There are two ways to get a WebAssembly.Memory
object. The first way is to construct it from JavaScript. The following snippet creates a new WebAssembly Memory instance with an initial size of 10 pages (640KiB), and a maximum size of 100 pages (6.4MiB). Its buffer
property will return an ArrayBuffer
.
var memory = new WebAssembly.Memory({initial:10, maximum:100});
The following example (see memory.html on GitHub, and view it live also) fetches and instantiates the loaded memory.wasm byte code using the WebAssembly.instantiateStreaming()
method, while importing the memory created in the line above. It then stores some values in that memory, then exports a function and uses it to sum some values.
WebAssembly.instantiateStreaming(fetch('memory.wasm'), { js: { mem: memory } })
.then(obj => {
var i32 = new Uint32Array(memory.buffer);
for (var i = 0; i < 10; i++) {
i32[i] = i;
}
var sum = obj.instance.exports.accumulate(0, 10);
console.log(sum);
});
The second way to get a WebAssembly.Memory object is to have it exported by a WebAssembly module. This memory can be accessed in the exports
property of the Web Assembly instance (after the memory is exported within the Web Assembly module). The following snippet imports a memory exported from WebAssembly with the name memory
, and then prints out the first element of the memory, interpreted as an Uint32Array.
WebAssembly.instantiateStreaming(fetch('memory.wasm'))
.then(obj => {
var i32 = new Uint32Array(obj.instance.exports.memory.buffer);
console.log(i32[0]);
});