/*

 * Copyright (c) 2011, 2019, 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.

 */

package jdk.vm.ci.hotspot;

import static jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.runtime;

import static jdk.vm.ci.hotspot.UnsafeAccess.UNSAFE;

import jdk.vm.ci.meta.Constant;

import jdk.vm.ci.meta.JavaConstant;

import jdk.vm.ci.meta.JavaKind;

import jdk.vm.ci.meta.MemoryAccessProvider;

import jdk.vm.ci.meta.PrimitiveConstant;

/**

 * HotSpot implementation of {@link MemoryAccessProvider}.

 */

class HotSpotMemoryAccessProviderImpl implements HotSpotMemoryAccessProvider {

    protected final HotSpotJVMCIRuntime runtime;

    HotSpotMemoryAccessProviderImpl(HotSpotJVMCIRuntime runtime) {

        this.runtime = runtime;

    }

    /**

     * Gets the object boxed by {@code base} that is about to have a value of kind {@code kind} read

     * from it at the offset {@code displacement}.

     *

     * @param base constant value containing the base address for a pending read

     * @return {@code null} if {@code base} does not box an object otherwise the object boxed in

     *         {@code base}

     */

    private static HotSpotObjectConstantImpl asObject(Constant base, JavaKind kind, long displacement) {

        if (base instanceof HotSpotObjectConstantImpl) {

            HotSpotObjectConstantImpl constant = (HotSpotObjectConstantImpl) base;

            HotSpotResolvedObjectType type = constant.getType();

            runtime().reflection.checkRead(constant, kind, displacement, type);

            return constant;

        }

        return null;

    }

    private boolean isValidObjectFieldDisplacement(Constant base, long displacement) {

        if (base instanceof HotSpotMetaspaceConstant) {

            MetaspaceObject metaspaceObject = HotSpotMetaspaceConstantImpl.getMetaspaceObject(base);

            if (metaspaceObject instanceof HotSpotResolvedObjectTypeImpl) {

                if (displacement == runtime.getConfig().javaMirrorOffset) {

                    // Klass::_java_mirror is valid for all Klass* values

                    return true;

                }

            } else {

                throw new IllegalArgumentException(String.valueOf(metaspaceObject));

            }

        }

        return false;

    }

    private static long asRawPointer(Constant base) {

        if (base instanceof HotSpotMetaspaceConstantImpl) {

            MetaspaceObject meta = HotSpotMetaspaceConstantImpl.getMetaspaceObject(base);

            return meta.getMetaspacePointer();

        } else if (base instanceof PrimitiveConstant) {

            PrimitiveConstant prim = (PrimitiveConstant) base;

            if (prim.getJavaKind().isNumericInteger()) {

                return prim.asLong();

            }

        }

        throw new IllegalArgumentException(String.valueOf(base));

    }

    private static long readRawValue(Constant baseConstant, long displacement, JavaKind kind, int bits) {

        HotSpotObjectConstantImpl base = asObject(baseConstant, kind, displacement);

        if (base != null) {

            switch (bits) {

                case Byte.SIZE:

                    return runtime().reflection.getByte(base, displacement);

                case Short.SIZE:

                    return runtime().reflection.getShort(base, displacement);

                case Integer.SIZE:

                    return runtime().reflection.getInt(base, displacement);

                case Long.SIZE:

                    return runtime().reflection.getLong(base, displacement);

                default:

                    throw new IllegalArgumentException(String.valueOf(bits));

            }

        } else {

            long pointer = asRawPointer(baseConstant);

            switch (bits) {

                case Byte.SIZE:

                    return UNSAFE.getByte(pointer + displacement);

                case Short.SIZE:

                    return UNSAFE.getShort(pointer + displacement);

                case Integer.SIZE:

                    return UNSAFE.getInt(pointer + displacement);

                case Long.SIZE:

                    return UNSAFE.getLong(pointer + displacement);

                default:

                    throw new IllegalArgumentException(String.valueOf(bits));

            }

        }

    }

    private boolean verifyReadRawObject(JavaConstant expected, Constant base, long displacement) {

        if (base instanceof HotSpotMetaspaceConstant) {

            MetaspaceObject metaspaceObject = HotSpotMetaspaceConstantImpl.getMetaspaceObject(base);

            if (metaspaceObject instanceof HotSpotResolvedObjectTypeImpl) {

                if (displacement == runtime.getConfig().javaMirrorOffset) {

                    HotSpotResolvedObjectTypeImpl type = (HotSpotResolvedObjectTypeImpl) metaspaceObject;

                    assert expected.equals(type.getJavaMirror());

                }

            }

        }

        return true;

    }

    private JavaConstant readRawObject(Constant baseConstant, long initialDisplacement, boolean compressed) {

        long displacement = initialDisplacement;

        JavaConstant ret;

        HotSpotObjectConstantImpl base = asObject(baseConstant, JavaKind.Object, displacement);

        if (base == null) {

            assert !compressed;

            displacement += asRawPointer(baseConstant);

            ret = runtime.getCompilerToVM().readUncompressedOop(displacement);

            assert verifyReadRawObject(ret, baseConstant, initialDisplacement);

        } else {

            assert runtime.getConfig().useCompressedOops == compressed;

            ret = runtime.getCompilerToVM().getObject(base, displacement);

        }

        return ret == null ? JavaConstant.NULL_POINTER : ret;

    }

    @Override

    public JavaConstant readPrimitiveConstant(JavaKind kind, Constant baseConstant, long initialDisplacement, int bits) {

        try {

            long rawValue = readRawValue(baseConstant, initialDisplacement, kind, bits);

            switch (kind) {

                case Boolean:

                    return JavaConstant.forBoolean(rawValue != 0);

                case Byte:

                    return JavaConstant.forByte((byte) rawValue);

                case Char:

                    return JavaConstant.forChar((char) rawValue);

                case Short:

                    return JavaConstant.forShort((short) rawValue);

                case Int:

                    return JavaConstant.forInt((int) rawValue);

                case Long:

                    return JavaConstant.forLong(rawValue);

                case Float:

                    return JavaConstant.forFloat(Float.intBitsToFloat((int) rawValue));

                case Double:

                    return JavaConstant.forDouble(Double.longBitsToDouble(rawValue));

                default:

                    throw new IllegalArgumentException("Unsupported kind: " + kind);

            }

        } catch (NullPointerException e) {

            return null;

        }

    }

    @Override

    public JavaConstant readObjectConstant(Constant base, long displacement) {

        if (base instanceof HotSpotObjectConstantImpl) {

            return readRawObject(base, displacement, runtime.getConfig().useCompressedOops);

        }

        if (!isValidObjectFieldDisplacement(base, displacement)) {

            return null;

        }

        if (base instanceof HotSpotMetaspaceConstant &&

            displacement == runtime.getConfig().javaMirrorOffset) {

            MetaspaceObject metaspaceObject = HotSpotMetaspaceConstantImpl.getMetaspaceObject(base);

            return ((HotSpotResolvedObjectTypeImpl) metaspaceObject).getJavaMirror();

        }

        return readRawObject(base, displacement, false);

    }

    @Override

    public JavaConstant readNarrowOopConstant(Constant base, long displacement) {

        JavaConstant res = readRawObject(base, displacement, true);

        return JavaConstant.NULL_POINTER.equals(res) ? HotSpotCompressedNullConstant.COMPRESSED_NULL : ((HotSpotObjectConstant) res).compress();

    }

    private HotSpotResolvedObjectTypeImpl readKlass(Constant base, long displacement, boolean compressed) {

        assert (base instanceof HotSpotMetaspaceConstantImpl) || (base instanceof HotSpotObjectConstantImpl) : base.getClass();

        if (base instanceof HotSpotMetaspaceConstantImpl) {

            return runtime.getCompilerToVM().getResolvedJavaType((HotSpotResolvedObjectTypeImpl) ((HotSpotMetaspaceConstantImpl) base).asResolvedJavaType(), displacement, compressed);

        } else {

            return runtime.getCompilerToVM().getResolvedJavaType(((HotSpotObjectConstantImpl) base), displacement, compressed);

        }

    }

    @Override

    public Constant readKlassPointerConstant(Constant base, long displacement) {

        HotSpotResolvedObjectTypeImpl klass = readKlass(base, displacement, false);

        if (klass == null) {

            return JavaConstant.NULL_POINTER;

        }

        return HotSpotMetaspaceConstantImpl.forMetaspaceObject(klass, false);

    }

    @Override

    public Constant readNarrowKlassPointerConstant(Constant base, long displacement) {

        HotSpotResolvedObjectTypeImpl klass = readKlass(base, displacement, true);

        if (klass == null) {

            return HotSpotCompressedNullConstant.COMPRESSED_NULL;

        }

        return HotSpotMetaspaceConstantImpl.forMetaspaceObject(klass, true);

    }

    @Override

    public Constant readMethodPointerConstant(Constant base, long displacement) {

        assert (base instanceof HotSpotObjectConstantImpl);

        HotSpotResolvedJavaMethodImpl method = runtime.getCompilerToVM().getResolvedJavaMethod((HotSpotObjectConstantImpl) base, displacement);

        return HotSpotMetaspaceConstantImpl.forMetaspaceObject(method, false);

    }

}