Use inlined FNV1a hash for String
...and do not use __symbolHash(). Although currently the VM also
uses FNV1a hash for Symbols, the __symbolHash() does not handle
properly character with codepoint 0 (because '\0' is used as a
string terminator). This causes problems with Unicode16/32Strigs whose
version of FNV1a hash is using object size from header to determine
string's end.
Added Symbol>>hash that actually *uses* the __symbolHash() to make
sure it's hash is the the same as used bu the VM. Symbols with zeroes
are rare and there's no Unicode16/32Symbol.
This commit fixes issue #65.
"
COPYRIGHT (c) 1998 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 }"
String variableByteSubclass:#ImmutableString
instanceVariableNames:''
classVariableNames:''
poolDictionaries:''
category:'System-Compiler-Support'
!
!ImmutableString class methodsFor:'documentation'!
copyright
"
COPYRIGHT (c) 1998 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, string literals in smalltalk are mutable objects. That
may lead to some subtle (and hard to find errors), if some method passes
a string constant as argument to someone else, who changes the
string using at:put: like messages. Since the string object is kept in
the first methods literals, the string 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 ImmutableString instead of Strings
for literals. Instances of ImmutableString 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 string literals entered in
a workspace somewhat strange: you cannot modify it any longer).
Turn the ImmutableString feature on by setting the Parsers class variable
'StringsAreImmutable' to true or use the new launchers settings menu.
ATTENTION:
there may be still code around which checks for explicit class being String
(both in Smalltalk and in primitive code). All code like foo 'class == String'
or '__isString()' will not work with ImmutableStrings. Use '__isStringLike()' instead.
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:]
ImmutableArray
Parser Scanner
[author:]
Claus Gittinger
"
! !
!ImmutableString class methodsFor:'queries'!
mutableClass
"answer an equivalent mustable class"
^ String
! !
!ImmutableString class methodsFor:'testing'!
hasImmutableInstances
^ true
! !
!ImmutableString methodsFor:'accessing'!
at:index put:value
"Trigger an error if an immutable string is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger."
self noModificationError.
^ super at:index put:value
"Created: / 3.8.1998 / 14:45:14 / cg"
!
basicAt:index put:value
"Trigger an error if an immutable string is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger."
self noModificationError.
^ super basicAt:index put:value
! !
!ImmutableString methodsFor:'converting'!
asImmutableString
^ self
!
asMutableCollection
"return a writable copy of myself"
^ self copy changeClassTo:String
! !
!ImmutableString methodsFor:'copying'!
postCopy
"when copied, make me a real (mutable) String"
self changeClassTo:String.
"Created: / 3.8.1998 / 14:46:45 / cg"
!
postDeepCopy
"when copied, make it me a real (mutable) String"
self changeClassTo:String.
"
'foobar' asImmutableString copy class
'foobar' asImmutableString shallowCopy class
'foobar' asImmutableString deepCopy class
"
!
shallowCopy
"when copying, return a real (mutable) String"
|sz|
sz := self size.
^ (String new:sz) replaceFrom:1 to:sz with:self startingAt:1
"
'hello world' asImmutableString shallowCopy
"
"Created: / 3.8.1998 / 14:47:00 / cg"
! !
!ImmutableString methodsFor:'private'!
species
"Copies should be mutable"
^ String
"Created: / 3.8.1998 / 14:47:58 / cg"
!
speciesForCopy
"Copies should be mutable"
^ String
"Created: / 3.8.1998 / 14:47:58 / cg"
! !
!ImmutableString methodsFor:'queries'!
isImmutable
^ true
! !
!ImmutableString 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
"Created: / 3.8.1998 / 14:48:29 / cg"
!
becomeNil
"trigger an error if I should become nil
(this would be an even more tricky manipulation)"
self noModificationError.
^ super becomeNil
"Created: / 3.8.1998 / 14:48:37 / cg"
! !
!ImmutableString class methodsFor:'documentation'!
version
^ '$Header: /cvs/stx/stx/libbasic/ImmutableString.st,v 1.16 2015-02-03 13:53:40 stefan Exp $'
!
version_CVS
^ '$Header: /cvs/stx/stx/libbasic/ImmutableString.st,v 1.16 2015-02-03 13:53:40 stefan Exp $'
! !