Calling a WebAssembly

A WebAssembly (abbreviated wasm) is a portable, binary format for holding compiled code that can be called from web client and server applications. General info. can be found here. Details on building and compiling a WebAssembly can be found here.

A WebAssembly can be called by a ClearBlade code-service running on V8. This example shows you how to call a WebAssembly from a V8 code-service. Creation of the WebAssembly is mentioned but is out of the scope of this document.

PREREQUISITES:

1. Tools required to compile a WebAssembly pre-installed. There are several such tools to choose from, e.g. assemblyscript NPM module. Building the WebAssembly is mentioned but is out of the scope of this document.

STEPS:

1. Create your WebAssembly. For example:

2. Edit and save the source…

   

   
   

   1. Build the WebAssembly (e.g. npm run asbuild)
      

   2. Look for the generated .wasm file (e.g. build/release.wasm). The .wasm can be renamed.
      

3. Upload the .wasm file to a Bucket:

   1. In a ClearBlade system choose Files then Add Bucket Set

      

      
      

   2. Name the new Bucket Set and choose the appropriate Platform Storage. Bucket Sets can be stored locally, in a Google Bucket or in an AWS S3 bucket.

      

      
      

      
      

   3. Select Add File, decide if the WebAssembly will be added to the Inbox, Outbox, or Sandbox folder. Then browse to your .wasm
      

      

      
      

4. Write the code-service:

   1. Make sure to make the clearblade_async library a dependency of the the code-service or any of its libraries.

   2. Choose Engine type V8

      

   3. Use a function like this for loading the WebAssembly:

      async function loadWasmFromBucket (deployment, file) {
              const fs = new ClearBladeAsync.FS(deployment)
              const resp = await fs.readFile(file)
              const mod = new WebAssembly.Module(resp)
              const instance = new WebAssembly.Instance(mod)
              return instance
        }
      

      This function may be added to a library that can be called from the code-service.
      

   4. Write the rest of the service, save and test