// The Nova Project by Ken Beckett.
// Copyright (C) 2007-2012 Inevitable Software, all rights reserved.
// Released under the Common Development and Distribution License, CDDL-1.0: http://opensource.org/licenses/cddl1.php
using System;
using Nova.Parsing;
namespace Nova.CodeDOM
{
/// <summary>
/// Shifts the bits of the left <see cref="Expression"/> to the LEFT by the number of bits indicated by the right <see cref="Expression"/>.
/// </summary>
public class LeftShift : BinaryShiftOperator
{
#region /* CONSTANTS */
/// <summary>
/// The internal name of the operator.
/// </summary>
public const string InternalName = NamePrefix + "LeftShift";
#endregion
#region /* CONSTRUCTORS */
/// <summary>
/// Create a <see cref="LeftShift"/> operator.
/// </summary>
public LeftShift(Expression left, Expression right)
: base(left, right)
{ }
#endregion
#region /* PROPERTIES */
/// <summary>
/// The symbol associated with the operator.
/// </summary>
public override string Symbol
{
get { return ParseToken; }
}
#endregion
#region /* METHODS */
/// <summary>
/// The internal name of the <see cref="BinaryOperator"/>.
/// </summary>
public override string GetInternalName()
{
return InternalName;
}
#endregion
#region /* PARSING */
/// <summary>
/// The token used to parse the code object.
/// </summary>
public const string ParseToken = "<<";
/// <summary>
/// The precedence of the operator.
/// </summary>
public const int Precedence = 320;
/// <summary>
/// True if the operator is left-associative, or false if it's right-associative.
/// </summary>
public const bool LeftAssociative = true;
internal static new void AddParsePoints()
{
Parser.AddOperatorParsePoint(ParseToken, Precedence, LeftAssociative, false, Parse);
}
/// <summary>
/// Parse a <see cref="LeftShift"/> operator.
/// </summary>
public static LeftShift Parse(Parser parser, CodeObject parent, ParseFlags flags)
{
return new LeftShift(parser, parent);
}
protected LeftShift(Parser parser, CodeObject parent)
: base(parser, parent)
{ }
/// <summary>
/// Get the precedence of the operator.
/// </summary>
public override int GetPrecedence()
{
return Precedence;
}
#endregion
#region /* RESOLVING */
/// <summary>
/// Perform a left shift of a constant object by a constant amount.
/// Supported left-side types are: enum, ulong, long, uint, int, ushort, short, char, byte, sbyte.
/// Right-side type should be 'int' with a 5 or 6 bit value.
/// </summary>
/// <returns>
/// The left constant shifted left by the right constant amount, using the appropriate result type, including
/// promoting smaller types to int. Returns null if the operation is invalid.
/// </returns>
protected override object EvaluateConstants(object leftConstant, object rightConstant)
{
// Check for null, string, and other invalid constants
if (leftConstant == null || rightConstant == null || leftConstant is string || rightConstant is string
|| leftConstant is bool || rightConstant is bool || leftConstant is decimal || rightConstant is decimal
|| leftConstant is double || rightConstant is double || leftConstant is float || rightConstant is float)
return null; // The operation is invalid
// Get the right shift count as an 'int'
if ((rightConstant is ulong && ((ulong)rightConstant > int.MaxValue))
|| (rightConstant is long && ((long)rightConstant < 0 || (long)rightConstant > int.MaxValue))
|| (rightConstant is uint && ((uint)rightConstant > int.MaxValue))
|| (rightConstant is int && ((int)rightConstant < 0))
|| (rightConstant is short && ((short)rightConstant < 0))
|| (rightConstant is sbyte && ((sbyte)rightConstant < 0)))
return null; // The operation is invalid
int right = (rightConstant is int ? (int)rightConstant : Convert.ToInt32(rightConstant));
// Handle enum constant - implicitly convert an enum type on the left to its underlying type
if (leftConstant is EnumConstant)
leftConstant = ((EnumConstant)leftConstant).ConstantValue;
if (leftConstant is ulong)
return ((ulong)leftConstant << right);
if (leftConstant is long)
return ((long)leftConstant << right);
if (leftConstant is uint)
return ((uint)leftConstant << right);
if (leftConstant is int)
return ((int)leftConstant << right);
// All other cases (with smaller integral types) get promoted to ints
return (Convert.ToInt32(leftConstant) << right);
}
#endregion
}
}