Parse Integer from Buffer

Question

I created this function to parse a Integer from a Buffer:

var makeInt = function(b1, b2, b3, b4) {
    return ((b1 <<  0) & 0x000000FF) +   
           ((b2 <<  8) & 0x0000FF00) + 
           ((b3 << 16) & 0x00FF0000) + 
           ((b4 << 24) & 0xFF000000);
}

From a buffer I read the Integer like that:

var buffer = new Buffer([0,0,15,47,0,0,0,64,0,0])

console.log(makeInt(buffer[3],buffer[2],buffer[1],buffer[0]))

=> 3887

What's the official Buffer function from https://nodejs.org/api/buffer.html that does the same like my makeInt function?

I tried https://nodejs.org/api/buffer.html#buffer_buf_readuintbe_offset_bytelength_noassert

But buf.readUIntLE(offset, byteLength[, noAssert]) returns:

buffer.readUIntLE(0, 3)

=> 983040

Why is it not returning 3887 != 983040?

Thanks

Aikon Mogwai · Accepted Answer · 2019-05-15 09:34:05Z

2

You use 4 bites, but passed 3. There are two ways to store number - little-endian and big-endian. It seems your code realized big-endian.

var buffer = new Buffer([0,0,15,47,0,0,0,64,0,0]);
console.log(buffer.readUIntBE(0, 4));

edited May 15, 2019 at 9:34

answered Jul 22, 2016 at 9:23

Aikon Mogwai

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1 Comment

John Smith Over a year ago

Works, Thanks a lot!

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