"

 COPYRIGHT (c) 2007 by eXept Software AG

              All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

"{ Package: 'stx:libbasic2' }"

Random subclass:#RandomGenerator

	instanceVariableNames:''

	classVariableNames:'RandFile SharedRandomGenerator'

	poolDictionaries:''

	category:'Magnitude-Numbers'

!

!RandomGenerator class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 2007 by eXept Software AG

              All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

!

documentation

"

    Warning: this generator should not be used for cryptographic work 

    unless: 

        1) you are running on linux, solaris or osx,

        2) you have a working /dev/urandom.

        3) you can trust your /dev/urandom (I don't really know if any/all of them are good)

    This is a Random number generator, 

    which uses either a OS random number generator (/dev/urandom),

    or an ST/X internal random number generator.

    [author:]

        Stefan Vogel

    [see also:]

        http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf

        Random HashRandom Rc4Stream

    [instance variables:]

    [class variables:]

        RandFile        the FileStream we get random numbers from

"

! !

!RandomGenerator class methodsFor:'initialization'!

initialize

    "want to be informed when returning from snapshot"

    ObjectMemory addDependent:self.

!

openRandFile

    "try to open a random device"

    |randDevName|

    RandFile isStream ifTrue:[

        RandFile close.

    ].

    RandFile := false.              "prevent retry"

    randDevName := self randPath.

    randDevName notNil ifTrue:[

        randDevName := randDevName asFilename.

        randDevName isReadable ifTrue:[

            RandFile := randDevName readStream

        ].

    ].

! !

!RandomGenerator class methodsFor:'instance creation'!

new

    "return a new random number generator.

     Try to get system random numbers from device (e.g. in LINUX).

     If no system random nubers are available, fall back to

     a cryptographic secure PRNG (part of the extra libcrypt package). 

     As last resort fallback to the cryptographic insecure linear builtin PRNG"

    |result|

    SharedRandomGenerator notNil ifTrue:[

        "each time, we do an new, add some entropy to the SharedGenerator"

        SharedRandomGenerator addEntropy:OperatingSystem getMicrosecondTime.

        ^ SharedRandomGenerator.

    ].

    [

        "fetch a random byte - and check if the OS generator works"

        result := OperatingSystem randomBytesInto:1.

    ] on:PrimitiveFailure do:[:ex| ].

    result notNil ifTrue:[

        "OperatingSystem knows how to get random bytes"

        RandFile := true.

        SharedRandomGenerator := self basicNew.

        ^ SharedRandomGenerator.

    ] ifFalse:[

        RandFile isNil ifTrue:[

            self openRandFile.

        ].

        RandFile isStream ifTrue:[

            SharedRandomGenerator := self basicNew.

            ^ SharedRandomGenerator.

        ].

    ].

    Rc4Cipher notNil ifTrue:[

        SharedRandomGenerator := Rc4Cipher random.

        ^ SharedRandomGenerator.

    ].

    SharedRandomGenerator := Random sharedGenerator.

    ^ SharedRandomGenerator.

! !

!RandomGenerator class methodsFor:'adding entropy'!

addEntropy:entropyBytes

    SharedRandomGenerator notNil ifTrue:[

        SharedRandomGenerator addEntropy:entropyBytes

    ].

! !

!RandomGenerator class methodsFor:'change & update'!

update:something with:aParameter from:changedObject

    "handle image restarts and flush any device resource handles"

    SharedRandomGenerator := nil.

    RandFile notNil ifTrue:[

        RandFile := nil.

        self openRandFile.

    ].

! !

!RandomGenerator class methodsFor:'queries'!

randPath

    "path to a file/device that is a source or random numbers"

    OperatingSystem isUNIXlike ifTrue:[^ '/dev/urandom'].

    ^ nil.

! !

!RandomGenerator methodsFor:'basic reading'!

nextByte

    "get the next random byte"

    RandFile == true ifTrue:[

        ^ OperatingSystem randomBytesInto:1.

    ].

    ^ RandFile nextByte

    "

      RandomGenerator new nextByte

    "

    "

     Distribution should be equal:

     |r bag|

     r := RandomGenerator new.

     bag := Bag new.

     1000000 timesRepeat:[

         bag add:(r nextByte).

     ].

     bag.

     Transcript showCR:bag contents

    "

    "Created: / 11.11.1999 / 09:25:39 / stefan"

!

nextBytes:cnt

    "get the next cnt random bytes"

    RandFile == true ifTrue:[

        ^ OperatingSystem randomBytesInto:(ByteArray new:cnt).

    ].

    ^ RandFile nextBytes:cnt.

    "

      RandomGenerator new nextBytes:4

    "

    "Created: / 11.11.1999 / 09:25:39 / stefan"

    "Modified: / 11.11.1999 / 09:52:26 / stefan"

! !

!RandomGenerator methodsFor:'reading'!

next

    "return the next random number in the range 0..1"

    ^ self nextInteger / 16r3fffffff asFloat

    "

     |r|

     r := RandomGenerator new.

     Transcript showCR:r next.

     Transcript showCR:r next.

     Transcript showCR:r next.

     Transcript showCR:r next.

    "

    "Modified: / 11.11.1999 / 10:31:35 / stefan"

!

nextBoolean

    "return true or false by random"

    ^ self nextByte <= 127

    "

     |r|

     r := RandomGenerator new.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

    "

    "

     Distribution should approach 50/50:

     |r bag|

     r := RandomGenerator new.

     bag := Bag new.

     1000000 timesRepeat:[

         bag add:(r nextBoolean).

     ].

     Transcript showCR:bag contents

    "

    "Created: / 11.11.1999 / 09:25:39 / stefan"

    "Modified: / 12.11.1999 / 17:22:01 / stefan"

!

nextCharacters:cnt

    "get the next cnt printable characters.

     We answer characters in the ascii range (codepoints 32 - 127)"

    |bytes string|

    bytes := self nextBytes:cnt.

    string := String new:cnt.

    bytes keysAndValuesDo:[:eachIndex :eachByte|

        string at:eachIndex put:(Character value:(eachByte \\ 95 + 32)).

    ].

    ^ string

    "

      RandomGenerator new nextCharacters:8

    "

!

nextIntegerBetween:start and:stop

    "return an integral random number between start and stop"

    |rnd range bytesNeeded|

    range := stop - start + 1.

    bytesNeeded := (range highBit + 15) // 8.

    "Fetch at least 2 bytes, otherwise we get some unbalanced distributions for small ranges"

    rnd := (LargeInteger digitBytes:(self nextBytes:bytesNeeded)) compressed.

    rnd := rnd \\ range.

    ^ rnd + start

    "

     |r|

     r := self new.

     Transcript showCR:(r nextIntegerBetween:1 and:10).

     Transcript showCR:(r nextIntegerBetween:1 and:10).

     Transcript showCR:(r nextIntegerBetween:1 and:10).

     Transcript showCR:(r nextIntegerBetween:1 and:10).

    "

    "

     |r bag|

     r := self new.

     bag := Bag new.

     1000000 timesRepeat:[

         bag add:(r nextIntegerBetween:-1 and:1).

     ].

     Transcript showCR:bag sortedCounts.

    "

    "

     |r bag|

     r := self new.

     bag := Bag new.

     1000000 timesRepeat:[

         bag add:(r nextIntegerBetween:1 and:3).

     ].

     Transcript showCR:bag sortedCounts.

     TestCase assert:(bag standardDeviation closeTo:(((3 squared - 1)/12) sqrt)).

    "

    "

     |r bag|

     r := self new.

     bag := Bag new.

     1000000 timesRepeat:[

         bag add:(r nextIntegerBetween:1 and:10).

     ].

     Transcript showCR:bag sortedCounts.

     TestCase assert:(bag standardDeviation closeTo:(((10 squared - 1)/12) sqrt)).

    "

    "Created: / 11.11.1999 / 10:28:36 / stefan"

! !

!RandomGenerator methodsFor:'writing'!

nextPut:something

    "change the random pool by feeding in something.

     Something should be some unpredictable, random event.

     Ignored here"

!

nextPutAll:something

    "change the random pool by feeding in something.

     Something should be some unpredictable, random event.

     Ignored here"

! !

!RandomGenerator class methodsFor:'documentation'!

version

!

version_CVS

! !

RandomGenerator initialize!