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Resolving Symbolic References in a CodeDOM (Part 7)

, 2 Dec 2012
Resolving symbolic references in a CodeDOM.
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// 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.Runtime.InteropServices;

using Nova.Parsing;

namespace Nova.CodeDOM
{
    /// <summary>
    /// Returns the size of the specified type.
    /// </summary>
    /// <remarks>
    /// This operator works only for value types, and can only be used in an unsafe context except
    /// for primitive integral types.  <see cref="Marshal.SizeOf(object)"/> can be used instead, but this size might
    /// vary from 'sizeof', because it won't include any padding used by the CLR.
    /// </remarks>
    public class SizeOf : TypeOperator
    {
        #region /* CONSTRUCTORS */

        /// <summary>
        /// Create a <see cref="SizeOf"/> operator.
        /// </summary>
        /// <param name="type">A TypeRef or an expression that evaluates to one.</param>
        public SizeOf(Expression type)
            : base(type)
        { }

        #endregion

        #region /* PROPERTIES */

        /// <summary>
        /// The symbol associated with the operator.
        /// </summary>
        public override string Symbol
        {
            get { return ParseToken; }
        }

        /// <summary>
        /// True if the expression is const.
        /// </summary>
        public override bool IsConst
        {
            get { return true; }
        }

        #endregion

        #region /* PARSING */

        /// <summary>
        /// The token used to parse the code object.
        /// </summary>
        public const string ParseToken = "sizeof";

        /// <summary>
        /// The precedence of the operator.
        /// </summary>
        public const int Precedence = 100;

        /// <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="SizeOf"/> operator.
        /// </summary>
        public static SizeOf Parse(Parser parser, CodeObject parent, ParseFlags flags)
        {
            return new SizeOf(parser, parent);
        }

        protected SizeOf(Parser parser, CodeObject parent)
            : base(parser, parent)
        {
            ParseKeywordAndArgument(parser, ParseFlags.Type);
        }

        /// <summary>
        /// Get the precedence of the operator.
        /// </summary>
        public override int GetPrecedence()
        {
            return Precedence;
        }

        #endregion

        #region /* RESOLVING */

        /// <summary>
        /// Evaluate the type of the <see cref="Expression"/>.
        /// </summary>
        /// <returns>The resulting <see cref="TypeRef"/> or <see cref="UnresolvedRef"/>.</returns>
        public override TypeRefBase EvaluateType(bool withoutConstants)
        {
            // The following built-in types result in constant sizes outside of unsafe code blocks:
            TypeRefBase typeRefBase = _expression.EvaluateType(withoutConstants);
            if (typeRefBase.IsSameRef(TypeRef.BoolRef) || typeRefBase.IsSameRef(TypeRef.SByteRef) || typeRefBase.IsSameRef(TypeRef.ByteRef))
                return new TypeRef(TypeRef.IntRef, 1);
            if (typeRefBase.IsSameRef(TypeRef.CharRef) || typeRefBase.IsSameRef(TypeRef.ShortRef) || typeRefBase.IsSameRef(TypeRef.UShortRef))
                return new TypeRef(TypeRef.IntRef, 2);
            if (typeRefBase.IsSameRef(TypeRef.IntRef) || typeRefBase.IsSameRef(TypeRef.UIntRef) || typeRefBase.IsSameRef(TypeRef.FloatRef))
                return new TypeRef(TypeRef.IntRef, 4);
            if (typeRefBase.IsSameRef(TypeRef.LongRef) || typeRefBase.IsSameRef(TypeRef.ULongRef) || typeRefBase.IsSameRef(TypeRef.DoubleRef))
                return new TypeRef(TypeRef.IntRef, 8);
            if (typeRefBase.IsSameRef(TypeRef.DecimalRef))
                return new TypeRef(TypeRef.IntRef, 16);

            // Otherwise, just return 'int'
            return TypeRef.IntRef;
        }

        #endregion
    }
}

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License

This article, along with any associated source code and files, is licensed under The Common Development and Distribution License (CDDL)

About the Author

KenBeckett
Software Developer (Senior)
United States United States
I've been writing software since the late 70's, currently focusing mainly on C#.NET. I also like to travel around the world, and I own a Chocolate Factory (sadly, none of my employees are oompa loompas).

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