2006/10/10, Mikhail Fursov <[EMAIL PROTECTED]>:
Dmitry,
I support your idea to clean up VM properties code. I do not like the
current state of the implementation too.
But I have a couple of questions:
1) Who is responsible to deallocate memory for hidden properties? E.g. the
same "const char*" value could be allocated with malloc or new or could be
the static value.
2) By adding hidden properties you introduce a new style of communication
between components. Why limit hidden properties with "const char*" values?
Are there any problems with void* ?
I think there is correlation between these 2 questions :). If we use
"const char*", we simply copy key and value when setting a property.
And this is impossible with void*.
BTW, there is alternative functionality named VMLocalStorage - so why
make properties competing with VMLS? Do we really need "hidden"
properties?
On 10/10/06, Geir Magnusson Jr. <[EMAIL PROTECTED]> wrote:
>
> Inline
>
> Dmitry Yershov wrote:
>
> [snip]
> >
> > VM properties proposal
> > ======================
> >
> > The general purpose of VM Properties subcomponent is to provide
> > centralized access to a common properties table. A property is meant
> > as a pair of <key> and <value>. The properties stored in VM Properties
> > table represent configuration settings for a separate component (such
> > as VMCore, GC, JIT etc) or for the whole system. Another use case for
> > the properties is communication between different components.
> >
> > Requirements
> > ============
> >
> > 1) The <key> and <value> are represented as string (i.e. char*).
>
> and I propose that on each operation, a copy is made, so that the caller
> frees the string that they got or gave.
>
> > 2) NULL values are allowed.
> > 3) VM Properties subcomponent exports its interface as part of VM
> > Core.
> > 4) There are two kind of properties
> > * Public properties are properties visible both to all VM
> > components and to Java applications (by means of
> > java.lang.System.getProperties() method).
> > * Hidden properties are used for VM components communication
> > only, not accessible from Java side.
> > 5) There is a way to set hidden properties through non standard
> > command line option ( -XDefine<key>=<value>).
> > 6) There is a way to get a list of defined properties which keys
> > begin with a particular prefix.
> > 7) Properties table should be thread safe.
> >
> > VM Properties usage scenario
> > ============================
> >
> > Components can define properties and lookup them by name. When
> > setting the property it can be marked either public or hidden. A
> > property should be marked as hidden if it is intended internal usage
> > only. Public properties are supposed to be visible from Java side also.
> > In the same time it is possible to obtain a list of all public
> properties
> > to pass them to Java side.
> >
> > Defined Interface functions
> > ===========================
> >
> > void set_property(const char * key, const char * value) - Sets the
> > public property. NULL values are supported.
> >
> > void set_hidden_property(const char * key, const char * value) -
> Sets
> > the hidden property. NULL values are supported.
> >
> > const char * get_property(const char * key) - Returns the value of
> the
> > property if it has been set by set_property function. Otherwise
> returns
> > NULL.
> >
> > const char * get_hidden_property(const char * key) - Returns the
> value
> > of the property if it has been set by set_hidden_property function.
> > Otherwise returns NULL.
> >
> > bool is_property_set(const char * key, bool hidden) - Checks if the
> > property is set.
> >
> > void unset_property(const char * key, bool hidden) - Unsets the
> property.
> >
> > char * * get_public_property_keys() - Returns an array of keys for
> all
> > public properties set.
> >
> > char * * get_properties_staring_with(const char * prefix, bool
> hidden) -
> > Returns an array of keys for all properties set whose keys start
> with
> > the prefix specified.
>
> 1) if this is a C++ class, lets drop the word 'property'
> 2) Don't hardcode 'hidden' into the API, as we may have other types down
> the road. Make it an argument
>
> set( key, val, type )
> get( key, type )
> is_set(key)
> unset(key)
> get_keys(type)
> ....
>
> >
> >
> > ------------------------------------------------------------------------
> >
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--
Mikhail Fursov
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