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javascriptc#type-conversiondecimal
Joe
Joe

Reputation: 1044

Converting a .NET Decimal format (System.Decimal) in a JavaScript ArrayBuffer to a JavaScript Number in JavaScript

In a web browser we receive binary structs in ArrayBuffers over WebSocket from a C# server that contain 128 bit .NET Decimal types.

We need to convert this to a native JavaScript Number.

How do we do this in JavaScript?

Upvotes: 1

Views: 401

Answers (1)

Dave Brushinski
Dave Brushinski

Reputation: 36

function DotNetDecimalToNumber(inputArrayBuffer, isLittleEndian = true){

    let dataview = new DataView(inputArrayBuffer);

    let scale = dataview.getUint8(2);
    let sign = dataview.getUint8(3);
    let hi32 = dataview.getUint32(4, isLittleEndian);
    let low64 = dataview.getBigUint64(8, isLittleEndian);

    let divisor = 1.0;

    while (scale-- > 0){
        divisor *= 10;
    }

    if (sign > 0){
        divisor *= -1;
    }

    let highPart = 0.0;

    if (hi32 > 0){
        highPart = hi32 / divisor;
        highPart *= 4294967296.0;
        highPart *= 4294967296.0;
    } else {
        highPart = 0.0;
    }

    return (Number(low64) / divisor) + highPart;

}

//Clamped number array equivalent of byte output from C# struct for Decimal -720819.587673906
let testNumber = [0, 0, 9, 128, 0, 0, 0, 0, 50, 111, 120, 227, 148, 143, 2, 0];

//Generates a Uint8Array and uses underlying ArrayBuffer, for this example
console.log(DotNetDecimalToNumber(new Uint8Array(testNumber).buffer, true));

//outputs -720819.587673906

This converts approximately 1000 Decimals per millisecond on my machine.

Upvotes: 2

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