convert form hex buffer to int using nodejs

Question

I have a hex buffer in Node js like this:

buffer <00 E0>

I need to convert to int using little endianess. So I would read E0 00 -> 57344

For the moment I use this method:

var str = "0x" + buffer [i] .toString ('16 '). toString + buffer [i-1] .toString ('16'). toString to convert to string

var result = parseInt (str).

This method works but sometimes I get errors like this: buffer [0] = 00 but I receve 0 instead 00 or 1 instead to 01 or 10,

Is there another way to get this convertons or to solve this problem?

Thank you

OfirD · Accepted Answer · 2020-09-09 18:28:25Z

1

Consider using the Buffer.readInt*LE or Buffer.readUInt*LE methods (the * stands for the integer size, LE for little endian). Taking your code as an example, you can use Buffer.readIntLE:

Buffer.from([ 0x00, 0xe0]).readUIntLE(0, 2)

If you have a variable buffer size:

var buffer = Buffer.from(bytes);
var result = buffer.readUIntLE(0, bytes.length) // assumes bytes.length is even

answered Sep 9, 2020 at 18:28

OfirD

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3 Comments

init Over a year ago

Thanks! I tried this method and its work, but reading doc:" Reads byteLength number of bytes from buf at the specified offset and interprets the result as an unsigned, little-endian integer supporting up to 48 bits of accuracy." When I have a want read a number of byte < 6 its works but when I need to convert a number of bytes > 6 (128 forx example) doesn't work. How can I convert it? Thanks

OfirD Over a year ago

You asked about working with an integer, so I assumed 32 bits. You can read a 64 bits buffer by using readBigInt64LE instead. More than that is not an integer anymore, so you'd need a more involved code.

init Over a year ago

Yes! In this cases I must convert to String. I read and covert to Integer before (using readUIntLE) and then I use fromCharCode(int) to get a String. Thanks!!

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