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, Jan 06 '14 at 11:06
possible duplicate of [Converting hexadecimal to float in javascript](http://stackoverflow.com/questions/5055723/converting-hexadecimal-to-float-in-javascript) — DontVoteMeDown, Jan 06 '14 at 11:08
@DeepakBhattarai this is the same approach as my answer. What exactly was the error? — Callahan, Jan 06 '14 at 11:09
@Callahan if we convert 0x8c42465d the float should be around 49.something — bring2dip, Jan 06 '14 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, Jan 06 '14 at 11:16
You still did not tell us what the result of the function is. — Callahan, Jan 06 '14 at 11:19
Ah I see now. How dumb, sry. How could I expect a float value from a function called `parseInt`... — Callahan, Jan 06 '14 at 11:26
Okay the problem here is that you would need to know the exact representation of your Hex number i.e. is it signed? and so on. You will be lucky if there is a ready to use function in javascript I think. — Callahan, Jan 06 '14 at 11:31
Please see [this question][1] and [this question][2]. [1]: http://stackoverflow.com/questions/57803/how-to-convert-decimal-to-hex-in-javascript [2]: http://stackoverflow.com/questions/5055723/converting-hexadecimal-to-float-in-javascript — Daew, Jan 06 '14 at 11:42

Sebastien C. · Answer 1 · 2015-07-01T16:34:34.233

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 01 '15 at 16:34

answered Jan 06 '14 at 11:45

Sebastien C.

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thanks this works too. but which one do i choose @callahan's one or your? – bring2dip Jan 06 '14 at 11:50
Well this one is only a bit longer. You should just take the version that you like more to see in your code. – Callahan Jan 06 '14 at 11:51
1

@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. – Sebastien C. Jan 06 '14 at 11:54
I will keep both."Looks like i have to call two of the functions randomly" – bring2dip Jan 06 '14 at 11:54
The node.js thing is a good point. Never coded javascript, did not think of that. – Callahan Jan 06 '14 at 11:56

score 0 · Accepted Answer · edited May 23 '17 at 12:13

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 '17 at 12:13

Community

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answered Jan 06 '14 at 11:07

Callahan

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@DeepakBhattarai Please try this one. I undeleted my answer and dont know if you get notified for this. – Callahan Jan 06 '14 at 11:34
I did this too, but it doesn't convert '42458c14' to 49.something which is what i need – bring2dip Jan 06 '14 at 11:38
@DeepakBhattarai There seems to be a `readFloatBE` version too. Maybe try that. – Callahan Jan 06 '14 at 11:41
well that works fine. edit your answer so that i can mark you – bring2dip Jan 06 '14 at 11:45

Convert hexadecimal to 32 float in javascript

2 Answers2