From: Victor Blaga <vic.blaga@...>
Date: 2012-03-17T02:50:26+09:00
Subject: Re: Converting Bignum into bytes

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Hi Martin,

Thank you for your answer. I also thought of this solution, but a little
bit the other way around, like this:

big = 11111111111111111111111111111111111111
bytes = [big.to_s(16)].pack("H*")
 => "\x85\xBE\xC1+K\x9A@\xD8\xF4\x83\xCB\x1Cq\xC7\x1Cp"
big2 = bytes.unpack("H*")[0].to_i(16)

However...
puts big2==big #=>false

Taking a closer look...
bytes.unpack("H*")[0]
 => "85bec12b4b9a40d8f483cb1c71c71c70"
compared to
big.to_s(16)
 => "85bec12b4b9a40d8f483cb1c71c71c7"

The base 16 length representation of big is 31 whereas the unpacked string
is 32 bytes.
I wonder is this a bug?

In any case I guess the solution is to pad the big.to_s(16) String with 0
on the left side until reaching a round (as in base 2 round) number :)

Kind regards,
Victor

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Hi Martin,<div><br></div><div>Thank you for your answer. I also thought of =
this solution, but a little bit the other way around, like this:</div><div>=
<div><br></div><div>big =3D 11111111111111111111111111111111111111</div><di=
v>
bytes =3D [big.to_s(16)].pack(&quot;H*&quot;)</div><div>=A0=3D&gt; &quot;\x=
85\xBE\xC1+K\x9A@\xD8\xF4\x83\xCB\x1Cq\xC7\x1Cp&quot;</div></div><div>big2 =
=3D bytes.unpack(&quot;H*&quot;)[0].to_i(16)<br></div><div><br></div><div>H=
owever...</div>
<div>puts big2=3D=3Dbig #=3D&gt;false</div><div><br></div><div>Taking a clo=
ser look...</div><div>bytes.unpack(&quot;H*&quot;)[0]</div><div>=A0=3D&gt; =
&quot;85bec12b4b9a40d8f483cb1c71c71c70&quot;</div><div>compared to</div><di=
v>big.to_s(16)</div>
<div>=A0=3D&gt; &quot;85bec12b4b9a40d8f483cb1c71c71c7&quot;<br></div><div><=
br></div><div>The base 16 length representation of big is 31 whereas the un=
packed string is 32 bytes.</div><div>I wonder is this a bug?</div><div><br>
</div><div>In any case I guess the solution is to pad the big.to_s(16) Stri=
ng with 0 on the left side until reaching a round (as in base 2 round) numb=
er :)</div><div><br></div><div>Kind regards,</div><div>Victor</div>

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