TinyCode competition - trial

[SimonH]

Tomorrow = exams

Good luck - but hopefully you won't need it!

[CaptainJester]

Can anyone tell me why my read pointer is not advancing?

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for(int a=in.read(),b=in.read();(a|b)>0;){     out.write(b);     out.write(a); }

Whenever I run this, it just goes into an infinite loop.  When I debug it, a and b keep reading the first 2 characters from the stream.

[noblemaster]

Consider: for(<part1>;<part2>;<part3>)...

<part1> is only executed ONCE and the beginning of the loop to initialize variables etc...

Games published by our own members! Check 'em out!

[Riven]

Ouch... 

Two new assignments:
http://213.247.55.3:8484/compileandrun/?assignment=capitalizer
http://213.247.55.3:8484/compileandrun/?assignment=barcode




I made the barcode assignment extra hard by not adding a space at the end.

[markush]

Ouch... 

Two new assignments:
http://213.247.55.3:8484/compileandrun/?assignment=capitalizer
http://213.247.55.3:8484/compileandrun/?assignment=barcode

85 bytes for capitalizer, but that has to go shorter...
there are 3 variables in there...
who needs 3 variables anyway?

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for(int c,i=0,s=0; (c=in.read())>0 ; out.write(c-(i++==s & c > 96 & c < 123?32:0)))       s =c == 32 ? i+1 : s;

for the barcode thingy 89 bytes

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int i,c; for(i=48;(c=in.read())>0;i=c==32?48:i+1)    if(c==32)out.write(i); if(i>0)out.write(i);

So lets start that shortening iteration again

Edit:
capitalizer down to 7170:

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for(int c,s=32; (c=in.read())>0;)    out.write(s=c-(s==32 & c > 96 & c < 123?32:0));

barcode down to 66 bytes:

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for(int c=1,i=48;c>0;i++){   c=in.read();   if(c<99){     out.write(i);     i=47;   } }

[Riven]

Capitalizer:

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for(int c,s=32; (c=in.read())>0;) out.write(s=s==c/96*32?c-s:c);

(61 bytes)

This was optimisation on the logic-level.
It didn't have anything to do with reasoning.

...

I have yet to figure out how it works..


Thanks markush, for the jump-start.

[Riven]

We need another operator eh?

1   2

s=s*3          --->>> s*=3; s=s==3?4:5;    --->>> s===3?4:5;

[timfoden]

Capitalizer:

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for(int c,s=32; (c=in.read())>0;) out.write(s=s==c/96*32?c-s:c);

(61 bytes)

The above code works with the test case, but IMO doesn't solve the spirit of the problem in all cases.

Try it with a test case that includes the end conditions: e.g.

"@ 2pm { today }, I saw a bear at the zoo "

The above code would change the @ { } chars.

Here's my current go @ Capitalizer:

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for(int c, p = 32; (c = in.read()) > 0; )  out.write( p = p == 32 & c > 96 & c < 123 ? c - p : c );

(67 bytes)

Cheers, Tim.

[Riven]

Yeah, I cheated. I removed the upper-bound check.

[timfoden]

Yeah, I cheated. I removed the upper-bound check.

Yes...  and the lower bound check is wrong... should be /97

Games published by our own members! Check 'em out!

[Riven]

I'll cry myself to sleep tonight.

[timfoden]

BinaryShrink

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for( int v = 1; (v += v + in.read() % 2) > 1; )   if( v > 255 )   {     out.write( v );     v = 1;   }

(61 bytes)

[CaptainJester]

Consider: for(<part1>;<part2>;<part3>)...

<part1> is only executed ONCE and the beginning of the loop to initialize variables etc...

doh 

Thanks.

[Mr_Light]

barcode down to 66 bytes:

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for(int c=1,i=48;c>0;i++){   c=in.read();   if(c<99){     out.write(i);     i=47;   } }

67 bytes:

1	out.write(new byte[] { 50,51,56,49,52,57,54,50,51,49,49,50,48,49,51 });

 

[Riven]

I'll add a bunch of testcases to each assignment, when I have time for it.

[Abuse]

hey Riven, I killed your server 

1	com.sun.org.apache.regexp.internal.recompile.main("".split(""));

(64 bytes)

[noblemaster]

 

[Riven]

WHAAAA

It was worse than you might every have thought...


There was a piece of user-submitted sourcecode processed by BASH...

That's like total control...

[Riven]

I'm not going to launch the http-server until I fixed this...


Hm... there is a System.exit(0) inside that method...

I really can't understand how that System.out (!!!) could end up in bash.

I mean... after System.exit(0) is called, the JVM is supposed to be dead, and everything that was buffered in System.out should be discarded, not writting into STDIN...

Anybody?

[Abuse]

yeah, it was the System.exit(0); that I was exploiting to terminate the vm....
Took me ages to think of a way to pass in a String[], to get the desired effect :-)

What was it that was written to stdin?
the socket input stream? or system.out?

Can you reproduce it?

Seems like a serious vm bug to me, it isn't like my code did anything that a normal java service couldn't do as the result of some kind of unrecoverable error.
Presumably it's the result of a thread race condition, as I guess our provided code is executing on it's own thread?

[Riven]

User-sourcecode is compiled by janino.

The compiled sourcecode cannot be sent to STDIN, because it only exists in bytecode-form.

I do a
System.out.println(code);
to monitor the submission you guys post.

Unfortunately, to enforce the time-limit of 100ms, I have to call Thread.stop() if the newly created thread running your code, runs out of time.
Now... before I even can call stop(), the System.exit(0) is already executed, so I doubt the problem is in that 'unsafe' method.

It feels like this was the actual chain of events:
1. System.out.println(code);
2. new Thread(){public void run(){System.exit(0);}}.start();

Result:
the bytes buffered in STDOUT get flushed to STDIN after termination.


Is it correct that you submitted this full block of code?

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com.sun.org.apache.regexp.internal.recompile.main("".split("")); out.write(str2arr("hello world!")); int a=0,i=0,b; while((b=in.read())>0) { a=a<<4|(b-'0'); if ((i^=1)==0) out.write(a); }

[Abuse]

nope, I only submitted

"com.sun.org.apache.regexp.internal.recompile.main("".split(""));"

The rest is nothing to do with me, never seen it before in my life.
"byte [] str2arr(String)" is one of your methods isn't it? declared in TinyCodeAssignment.
Was that just someone attempting to access this method from their own code?

[Abuse]

The compiled sourcecode cannot be sent to STDIN, because it only exists in bytecode-form.

I was thinking more of the source code that is embedded in the html page served back to the client?

[Riven]

It was part of the sourcecode I posted in this thread (many many lines).


Somebody thought he could access the str2arr or arr2str because it was defined in the posted TinyCodeAssignment class.

[Riven]

The code sent back to the client doesn't have < and >, only &lt; and &gt; to prevent HTML-tags (and scripts!) breaking out of the <textarea></textarea>

[Riven]

Anyway, as you can see in the screenshot, the JVM is shutdown after your one-line submission, yet the next (?) submission is executed in BASH...


I'll investigate tomorrow, and go to bed now. It's 02:00, and I got yet another exam tomorrow.

[Abuse]

Eagerly awaiting my gold 'I crashed the server' badge 

[Riven]

Bah, I didn't go to bed!


I found it...

it wasn't that spooky. If you type something in Bash, while a program is running, it's sent to STDIN.
If you type CTRL-C, the bytes in System.in are discarded.
If System.exit(0) is invoked, the bytes in System.in are passed to STDIN of Bash (as in: if the child-process doesn't handle it, the parent process will)

So... it turned out I probably pasted that code accidently yesterday, and never noticed.


(...working on the badge)

[Riven]

[Riven]

I'm hosting it again, now allowing uppercase characters, but no unicode.

It only allows a "." if it is followed by "read(" or "write(".

I think this should catch all random acts of vandalism


Please report exploits... in private-mail on jgo