Who runs the Internet?

Cheers,

Alan

-----
At 7:07 PM -0400 10/13/02, PhiHo Hoang wrote:
>Who's flying the plane ?
>
>Cheers,
>
>PhiHo.
>
>----- Original Message -----
>From: "Alan Kay" <Alan.Kay at squeakland.org>
>To: <squeak-dev at lists.squeakfoundation.org>
>Sent: Sunday, October 13, 2002 7:51 PM
>Subject: Re: Object Format
>
>
>>  Depends on who's flying the plane ...
>>
>>  Cheers,
>>
>>  Alan
>>  -----
>>
>>  At 6:47 PM -0400 10/13/02, PhiHo Hoang wrote:
>>  >Hi Ian,
>>  >
>>  >>  You might also find the following useful:
>>  >>
>>  >>    http://www-sor.inria.fr/~piumarta/esug98/slides.ps.gz
>>  >>
>>  >>  starting around page 33.
>>  >
>>  >     Indeed, the whole document is very useful and interesting to read.
>>  >
>>  >     Thanks a lot, Ian.
>>  >
>>  >     BTW, were you teasing ?
>>  >
>>  >     On page 17 you mentioned a 'violently stripped' thingy. ;-)
>>  >
>>  >     Where can I find such a beauty ?
>>  >
>>  >     Of course, I would love to lay my hand on an 'eXtremely violently
>>  >stripped' one.
>>  >
>>  >     The smaller the more fun. Size does matter ;-)
>>  >
>>  >     Again, many thanks for the explanation and the document.
>>  >
>>  >     Cheers,
>>  >
>>  >     PhiHo.
>>  >
>>  >     P.S: Now I also understand what it means by Blue Plane and Pink
>Plane.
>>  >     Just wondering what colorful plane is Squeak now riding.
>>  >     (Are Grey or Black also considered colors ? )
>>  >
>>  >
>>  >----- Original Message -----
>>  >From: "Ian Piumarta" <ian.piumarta at inria.fr>
>>  >To: <phiho.hoang at rogers.com>
>>  >Cc: <squeak-dev at lists.squeakfoundation.org>
>>  >Sent: Sunday, October 13, 2002 4:47 PM
>>  >Subject: Re: Object Format
>>  >
>>  >
>>  >>  On Sun, 13 Oct 2002, PhiHo Hoang wrote:
>>  >>  > - 4 bits object format
>>  >>  >
>>  >>  > What is this 4-bit 'object format' field.
>>  >>
>>  >>  It tells you about what the instance contains.
>>  >>
>>  >>  The top bit (bit 3) is 1 for byte objects, 0 for word/pointer objects.
>>  >>
>>  >>  If the top bit is zero (words/pointers) then:
>>  >>  Bit 2 is 0 for pointer objects, 1 for words.
>>  >>  Bit 1 is set if there are indexable fields, 0 if there are none.
>>  >>  Bit 0 is set if there are fixed fields (named inst vars), otherwise 0.
>>  >>
>>  >>  A "word" object (bit 2 set) that has neither indexable nor fixed
>fields
>>  >>  (bits 1 and 0 clear) contains weak references and may have both fixed
>and
>>  >>  indexable fields.  (Unless the object contains only fixed fields then
>you
>>  >>  have to follow the class pointer and look in the class's
>"instanceSize"
>>  >>  field to find out how many fixed fields are in it.)
>>  >>
>>  >>  If bit 3 is set (byte object) then bit 2 tells you whether it's a
>compiled
>>  >>  method (set means it's compiled method).  Methods start with an extra
>>  >>  header word (look in class CompiledMethod to see what it contains)
>>  >>  followed by zero or more real pointers (the literals of the method).
>>  >>  After the pointers they turn into byte objects again.  Bits 1 and 0
>(of
>>  >>  any byte object) are the number of bytes by which the size header (or
>size
>>  >>  field in the base header) is too large (since a bytes object might be
>0,
>>  >>  1, 2 or 3 bytes short of an integral number of words long).
>>  >>
>>  >>  To summarise, if we consider the format as an integer from 0 to 15, we
>>  >>  get:
>>  >>
>>  >>  0     0000 no fields
>>  >>  1     0001 fixed fields only (all containing pointers)
>>  >>  2     0010 indexable fields only (all containing pointers)
>>  >>  3     0011 both fixed and indexable fields (all containing pointers)
>>  >>  4     0100 both fixed and indexable weak fields (all containing
>pointers).
>>  >>  5     0101 unused
>>  >>  6     0110 indexable word fields only (no pointers)
>>  >>  7     0111 unused
>>  >>  8-11  10xx indexable byte fields only (no pointers)
>>  >>  12-15 11xx compiled methods: # of literal oops specified in method
>header
>>  >>
>>  >>  > Where can I find further detailed information about this 'object
>>  >format'.
>>  >>
>>  >>  Browse class ObjectMemory in the image, and the object access
>primitives
>>  >>  in class Interpreter.
>>  >>
>  > >>  You might also find the following useful:
>>  >>
>>  >>    http://www-sor.inria.fr/~piumarta/esug98/slides.ps.gz
>>  >>
>>  >>  starting around page 33.
>>  >>
>>  >>  Regards,
>>  >>  Ian
>>  >>
>>  >>
>>  >>
>>  >>
>>  >>
>>
>>
>>  --
>>


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