// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
// Licensed under the MIT License:
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package org.capnproto;

import java.nio.ByteBuffer;

final class WirePointer {
    public static final byte STRUCT = 0;
    public static final byte LIST = 1;
    public static final byte FAR = 2;
    public static final byte OTHER = 3;

    public static boolean isNull(long wirePointer) {
        return wirePointer == 0;
    }

    public static int offsetAndKind(long wirePointer) {
        return (int) wirePointer;
    }

    public static byte kind(long wirePointer) {
        return (byte)(offsetAndKind(wirePointer) & 3);
    }

    public static int target(int offset, long wirePointer) {
        /* The [wirePointer] Offset (the "B" section) is "Signed",
           so use signed >> operator. */
        return offset + 1 + (offsetAndKind(wirePointer) >> 2);
    }

    public static void setKindAndTarget(ByteBuffer buffer, int offset, byte kind, int targetOffset) {
        buffer.putInt(offset * 8,
                      (((targetOffset - offset) - 1) << 2) | kind);
    }

    public static void setKindWithZeroOffset(ByteBuffer buffer, int offset, byte kind) {
        buffer.putInt(offset * Constants.BYTES_PER_WORD, kind);
    }

    public static void setKindAndTargetForEmptyStruct(ByteBuffer buffer, int offset) {
        //# This pointer points at an empty struct. Assuming the
        //# WirePointer itself is in-bounds, we can set the target to
        //# point either at the WirePointer itself or immediately after
        //# it. The latter would cause the WirePointer to be "null"
        //# (since for an empty struct the upper 32 bits are going to
        //# be zero). So we set an offset of -1, as if the struct were
        //# allocated immediately before this pointer, to distinguish
        //# it from null.

        buffer.putInt(offset * 8, 0xfffffffc);
    }

    public static void setOffsetAndKind(ByteBuffer buffer, int offset, int offsetAndKind) {
        buffer.putInt(offset * 8, offsetAndKind);
    }

    public static int inlineCompositeListElementCount(long wirePointer) {
        return offsetAndKind(wirePointer) >>> 2;
    }

    public static void setKindAndInlineCompositeListElementCount(ByteBuffer buffer,
                                                                 int offset,
                                                                 byte kind,
                                                                 int elementCount) {
        buffer.putInt(offset * 8, (elementCount << 2) | kind);
    }

    public static int upper32Bits(long wirePointer) {
        return (int)(wirePointer >>> 32);
    }
}
