WASM JavaScript Utils

A tiny modular collection of JavaScript Utils for use with WASM Modules.

Deps to use with a wasm module Instance:

• logger - Logs strings from WASM code.
• stack - Stack
• heap - JavaScript implementation of malloc, free to pass into wasm.
• types - Helper methods for seamless mapping of JS object to WASM memory

Types

The types module provides a method of mapping a JavaScript object to a section of WASM memory. Allowing you to set and get values from a memory buffer seamlessly.

• types.define(typedef) -> struct(DataView)

  • Param: typedef - Object where keys are mapped to low level C-like typedefs

  • Returns: struct(DataView) - A new typedef which can be attached to a generic DataView object.

    • struct.size - Size of the defined struct in bytes.

  • Example:

    Assuming you already have a wasm module setup:

    // let's say you have a wasm function which creates a new pointer to C struct
    // This struct contains { float x; float y; float z; }
    const ptr = wasmExports.createVec3(-1, -1, -1);
    
    // You can create a new Object in JavaScript to access the data pointed to by the pointer
    const vec3Struct = types.define({
      x: types.f32,
      y: types.f32,
      z: types.f32
    });
    
    // vec3Struct can now map to a 12 continues bytes in our memory buffer
    console.log(vec3Struct.size); // 12
    
    // Create a DataView to access the data within wasmMemory.buffer
    const vec3Dataview = new DataView(wasMemory.buffer, ptr, vec3Struct.size);
    
    const myVector = vec3Struct(vec3DataView);
    
    console.log(myVector.x); // -1
    console.log(myVector.y); // -1
    console.log(myVector.z); // -1
    
    // WASM changes will reflect in our JS struct
    wasmExports.setVec3X(ptr, 128);
    
    console.log(myVector.x); // 128
    
    // ... and vice-versa
    myVector.y = 100;
    
    wasmExports.logVec3Y(ptr); // 100

    structs can be nested:

    const objectStruct = types.define({
      value: types.u32, // unsigned 32 bit integer
      position: vec3Struct
    });
    
    console.log(objectStruct.size); // 16
    
    // Let's say this wasm function returns a pointer to object with position set to 100, 100, 0
    const objPtr = wasmExports.createObject();
    
    // ... we create the dataView etc.,
    
    const myObject = objectStruct(objectDataView);
    
    console.log(myObject.position.x); // 100
    console.log(myObject.position.y); // 100
    console.log(myObject.position.z); // 0