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1 /*
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2 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // arrayOopDesc is the abstract baseclass for all arrays.
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26
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27 class arrayOopDesc : public oopDesc {
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28 friend class VMStructs;
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29 private:
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30 int _length; // number of elements in the array
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31
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32 public:
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33 // Interpreter/Compiler offsets
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34 static int length_offset_in_bytes() { return offset_of(arrayOopDesc, _length); }
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35 static int base_offset_in_bytes(BasicType type) { return header_size(type) * HeapWordSize; }
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36
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37 // Returns the address of the first element.
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38 void* base(BasicType type) const { return (void*) (((intptr_t) this) + base_offset_in_bytes(type)); }
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39
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40 // Tells whether index is within bounds.
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41 bool is_within_bounds(int index) const { return 0 <= index && index < length(); }
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42
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43 // Accessores for instance variable
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44 int length() const { return _length; }
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45 void set_length(int length) { _length = length; }
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46
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47 // Header size computation.
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48 // Should only be called with constants as argument (will not constant fold otherwise)
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49 static int header_size(BasicType type) {
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50 return Universe::element_type_should_be_aligned(type)
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51 ? align_object_size(sizeof(arrayOopDesc)/HeapWordSize)
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52 : sizeof(arrayOopDesc)/HeapWordSize;
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53 }
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54
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55 // This method returns the maximum length that can passed into
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56 // typeArrayOop::object_size(scale, length, header_size) without causing an
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57 // overflow. We substract an extra 2*wordSize to guard against double word
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58 // alignments. It gets the scale from the type2aelembytes array.
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59 static int32_t max_array_length(BasicType type) {
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60 assert(type >= 0 && type < T_CONFLICT, "wrong type");
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61 assert(type2aelembytes[type] != 0, "wrong type");
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62 // We use max_jint, since object_size is internally represented by an 'int'
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63 // This gives us an upper bound of max_jint words for the size of the oop.
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64 int32_t max_words = (max_jint - header_size(type) - 2);
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65 int elembytes = (type == T_OBJECT) ? T_OBJECT_aelem_bytes : type2aelembytes[type];
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66 jlong len = ((jlong)max_words * HeapWordSize) / elembytes;
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67 return (len > max_jint) ? max_jint : (int32_t)len;
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68 }
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69
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70 };
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