duke@435: /*
coleenp@4037:  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #ifndef SHARE_VM_OOPS_ARRAYOOP_HPP
stefank@2314: #define SHARE_VM_OOPS_ARRAYOOP_HPP
stefank@2314: 
stefank@2314: #include "memory/universe.inline.hpp"
stefank@2314: #include "oops/oop.hpp"
stefank@2314: 
coleenp@548: // arrayOopDesc is the abstract baseclass for all arrays.  It doesn't
coleenp@548: // declare pure virtual to enforce this because that would allocate a vtbl
coleenp@548: // in each instance, which we don't want.
coleenp@548: 
coleenp@548: // The layout of array Oops is:
coleenp@548: //
coleenp@548: //  markOop
coleenp@4037: //  Klass*    // 32 bits if compressed but declared 64 in LP64.
coleenp@548: //  length    // shares klass memory or allocated after declared fields.
coleenp@548: 
duke@435: 
duke@435: class arrayOopDesc : public oopDesc {
duke@435:   friend class VMStructs;
coleenp@548: 
coleenp@548:   // Interpreter/Compiler offsets
coleenp@548: 
coleenp@548:   // Header size computation.
coleenp@548:   // The header is considered the oop part of this type plus the length.
coleenp@548:   // Returns the aligned header_size_in_bytes.  This is not equivalent to
kvn@600:   // sizeof(arrayOopDesc) which should not appear in the code.
coleenp@548:   static int header_size_in_bytes() {
kvn@600:     size_t hs = align_size_up(length_offset_in_bytes() + sizeof(int),
kvn@600:                               HeapWordSize);
coleenp@548: #ifdef ASSERT
coleenp@548:     // make sure it isn't called before UseCompressedOops is initialized.
coleenp@548:     static size_t arrayoopdesc_hs = 0;
coleenp@548:     if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
coleenp@548:     assert(arrayoopdesc_hs == hs, "header size can't change");
coleenp@548: #endif // ASSERT
coleenp@548:     return (int)hs;
coleenp@548:   }
duke@435: 
duke@435:  public:
coleenp@548:   // The _length field is not declared in C++.  It is allocated after the
coleenp@548:   // declared nonstatic fields in arrayOopDesc if not compressed, otherwise
coleenp@548:   // it occupies the second half of the _klass field in oopDesc.
coleenp@548:   static int length_offset_in_bytes() {
ehelin@5694:     return UseCompressedClassPointers ? klass_gap_offset_in_bytes() :
coleenp@548:                                sizeof(arrayOopDesc);
coleenp@548:   }
coleenp@548: 
coleenp@548:   // Returns the offset of the first element.
coleenp@548:   static int base_offset_in_bytes(BasicType type) {
coleenp@548:     return header_size(type) * HeapWordSize;
coleenp@548:   }
duke@435: 
duke@435:   // Returns the address of the first element.
coleenp@548:   void* base(BasicType type) const {
coleenp@548:     return (void*) (((intptr_t) this) + base_offset_in_bytes(type));
coleenp@548:   }
duke@435: 
duke@435:   // Tells whether index is within bounds.
duke@435:   bool is_within_bounds(int index) const        { return 0 <= index && index < length(); }
duke@435: 
coleenp@548:   // Accessors for instance variable which is not a C++ declared nonstatic
coleenp@548:   // field.
coleenp@548:   int length() const {
coleenp@548:     return *(int*)(((intptr_t)this) + length_offset_in_bytes());
coleenp@548:   }
coleenp@548:   void set_length(int length) {
coleenp@548:     *(int*)(((intptr_t)this) + length_offset_in_bytes()) = length;
coleenp@548:   }
duke@435: 
coleenp@548:   // Should only be called with constants as argument
coleenp@548:   // (will not constant fold otherwise)
coleenp@548:   // Returns the header size in words aligned to the requirements of the
coleenp@548:   // array object type.
duke@435:   static int header_size(BasicType type) {
coleenp@548:     size_t typesize_in_bytes = header_size_in_bytes();
coleenp@548:     return (int)(Universe::element_type_should_be_aligned(type)
kvn@1926:       ? align_object_offset(typesize_in_bytes/HeapWordSize)
coleenp@548:       : typesize_in_bytes/HeapWordSize);
duke@435:   }
duke@435: 
jcoomes@916:   // Return the maximum length of an array of BasicType.  The length can passed
jcoomes@916:   // to typeArrayOop::object_size(scale, length, header_size) without causing an
brutisso@3266:   // overflow. We also need to make sure that this will not overflow a size_t on
brutisso@3266:   // 32 bit platforms when we convert it to a byte size.
duke@435:   static int32_t max_array_length(BasicType type) {
duke@435:     assert(type >= 0 && type < T_CONFLICT, "wrong type");
kvn@464:     assert(type2aelembytes(type) != 0, "wrong type");
brutisso@3266: 
brutisso@3271:     const size_t max_element_words_per_size_t =
brutisso@3271:       align_size_down((SIZE_MAX/HeapWordSize - header_size(type)), MinObjAlignment);
brutisso@3271:     const size_t max_elements_per_size_t =
brutisso@3271:       HeapWordSize * max_element_words_per_size_t / type2aelembytes(type);
brutisso@3266:     if ((size_t)max_jint < max_elements_per_size_t) {
brutisso@3271:       // It should be ok to return max_jint here, but parts of the code
brutisso@3271:       // (CollectedHeap, Klass::oop_oop_iterate(), and more) uses an int for
brutisso@3271:       // passing around the size (in words) of an object. So, we need to avoid
brutisso@3271:       // overflowing an int when we add the header. See CRs 4718400 and 7110613.
brutisso@3271:       return align_size_down(max_jint - header_size(type), MinObjAlignment);
jcoomes@916:     }
brutisso@3266:     return (int32_t)max_elements_per_size_t;
brutisso@3266:   }
jcoomes@916: 
brutisso@3266: // for unit testing
brutisso@3266: #ifndef PRODUCT
brutisso@3266:   static bool check_max_length_overflow(BasicType type);
brutisso@3266:   static int32_t old_max_array_length(BasicType type);
stefank@3335:   static void test_max_array_length();
brutisso@3266: #endif
duke@435: };
stefank@2314: 
stefank@2314: #endif // SHARE_VM_OOPS_ARRAYOOP_HPP