Of variables, values, and vtables

[Dan Sugalski]

Okay, folks, I'm back from travel, at least for a little while. My
short term goals are:

*) Finish up the calling convention changes
*) Spec the PMC changes
*) Spec the vtable changes
*) Get exceptions fully defined and a preliminary implementation

The variable/vtable stuff should be done in the next day or two. The
calling convention stuff may be done a little earlier or later,
depending on how things go.
--
Dan

--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
d...@sidhe.org have teddy bears and even
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[Leopold Toetsch]

Dan Sugalski wrote:

> *) Spec the vtable changes

Starting from my proposal ...

Subject: [RFC] 2. Proposal for _keyed opcodes

.... I have some more implementation details, WRT _keyed.

- An aggregate should provide these vtable methods:

* entry_type ... get info about the aggregates storage entry:
possible values are:
- int ... e.g. (packed) int array like current intlist
- float ... (packed) float
- UnionVal
- TypedUnionVal ... current HASH_ENTRY
- PMC

* get_entryp(PMC *key) ... get a pointer to an aggregates store entry
of above type, resolve compound keys if necessary
* get_entryp_int(INTVAL intkey) ... optimized version

These 3 methods ought to be enough, to implement all current _keyed
methods. And, with the proposed keyed ops, they should be usable for all
combinations of _keyed access.

get_integer_keyed => i = get_entryp(key)->u.int_val (for Union)
set_integer => get_entryp(key)->set_integer(i) (for PMC)
get_integer_keyed_int: i = *get_entryp(idx) (intarray)
....and so on

Aggregates that support autovivification have one additional method:

* set_entryp(PMC *key) which is the same as the get_entryp() accept, it
tells the aggregate that usage is LHS and that it might autovivify
intermediate aggregates. An aggregate not supporting this, sets both
methods to get_entryp().

Based on intlist.pmc (s. Subject: "[PATCH] direct accesss for intlist 10
times faster") we could implement intarray (packed int) floatarray
(packed float) array (PMC with bounds checking) and perlarray.

GC considerations: In a keyed access sequence the pointers returned by
get_entryp must not move (vv the underlaying store of course). To
simplify this goal, I would turn off GC during string_compare (used by
PerlHash).

Comments welcome,
leo