examples to read and create Uint8Array (#197)

Author: vmoroz

typed_array_to_native/node-addon-api/binding.gyp

@@ -0,0 +1,14 @@
+{
+  "targets": [
+    {
+      "target_name": "typed_array_to_native",
+      "cflags!": [ "-fno-exceptions" ],
+      "cflags_cc!": [ "-fno-exceptions" ],
+      "sources": [ "typed_array_to_native.cc" ],
+      "include_dirs": [
+        "<!@(node -p \"require('node-addon-api').include\")"
+      ],
+      'defines': [ 'NAPI_DISABLE_CPP_EXCEPTIONS' ],
+    }
+  ]
+}

typed_array_to_native/node-addon-api/index.js

@@ -0,0 +1,15 @@
+const binding = require('bindings')('typed_array_to_native');
+
+{
+    const byteArray = Uint8Array.from([10, 20, 30, 50, 25, 17]);
+    console.log("byteArray: ", byteArray);
+    binding.AcceptByteArray(byteArray);
+}
+console.log("---------");
+
+{
+    const array = [7, 15, 26, 58, 64];
+    console.log("array: ", array);
+    const byteArray = binding.CreateByteArray(array);
+    console.log("byteArray: ", byteArray);
+}

typed_array_to_native/node-addon-api/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "typed_array_to_native",
+  "version": "0.0.0",
+  "description": "Shows how to read and create typed arrays",
+  "main": "index.js",
+  "private": true,
+  "dependencies": {
+    "bindings": "~1.2.1",
+    "node-addon-api": "^1.0.0"
+  },
+  "scripts": {
+    "test": "node index.js"
+  }
+}

typed_array_to_native/node-addon-api/typed_array_to_native.cc

@@ -0,0 +1,108 @@
+#include <napi.h>
+#include <cstdio>
+
+static Napi::Value AcceptByteArray(const Napi::CallbackInfo& info) {
+  if (info.Length() != 1) {
+    Napi::Error::New(info.Env(), "Expected exactly one argument")
+        .ThrowAsJavaScriptException();
+    return info.Env().Undefined();
+  }
+
+  if (!info[0].IsTypedArray()) {
+    Napi::Error::New(info.Env(), "Expected a TypedArray")
+        .ThrowAsJavaScriptException();
+    return info.Env().Undefined();
+  }
+  Napi::TypedArray typedArray = info[0].As<Napi::TypedArray>();
+
+  if (typedArray.TypedArrayType() != napi_uint8_array) {
+    Napi::Error::New(info.Env(), "Expected an Uint8Array")
+        .ThrowAsJavaScriptException();
+    return info.Env().Undefined();
+  }
+  Napi::Uint8Array uint8Array = typedArray.As<Napi::Uint8Array>();
+
+  // Copy to std::vector<uint8_t>:
+  std::vector<uint8_t> bytes(uint8Array.Data(),
+                             uint8Array.Data() + uint8Array.ElementLength());
+  printf("std::vector<uint8_t> from Uint8Array: [");
+  for (uint8_t byte : bytes) {
+    printf("%d, ", byte);
+  }
+  printf("\b\b]\n");
+
+  return info.Env().Undefined();
+}
+
+static Napi::Value CreateByteArray(const Napi::CallbackInfo& info) {
+  if (info.Length() != 1) {
+    Napi::Error::New(info.Env(), "Expected exactly one argument")
+        .ThrowAsJavaScriptException();
+    return info.Env().Undefined();
+  }
+
+  if (!info[0].IsArray()) {
+    Napi::Error::New(info.Env(), "Expected an Array")
+        .ThrowAsJavaScriptException();
+    return info.Env().Undefined();
+  }
+  Napi::Array array = info[0].As<Napi::Array>();
+  size_t arrayLength = array.Length();
+
+  // Create std::vector<uint8_t> out of array.
+  // We allocate it on the heap to allow wrapping it up into ArrayBuffer.
+  std::unique_ptr<std::vector<uint8_t>> nativeArray =
+      std::make_unique<std::vector<uint8_t>>(arrayLength, 0);
+  for (size_t i = 0; i < arrayLength; ++i) {
+    Napi::Value arrayItem = array[i];
+    if (!arrayItem.IsNumber()) {
+      Napi::Error::New(info.Env(), "Expected a Number as Array Item")
+          .ThrowAsJavaScriptException();
+      return info.Env().Undefined();
+    }
+    Napi::Number number = arrayItem.As<Napi::Number>();
+    double numberValue = number.DoubleValue();
+    if (numberValue < 0 || numberValue > 255) {
+      Napi::Error::New(info.Env(),
+                       "Array Item Number value is out of range [0..255]")
+          .ThrowAsJavaScriptException();
+      return info.Env().Undefined();
+    }
+
+    (*nativeArray)[i] = static_cast<uint8_t>(numberValue);
+  }
+
+  printf("std::vector<uint8_t> from Array: [");
+  for (uint8_t byte : *nativeArray) {
+    printf("%d, ", byte);
+  }
+  printf("\b\b]\n");
+
+  // Wrap up the std::vector into the ArrayBuffer.
+  // Note: instead of wrapping the std::vector we could allow ArrayBuffer to
+  // create internal storage that copies the std::vector, but it is less
+  // efficient because it requires an extra memory allocation.
+  Napi::ArrayBuffer arrayBuffer = Napi::ArrayBuffer::New(
+      info.Env(),
+      nativeArray->data(),
+      arrayLength /* size in bytes */,
+      [](Napi::Env /*env*/, void* /*data*/, std::vector<uint8_t>* hint) {
+        std::unique_ptr<std::vector<uint8_t>> vectorPtrToDelete(hint);
+      },
+      nativeArray.get());
+  // The finalizer is responsible for deleting the vector: release the
+  // unique_ptr ownership.
+  nativeArray.release();
+
+  Napi::Uint8Array byteArray = Napi::Uint8Array::New(info.Env(), arrayLength, arrayBuffer, 0);
+  
+  return byteArray;
+}
+
+static Napi::Object Init(Napi::Env env, Napi::Object exports) {
+  exports["AcceptByteArray"] = Napi::Function::New(env, AcceptByteArray);
+  exports["CreateByteArray"] = Napi::Function::New(env, CreateByteArray);
+  return exports;
+}
+
+NODE_API_MODULE(NODE_GYP_MODULE_NAME, Init)