1 /*
   2  * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 package jdk.vm.ci.meta;
  24 
  25 /**
  26  * Provides memory access operations for the target VM.
  27  */
  28 public interface MemoryAccessProvider {
  29 
  30     /**
  31      * Reads a value of this kind using a base address and a displacement. No bounds checking or
  32      * type checking is performed. Returns {@code null} if the value is not available at this point.
  33      *
  34      * @param base the base address from which the value is read.
  35      * @param displacement the displacement within the object in bytes
  36      * @return the read value encapsulated in a {@link JavaConstant} object, or {@code null} if the
  37      *         value cannot be read.
  38      */
  39     JavaConstant readUnsafeConstant(JavaKind kind, JavaConstant base, long displacement);
  40 
  41     /**
  42      * Reads a primitive value using a base address and a displacement.
  43      *
  44      * @param kind the {@link JavaKind} of the returned {@link JavaConstant} object
  45      * @param base the base address from which the value is read
  46      * @param displacement the displacement within the object in bytes
  47      * @param bits the number of bits to read from memory
  48      * @return the read value encapsulated in a {@link JavaConstant} object of {@link JavaKind} kind
  49      */
  50     JavaConstant readPrimitiveConstant(JavaKind kind, Constant base, long displacement, int bits);
  51 
  52     /**
  53      * Reads a Java {@link Object} value using a base address and a displacement.
  54      *
  55      * @param base the base address from which the value is read
  56      * @param displacement the displacement within the object in bytes
  57      * @return the read value encapsulated in a {@link Constant} object
  58      */
  59     JavaConstant readObjectConstant(Constant base, long displacement);
  60 }