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/*
* Copyright (c) 2000, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#ifndef SHARE_MEMORY_MEMREGION_HPP
#define SHARE_MEMORY_MEMREGION_HPP
#include "memory/allocation.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"
// A very simple data structure representing a contiguous region
// region of address space.
// Note that MemRegions are typically passed by value, not by reference.
// The intent is that they remain very small and contain no
// objects. The copy constructor and destructor must be trivial,
// to support optimization for pass-by-value.
// These should almost never be allocated in heap but we do
// create MemRegions (in CardTable and G1CMRootMemRegions) on the heap so operator
// new and operator new [] were added for these special cases.
class MemRegion {
friend class VMStructs;
private:
HeapWord* _start;
size_t _word_size;
public:
MemRegion() : _start(NULL), _word_size(0) {};
MemRegion(HeapWord* start, size_t word_size) :
_start(start), _word_size(word_size) {};
MemRegion(HeapWord* start, HeapWord* end) :
_start(start), _word_size(pointer_delta(end, start)) {
assert(end >= start, "incorrect constructor arguments");
}
MemRegion(MetaWord* start, MetaWord* end) :
_start((HeapWord*)start), _word_size(pointer_delta(end, start)) {
assert(end >= start, "incorrect constructor arguments");
}
MemRegion intersection(const MemRegion mr2) const;
// regions must overlap or be adjacent
MemRegion _union(const MemRegion mr2) const;
// minus will fail a guarantee if mr2 is interior to this,
// since there's no way to return 2 disjoint regions.
MemRegion minus(const MemRegion mr2) const;
HeapWord* start() const { return _start; }
HeapWord* end() const { return _start + _word_size; }
HeapWord* last() const { return _start + _word_size - 1; }
void set_start(HeapWord* start) { _start = start; }
void set_end(HeapWord* end) { _word_size = pointer_delta(end, _start); }
void set_word_size(size_t word_size) {
_word_size = word_size;
}
bool contains(const MemRegion mr2) const {
return _start <= mr2._start && end() >= mr2.end();
}
bool contains(const void* addr) const {
return addr >= (void*)_start && addr < (void*)end();
}
bool equals(const MemRegion mr2) const {
// first disjunct since we do not have a canonical empty set
return ((is_empty() && mr2.is_empty()) ||
(start() == mr2.start() && end() == mr2.end()));
}
size_t byte_size() const { return _word_size * sizeof(HeapWord); }
size_t word_size() const { return _word_size; }
bool is_empty() const { return word_size() == 0; }
// Creates and initializes an array of MemRegions of the given length.
static MemRegion* create_array(size_t length, MEMFLAGS flags);
static void destroy_array(MemRegion* array, size_t length);
};
// For iteration over MemRegion's.
class MemRegionClosure : public StackObj {
public:
virtual void do_MemRegion(MemRegion mr) = 0;
};
// A ResourceObj version of MemRegionClosure
class MemRegionClosureRO: public MemRegionClosure {
public:
void* operator new(size_t size) throw() {
return resource_allocate_bytes(size);
}
void operator delete(void* p) {} // nothing to do
};
#endif // SHARE_MEMORY_MEMREGION_HPP
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