Convert hexadecimal to 32 float in javascript

Question

I have this function in php that would convert hexadecimal to 32 float in php. How do you do it in Javascript

public static function hexTo32Float($val)
{
    $packed=pack("H*",$val);
    $reversedpac=strrev($packed);
    $unpack=unpack( "f",$reversedpac);

    return array_shift($unpack);
}

well i have tried this which i found somewhere here but id didn't work. return parseInt("0x"+hexNumber); — bring2dip
– bring2dip, Commented Jan 6, 2014 at 11:06
possible duplicate of Converting hexadecimal to float in javascript — DontVoteMeDown
– DontVoteMeDown, Commented Jan 6, 2014 at 11:08
@DeepakBhattarai this is the same approach as my answer. What exactly was the error? — Callahan
– Callahan, Commented Jan 6, 2014 at 11:09
@Callahan if we convert 0x8c42465d the float should be around 49.something — bring2dip
– bring2dip, Commented Jan 6, 2014 at 11:15
@DeepakBhattarai Are you sure that hexNumber did not already contain a 0x prefix? In that case the output would have been 0 for your input. — Callahan
– Callahan, Commented Jan 6, 2014 at 11:16

Sebastien C. · Accepted Answer · 2015-07-01 16:34:34Z

2

What about playing with TypedArray (that will only work with recent browsers) ?

var intData = Uint32Array(1);
intData[0] = parseInt("42458c14", 16);
var dataAsFloat = new Float32Array(intData.buffer);
var result = dataAsFloat[0];
// result == 49.38679504394531

EDIT (one year later ...) : It does seem that the result could depend on whether or not your CPU is big indian or little indian. Be careful when using this.

edited Jul 1, 2015 at 16:34

answered Jan 6, 2014 at 11:45

Sebastien C.

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5 Comments

bring2dip Over a year ago

thanks this works too. but which one do i choose @callahan's one or your?

Callahan Over a year ago

Well this one is only a bit longer. You should just take the version that you like more to see in your code.

Sebastien C. Over a year ago

@callahan's answer uses the Buffer object which doesn't seems to be a part of html5. If you're doing it in a browser, you should prefer my version. If you're using Node.js, his solution is better.

bring2dip Over a year ago

I will keep both."Looks like i have to call two of the functions randomly"

Callahan Over a year ago

The node.js thing is a good point. Never coded javascript, did not think of that.

Community · Accepted Answer · 2017-05-23 12:13:46Z

0

After a complete BS answer try the following I found in the answer to this question:
var b = new Buffer(hexNumber, 'hex').readFloatBE(0).
edit: The fault was the usage of readFloatLE here.
For further explanation: The point here is that readFloatXX() expects buffer contents as two's complement signed values. I guess readFloatLE is the version for unsigned floats (could not find that in the docs, though).

edited May 23, 2017 at 12:13

CommunityBot

11 silver badge

answered Jan 6, 2014 at 11:07

Callahan

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4 Comments

Callahan Over a year ago

@DeepakBhattarai Please try this one. I undeleted my answer and dont know if you get notified for this.

bring2dip Over a year ago

I did this too, but it doesn't convert '42458c14' to 49.something which is what i need

Callahan Over a year ago

@DeepakBhattarai There seems to be a readFloatBE version too. Maybe try that.

bring2dip Over a year ago

well that works fine. edit your answer so that i can mark you

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