"

 COPYRIGHT (c) 2009 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:libbasic' }"

"{ NameSpace: Smalltalk }"

ByteArray variableByteSubclass:#ImmutableByteArray

	instanceVariableNames:''

	classVariableNames:''

	poolDictionaries:''

	category:'System-Compiler-Support'

!

!ImmutableByteArray class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 2009 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

"

    By default, byte array literals in smalltalk are mutable objects. That

    may lead to some subtle (and hard to find errors), if some method passes

    a literal byte-array object as argument to someone else, who changes the

    bytearray using at:put: like messages. Since the bytearray object is kept in

    the first methods literals, the bytearray constant has now been changed without

    having the method's sourcecode reflect this. Thus, the method will

    behave differently from what its source may make you think.

    To help finding this kind of 'feature/bug', the compiler can be

    configured to create instances of this ImmutableByteArray instead of ByteArrays

    for literals. Instances of ImmutableByteArray catch storing accesses and

    enter the debugger. Although useful, this feature is disabled by default

    for compatibility to other smalltalk implementations.

    (Also, if turned on, this makes inspecting bytearray literals entered in

     a workspace somewhat strange: you cannot modify it any longer).

    Turn the ImmutableArray feature on, by setting the Parser's class variable

    'ArraysAreImmutable' to true or use the new launchers settings menu.

    This class should be used only by the compiler.

    ATTENTION:

        there may be still code around which checks for explicit class being ByteArray

        (both in Smalltalk and in primitive code). All code like foo 'class == ByteArray'

        or '__isByteArray()' will not work with ImmutableByteArrays - consider using '__isByteArrayLike()'.

        A somewhat better approach would be to either add a flag to the object (mutability)

        and check this dynamically (expensive) or to place immutable objects into a readonly

        memory segment (the good solution). We will eventually implement the second in the future...

    [see also:]

        ImmutableString

        ImmutableArray

        Parser Scanner

    [author:]

        Claus Gittinger

"

! !

!ImmutableByteArray class methodsFor:'queries'!

mutableClass

    "answer an equivalent mustable class"

    ^ ByteArray

! !

!ImmutableByteArray class methodsFor:'testing'!

hasImmutableInstances

    ^ true

! !

!ImmutableByteArray methodsFor:'accessing'!

at:index put:value

    "Trigger an error if an immutable bytearray is stored into.

     The store will be performed (for compatibility reasons) if you continue

     in the debugger."

    self noModificationError.

    ^ super at:index put:value

!

basicAt:index put:value

    "Trigger an error if an immutable bytearray is stored into.

     The store will be performed (for compatibility reasons) if you continue

     in the debugger."

    self noModificationError.

    ^ super basicAt:index put:value

! !

!ImmutableByteArray methodsFor:'converting'!

asByteArray

    "return the receiver as a (mutable) byteArray"

    ^ self copy changeClassTo: ByteArray

    "

     #[1 2 3 4] asImmutableByteArray asByteArray

    "

!

asImmutableByteArray

    ^ self

!

asMutableCollection

    "return a writable copy of myself"

    ^ self copy changeClassTo:ByteArray

! !

!ImmutableByteArray methodsFor:'copying'!

postCopy

    "when copied, make me a real (mutable) ByteArray"

    self changeClassTo:ByteArray.

!

postDeepCopy

    "when copied, make me a real (mutable) ByteArray"

    self changeClassTo:ByteArray.

    "

     #[1 2 3 4] asImmutableByteArray copy          class

     #[1 2 3 4] asImmutableByteArray shallowCopy   class

     #[1 2 3 4] asImmutableByteArray deepCopy      class

    "

!

shallowCopy

    "when copying, return a real (mutable) ByteArray"

    |sz|

    sz := self size.

    ^ (ByteArray new:sz) replaceBytesFrom:1 to:sz with:self startingAt:1

    "

     #[1 2 3 4] asImmutableByteArray shallowCopy

    "

! !

!ImmutableByteArray methodsFor:'printing & storing'!

displayOn:aGCOrStream

    "/ what a kludge - Dolphin and Squeak mean: printOn: a stream;

    "/ ST/X (and some old ST80's) mean: draw-yourself on a GC.

    (aGCOrStream isStream) ifTrue:[

        self storeOn:aGCOrStream.

        aGCOrStream nextPutAll:'"immutable"'.

        ^ self.

    ].

    super displayOn:aGCOrStream.

! !

!ImmutableByteArray methodsFor:'private'!

species

    "Copies should be mutable"

    ^ ByteArray

!

speciesForCopy

    "Copies should be mutable"

    ^ ByteArray

! !

!ImmutableByteArray methodsFor:'queries'!

isImmutable

    ^ true

!

isLiteral

    "return true, if the receiver can be used as a literal constant in ST syntax

     (i.e. can be used in constant arrays)"

    "yes, I must be"

    ^ true

! !

!ImmutableByteArray methodsFor:'specials'!

become:anotherObject

    "trigger an error if I should become something else

     (this would be an even more tricky manipulation)"

    self noModificationError.

    ^ super become:anotherObject

!

becomeNil

    "trigger an error if I should become nil

     (this would be an even more tricky manipulation)"

    self noModificationError.

    ^ super becomeNil

! !

!ImmutableByteArray class methodsFor:'documentation'!

version_CVS

    ^ '$Header$'

! !