-@page
-@node Memory Management
-@chapter Memory Management and Garbage Collection
-
-@menu
-* Garbage Collection::
-* Weak References::
-* Guardians::
-@end menu
-
-
-@node Garbage Collection
-@section Garbage Collection
-
-[FIXME: this is pasted in from Tom Lord's original guile.texi and should
-be reviewed]
-
-@deffn {Scheme Procedure} gc
-@deffnx {C Function} scm_gc ()
-Scans all of SCM objects and reclaims for further use those that are
-no longer accessible.
-@end deffn
-
-@deffn {Scheme Procedure} gc-stats
-@deffnx {C Function} scm_gc_stats ()
-Return an association list of statistics about Guile's current
-use of storage.
-@end deffn
-
-@deffn {Scheme Procedure} object-address obj
-@deffnx {C Function} scm_object_address (obj)
-Return an integer that for the lifetime of @var{obj} is uniquely
-returned by this function for @var{obj}
-@end deffn
-
-
-@node Weak References
-@section Weak References
-
-[FIXME: This chapter is based on Mikael Djurfeldt's answer to a question
-by Michael Livshin. Any mistakes are not theirs, of course. ]
-
-Weak references let you attach bookkeeping information to data so that
-the additional information automatically disappears when the original
-data is no longer in use and gets garbage collected. In a weak key hash,
-the hash entry for that key disappears as soon as the key is no longer
-referenced from anywhere else. For weak value hashes, the same happens
-as soon as the value is no longer in use. Entries in a doubly weak hash
-disappear when either the key or the value are not used anywhere else
-anymore.
-
-Property lists offer the same kind of functionality as weak key hashes
-in many situations. (@pxref{Property Lists})
-
-Here's an example (a little bit strained perhaps, but one of the
-examples is actually used in Guile):
-
-Assume that you're implementing a debugging system where you want to
-associate information about filename and position of source code
-expressions with the expressions themselves.
-
-Hashtables can be used for that, but if you use ordinary hash tables
-it will be impossible for the scheme interpreter to "forget" old
-source when, for example, a file is reloaded.
-
-To implement the mapping from source code expressions to positional
-information it is necessary to use weak-key tables since we don't want
-the expressions to be remembered just because they are in our table.
-
-To implement a mapping from source file line numbers to source code
-expressions you would use a weak-value table.
-
-To implement a mapping from source code expressions to the procedures
-they constitute a doubly-weak table has to be used.
-
-@menu
-* Weak key hashes::
-* Weak vectors::
-@end menu
-
-
-@node Weak key hashes
-@subsection Weak key hashes
-
-@deffn {Scheme Procedure} make-weak-key-hash-table size
-@deffnx {Scheme Procedure} make-weak-value-hash-table size
-@deffnx {Scheme Procedure} make-doubly-weak-hash-table size
-@deffnx {C Function} scm_make_weak_key_hash_table (size)
-@deffnx {C Function} scm_make_weak_value_hash_table (size)
-@deffnx {C Function} scm_make_doubly_weak_hash_table (size)
-Return a weak hash table with @var{size} buckets. As with any
-hash table, choosing a good size for the table requires some
-caution.
-
-You can modify weak hash tables in exactly the same way you
-would modify regular hash tables. (@pxref{Hash Tables})
-@end deffn
-
-@deffn {Scheme Procedure} weak-key-hash-table? obj
-@deffnx {Scheme Procedure} weak-value-hash-table? obj
-@deffnx {Scheme Procedure} doubly-weak-hash-table? obj
-@deffnx {C Function} scm_weak_key_hash_table_p (obj)
-@deffnx {C Function} scm_weak_value_hash_table_p (obj)
-@deffnx {C Function} scm_doubly_weak_hash_table_p (obj)
-Return @code{#t} if @var{obj} is the specified weak hash
-table. Note that a doubly weak hash table is neither a weak key
-nor a weak value hash table.
-@end deffn
-
-@deffn {Scheme Procedure} make-weak-value-hash-table k
-@end deffn
-
-@deffn {Scheme Procedure} weak-value-hash-table? x
-@end deffn
-
-@deffn {Scheme Procedure} make-doubly-weak-hash-table k
-@end deffn
-
-@deffn {Scheme Procedure} doubly-weak-hash-table? x
-@end deffn
-
-
-@node Weak vectors
-@subsection Weak vectors
-
-Weak vectors are mainly useful in Guile's implementation of weak hash
-tables.
-
-@deffn {Scheme Procedure} make-weak-vector size [fill]
-@deffnx {C Function} scm_make_weak_vector (size, fill)
-Return a weak vector with @var{size} elements. If the optional
-argument @var{fill} is given, all entries in the vector will be
-set to @var{fill}. The default value for @var{fill} is the
-empty list.
-@end deffn
-
-@deffn {Scheme Procedure} weak-vector . l
-@deffnx {Scheme Procedure} list->weak-vector l
-@deffnx {C Function} scm_weak_vector (l)
-Construct a weak vector from a list: @code{weak-vector} uses
-the list of its arguments while @code{list->weak-vector} uses
-its only argument @var{l} (a list) to construct a weak vector
-the same way @code{list->vector} would.
-@end deffn
-
-@deffn {Scheme Procedure} weak-vector? obj
-@deffnx {C Function} scm_weak_vector_p (obj)
-Return @code{#t} if @var{obj} is a weak vector. Note that all
-weak hashes are also weak vectors.
-@end deffn
-
-
-@node Guardians
-@section Guardians
-
-@deffn {Scheme Procedure} make-guardian [greedy?]
-@deffnx {C Function} scm_make_guardian (greedy_p)
-Create a new guardian.
-A guardian protects a set of objects from garbage collection,
-allowing a program to apply cleanup or other actions.
-
-@code{make-guardian} returns a procedure representing the guardian.
-Calling the guardian procedure with an argument adds the
-argument to the guardian's set of protected objects.
-Calling the guardian procedure without an argument returns
-one of the protected objects which are ready for garbage
-collection, or @code{#f} if no such object is available.
-Objects which are returned in this way are removed from
-the guardian.
-
-@code{make-guardian} takes one optional argument that says whether the
-new guardian should be greedy or sharing. If there is any chance
-that any object protected by the guardian may be resurrected,
-then you should make the guardian greedy (this is the default).
-
-See R. Kent Dybvig, Carl Bruggeman, and David Eby (1993)
-"Guardians in a Generation-Based Garbage Collector".
-ACM SIGPLAN Conference on Programming Language Design
-and Implementation, June 1993.
-
-(the semantics are slightly different at this point, but the
-paper still (mostly) accurately describes the interface).
-@end deffn
-
-@deffn {Scheme Procedure} destroy-guardian! guardian
-@deffnx {C Function} scm_destroy_guardian_x (guardian)
-Destroys @var{guardian}, by making it impossible to put any more
-objects in it or get any objects from it. It also unguards any
-objects guarded by @var{guardian}.
-@end deffn
-
-@deffn {Scheme Procedure} guardian-greedy? guardian
-@deffnx {C Function} scm_guardian_greedy_p (guardian)
-Return @code{#t} if @var{guardian} is a greedy guardian, otherwise @code{#f}.
-@end deffn
-
-@deffn {Scheme Procedure} guardian-destroyed? guardian
-@deffnx {C Function} scm_guardian_destroyed_p (guardian)
-Return @code{#t} if @var{guardian} has been destroyed, otherwise @code{#f}.
-@end deffn
-
-
-@page
-@node Objects
-@chapter Objects
-
-@deffn {Scheme Procedure} entity? obj
-@deffnx {C Function} scm_entity_p (obj)
-Return @code{#t} if @var{obj} is an entity.
-@end deffn
-
-@deffn {Scheme Procedure} operator? obj
-@deffnx {C Function} scm_operator_p (obj)
-Return @code{#t} if @var{obj} is an operator.
-@end deffn
-
-@deffn {Scheme Procedure} set-object-procedure! obj proc
-@deffnx {C Function} scm_set_object_procedure_x (obj, proc)
-Set the object procedure of @var{obj} to @var{proc}.
-@var{obj} must be either an entity or an operator.
-@end deffn
-
-@deffn {Scheme Procedure} make-class-object metaclass layout
-@deffnx {C Function} scm_make_class_object (metaclass, layout)
-Create a new class object of class @var{metaclass}, with the
-slot layout specified by @var{layout}.
-@end deffn
-
-@deffn {Scheme Procedure} make-subclass-object class layout
-@deffnx {C Function} scm_make_subclass_object (class, layout)
-Create a subclass object of @var{class}, with the slot layout
-specified by @var{layout}.
-@end deffn
-
-
-@c Local Variables:
-@c TeX-master: "guile.texi"
-@c End:
HCoop / bpt / guile.git / blobdiff