Comment on Tutorial - Convert a hex string into a 32-bit IEEE 754 float number in PHP By Julian L



Comment Added by : Mark

Comment Added at : 2015-02-02 14:42:56

Comment on Tutorial : Convert a hex string into a 32-bit IEEE 754 float number in PHP By Julian L
My code:

$hex=array('C4028000','457F9000','2D7F5','0002D7F5','47D9F95E','000040E4');

foreach($hex as $h){
echo $h.'='.hexTo32Float($h).'<br>';
}

function hexTo32Float($strHex) {
$v = hexdec($strHex);
$x = ($v & ((1 << 23) - 1)) + (1 << 23) * ($v >> 31 | 1);
$exp = ($v >> 23 & 0xFF) - 127;
return $x * pow(2, $exp - 23);
}

This outputs:

C4028000=522
457F9000=4089
2D7F5=6.0080426430695E-39
0002D7F5=6.0080426430695E-39
47D9F95E=111602.734375
000040E4=5.8891109391561E-39

The first output differs from yours as it is positive. The other values match yours. However, the last one (000040E4=5.8891109391561E-39) doesn't agree with http://babbage.cs.qc.cuny.edu/IEEE-754/index.xhtml, which tells me the decimal value of 000040E4 is 2.3278370089363861182184995837612086772827711378452680000428418331977209465577516311896033585071563720703125E-41

And http://babbage.cs.qc.cuny.edu/IEEE-754.old/32bit.html tells me it should be: 2.327837008936386e-41

Is this an error in the function or an error on the other site?

Cheers,
Mark.


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Archived Comments

1. it was nice and helpful for me.
View Tutorial          By: mayank at 2015-03-01 08:35:48

2. Good one ! and simple tutorial
View Tutorial          By: Sim at 2011-02-24 01:57:53

3. this code should be commented I mean a lot of comm
View Tutorial          By: mmmm at 2012-03-31 00:44:41

4. Very useful tutorial. But if same code is executed
View Tutorial          By: Jitendra Kumar Mahto at 2011-08-12 15:10:14

5. Good Example
View Tutorial          By: Naresh at 2015-02-03 07:41:40

6. Daniel Jonsson, you should be thankful to this art
View Tutorial          By: dole at 2011-11-12 06:44:42

7. Thanks a lot Ramlak! This is still very useful af
View Tutorial          By: Jacky at 2009-08-08 23:49:12

8. the best!! it helps me a lot.....
View Tutorial          By: shin at 2009-02-15 18:12:31

9. Very good for the example......
View Tutorial          By: Tuhin Subhra Mandal at 2012-10-14 12:22:01

10. fantastic tutorial and very well explained, I've o
View Tutorial          By: Francis at 2011-08-14 19:57:18