| /* |
| * Copyright (c) 1997, 2016, 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_VM_OOPS_ARRAYOOP_HPP |
| #define SHARE_VM_OOPS_ARRAYOOP_HPP |
| |
| #include "memory/universe.inline.hpp" |
| #include "oops/oop.hpp" |
| #include "utilities/align.hpp" |
| |
| // arrayOopDesc is the abstract baseclass for all arrays. It doesn't |
| // declare pure virtual to enforce this because that would allocate a vtbl |
| // in each instance, which we don't want. |
| |
| // The layout of array Oops is: |
| // |
| // markOop |
| // Klass* // 32 bits if compressed but declared 64 in LP64. |
| // length // shares klass memory or allocated after declared fields. |
| |
| |
| class arrayOopDesc : public oopDesc { |
| friend class VMStructs; |
| friend class arrayOopDescTest; |
| |
| // Interpreter/Compiler offsets |
| |
| // Header size computation. |
| // The header is considered the oop part of this type plus the length. |
| // Returns the aligned header_size_in_bytes. This is not equivalent to |
| // sizeof(arrayOopDesc) which should not appear in the code. |
| static int header_size_in_bytes() { |
| size_t hs = align_up(length_offset_in_bytes() + sizeof(int), |
| HeapWordSize); |
| #ifdef ASSERT |
| // make sure it isn't called before UseCompressedOops is initialized. |
| static size_t arrayoopdesc_hs = 0; |
| if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs; |
| assert(arrayoopdesc_hs == hs, "header size can't change"); |
| #endif // ASSERT |
| return (int)hs; |
| } |
| |
| public: |
| // The _length field is not declared in C++. It is allocated after the |
| // declared nonstatic fields in arrayOopDesc if not compressed, otherwise |
| // it occupies the second half of the _klass field in oopDesc. |
| static int length_offset_in_bytes() { |
| return UseCompressedClassPointers ? klass_gap_offset_in_bytes() : |
| sizeof(arrayOopDesc); |
| } |
| |
| // Returns the offset of the first element. |
| static int base_offset_in_bytes(BasicType type) { |
| return header_size(type) * HeapWordSize; |
| } |
| |
| // Returns the address of the first element. |
| void* base(BasicType type) const { |
| return (void*) (((intptr_t) this) + base_offset_in_bytes(type)); |
| } |
| |
| // Tells whether index is within bounds. |
| bool is_within_bounds(int index) const { return 0 <= index && index < length(); } |
| |
| // Accessors for instance variable which is not a C++ declared nonstatic |
| // field. |
| int length() const { |
| return *(int*)(((intptr_t)this) + length_offset_in_bytes()); |
| } |
| void set_length(int length) { |
| *(int*)(((intptr_t)this) + length_offset_in_bytes()) = length; |
| } |
| |
| // Should only be called with constants as argument |
| // (will not constant fold otherwise) |
| // Returns the header size in words aligned to the requirements of the |
| // array object type. |
| static int header_size(BasicType type) { |
| size_t typesize_in_bytes = header_size_in_bytes(); |
| return (int)(Universe::element_type_should_be_aligned(type) |
| ? align_object_offset(typesize_in_bytes/HeapWordSize) |
| : typesize_in_bytes/HeapWordSize); |
| } |
| |
| // Return the maximum length of an array of BasicType. The length can passed |
| // to typeArrayOop::object_size(scale, length, header_size) without causing an |
| // overflow. We also need to make sure that this will not overflow a size_t on |
| // 32 bit platforms when we convert it to a byte size. |
| static int32_t max_array_length(BasicType type) { |
| assert(type >= 0 && type < T_CONFLICT, "wrong type"); |
| assert(type2aelembytes(type) != 0, "wrong type"); |
| |
| const size_t max_element_words_per_size_t = |
| align_down((SIZE_MAX/HeapWordSize - header_size(type)), MinObjAlignment); |
| const size_t max_elements_per_size_t = |
| HeapWordSize * max_element_words_per_size_t / type2aelembytes(type); |
| if ((size_t)max_jint < max_elements_per_size_t) { |
| // It should be ok to return max_jint here, but parts of the code |
| // (CollectedHeap, Klass::oop_oop_iterate(), and more) uses an int for |
| // passing around the size (in words) of an object. So, we need to avoid |
| // overflowing an int when we add the header. See CRs 4718400 and 7110613. |
| return align_down(max_jint - header_size(type), MinObjAlignment); |
| } |
| return (int32_t)max_elements_per_size_t; |
| } |
| |
| }; |
| |
| #endif // SHARE_VM_OOPS_ARRAYOOP_HPP |