add call_indirect example

#7-call-indirect/call.js

@@ -0,0 +1,61 @@
+
+module.exports = loadWebAssembly
+
+loadWebAssembly.supported = typeof WebAssembly !== 'undefined'
+
+function loadWebAssembly (opts) {
+  if (!loadWebAssembly.supported) return null
+
+  var imp = opts && opts.imports
+  var wasm = toUint8Array('AGFzbQEAAAABBQFgAAF/AwQDAAAABAUBcAECAgYGAX8BQX8LBxACBXRhYmxlAQAEbWFpbgAACQgBAEEACwIBAgomAxoAIwBBAWokACMAQQFLBEBBACQACyMAEQAACwQAQQoLBABBFAs=')
+  var ready = null
+
+  var mod = {
+    buffer: wasm,
+    memory: null,
+    exports: null,
+    realloc: realloc,
+    onload: onload
+  }
+
+  onload(function () {})
+
+  return mod
+
+  function realloc (size) {
+    mod.exports.memory.grow(Math.ceil(Math.abs(size - mod.memory.length) / 65536))
+    mod.memory = new Uint8Array(mod.exports.memory.buffer)
+  }
+
+  function onload (cb) {
+    if (mod.exports) return cb()
+
+    if (ready) {
+      ready.then(cb.bind(null, null)).catch(cb)
+      return
+    }
+
+    try {
+      if (opts && opts.async) throw new Error('async')
+      setup({instance: new WebAssembly.Instance(new WebAssembly.Module(wasm), imp)})
+    } catch (err) {
+      ready = WebAssembly.instantiate(wasm, imp).then(setup)
+    }
+
+    onload(cb)
+  }
+
+  function setup (w) {
+    mod.exports = w.instance.exports
+    mod.memory = mod.exports.memory && mod.exports.memory.buffer && new Uint8Array(mod.exports.memory.buffer)
+  }
+}
+
+function toUint8Array (s) {
+  if (typeof atob === 'function') return new Uint8Array(atob(s).split('').map(charCodeAt))
+  return new (require('buf' + 'fer').Buffer)(s, 'base64')
+}
+
+function charCodeAt (c) {
+  return c.charCodeAt(0)
+}

#7-call-indirect/call.wat

@@ -0,0 +1,35 @@
+;; This example shows the way to change export table.
+(module
+  (table anyfunc (elem $internal_function$1 $internal_function$2))
+
+  (type $type_t (func (result i32)))
+
+  (export "table" (table 0))
+  (export "main" (func $public_function))
+
+  (global $i (mut i32) (i32.const -1))
+
+  ;; public exported function
+  (func $public_function (type $type_t)
+    ;; change ptr to internal function.
+    ;; ++i
+    (set_global $i (i32.add (get_global $i) (i32.const 1)))
+
+    ;; if (i > 1) i = 0
+    (if (i32.gt_u (get_global $i) (i32.const 1))
+      (set_global $i (i32.const 0))
+    )
+
+    ;; proxy to internal function
+    ;; use dynamic linking
+    (call_indirect $type_t (get_global $i))
+  )
+
+  (func $internal_function$1 (type $type_t)
+    (i32.const 10)
+  )
+
+  (func $internal_function$2 (type $type_t)
+    (i32.const 20)
+  )
+)

#7-call-indirect/index.js

@@ -0,0 +1,6 @@
+const wasm = require('./call')().exports
+
+console.log(wasm.main())  // 10
+console.log(wasm.main())  // 20
+console.log(wasm.main())  // 10
+console.log(wasm.main())  // 20