"{ Package: 'stx:libbasic2' }"

Object subclass:#RandomGenerator

	instanceVariableNames:''

	classVariableNames:'RandFile'

	poolDictionaries:''

	category:'Magnitude-Numbers'

!

!RandomGenerator class methodsFor:'documentation'!

documentation

"

    This is a Random number generator, which uses either a OS random number generator,

    or a ST/X internal random number generator.

    [author:]

        Stefan Vogel

    [see also:]

        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"

    RandFile isNil ifTrue:[

        self openRandFile.

    ].

    RandFile isStream ifTrue:[

        ^ self basicNew.

    ].

    Rc4Cipher notNil ifTrue:[

        ^ Rc4Cipher random

    ].

    ^ Random sharedGenerator

!

random

    "alias for new - protocol compatibility with StreamCiphers"

    ^ self new

! !

!RandomGenerator class methodsFor:'change & update'!

update:something with:aParameter from:changedObject

    "handle image restarts and flush any device resource handles"

    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:'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"

!

nextBetween:start and:stop

    "return a random number between start and stop."

    |rnd|

    rnd := self next.

    rnd := rnd * (stop - start) asFloat.

    rnd := rnd + start asFloat.

    ^ rnd

    "

     |r|

     r := RandomGenerator new.

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

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

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

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

    "

    "Created: / 11.11.1999 / 10:27:56 / 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.

    "

    "

     |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"

!

nextByte

    "get the next random byte"

    ^ RandFile nextByte

    "

      RandomGenerator new nextByte

    "

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

!

nextBytes:cnt

    "get the next cnt random bytes"

    ^ RandFile nextBytes:cnt.

    "

      RandomGenerator new nextBytes:4

    "

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

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

!

nextInteger

    "return the next integral random number,

     in the range 0 .. 16r3FFFFFFF."

    |res|

    res := self nextBytes:4.

    ^ ((((((res at:1) bitAnd:16r3F) * 256) + (res at:2)) * 256) + (res at:3)) * 256 + (res at:4)

    "

     |r|

     r := RandomGenerator new.

     Transcript showCR:r nextInteger.

     Transcript showCR:r nextInteger.

     Transcript showCR:r nextInteger.

     Transcript showCR:r nextInteger.

    "

    "Modified: / 11.11.1999 / 10:08:10 / stefan"

!

nextIntegerBetween:start and:stop

    "return an integral random number between start and stop"

    |rnd|

    rnd := self next.                               

    rnd := rnd * ((stop - start) asFloat + 1.0).    

    ^ rnd truncated + start

    "

     |r|

     r := RandomGenerator 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 := RandomGenerator new.

     bag := Bag new.

     1000000 timesRepeat:[

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

     ].

     Transcript showCR:bag contents

    "

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

!

nextMatchFor: aNumber

    "generate the next random, return true iff it has the same

     value as aNumber. Redefined to avoid endless reading."

    ^self next = aNumber

    "Created: / 11.11.1999 / 10:29:32 / 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

    ^ '$Header: /cvs/stx/stx/libbasic2/RandomGenerator.st,v 1.1 2006-03-10 08:51:39 stefan Exp $'

! !

RandomGenerator initialize!