//
// const.cs: Constant declarations.
//
// Author:
// Miguel de Icaza (miguel@ximian.com)
// Marek Safar (marek.safar@seznam.cz)
//
// (C) 2001 Ximian, Inc.
//
//
namespace Mono.CSharp {
using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Collections;
public interface IConstant
{
void CheckObsoleteness (Location loc);
bool ResolveValue ();
Constant CreateConstantReference (Location loc);
}
public class Const : FieldBase, IConstant {
protected Constant value;
bool in_transit;
bool resolved;
bool define_called;
public const int AllowedModifiers =
Modifiers.NEW |
Modifiers.PUBLIC |
Modifiers.PROTECTED |
Modifiers.INTERNAL |
Modifiers.PRIVATE;
public Const (DeclSpace parent, Expression constant_type, string name,
Expression expr, int mod_flags, Attributes attrs, Location loc)
: base (parent, constant_type, mod_flags, AllowedModifiers,
new MemberName (name, loc), attrs)
{
initializer = expr;
ModFlags |= Modifiers.STATIC;
}
protected override bool CheckBase ()
{
// Constant.Define can be called when the parent type hasn't yet been populated
// and it's base types need not have been populated. So, we defer this check
// to the second time Define () is called on this member.
if (Parent.PartialContainer.BaseCache == null)
return true;
return base.CheckBase ();
}
///
/// Defines the constant in the @parent
///
public override bool Define ()
{
// Because constant define can be called from other class
if (define_called) {
CheckBase ();
return FieldBuilder != null;
}
define_called = true;
if (!base.Define ())
return false;
Type ttype = MemberType;
if (!IsConstantTypeValid (ttype)) {
Error_InvalidConstantType (ttype, Location);
return false;
}
// If the constant is private then we don't need any field the
// value is already inlined and cannot be referenced
//if ((ModFlags & Modifiers.PRIVATE) != 0 && RootContext.Optimize)
// return true;
while (ttype.IsArray)
ttype = TypeManager.GetElementType (ttype);
FieldAttributes field_attr = FieldAttributes.Static | Modifiers.FieldAttr (ModFlags);
// Decimals cannot be emitted into the constant blob. So, convert to 'readonly'.
if (ttype == TypeManager.decimal_type) {
field_attr |= FieldAttributes.InitOnly;
} else {
field_attr |= FieldAttributes.Literal;
}
FieldBuilder = Parent.TypeBuilder.DefineField (Name, MemberType, field_attr);
TypeManager.RegisterConstant (FieldBuilder, this);
if (ttype == TypeManager.decimal_type)
Parent.PartialContainer.RegisterFieldForInitialization (this,
new FieldInitializer (FieldBuilder, initializer));
return true;
}
public static bool IsConstantTypeValid (Type t)
{
if (TypeManager.IsBuiltinOrEnum (t))
return true;
if (t.IsPointer || t.IsValueType)
return false;
if (TypeManager.IsGenericParameter (t))
return false;
return true;
}
///
/// Emits the field value by evaluating the expression
///
public override void Emit ()
{
if (!ResolveValue ())
return;
if (FieldBuilder == null)
return;
if (value.Type == TypeManager.decimal_type) {
Decimal d = ((DecimalConstant)value).Value;
int[] bits = Decimal.GetBits (d);
object[] args = new object[] { (byte)(bits [3] >> 16), (byte)(bits [3] >> 31), (uint)bits [2], (uint)bits [1], (uint)bits [0] };
CustomAttributeBuilder cab = new CustomAttributeBuilder (TypeManager.decimal_constant_attribute_ctor, args);
FieldBuilder.SetCustomAttribute (cab);
}
else{
FieldBuilder.SetConstant (value.GetTypedValue ());
}
base.Emit ();
}
public static void Error_ExpressionMustBeConstant (Location loc, string e_name)
{
Report.Error (133, loc, "The expression being assigned to `{0}' must be constant", e_name);
}
public static void Error_CyclicDeclaration (MemberCore mc)
{
Report.Error (110, mc.Location, "The evaluation of the constant value for `{0}' involves a circular definition",
mc.GetSignatureForError ());
}
public static void Error_ConstantCanBeInitializedWithNullOnly (Location loc, string name)
{
Report.Error (134, loc, "`{0}': the constant of reference type other than string can only be initialized with null",
name);
}
public static void Error_InvalidConstantType (Type t, Location loc)
{
Report.Error (283, loc, "The type `{0}' cannot be declared const", TypeManager.CSharpName (t));
}
#region IConstant Members
public bool ResolveValue ()
{
if (resolved)
return value != null;
SetMemberIsUsed ();
if (in_transit) {
Error_CyclicDeclaration (this);
// Suppress cyclic errors
value = New.Constantify (MemberType);
resolved = true;
return false;
}
in_transit = true;
// TODO: IResolveContext here
EmitContext ec = new EmitContext (
this, Parent, Location, null, MemberType, ModFlags);
ec.InEnumContext = this is EnumMember;
value = DoResolveValue (ec);
in_transit = false;
resolved = true;
return value != null;
}
protected virtual Constant DoResolveValue (EmitContext ec)
{
Constant value = initializer.ResolveAsConstant (ec, this);
if (value == null)
return null;
Constant c = value.ConvertImplicitly (MemberType);
if (c == null) {
if (!MemberType.IsValueType && MemberType != TypeManager.string_type && !value.IsDefaultValue)
Error_ConstantCanBeInitializedWithNullOnly (Location, GetSignatureForError ());
else
value.Error_ValueCannotBeConverted (null, Location, MemberType, false);
}
return c;
}
public virtual Constant CreateConstantReference (Location loc)
{
if (value == null)
return null;
return Constant.CreateConstant (value.Type, value.GetValue(), loc);
}
#endregion
}
public class ExternalConstant : IConstant
{
FieldInfo fi;
object value;
public ExternalConstant (FieldInfo fi)
{
this.fi = fi;
}
private ExternalConstant (FieldInfo fi, object value):
this (fi)
{
this.value = value;
}
//
// Decimal constants cannot be encoded in the constant blob, and thus are marked
// as IsInitOnly ('readonly' in C# parlance). We get its value from the
// DecimalConstantAttribute metadata.
//
public static IConstant CreateDecimal (FieldInfo fi)
{
if (fi is FieldBuilder)
return null;
object[] attrs = fi.GetCustomAttributes (TypeManager.decimal_constant_attribute_type, false);
if (attrs.Length != 1)
return null;
IConstant ic = new ExternalConstant (fi,
((System.Runtime.CompilerServices.DecimalConstantAttribute) attrs [0]).Value);
return ic;
}
#region IConstant Members
public void CheckObsoleteness (Location loc)
{
ObsoleteAttribute oa = AttributeTester.GetMemberObsoleteAttribute (fi);
if (oa == null) {
return;
}
AttributeTester.Report_ObsoleteMessage (oa, TypeManager.GetFullNameSignature (fi), loc);
}
public bool ResolveValue ()
{
if (value != null)
return true;
value = fi.GetValue (fi);
return true;
}
public Constant CreateConstantReference (Location loc)
{
return Constant.CreateConstant (fi.FieldType, value, loc);
}
#endregion
}
}