Hi Tobias,

TheRandom should be re-seeded on startup, so that images don't generate 
the same UUIDs.
Integer >> atRandom: creates a random number between 1 and the receiver,
so 16rffffffffffffffffffffffffffffffff atRandom: TheRandom won't create
all possible 128-bit values. It's also a bit slow to create an 
intermediate Integer objects for this, so I suggest you should use Random 
>> #nextBytes:into:startingAt: instead to fill the UUID object with random
bytes.

Levente

On Mon, 19 Oct 2015, Tobias Pape wrote:

> Hi all
>
> Don't hold back your comments.
> I'd like to put this into trunk and enable people not to have to install
> libuuid1:i386 in their shiny new 64-bit Linux environment ;)
>
> Best regards
> 	-Tobias
>
> On 19.10.2015, at 21:28, commits at source.squeak.org wrote:
>
>> Tobias Pape uploaded a new version of Network to project The Inbox:
>> http://source.squeak.org/inbox/Network-topa.165.mcz
>>
>> ==================== Summary ====================
>>
>> Name: Network-topa.165
>> Author: topa
>> Time: 19 October 2015, 11:28:20.052 pm
>> UUID: b4b1febc-df00-4213-b76f-c007b06bb2e2
>> Ancestors: Network-ul.164
>>
>> Simplify and speed up non-primitive UUID generation (hat-tip to Martin McClure <martin.mcclure at gemtalksystems.com>)
>>
>> Instead of generating all parts of the UUID separately, we generate
>> a single, 128-bit number and modify it slightly to match the UUID definition.
>> This complies with RFC 4122, Sec. 4.4.
>>
>> This approach is 2500 times faster than the old method and only about 3 times
>> slower than the primitive. Hence, we disable the primitive and no longer need
>> to rely on the UUIDPlugin to be present.
>>
>> Informational: The Timings:
>>
>> {
>> 'Pure allocation' -> [UUID basicNew: 16] bench.
>> 'Primitive + alloc' -> [(UUID basicNew: 16) primMakeUUID] bench.
>> 'Old +  alloc' -> [|u| u := (UUID basicNew: 16). UUIDGeneratorOld new generateBytes: u forVersion: 4] bench.
>> 'New + alloc' -> [|u| u := (UUID basicNew: 16). UUIDGeneratorNew new generateBytes: u forVersion: 4] bench.
>> }.
>> "{
>> 'Pure allocation'->'56,500,000 per second. 17.7 nanoseconds per run.' .
>> 'Primitive + alloc'->'1,510,000 per second. 663 nanoseconds per run.' .
>> 'Old +  alloc'->'202 per second. 4.95 milliseconds per run.' .
>> 'New + alloc'->'519,000 per second. 1.93 microseconds per run.'
>> }."
>>
>> =============== Diff against Network-ul.164 ===============
>>
>> Item was changed:
>>  ----- Method: String>>asAlphaNumeric:extraChars:mergeUID: (in category '*network-uuid') -----
>>  asAlphaNumeric: totalSize extraChars: additionallyAllowed mergeUID: minimalSizeOfRandomPart
>>  	"Generates a String with unique identifier ( UID ) qualities, the difference to a
>>  	 UUID is that its beginning is derived from the receiver, so that it has a meaning
>>  	 for a human reader.
>>
>>  	 Answers a String of totalSize, which consists of 3 parts
>>  	 1.part: the beginning of the receiver only consisting of
>>  		a-z, A-Z, 0-9 and extraChars in Collection additionallyAllowed ( which can be nil )
>>  	 2.part: a single _
>>  	 3.part: a ( random ) UID of size >= minimalSizeOfRandomPart consisting of
>>  		a-z, A-Z, 0-9
>>
>>  	 Starting letters are capitalized.
>>  	 TotalSize must be at least 1.
>>  	 Exactly 1 occurrence of $_ is guaranteed ( unless additionallyAllowed includes $_ ).
>>  	 The random part has even for small sizes good UID qualitites for many practical purposes.
>>  	 If only lower- or uppercase letters are demanded, simply convert the answer with
>>  	 say #asLowercase. The probability of a duplicate will rise only moderately ( see below ).
>>
>>  	 Example:
>>  		size of random part = 10
>>  		in n generated UIDs the chance p of having non-unique UIDs is
>>  			n = 10000 ->  p < 1e-10		if answer is reduced to lowerCase: p < 1.4 e-8
>>  			n = 100000 -> p < 1e-8
>>  		at the bottom is a snippet for your own calculations
>>  		Note: the calculated propabilites are theoretical,
>>  			for the actually used random generator they may be much worse"
>>
>>  	| stream out sizeOfFirstPart index ascii ch skip array random |
>>  	totalSize > minimalSizeOfRandomPart
>>  		ifFalse: [ self errorOutOfBounds ].
>>  	stream := ReadStream on: self.
>>  	out := WriteStream on: ( String new: totalSize ).
>>  	index := 0.
>>  	skip := true.
>>  	sizeOfFirstPart := totalSize - minimalSizeOfRandomPart - 1.
>>  	[ stream atEnd or: [ index >= sizeOfFirstPart ]]
>>  	whileFalse: [
>>  		((( ascii := ( ch := stream next ) asciiValue ) >= 65 and: [ ascii <= 90 ]) or: [
>>  			( ascii >= 97 and: [ ascii <= 122 ]) or: [
>>  			ch isDigit or: [
>>  			additionallyAllowed notNil and: [ additionallyAllowed includes: ch ]]]])
>>  		ifTrue: [
>>  			skip
>>  				ifTrue: [ out nextPut: ch asUppercase ]
>>  				ifFalse: [ out nextPut: ch ].
>>  			index := index + 1.
>>  			skip := false ]
>>  		ifFalse: [ skip := true ]].
>>  	out nextPut: $_.
>>  	array := Array new: 62.
>>  	1 to: 26 do: [ :i |
>>  		array at: i put: ( i + 64 ) asCharacter.
>>  		array at: i + 26 put: ( i + 96 ) asCharacter ].
>>  	53 to: 62 do: [ :i |
>>  		array at: i put: ( i - 5 ) asCharacter ].
>> + 	random := ThreadSafeRandom value.
>> - 	random := UUIDGenerator default randomGenerator.
>>  	totalSize - index - 1 timesRepeat: [
>>  		out nextPut: ( array atRandom: random )].
>>  	^out contents
>>
>>  	"	calculation of probability p for failure of uniqueness in n UIDs
>>  		Note: if answer will be converted to upper or lower case replace 62 with 36
>>  	| n i p all |
>>  	all := 62 raisedTo: sizeOfRandomPart.
>>  	i := 1.
>>  	p := 0.0 .
>>  	n := 10000.
>>  	[ i <= n ]
>>  	whileTrue: [
>>  		p := p + (( i - 1 ) / all ).
>>  		i := i + 1 ].
>>  	p
>>
>>  	approximation formula: n squared / ( 62.0 raisedTo: sizeOfRandomPart ) / 2
>>  	"
>>
>>  	"'Crop SketchMorphs and Grab Screen Rect to JPG'
>>  			asAlphaNumeric: 31 extraChars: nil mergeUID: 10
>>  	 			'CropSketchMorphsAndG_iOw94jquN6'
>>  	 'Monticello'
>>  			asAlphaNumeric: 31 extraChars: nil mergeUID: 10
>>  				'Monticello_kp6aV2l0IZK9uBULGOeG'
>>  	 'version-', ( '1.1.2' replaceAll: $. with: $- )
>>  			asAlphaNumeric: 31 extraChars: #( $- ) mergeUID: 10
>>  				'Version-1-1-2_kuz2tMg2xX9iRLDVR'"
>>  		!
>>
>> Item was changed:
>>  ----- Method: UUID>>initialize (in category 'initalize-release') -----
>>  initialize
>> + 	self makeUUID.!
>> - 	self primMakeUUID.!
>>
>> Item was added:
>> + ----- Method: UUID>>makeUUID (in category 'as yet unclassified') -----
>> + makeUUID
>> + 	UUIDGenerator default generateBytes: self forVersion: 4.!
>>
>> Item was changed:
>>  ----- Method: UUID>>primMakeUUID (in category 'system primitives') -----
>>  primMakeUUID
>>  	<primitive: 'primitiveMakeUUID' module: 'UUIDPlugin'>
>> + 	self makeUUID!
>> - 	UUIDGenerator default generateBytes: self forVersion: 4.!
>>
>> Item was changed:
>>  Object subclass: #UUIDGenerator
>> + 	instanceVariableNames: 'bits'
>> + 	classVariableNames: 'Default TheRandom TheSemaphore'
>> - 	instanceVariableNames: 'timeLow timeMid timeHiAndVersion clockSeqHiAndReserved clockSeqLow node randomCounter randomGenerator semaphoreForGenerator'
>> - 	classVariableNames: 'Default'
>>  	poolDictionaries: ''
>>  	category: 'Network-UUID'!
>>
>> + !UUIDGenerator commentStamp: 'topa 10/19/2015 23:23:19' prior: 0!
>> + I generate a pseudo-random UUID by asking Random for a 128 bit value.
>> - !UUIDGenerator commentStamp: '<historical>' prior: 0!
>> - This class generates a pseudo-random UUID
>> - by John M McIntosh johnmci at smalltalkconsulting.com
>>
>> + See https://tools.ietf.org/html/rfc4122.html#section-4.4 for reference.!
>> - See http://www.webdav.org/specs/draft-leach-uuids-guids-01.txt!
>>
>> Item was changed:
>>  ----- Method: UUIDGenerator class>>initialize (in category 'class initialization') -----
>>  initialize
>> + 	TheRandom := Random new.
>> + 	TheSemaphore := Semaphore forMutualExclusion.
>>  	Smalltalk addToStartUpList: self after: nil.!
>>
>> Item was changed:
>>  ----- Method: UUIDGenerator>>generateFieldsVersion4 (in category 'instance creation') -----
>>  generateFieldsVersion4
>> +
>> + 	TheSemaphore critical: [
>> + 		bits := 16rffffffffffffffffffffffffffffffff atRandom: TheRandom. "128 bit"].!
>> -
>> - 	timeLow := self generateRandomBitsOfLength: 32.
>> - 	timeMid := self generateRandomBitsOfLength: 16.
>> - 	timeHiAndVersion := 16r4000 bitOr: (self generateRandomBitsOfLength: 12).
>> - 	clockSeqHiAndReserved := 16r80 bitOr: (self generateRandomBitsOfLength: 6).
>> - 	clockSeqLow := self generateRandomBitsOfLength: 8.
>> - 	node := self generateRandomBitsOfLength: 48.
>> - 	!
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>generateOneOrZero (in category 'generator') -----
>> - generateOneOrZero
>> - 	^self semaphoreForGenerator
>> - 		critical: [| value |
>> - 			value := self randomGenerator next.
>> - 			self randomCounter: self randomCounter + 1.
>> - 			self randomCounter > 100000
>> - 				ifTrue: [self setupRandom].
>> - 			value < 0.5
>> - 				ifTrue: [0]
>> - 				ifFalse: [1]].!
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>generateRandomBitsOfLength: (in category 'generator') -----
>> - generateRandomBitsOfLength: aNumberOfBits
>> - | target |
>> - 	target := 0.
>> - 	aNumberOfBits isZero ifTrue: [^target].
>> - 	target := self generateOneOrZero.
>> - 	(aNumberOfBits - 1)  timesRepeat:
>> - 		[target := (target bitShift: 1)  bitOr: self generateOneOrZero].
>> - 	^target!
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>initialize (in category 'instance creation') -----
>> - initialize
>> - 	self setupRandom.
>> - 	semaphoreForGenerator := Semaphore forMutualExclusion.
>> - 	!
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>makeSeed (in category 'random seed') -----
>> - makeSeed
>> - 	"Try various methods of getting good seeds"
>> - 	| seed |
>> - 	seed := self makeUnixSeed.
>> - 	seed ifNotNil: [^seed].
>> -
>> - 	"not sure if this is reliably random... commented out for now. -dew"
>> - 	"seed := self makeSeedFromSound.
>> - 	seed ifNotNil: [^seed]."
>> -
>> - 	"default"
>> - 	[seed := (Time millisecondClockValue bitAnd: 16r3FFFFFFF) bitXor: self hash.
>> - 	seed := seed bitXor: (Time totalSeconds bitAnd: 16r3FFFFFFF).
>> - 	seed = 0] whileTrue: ["Try again if ever get a seed = 0"].
>> -
>> - 	^seed
>> - !
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>makeSeedFromSound (in category 'random seed') -----
>> - makeSeedFromSound
>> - 	^[SoundService default randomBitsFromSoundInput: 32]
>> - 		ifError: [nil].!
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>makeUnixSeed (in category 'random seed') -----
>> - makeUnixSeed
>> -
>> - 	^[
>> - 		StandardFileStream readOnlyFileNamed: '/dev/urandom' do: [ :stream |
>> - 			stream binary.
>> - 			(Integer
>> - 				byte1: stream next
>> - 				byte2: stream next
>> - 				byte3: stream next
>> - 				byte4: stream next) ] ]
>> - 		on: Error
>> - 		do: [ nil ]!
>>
>> Item was changed:
>>  ----- Method: UUIDGenerator>>placeFields: (in category 'instance creation') -----
>>  placeFields: aByteArray
>>
>> + 	| version fixed |
>> + 	bits isLarge
>> + 		ifTrue: [	aByteArray replaceFrom: 1 to: bits size with: bits]
>> + 		ifFalse: [aByteArray unsignedLongAt: 1 put: bits bigEndian: false].
>> +
>> + 	version := ((aByteArray at: 7) bitAnd: 16r0F) bitOr: 16r40. "Version 4"
>> + 	fixed := ((aByteArray at: 9) bitAnd: 16r3F) bitOr: 16r80. "Fixed 8..b value"
>> + 	aByteArray
>> + 		at: 7 put: version;
>> + 		at: 9 put: fixed.!
>> - 	aByteArray at: 1 put: ((timeLow bitShift: -24) bitAnd: 16rFF).
>> - 	aByteArray at: 2 put: ((timeLow bitShift: -16) bitAnd: 16rFF).
>> - 	aByteArray at: 3 put: ((timeLow bitShift: -8) bitAnd: 16rFF).
>> - 	aByteArray at: 4 put: (timeLow bitAnd: 16rFF).
>> - 	aByteArray at: 5 put: ((timeMid bitShift: -8) bitAnd: 16rFF).
>> - 	aByteArray at: 6 put: (timeMid bitAnd: 16rFF).
>> - 	aByteArray at: 7 put: ((timeHiAndVersion bitShift: -8) bitAnd: 16rFF).
>> - 	aByteArray at: 8 put: (timeHiAndVersion bitAnd: 16rFF).
>> - 	aByteArray at: 9 put: clockSeqHiAndReserved.
>> - 	aByteArray at: 10 put: clockSeqLow.
>> - 	0 to: 5 do: [:i |
>> - 		aByteArray at: 11 + i put: ((node bitShift: (-8*i)) bitAnd: 16rFF)]
>> - !
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>randomCounter (in category 'accessors and mutators') -----
>> - randomCounter
>> - 	^randomCounter!
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>randomCounter: (in category 'accessors and mutators') -----
>> - randomCounter: aNumber
>> - 	randomCounter := aNumber
>> - !
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>randomGenerator (in category 'accessors and mutators') -----
>> - randomGenerator
>> - 	^randomGenerator
>> - !
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>randomGenerator: (in category 'accessors and mutators') -----
>> - randomGenerator: aGenerator
>> - 	randomGenerator := aGenerator
>> - !
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>semaphoreForGenerator (in category 'accessors and mutators') -----
>> - semaphoreForGenerator
>> - 	^semaphoreForGenerator!
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>semaphoreForGenerator: (in category 'accessors and mutators') -----
>> - semaphoreForGenerator: aSema
>> - 	semaphoreForGenerator := aSema
>> - !
>>
>> Item was removed:
>> - ----- Method: UUIDGenerator>>setupRandom (in category 'instance creation') -----
>> - setupRandom
>> - 	randomCounter := 0.
>> - 	randomGenerator := Random seed: self makeSeed.!
>>
>>
>
>
>