host

AssemblyScript WASM - Host Interface & Interaction

This example package demonstrates compiling a simple AssemblyScript program, host.ts which access various constants and functions made available by the host environment.

Installing Dependencies

from the project root:

npm install

Compiling AssemblyScript to WASM

To compile the host.ts code to a WASM binary:

npm run build

A host.wasm file will be produced in the build directory

Testing

Test the module outside of the context of the blockchain:

npm test

This will run NodeJS based tests in the test directory. For example in host.unit.spec.js test instantiation of the compiled WASM module, and assertions to verify its API and behavior:

describe('Host Constant', function () {
        it('Get Count Constant', async function () {
            const count = module.getHostCount();
            assert.strictEqual(count, 9001);
        });
    ...
    });

API

getHostCount() - i32

Return the count constant exposed by the host

getHostAdd(i32 x, i32 y) - i32

Return the result of adding x and y on the host

getHostMessage() - string(i32)

Returns a pointer to the message string exposed by the host