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<?xml-stylesheet type="text/xsl" href="https://community.arm.com/utility/feedstylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>Rare/Unique requirement</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/24200/rare-unique-requirement</link><description> 
Hey dude, 

 
I need some code to do some big math. 

 
Like 12345678901234567890 x 987654321987654321 

 
Must be in C and must be documented correctly. 

 
Has anybody got some sourcecode? 

 
Respect. 
 </description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: Rare/Unique requirement</title><link>https://community.arm.com/thread/52180?ContentTypeID=1</link><pubDate>Wed, 06 Aug 2008 04:49:25 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:ab930d17-7d2c-4189-86fc-830e2c413d9c</guid><dc:creator>Dan Henry</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;a href="http://www.google.com/search?q=bignum+arithmetic"&gt;www.google.com/search&lt;/a&gt;&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Rare/Unique requirement</title><link>https://community.arm.com/thread/52178?ContentTypeID=1</link><pubDate>Wed, 06 Aug 2008 04:17:59 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:22ba5156-2714-4bd4-86dd-af64eb93a9bb</guid><dc:creator>Christoph Franck</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;I need some code to do some big math.&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
Define &amp;quot;big&amp;quot;. As in &amp;quot;how many bits does the biggest number that
will every occur have&amp;quot;.&lt;/p&gt;

&lt;p&gt;
&lt;i&gt;Like 12345678901234567890 x 987654321987654321&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
That would amount to multiplying two 64-bit integers to get a
128-bit result. Since the compiler can natively work with 64-bit
integers, this means four multiplications, some additions, and some
overflow checking. Unfortunately, the latter is much easier (since
it&amp;#39;s pretty much automatic) in assembly than in C (where it requires
extra checks).&lt;/p&gt;

&lt;p&gt;
&lt;i&gt;Has anybody got some sourcecode?&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
Please specify your requirements more clearly. What&amp;#39;s the bit
width of the numbers you&amp;#39;re working with, which arithmetic operations
do you require, etc.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>