Unreliable data stream

Question

Your challenge is to golf a program that mimics a data transmission stream. Your program should read input from stdin and output it directly to stdout. To make the problem more interesting, the output stream is 'faulty', and must meet several requirements:

1. There should be a 10% chance that each character is shifted +1 ascii code (ex 'a' becomes 'b', '9' becomes ':'), etc.
2. The input and output should only cover printable ascii values ('!' through '~', decimal 33 through decimal 126, inclusive). If the random +1 occurs on a '~' (decimal 126), a '!' (decimal 33) should be output instead.
3. If three characters are randomly shifted in a row, the program should output "ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR" (trailing newline optional) and halt execution.

To simplify the problem, here are a few other criteria:

1. You can assume the input will always be valid; that is, it will only contain values '!' through '~'.
2. The program should continue on until three characters are randomly shifted in a row; it's safe to assume that EOF will never occur.
3. The randomness must differ across runs; if your random number generator needs to be seeded to get an unique result each run, then your code needs to seed it.
4. You must write a program, not a function.
5. You must take input from stdin and write output to stdout.
6. You may not use any external libraries or resources.
7. Your code must have a freely available and working intrepreter or compiler.

Standard code-golf rules apply. Winner is whoever has the shortest program posted two weeks from now (Thursday, Feb 20th, 2014).

Answer 1

Befunge-98, 166 159 156 155 148

This one improves on the other excellent Befunge answer with the correct probability (1/10) and is slightly more compact:

~>?#v?1+\1>+\:'~1+-4k#x07_$'!>,:3-!#v_
>#?>>>\$\0^>
^<<
A"##  "CT YOUR SYSTEM ADMINISTRATOR"<@,kM'"ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONT

Answer 2

C, 168 characters

i;main(c){for(srand(&c);i++<3;putchar(rand()%10?i=0,c:c-126?c+1:33))c=getchar();
puts("ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR");}

This solution's seeding of the PRNG takes advantage of the fact that modern OSes change the stack's location in memory on each run, as a basic measure against stack-smashing exploits.

Answer 3

Ruby, 156

e=3
putc(($_.ord-33+r=rand(10)/9)%94+33)/e=r>0?e-r :3while gets(1)rescue$><<'ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR'

Answer 4

Batch - 359

Open to suggestions to make it completely compliant to the challenge rules.

I will work on making it smaller / better - I wanted to post it while it's working, before I break it.

@echo off&setLocal enableDelayedExpansion&for /L %%a in (33,1,126)do cmd/cexit %%a&set %%a=!=exitcodeAscii!
set a=%~1
:l
if defined a (
set c=!a:~0,1!&set a=!a:~1!&set b=0&set/ar=%RANDOM%*10/32768+1
if !r!==1 for /L %%b in (33,1,126)do (
if !b!==1 echo !%%b!>>f
if "!c!"=="!%%b!" set b=1
)
if !b!==1 set/pc=<f&del f
set o=%o%!c!&goto l
) 
echo %o%

There are definitely quite a few ways to golf it down.

h:\uprof>UDS.bat "test ing"
tesu inh

h:\uprof>UDS.bat "test ing"
tfsu ing

Un-golfed -

@echo off
setLocal enableDelayedExpansion
for /L %%a in (33,1,126) do (
    cmd /c exit %%a
    set %%a=!=exitcodeAscii!
)
set a=%~1
:l
if defined a (
    set c=!a:~0,1!
    set a=!a:~1!
    set b=0
    set /a r=%RANDOM%*10/32768+1
    if !r!==1 for /L %%b in (33,1,126) do (
        if !b!==1  echo !%%b!>>f
        if "!c!"=="!%%b!" set b=1
    )
    if !b!==1 set /p c=<f& del f
    set o=%o%!c!
    goto l
) 
echo %o%

Answer 5

PHP 190

that's the further i could golf it, but i think it's pretty good that it is less than 100 chars from the leading

<? while($a=fread(STDIN,1)){if(!rand(0,9)){$a=$a=='~'?'!':chr(ord($a)+1);@$i+=1;$i>2&&die("ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR");}else$i=0;echo$a;}

Answer 6

C# - 346 330 313 309 297 288 278 274

Kinda long but does the job.

using System;class m{static void Main(){int c=0;var r=new Random();while(c<3){int n=r.Next(10);var j=Console.In.Read();Console.Write((char)(n<1?j>'}'?'!':++j:j));c=n<1?c+1:0;}Console.Write("ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR");}}

Answer 7

sh bash, on OSX, 211, 208, 203, 200, 196, 185

IFS=
while read -n1 a;do
((RANDOM>3276))&&echo $a&&t=0||{
tr !-}~ \"-~!<<<$a
((t++==2))&&echo ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR&&exit
}
done

Slightly better than 10% since random will generate numbers between 0 and 32767, so really it's 3,277 in 32,768 odds (10.0006%).

Thanks, @Gilles (but not sure what you mean about the while restructure. had some other ideas in the shower, too.

Answer 8

C, 260 257 237 225 189 174

My first golf, suggestions appreciated.

n;main(){for(srand(&n);n!=3;putchar((getchar()+(rand()%10==7?!!++n:(n=0))-33%94)+33));puts("ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR");}

7 is very random.

Compiling will give you warnings.

Thanks for help from breadbox and Josh.

Answer 9

Vyxal s, 63 bytes

ƛ₀℅‹¬;:ĠṠ3<A[?C+₇‹33VC|`»ȯ ¬⋎ 4625: un₆¬×→ »ȯ, ƛṙ λḊ λ¢ ƛβ ↑Ẇ`⇧

Try it Online!

ƛ    ;                      # Map input to...
 ₀℅‹¬                       # 1 with chance 10%
      :ĠṠ                   # Get sums of groups of identical run lengths
         3<A[               # If all are less than 3 (no error)
             ?C+            # Add randoms to input charcodes
                ₇‹33V       # Replace 127 with 33
                     C      # Get charcodes
                      |`... # Else output the string

Answer 10

JavaScript (Node.js), 215 bytes

for(z=1,r='';z<<=9;z|=y+''==x,r+=y>'~'?'!':y)require('fs').readSync(0,x=Buffer(1),0,1),y=x.map(t=>t+(Math.random()<.1));console.log(r+'ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR')

Try it online!

Answer 11

05AB1E, 65 64 63 bytes

v9°Ω})DÅγsÏ3åi.•kUàø¸àŸ´•uŽIZ‘‰ëƒË ÿ: ÿ‰ë,‚µ€Í€ž‚«¢é‘ësÇ+ƵQ33:ç

Try it online!

Answer 12

Kotlin, 357 355 bytes

2 bytes saved after discovering this

import java.util.*import kotlin.random.*import kotlin.random.Random
var c=0
fun main(){var a =Scanner(System.`in`).next().toMutableList()
for(i in a.indices){if(Random.nextUInt()%10u<1u){c++;if(a[i]=='~')a[i]='!' else a[i]=a[i]+1}else if(c<3)c=0}
if(c>2)print("ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR")else print(a)}

Try it online!

I've noticed that adding newlines causes the same amount of bytes to accumulate compared to adding a semicolon. hence why it isnYt so one liney. this of course does not work with tio.run as it requires input. If you see any places where there could be any kind of improvement please tell.

Ungolfed version

import java.util.*import kotlin.random.*import kotlin.random.Random
var c =0
fun main()
{
    var a = Scanner(System.`in`).next().toMutableList()
    for(i in a.indices){
        if(Random.nextUInt()%10u<1u)
        {
            c++
            if(a[i]=='~') a[i]='!'
            else a[i]=a[i]+1
        }
        else if(c<3)c=0
    }
    if(c>2) print("ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR")
    else print(a)
}

Try it online!

    import java.util.*;import kotlin.random.Random;import kotlin.random.*
    var c=0
    fun main(){var a =Scanner(System.`in`).next().toMutableList()
    for(i in a.indices){if(Random.nextUInt()%10u<1u){c++;if(a[i]=='~')a[i]='!' else a[i]=a[i]+1}else if(c<3)c=0}
    if(c>2)print("ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR")else print(a)}