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我有一个使用谷歌平面缓冲区的 nodejs 应用程序。

饮料模式的 fbs 文件：

namespace MyAlcoholist;

table Drink {
drink_type_name: string;
drink_company_name: string;
drink_brand_name: string;
drink_flavor_type_name : string;
liquid_color_type_name : string;
liquid_color_is_transparent : bool;
alcohol_vol : float;
calories_for_100g : uint;
global_image_id: uint;
drink_flavor_id: uint;
}

table Drinks { drinks:[Drink]; }

root_type Drinks;

编译它flatc -s drinks.fbs，它生成了js文件drinks_generated.js。到目前为止，一切都很好。

我在我的 nodejs 服务器中使用以下代码从数组中准备和创建平面缓冲区：

flatBuffersUtil.js

var flatbuffers = require('../js/flatbuffers').flatbuffers;
var builder = new flatbuffers.Builder();

var drinks = require('../fbs/drinks_generated').MyAlcoholist; // Generated by `flatc`.

function drinkArrayToBuffer(drinkArray) {
var drinksVectArray = [];
drinkArray.forEach(function (element, index, array) {
    var drinkObj = element;
    var drinkBrandName = builder.createString(drinkObj.drink_brand_name);
    var drinkCompanyName = builder.createString(drinkObj.drink_company_name);
    var drinkflavorTypeName = builder.createString(drinkObj.drink_flavor_type_name);
    var drinkTypeName = builder.createString(drinkObj.drink_type_name);
    var liquidColorTypeName = builder.createString(drinkObj.liquid_color_type_name);
    drinks.Drink.startDrink(builder);
    drinks.Drink.addAlcoholVol(builder, drinkObj.alcohol_vol);
    drinks.Drink.addCaloriesFor100g(builder, drinkObj.calories_for_100g);
    drinks.Drink.addDrinkBrandName(builder, drinkBrandName);
    drinks.Drink.addDrinkCompanyName(builder, drinkCompanyName);
    drinks.Drink.addDrinkFlavorId(builder, drinkObj.drink_flavor_id);
    drinks.Drink.addDrinkFlavorTypeName(builder, drinkflavorTypeName);
    drinks.Drink.addDrinkTypeName(builder, drinkTypeName);
    drinks.Drink.addGlobalImageId(builder, drinkObj.global_image_id);
    drinks.Drink.addLiquidColorIsTransparent(builder, drinkObj.is_transparent);
    drinks.Drink.addLiquidColorTypeName(builder, liquidColorTypeName);
    var drink = drinks.Drink.endDrink(builder);
    drinksVectArray.push(drink);
})
var drinksVect = drinks.Drinks.createDrinksVector(builder, drinksVectArray);
builder.finish(drinksVect);
var buf = builder.dataBuffer();
var drinksArray = drinks.Drinks.getRootAsDrinks(buf);
return buf;
}

module.exports.drinkArrayToBuffer = drinkArrayToBuffer;

flatBuffersUtil.js 的用法：

...
var data = flatBuffersUtil.drinkArrayToBuffer(result);
res.send(data);

当我收到缓冲区时，客户端使用 angularjs 1.5.0 完成，我尝试使用以下代码从中创建一个对象：

在主索引文件中：

<script type="text/javascript" src="js/flatbuffers.js"></script>
<script type="text/javascript" src="js/fbs/drinks_generated.js"></script>

然后在角度控制器中：

           $http({
                data: data,
                method: 'POST',
                url: 'https://myalcoholist.com:8888/drink/get_list/all_drinks',
            }).then(function successCallback(response) {
                var buffer = response.data;
                var drinks = MyAlcoholist.Drinks.getRootAsDrinks(buffer);
                deferred.resolve(drinks);
                // this callback will be called asynchronously
                // when the response is available
            }, function errorCallback(response) {
                // called asynchronously if an error occurs
                // or server returns response with an error status.
            });

问题是函数MyAlcoholist.Drinks.getRootAsDrinks(buffer);失败并出现以下错误：

TypeError: bb.position is not a function
at Function.MyAlcoholist.Drinks.getRootAsDrinks (drinks_generated.js:256)
at successCallback (admin-drinks-controller.js:22)
at angular.js:15552
at m.$eval (angular.js:16820)
at m.$digest (angular.js:16636)
at m.$apply (angular.js:16928)
at g (angular.js:11266)
at t (angular.js:11464)
at XMLHttpRequest.u.onload (angular.js:11405)

现在.. 生成的drinks_generated.js 文件中的函数代码如下：

MyAlcoholist.Drinks.getRootAsDrinks = function(bb, obj) {
return (obj || new MyAlcoholist.Drinks).__init(bb.readInt32(bb.position()) + bb.position(), bb);
};

所以 bb 应该是一个带有函数 position() 的字节缓冲区类型，但我收到的是一个字节对象。我想我需要先或以某种方式对其进行类型转换......但这只是一个猜测。

有任何想法吗？

更新

好的，首先我将drinksArrayToBuffer 函数修改为以下代码：

function drinkArrayToBuffer(drinkArray) {
var drinksVectArray = [];
drinkArray.forEach(function (element, index, array) {
    var drinkObj = element;
    var drinkBrandName = builder.createString(drinkObj.drink_brand_name);
    var drinkCompanyName = builder.createString(drinkObj.drink_company_name);
    var drinkflavorTypeName = builder.createString(drinkObj.drink_flavor_type_name);
    var drinkTypeName = builder.createString(drinkObj.drink_type_name);
    var liquidColorTypeName = builder.createString(drinkObj.liquid_color_type_name);
    drinks.Drink.startDrink(builder);
    drinks.Drink.addAlcoholVol(builder, drinkObj.alcohol_vol);
    drinks.Drink.addCaloriesFor100g(builder, drinkObj.calories_for_100g);
    drinks.Drink.addDrinkBrandName(builder, drinkBrandName);
    drinks.Drink.addDrinkCompanyName(builder, drinkCompanyName);
    drinks.Drink.addDrinkFlavorId(builder, drinkObj.drink_flavor_id);
    drinks.Drink.addDrinkFlavorTypeName(builder, drinkflavorTypeName);
    drinks.Drink.addDrinkTypeName(builder, drinkTypeName);
    drinks.Drink.addGlobalImageId(builder, drinkObj.global_image_id);
    drinks.Drink.addLiquidColorIsTransparent(builder, drinkObj.is_transparent);
    drinks.Drink.addLiquidColorTypeName(builder, liquidColorTypeName);
    var drink = drinks.Drink.endDrink(builder);
    drinksVectArray.push(drink);
})
var drinksVect = drinks.Drinks.createDrinksVector(builder, drinksVectArray);
drinks.Drinks.startDrinks(builder);
drinks.Drinks.addDrinks(builder, drinksVect);
var endDrinksOffset = drinks.Drinks.endDrinks(builder);
drinks.Drinks.finishDrinksBuffer(builder, endDrinksOffset);
var buf = builder.dataBuffer();
return buf;
}

现在在服务器端，我能够反序列化缓冲区并正确使用数据。问题在于客户端的反序列化。

在我发送缓冲区后，客户端收到以下对象：

Object
 bytes_: Object  
 position_: 7148
 __proto__: Object

现在.. 我创建了以下函数来将缓冲区转换为客户端的 json 对象：

function drinksByteArrayToArray(buffer) {
var res = [];
var byteBuffer =new flatbuffers.ByteBuffer(buffer);
var drinks = MyAlcoholist.Drinks.getRootAsDrinks(byteBuffer);
var drinksLength = drinks.drinksLength();
for (var i=0;i<drinksLength;i++) {
    var drink = drinks.drinks(i);
    var drinkObj = {
        drink_flavor_id: drink.drinkFlavorId(),
        drink_type_name: drink.drinkTypeName(),
        drink_company_name: drink.drinkCompanyName(),
        drink_brand_name: drink.drinkBrandName(),
        drink_flavor_type_name: drink.drinkFlavorTypeName(),
        liquid_color_type_name: drink.liquidColorTypeName(),
        is_transparent: drink.liquidColorIsTransparent(),
        alcohol_vol: drink.alcoholVol(),
        calories_for_100g: drink.caloriesFor100g(),
        global_image_id: drink.globalImageId
    }
    res.push(drinkObj);
}
return res;
}

当我执行此功能时，饮料的长度为零。所以缓冲区似乎是空的。

现在我认为问题出在以下代码上：

var byteBuffer =new flatbuffers.ByteBuffer(buffer);

我想我需要以其他方式将数据转换为字节缓冲区。

我知道我需要提供flatbuffers.ByteBuffer一个字节数组，所以我尝试做以下事情：

var byteBuffer =new flatbuffers.ByteBuffer(buffer.bytes_);

但结果是一样的。

有任何想法吗？

4

1 回答 1

6

谢谢你的支持。我终于能够找到解决方案。我缺少的是在设置字节后在 byteBuffer 上使用 setPosition 。为什么？我不知道！我所知道的是我试过了，现在它可以工作了。

所以我正在发送包含数据的字节_和位置_的整个缓冲区......我猜......长度或其他东西。所以在我在客户端发送缓冲区之后，我执行这两个命令：

var byteBuffer =new flatbuffers.ByteBuffer(buffer.bytes_);
byteBuffer.setPosition(buffer.position_);

如果有人可以在这里协助提供有关我为什么需要这样做的更多信息，那将是膨胀:)无论如何...它有效！

更新

我在https://github.com/google/flatbuffers/issues/3781上打开了一个问题，我得到了答案:)

https://github.com/google/flatbuffers/blob/master/tests/JavaScriptTest.js中有示例。序列化一个平面缓冲区：

var fbb = new flatbuffers.Builder();
// ... build the flatbuffer ...
var uint8Array = fbb.asUint8Array();

反序列化一个平面缓冲区：

var bb = new flatbuffers.ByteBuffer(uint8Array);
var drinks = MyAlcoholist.Drinks.getRootAsDrinks(bb);

谢谢！

于 2016-02-20T17:27:39.717 回答