Archive for April, 2009

0

Determining if an IP is within a specific range: redux

Posted by Chris
April 30, 2009

Submarine NetI was reading Paul Gregg’s very clear explanation of “classless” ranges comparison when I realized that his code was not as “bare metal” as could be.

So, here is the code I’ve been using in nextBBS.
It only accepts ranges in the form “x.x.x.x/b” but it’s short and all I needed, really.

?View Code PHP
function isSubnet($subnet, $ip)
{
    // Classless (in more than one way) comparison
    $cursubnet = explode('/', $subnet);
    $longsubnet = ip2long($cursubnet[0]);
    $longip = ip2long($ip);
 
    if(count($cursubnet)<2)
    {
        // Compare IP itself
        return ($longip==$longsubnet);
    }
 
    // IPv4 only!
    $subnetmask = 0xffffffff << (32-$cursubnet[1]);
    return (($longip & $subnetmask) == ($longsubnet & $subnetmask));
}

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9

One-line variables swap in PHP, Ruby, Perl, Python and C

Posted by Chris
April 24, 2009

Joy in BlueToday’s fun and games: let’s swap a few variables without using more variables than necessary.

Let me know if you disagree with any of this…

?View Code PHP
$a = 1;
$b = 2;
list($a, $b) = array($b, $a);
print "a=$a, b=$b\n";
?View Code RUBY
a = 1
b = 2
a, b = b, a
puts "a=#{a}, b=#{b}\n"
?View Code PERL
my $a = 1;
my $b = 2;
($a, $b) = ($b, $a);
print "a=$a, b=$b\n";
?View Code PYTHON
a=1
b=2
a, b = b, a
print 'a=%i, b=%i' % (a, b)

And now, good old C. Let’s use the only method that does not generate an overflow…first, for integer types:

?View Code C
int a=0, b=27;
a=(a^(b=(a=a^b)^b));
printf("a=%d, b=%d\n", a, b);

“Well,” you may say, “but what about pointers arithmetic? Any solution?”
Why, yes. That’s what I came up with after 15 minutes of fiddling:

?View Code C
char *a = "one", *b = "two";
a=(void *)(((long)a)^(long)(b=(void *)(((long)(a=(void *)((long)a^(long)b)))^(long)b)));
printf("a=%s, b=%s\n", a, b);

Note the use of void *, which allows me to ignore the pointer type. And, yes, I know, a C++ compiler may not really like this syntax. This may be doable using templates but I haven’t looked into that.
Sorry, I haven’t looked into Erlang or Haskell yet…

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0

Bespin in Titanium: From The Jaws Of Victory…

Posted by Chris
April 6, 2009

bespin is really an intriguing project. Since I’ve grown frustrated with the inconsistencies between the various code editors that I have been using — I work on Leopard at home and Ubuntu at work — I thought that creating my own editor would be the answer to that. Nothing fancy, mind you. Just something consistent.

My first impulse was to use Flex. And it almost worked! Using mx:html I was able to wrap a nice web page in an otherwise very ActionScript-y application.
And then, catastrophe! Flex Webkit’s canvas implementation is subpar and I could only get a very mamed version of bespin. Nothing usable, anyway.

Thus, I turned to Titanium.
After some light trial and error, I got it to work!

Unfortunately, the result is less than awesome: Titanium’s Webkit gets easily overwhelmed and, worse, crashes reliably ( :g: ) as soon as I ask it to do some medium lifting.

This video shows the original victory followed by the vexing defeat:

Note that, to get it to work, I replaced embed.js with my own version that works around any dojo.request()/eval issue:

?View Code JAVASCRIPT
(function() {
    // -- Load Script
    var loadme = new Array();
    var loadScript = function(src, onload) {
        var embedscript = document.createElement("script");
        embedscript.type = "text/javascript";
        embedscript.src = src;
        embedscript.onload = onload;
        document.getElementsByTagName("head")[0].appendChild(embedscript);
    }
    var onScriptLoaded = function() {
        var src = loadme.shift();
        if(src)
            loadScript(src, onScriptLoaded);
    }
 
    var componentRequires = function() {
        dojo.require("bespin.bespin");
 
        dojo.require("bespin.util.canvas");
        dojo.require("bespin.util.keys");
        dojo.require("bespin.util.navigate");
        dojo.require("bespin.util.path");
        dojo.require("bespin.util.tokenobject");
        dojo.require("bespin.util.util");
        dojo.require("bespin.util.mousewheelevent");
        dojo.require("bespin.util.urlbar");
 
        dojo.require("bespin.client.filesystem");
        dojo.require("bespin.client.settings");
        dojo.require("bespin.client.status");
        dojo.require("bespin.client.server");
        dojo.require("bespin.client.session");
 
        dojo.require("bespin.editor.actions");
        dojo.require("bespin.editor.clipboard");
        dojo.require("bespin.editor.cursor");
        dojo.require("bespin.editor.editor");
        dojo.require("bespin.editor.events");
        dojo.require("bespin.editor.model");
        dojo.require("bespin.editor.toolbar");
        dojo.require("bespin.editor.themes");
        dojo.require("bespin.editor.undo");
 
        dojo.require("bespin.syntax.base"); 
        dojo.require("bespin.syntax.simple._base");
 
        dojo.require("bespin.cmd.commandline");
        dojo.require("bespin.cmd.commands");
        dojo.require("bespin.cmd.editorcommands");
 
        dojo.require("th.helpers"); // -- Thunderhead... hooooo
        dojo.require("th.css");
        dojo.require("th.th");
        dojo.require("th.models");
        dojo.require("th.borders");
        dojo.require("th.components");      
    }
 
    loadScript("js/dojo/dojo.js.uncompressed.js", function() {
        dojo.require = function(src) {          
            loadme.push('js/' + src.replace(/\./g, '/') + '.js');
        }
        componentRequires();
        dojo.require("bespin.editor.component");
        loadScript(loadme.shift(), onScriptLoaded);
    });
})();

As you can see, I override dojo.request() with my own, stack up all the component names, then load them one by one, waiting for each to be fully loaded before moving on.

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