d/source/zap/WirePointer.d

// 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.

module zap.WirePointer;

import java.nio.ByteBuffer;

import zap.Constants;

struct WirePointer
{
public: //Variables.
	static enum byte STRUCT = 0;
	static enum byte LIST = 1;
	static enum byte FAR = 2;
	static enum byte OTHER = 3;

public: //Methods.
	static bool isNull(long wirePointer)
	{
		return wirePointer == 0;
	}
	
	static int offsetAndKind(ulong wirePointer)
	{
		return cast(int)(wirePointer & 0xffffffff);
	}
	
	static byte kind(long wirePointer)
	{
		return cast(byte)(offsetAndKind(wirePointer) & 3);
	}
	
	static int target(int offset, long wirePointer)
	{
		return offset + 1 + (offsetAndKind(wirePointer) >> 2);
	}
	
	static void setKindAndTarget(ref ByteBuffer buffer, int offset, byte kind, int targetOffset)
	{
		buffer.put!int(offset * 8, (((targetOffset - offset) - 1) << 2) | kind);
	}
	
	static void setKindWithZeroOffset(ref ByteBuffer buffer, int offset, byte kind)
	{
		buffer.put!int(offset * Constants.BYTES_PER_WORD, kind);
	}
	
	static void setKindAndTargetForEmptyStruct(ref 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.put!int(offset * 8, 0xfffffffc);
	}
	
	static void setOffsetAndKind(ref ByteBuffer buffer, int offset, int offsetAndKind)
	{
		buffer.put!int(offset * 8, offsetAndKind);
	}
	
	static int inlineCompositeListElementCount(long wirePointer)
	{
		return offsetAndKind(wirePointer) >>> 2;
	}
	
	static void setKindAndInlineCompositeListElementCount(ref ByteBuffer buffer, int offset, byte kind, int elementCount)
	{
		int lval = (elementCount << 2) | kind;
		buffer.put!int(offset * 8, (elementCount << 2) | kind);
	}
	
	static int upper32Bits(long wirePointer)
	{
		return cast(int)(wirePointer >>> 32);
	}
}