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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
using static Microsoft.Interop.MarshallerHelpers;
namespace Microsoft.Interop
{
public sealed class Utf16StringMarshaller : ConditionalStackallocMarshallingGenerator
{
// [Compat] Equivalent of MAX_PATH on Windows to match built-in system
// The assumption is file paths are the most common case for marshalling strings,
// so the threshold for optimized allocation is based on that length.
private const int StackAllocBytesThreshold = 260 * sizeof(ushort);
private static readonly TypeSyntax NativeType = PointerType(PredefinedType(Token(SyntaxKind.UShortKeyword)));
private static string PinnedIdentifier(string nativeIdentifier) => $"{nativeIdentifier}__pinned";
public override ArgumentSyntax AsArgument(TypePositionInfo info, StubCodeContext context)
{
string identifier = context.GetIdentifiers(info).native;
if (info.IsByRef)
{
// &<nativeIdentifier>
return Argument(
PrefixUnaryExpression(
SyntaxKind.AddressOfExpression,
IdentifierName(identifier)));
}
else if (context.SingleFrameSpansNativeContext)
{
// (ushort*)<pinned>
return Argument(
CastExpression(
AsNativeType(info),
IdentifierName(PinnedIdentifier(identifier))));
}
// <nativeIdentifier>
return Argument(IdentifierName(identifier));
}
public override TypeSyntax AsNativeType(TypePositionInfo info)
{
// ushort*
return NativeType;
}
public override ParameterSyntax AsParameter(TypePositionInfo info)
{
// ushort**
// or
// ushort*
var type = info.IsByRef
? PointerType(AsNativeType(info))
: AsNativeType(info);
return Parameter(Identifier(info.InstanceIdentifier))
.WithType(type);
}
public override IEnumerable<StatementSyntax> Generate(TypePositionInfo info, StubCodeContext context)
{
(string managedIdentifier, string nativeIdentifier) = context.GetIdentifiers(info);
if (context.SingleFrameSpansNativeContext && !info.IsByRef && !info.IsManagedReturnPosition)
{
if (context.CurrentStage == StubCodeContext.Stage.Pin)
{
// fixed (char* <pinned> = <managedIdentifier>)
yield return FixedStatement(
VariableDeclaration(
PointerType(PredefinedType(Token(SyntaxKind.CharKeyword))),
SingletonSeparatedList(
VariableDeclarator(Identifier(PinnedIdentifier(nativeIdentifier)))
.WithInitializer(EqualsValueClause(IdentifierName(managedIdentifier))))),
EmptyStatement());
}
yield break;
}
switch (context.CurrentStage)
{
case StubCodeContext.Stage.Setup:
if (TryGenerateSetupSyntax(info, context, out StatementSyntax conditionalAllocSetup))
yield return conditionalAllocSetup;
break;
case StubCodeContext.Stage.Marshal:
if (info.RefKind != RefKind.Out)
{
foreach (var statement in GenerateConditionalAllocationSyntax(
info,
context,
StackAllocBytesThreshold))
{
yield return statement;
}
}
break;
case StubCodeContext.Stage.Unmarshal:
if (info.IsManagedReturnPosition || (info.IsByRef && info.RefKind != RefKind.In))
{
// <managed> = <native> == null ? null : new string((char*)<native>);
yield return ExpressionStatement(
AssignmentExpression(
SyntaxKind.SimpleAssignmentExpression,
IdentifierName(managedIdentifier),
ConditionalExpression(
BinaryExpression(
SyntaxKind.EqualsExpression,
IdentifierName(nativeIdentifier),
LiteralExpression(SyntaxKind.DefaultLiteralExpression)),
LiteralExpression(SyntaxKind.NullLiteralExpression),
ObjectCreationExpression(
PredefinedType(Token(SyntaxKind.StringKeyword)),
ArgumentList(SingletonSeparatedList<ArgumentSyntax>(
Argument(
CastExpression(
PointerType(PredefinedType(Token(SyntaxKind.CharKeyword))),
IdentifierName(nativeIdentifier))))),
initializer: null))));
}
break;
case StubCodeContext.Stage.Cleanup:
yield return GenerateConditionalAllocationFreeSyntax(info ,context);
break;
}
}
public override bool UsesNativeIdentifier(TypePositionInfo info, StubCodeContext context) => true;
public override bool SupportsByValueMarshalKind(ByValueContentsMarshalKind marshalKind, StubCodeContext context) => false;
protected override ExpressionSyntax GenerateAllocationExpression(
TypePositionInfo info,
StubCodeContext context,
SyntaxToken byteLengthIdentifier,
out bool allocationRequiresByteLength)
{
allocationRequiresByteLength = false;
return CastExpression(
AsNativeType(info),
StringMarshaller.AllocationExpression(CharEncoding.Utf16, context.GetIdentifiers(info).managed));
}
protected override ExpressionSyntax GenerateByteLengthCalculationExpression(TypePositionInfo info, StubCodeContext context)
{
// +1 for null terminator
// *2 for number of bytes per char
// int <byteLen> = (<managed>.Length + 1) * 2;
return
BinaryExpression(
SyntaxKind.MultiplyExpression,
ParenthesizedExpression(
BinaryExpression(
SyntaxKind.AddExpression,
MemberAccessExpression(
SyntaxKind.SimpleMemberAccessExpression,
IdentifierName(context.GetIdentifiers(info).managed),
IdentifierName("Length")),
LiteralExpression(SyntaxKind.NumericLiteralExpression, Literal(1)))),
LiteralExpression(SyntaxKind.NumericLiteralExpression, Literal(2)));
}
protected override StatementSyntax GenerateStackallocOnlyValueMarshalling(
TypePositionInfo info,
StubCodeContext context,
SyntaxToken byteLengthIdentifier,
SyntaxToken stackAllocPtrIdentifier)
{
// ((ReadOnlySpan<char>)<managed>).CopyTo(new Span<char>(<stackAllocPtr>, <managed>.Length + 1));
return
ExpressionStatement(
InvocationExpression(
MemberAccessExpression(
SyntaxKind.SimpleMemberAccessExpression,
ParenthesizedExpression(
CastExpression(
GenericName(Identifier("System.ReadOnlySpan"),
TypeArgumentList(SingletonSeparatedList<TypeSyntax>(
PredefinedType(Token(SyntaxKind.CharKeyword))))),
IdentifierName(context.GetIdentifiers(info).managed))),
IdentifierName("CopyTo")),
ArgumentList(
SeparatedList(new [] {
Argument(
ObjectCreationExpression(
GenericName(Identifier(TypeNames.System_Span),
TypeArgumentList(SingletonSeparatedList<TypeSyntax>(
PredefinedType(Token(SyntaxKind.CharKeyword))))),
ArgumentList(
SeparatedList(new []{
Argument(IdentifierName(stackAllocPtrIdentifier)),
Argument(IdentifierName(byteLengthIdentifier))})),
initializer: null))}))));
}
protected override ExpressionSyntax GenerateFreeExpression(
TypePositionInfo info,
StubCodeContext context)
{
return StringMarshaller.FreeExpression(context.GetIdentifiers(info).native);
}
}
}
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