rid uint32) int32 {
log.Log("Hello World!")
return 0
}
​

Build the WASM module for W3bstream

install required imports (in this case, the W3bstream Go SDK):
go mod tidy
make sure you have TinyGo installed in your system, then buuild the module with:
tinygo build -o helloworld.wasm -scheduler=none --no-debug -target=wasi helloworld.go
At the end of the building process, the file helloworld.wasm can be found in the current folder.

Test Hello World in W3bstream!

Once you built the Hello World! example as a WASM module, you can upload and deploy it to the W3bstream node as explained in the Get Started section of this documentation:
then use the W3bstream Studio to send any message to your project (make sure the applet is running!):
finally, check the log of your W3bstream node: you should see the "Hello World!" string printed:
...
// W3bstream calling the "start" handler upon message received
{
"@lv": "info",
"@prj": "srv-applet-mgr",
"@ts": "20221102-140006.340Z",
"msg": "call handler:start"
}
// This is the log from the start function
{
"@applet": "MyApplet",
"@lv": "info",
"@namespace": "HelloWorldProject",
"@prj": "srv-applet-mgr",
"@src": "wasm",
"@ts": "20221102-140006.340Z",
"msg": "Hello World!"
}