如何桥接JavaScript（ragged）数组和std :: vector< std :: vector< T>>目的？ [英] How to bridge a JavaScript (ragged) array and an std::vector<std::vector<T>> object?

问题描述

在JavaScript中，我有一个行列表，每个行由不定数量的点组成，每个都有 [x，y] 。所以它是一个三维粗糙的数组。现在我需要将它传递给我的C ++代码与帮助emscripten（ embind ）。这里是C ++函数的声明：

  Eigen :: MatrixXd f（const std :: vector< std :: vector& ：vector< double>>>& lines）; 
  

我想得到一个列表列表（ [[m11，调用 f 后在JavaScript中调用[m12]，[m22，m22]，...]如何在这种情况下编写绑定代码（例如 EMSCRIPTEN_BINDINGS 中的内容）？

UPDATE ：我现在可以把JavaScript数组传递给C ++。绑定部分是

  typedef std :: vector< double>点; 
 typedef std :: vector< Point>线; 
 EMSCRIPTEN_BINDINGS（module）{
 register_vector< Line>（LineArray）; 
 register_vector< Point>（Line）; 
 register_vector< double>（Point）; 
 emscripten :: function（f_wrapper，& f_wrapper）; 
} 
  

其中 f_wrapper f 但返回向量< vector< double>> 而不是 MatrixXd 。现在的问题是，我只能得到一个空的JavaScript对象调用 f_wrapper 后。 JavaScript是

  var Module = require（'./ bind.js'）; // em ++的输出
 var cppAllLines = new Module.LineArray（）; 
 //一些初始化
 var result = Module.f_wrapper（cppAllLines）; //一个空的Line对象
  

任何想法？

  std :: vector< std :: vector< double>> f_wrapper（...）; 
  

至Javascript

  var result = Module.f_wrapper（...）; 
  

结果对象不是一个Javascript数组它实现 length 属性或数组索引访问，因此如果使用这些访问它的数据，它可以显示为空。

但它会暴露 get 和 size 函数以访问向量：

  console.log（'Back from C ++'，result.size（），result.get（0）.get（1） 
  

（double get 返回向量的向量）

为了完整性，查看返回的对象的原型，它似乎暴露了以下函数。

• get


• push_back


• resize


• 设定


• size

稍微不一致，它暴露 get 和 set 函数，而不是等价于C ++ 在 功能。我怀疑自 在 返回一个允许它作为setter使用的引用，这在Javascript中是不可能的。

In JavaScript I have a list of "lines", each of which consists of indefinite number of "points", each of which has a form of [x, y]. So it is a 3D ragged array. Now I need to pass it to my C++ code with the help from emscripten (embind). Here's declaration of the C++ function:

Eigen::MatrixXd f(const std::vector<std::vector<std::vector<double>>>& lines);

And I would like to get a list of lists ([[m11, m12],[m22, m22],...]) in JavaScript after calling f. How to write the binding code in this case (the stuff inside EMSCRIPTEN_BINDINGS, for example)?

UPDATE: I can now pass the JavaScript array to C++. The binding part is something like

typedef std::vector<double> Point;
typedef std::vector<Point> Line;
EMSCRIPTEN_BINDINGS(module) {
  register_vector<Line>("LineArray");
  register_vector<Point>("Line");
  register_vector<double>("Point");
  emscripten::function("f_wrapper", &f_wrapper);
}

where f_wrapper calls f but returns vector<vector<double>> instead of MatrixXd. Now the problem is that I can only get an empty JavaScript object after calling f_wrapper. The JavaScript is

var Module = require('./bind.js'); // the output of em++
var cppAllLines = new Module.LineArray();
// some initialization
var result = Module.f_wrapper(cppAllLines); // an empty "Line" object

Any ideas?

解决方案

When passing an embound vector from a C++ function, such as

std::vector<std::vector<double>> f_wrapper(...);

to Javascript

var result = Module.f_wrapper(...);

The result object is not a Javascript array that implements length property or array-indexed access, so it can appear "empty" if using these to access its data.

But it does expose get and size functions to access the vector:

console.log('Back from C++', result.size(), result.get(0).get(1));

(The double get is because we're returning a vector of vectors)

For completeness, looking into the prototype of the object returned, it seems to expose the following functions.

• get
• push_back
• resize
• set
• size

Slightly inconsistently it exposes get and set functions rather than an equivalent of the C++ at function. I suspect that it's not possible for an exactly equivalent function since at returns a reference which allows it to be used as a setter, which isn't possible in Javascript.

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