store: Wasm 文字指令

(module

  (memory $memory 1)
  (export "memory" (memory $memory))

  (func (export "store_in_mem") (param $num i32)
    i32.const 0
    local.get $num

    ;; store $num at position 0
    i32.store
  )

)

const url = "{%wasm-url%}";
const result = await WebAssembly.instantiateStreaming(fetch(url));

const store_in_mem = result.instance.exports.store_in_mem;
const memory = result.instance.exports.memory;

store_in_mem(100);

const dataView = new DataView(memory.buffer);
const first_number_in_mem = dataView.getUint32(0, true);

console.log(first_number_in_mem);
// Expected output: 100

;; Store value in default memory at particular offset
i32.const 0 ;; stack variable with offset in memory to store the number
i32.const 20 ;; stack variable with the number to store
i32.store ;; store in default memory

;; Store using S-function (same values and offset)
(i32.store (i32.const 0) (i32.const 20))

;; Store in memory referenced by its index
i32.const 0 ;; offset in memory to store the number
i32.const 20 ;; the number to store
i32.store (memory 2)  ;; store in memory with index 2

;; Store in memory referenced by its name
i32.const 0 ;; offset to store the number
i32.const 20 ;; the number to store
i32.store (memory $memoryName)  ;; store in memory with name "$memoryName"

;; Store in same memory using an S function
(i32.store (memory $memoryName) (i32.const 0) (i32.const 20))