将协议缓冲区中的二进制双精度数组转换为 javascript 数字

问题描述：

我正在使用 zeroMQ 上的协议缓冲区将图形数据从 C++ 发送到 Javascript 前端:

I'm using protocol buffers over zeroMQ to send graph data from C++ to a Javascript frontend:

message RawData
{
   Type type = 1;
   bytes data = 2;
}

当我调用 RawData.getData() 时，我得到这样的信息(通常更长):

when i call RawData.getData() i get something like this (usually much longer):

数据:0, 0, 0, 0, 0, 0, 0, 0, 64, 1, 118, 62, 112, 8, 12, 63

这是两个 8 字节的数字，其中数组中的每个索引为 1 个字节.

This is two 8 bytes numbers, where each index in the array is 1 byte.

如何在 Javascript 中将其转换为双重表示?

How do I convert this into double representation in Javascript?

我最终将协议缓冲区消息更改为 repeated double data = 2;

i ended up changing the protocol buffer message to repeated double data = 2;

这消除了转换的需要

答

只需将结果分成 8 个元素部分，并使用 ArrayBuffer 和 Dataview 挂载数字.示例:

Just divide the result in 8 elements parts and use ArrayBuffer and Dataview to mount the number. Example:

function splitData(data) {
    return data.reduce(function(a, b, c){
        if(c % 8 == 0  && c !== 0){
            a.push([]); };
        a[a.length - 1].push(b);
        return a;
    }, [[]]);
}

function computeValues(data, littleEndian = false) {
    var res = [];
	splitData(data).forEach(numberElement=>{
        var buffer = new ArrayBuffer(8);
        var dv = new DataView(buffer);
        numberElement.forEach((val, ix)=>dv.setUint8(littleEndian ? 7 - ix : ix, val));
        res.push(dv.getFloat64(0));
    });
    return res;
}


var data = [0, 0, 0, 0, 0, 0, 0, 0, 64, 1, 118, 62, 112, 8, 12, 63];
console.log(computeValues(data));
console.log(computeValues(data, true));

data.reduce 函数取自这个 SO 答案:将一个 JS 数组拆分成 N 个数组

The data.reduce function is taken from this SO answer: Splitting a JS array into N arrays

JSFiddle:https://jsfiddle.net/z3fL39sr/12/

littleEndian 参数指的是字节的顺序.如果最重要的在前，则将 littleEndian 设置为 true.如果需要，此页面解释了字节序:https://www.cs.umd.edu/class/sum2003/cmsc311/Notes/Data/endian.html

littleEndian parameter refers to the order of the bytes. If the most significant came first, set littleEndian to true. This page explains about endianess if you need it: https://www.cs.umd.edu/class/sum2003/cmsc311/Notes/Data/endian.html

将协议缓冲区中的二进制双精度数组转换为 javascript 数字

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