"

 COPYRIGHT (c) 1995 by Claus Gittinger

	      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.

"

Object subclass:#ExternalAddress

	 instanceVariableNames:'address*'

	 classVariableNames:''

	 poolDictionaries:''

	 category:'System-Support'

!

!ExternalAddress class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1995 by Claus Gittinger

	      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

"

    Instances of this class represent external (non-Smalltalk) addresses.

    They are only useful to represent handles as returned by C functions

    as smalltalk objects. For example, Window- or WidgetIDs (which are actually

    32 bit pointers) should be represented this way.

    (you should not use SmallIntegers for this, since they can only represent 31

     bits; LargeIntegers could be used in theory, but it is not a very good style

     to do so, since it makes things a bit cryptic - having ExternalAddresses

     around makes things pretty clear in inspectors etc.).

    There is not much you can do with ExternalAddresses on the smalltalk level;

    creation/use is mostly in primitive C-code via 

    __MKEXTERNALADDRESS(voidPtr) and __ExternalAddressVal(obj).

    ExternallAddresses are much like ExternalBytes - however, the latter

    allow you to access bytes via indexed at:/at:put: messages.

    ExternallAddresses do not allow such accesses (they are meant to remain

    anonymous).

"

!

examples

"

    To pass some C-pointer from primitive code to smalltalk:

	...

	RETURN (__MKEXTERNALADDRESS(foo));

    pass it back to C and use it there:

	...

	if (__isExternalAddress(anExternalAddress)) {

	    ptr = __externalAddressVal(anExternalAddress));

	}

	...

    concrete example:

	test1

	%{

	    static char foo[] = {'h', 'e' ,'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd', '\n'};

	    RETURN (__MKEXTERNALADDRESS(foo));

	%}

	test2:anExternalAddress

	%{

	    if (__isExternalAddress(anExternalAddress)) {

		printf(__externalAddressVal(anExternalAddress));

		RETURN (self);

	    }

	%}

"

! !

!ExternalAddress class methodsFor:'queries'!

isBuiltInClass

    "known by the runtime system"

    ^ true

! !

!ExternalAddress methodsFor:'accessing'!

address

    "return the start address as an integer"

%{  /* NOCONTEXT */

    unsigned addr;

    addr = (unsigned)_INST(address_);

    RETURN ( __MKUINT(addr));

%}

! !

!ExternalAddress methodsFor:'comparing'!

= anExternalAddress

    "return true, if two externalAddress instance represent the same

     C pointer"

%{  /* NOCONTEXT */

    if (__isExternalAddress(anExternalAddress)

     && (__externalAddressVal(self) == __externalAddressVal(anExternalAddress))) {

	RETURN (true);

    }

%}.

    ^ false

!

hash

    "return a number useful for hashing"

%{  /* NOCONTEXT */

    unsigned addr = (unsigned) __externalAddressVal(self);

    RETURN (__MKSMALLINT(addr >> 2));

%}

! !

!ExternalAddress methodsFor:'converting'!

asExternalBytes

    "return an ExternalBytes object pointing to where the receiver points to.

     Use of this is not recommended; primitives which return externalAddresses

     dont think that access to the memory is required/useful, while primitives

     which do think so should return an externalBytes instance right away."

    ^ ExternalBytes address:(self address)

! !

!ExternalAddress methodsFor:'printing & storing'!

displayString

    ^ 'ExternalAddress at:' , (self address printStringRadix:16)

! !

!ExternalAddress class methodsFor:'documentation'!

version

    ^ '$Header: /cvs/stx/stx/libbasic/ExternalAddress.st,v 1.1 1996-01-11 13:18:04 cg Exp $'

! !