From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- libjava/java/lang/ref/natReference.cc | 377 ++++++++++++++++++++++++++++++++++ 1 file changed, 377 insertions(+) create mode 100644 libjava/java/lang/ref/natReference.cc (limited to 'libjava/java/lang/ref/natReference.cc') diff --git a/libjava/java/lang/ref/natReference.cc b/libjava/java/lang/ref/natReference.cc new file mode 100644 index 000000000..ac7272cf5 --- /dev/null +++ b/libjava/java/lang/ref/natReference.cc @@ -0,0 +1,377 @@ +// natReference.cc - Native code for References + +/* Copyright (C) 2001, 2002, 2003, 2005, 2006 Free Software Foundation + + This file is part of libgcj. + +This software is copyrighted work licensed under the terms of the +Libgcj License. Please consult the file "LIBGCJ_LICENSE" for +details. */ + +// Written by Tom Tromey + +#include + +#include +#include +#include +#include +#include +#include +#include +#include + +static void finalize_reference (jobject ref); +static void finalize_referred_to_object (jobject obj); + + + +enum weight +{ + SOFT = 0, + WEAK = 1, + FINALIZE = 2, + PHANTOM = 3, + + // This is used to mark the head of a list. + HEAD = 4, + + // This is used to mark a deleted item. + DELETED = 5 +}; + +// Objects of this type are used in the hash table to keep track of +// the mapping between a finalizable object and the various References +// which refer to it. +struct object_list +{ + // The reference object. This is NULL for FINALIZE weight. + jobject reference; + + // The weight of this object. + enum weight weight; + + // Next in list. + object_list *next; +}; + +// Hash table used to hold mapping from object to References. The +// object_list item in the hash holds the object itself in the +// reference field; chained to it are all the references sorted in +// order of weight (lowest first). +static object_list *hash = NULL; + +// Number of slots used in HASH. +static int hash_count = 0; + +// Number of slots total in HASH. Must be power of 2. +static int hash_size = 0; + +#define DELETED_REFERENCE ((jobject) -1) + +static object_list * +find_slot (jobject key) +{ + jint hcode = _Jv_HashCode (key); + /* step must be non-zero, and relatively prime with hash_size. */ + jint step = (hcode ^ (hcode >> 16)) | 1; + int start_index = hcode & (hash_size - 1); + int index = start_index; + int deleted_index = -1; + do + { + object_list *ptr = &hash[index]; + if (ptr->reference == key) + return ptr; + else if (ptr->reference == NULL) + { + if (deleted_index == -1) + return ptr; + else + return &hash[deleted_index]; + } + else if (ptr->weight == DELETED) + { + deleted_index = index; + JvAssert (ptr->reference == DELETED_REFERENCE); + } + index = (index + step) & (hash_size - 1); + } + while (index != start_index); + // Note that we can have INDEX == START_INDEX if the table has no + // NULL entries but does have DELETED entries. + JvAssert (deleted_index >= 0); + return &hash[deleted_index]; +} + +static void +rehash () +{ + if (hash == NULL) + { + hash_size = 1024; + hash = (object_list *) _Jv_Malloc (hash_size * sizeof (object_list)); + memset (hash, 0, hash_size * sizeof (object_list)); + } + else + { + object_list *old = hash; + int i = hash_size; + + hash_size *= 2; + hash = (object_list *) _Jv_Malloc (hash_size * sizeof (object_list)); + memset (hash, 0, hash_size * sizeof (object_list)); + + while (--i >= 0) + { + if (old[i].reference == NULL || old[i].weight == DELETED) + continue; + object_list *newslot = find_slot (old[i].reference); + *newslot = old[i]; + } + + _Jv_Free (old); + } +} + +// Remove a Reference. +static void +remove_from_hash (jobject obj) +{ + java::lang::ref::Reference *ref + = reinterpret_cast (obj); + object_list *head = find_slot (ref->copy); + + // We might have found a new slot. We can just ignore that here. + if (head->reference != ref->copy) + return; + + object_list **link = &head->next; + head = head->next; + + while (head && head->reference != ref) + { + link = &head->next; + head = head->next; + } + + // Remove the slot. + if (head) + { + *link = head->next; + _Jv_Free (head); + } +} + +// Return list head if object is in hash, NULL otherwise. +object_list * +in_hash (jobject obj) +{ + // The hash table might not yet be initialized. + if (hash == NULL) + return NULL; + object_list *head = find_slot (obj); + if (head->reference != obj) + return NULL; + return head; +} + +// FIXME what happens if an object's finalizer creates a Reference to +// the object, and the object has never before been added to the hash? +// Madness! + +// Add an item to the hash table. If the item is new, we also add a +// finalizer item. We keep items in the hash table until they are +// completely collected; this lets us know when an item is new, even +// if it has been resurrected after its finalizer has been run. +static void +add_to_hash (java::lang::ref::Reference *the_reference) +{ + JvSynchronize sync (java::lang::ref::Reference::lock); + + if (3 * hash_count >= 2 * hash_size) + rehash (); + + // Use `copy' here because the `referent' field has been cleared. + jobject referent = the_reference->copy; + object_list *item = find_slot (referent); + if (item->reference == NULL || item->reference == DELETED_REFERENCE) + { + // New item, so make an entry for the finalizer. + item->reference = referent; + item->weight = HEAD; + + item->next = (object_list *) _Jv_Malloc (sizeof (object_list)); + item->next->reference = NULL; + item->next->weight = FINALIZE; + item->next->next = NULL; + ++hash_count; + } + + object_list *n = (object_list *) _Jv_Malloc (sizeof (object_list)); + n->reference = the_reference; + + enum weight w = PHANTOM; + if (java::lang::ref::SoftReference::class$.isInstance (the_reference)) + w = SOFT; + else if (java::lang::ref::WeakReference::class$.isInstance (the_reference)) + w = WEAK; + n->weight = w; + + object_list **link = &item->next; + object_list *iter = *link; + while (iter && iter->weight < n->weight) + { + link = &iter->next; + iter = *link; + } + n->next = *link; + *link = n; +} + +// Add a FINALIZE entry if one doesn't exist. +static void +maybe_add_finalize (object_list *entry, jobject obj) +{ + object_list **link = &entry->next; + object_list *iter = *link; + while (iter && iter->weight < FINALIZE) + { + link = &iter->next; + iter = *link; + } + + // We want at most one FINALIZE entry in the queue. + if (iter && iter->weight == FINALIZE) + return; + + object_list *n = (object_list *) _Jv_Malloc (sizeof (object_list)); + n->reference = obj; + n->weight = FINALIZE; + n->next = *link; + *link = n; +} + +// This is called when an object is ready to be finalized. This +// actually implements the appropriate Reference semantics. +static void +finalize_referred_to_object (jobject obj) +{ + JvSynchronize sync (java::lang::ref::Reference::lock); + + object_list *list = find_slot (obj); + object_list *head = list->next; + if (head == NULL) + { + // We have a truly dead object: the object's finalizer has been + // run, all the object's references have been processed, and the + // object is unreachable. There is, at long last, no way to + // resurrect it. + list->reference = DELETED_REFERENCE; + list->weight = DELETED; + --hash_count; + return; + } + + enum weight w = head->weight; + if (w == FINALIZE) + { + // Update the list first, as _Jv_FinalizeString might end up + // looking at this data structure. + list->next = head->next; + _Jv_Free (head); + + // If we have a Reference A to a Reference B, and B is + // finalized, then we have to take special care to make sure + // that B is properly deregistered. This is super gross. FIXME + // will it fail if B's finalizer resurrects B? + if (java::lang::ref::Reference::class$.isInstance (obj)) + finalize_reference (obj); + else if (obj->getClass() == &java::lang::String::class$) + _Jv_FinalizeString (obj); + else + _Jv_FinalizeObject (obj); + } + else if (w != SOFT || _Jv_GCCanReclaimSoftReference (obj)) + { + // If we just decided to reclaim a soft reference, we might as + // well do all the weak references at the same time. + if (w == SOFT) + w = WEAK; + + while (head && head->weight <= w) + { + java::lang::ref::Reference *ref + = reinterpret_cast (head->reference); + if (! ref->cleared) + ref->enqueue (); + + object_list *next = head->next; + _Jv_Free (head); + head = next; + } + list->next = head; + } + + // Re-register this finalizer. We always re-register because we + // can't know until the next collection cycle whether or not the + // object is truly unreachable. + _Jv_RegisterFinalizer (obj, finalize_referred_to_object); +} + +// This is called when a Reference object is finalized. If there is a +// Reference pointing to this Reference then that case is handled by +// finalize_referred_to_object. +static void +finalize_reference (jobject ref) +{ + JvSynchronize sync (java::lang::ref::Reference::lock); + remove_from_hash (ref); + // The user might have a subclass of Reference with a finalizer. + _Jv_FinalizeObject (ref); +} + +void +_Jv_RegisterStringFinalizer (jobject str) +{ + // This function might be called before any other Reference method, + // so we must ensure the class is initialized. + _Jv_InitClass (&java::lang::ref::Reference::class$); + JvSynchronize sync (java::lang::ref::Reference::lock); + // If the object is in our hash table, then we might need to add a + // new FINALIZE entry. Otherwise, we just register an ordinary + // finalizer. + object_list *entry = in_hash (str); + if (entry) + maybe_add_finalize (entry, str); + else + _Jv_RegisterFinalizer ((void *) str, _Jv_FinalizeString); +} + +void +::java::lang::ref::Reference::create (jobject ref) +{ + // Nothing says you can't make a Reference with a NULL referent. + // But there's nothing to do in such a case. + referent = reinterpret_cast (ref); + copy = referent; + if (referent != NULL) + { + JvSynchronize sync (java::lang::ref::Reference::lock); + // `this' is a new Reference object. We register a new + // finalizer for pointed-to object and we arrange a special + // finalizer for ourselves as well. + _Jv_RegisterFinalizer (this, finalize_reference); + _Jv_RegisterFinalizer (referent, finalize_referred_to_object); + gnu::gcj::RawData **p = &referent; + _Jv_GCRegisterDisappearingLink ((jobject *) p); + add_to_hash (this); + } +} + +::java::lang::Object * +::java::lang::ref::Reference::get() +{ + JvSynchronize sync (lock); + return referent; +} -- cgit v1.2.3