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StructMetadataLayout.h
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//===--- StructMetadataLayout.h - CRTP for struct metadata ------*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// A CRTP class useful for laying out struct metadata.
//
//===----------------------------------------------------------------------===//
#ifndef SWIFT_IRGEN_STRUCTMETADATALAYOUT_H
#define SWIFT_IRGEN_STRUCTMETADATALAYOUT_H
#include "MetadataLayout.h"
namespace swift {
namespace irgen {
/// A CRTP class for laying out struct metadata.
///
/// This produces an object corresponding to the StructMetadata type.
/// It does not itself doing anything special for metadata templates.
template <class Impl> class StructMetadataLayout : public MetadataLayout<Impl> {
typedef MetadataLayout<Impl> super;
protected:
using super::IGM;
using super::asImpl;
/// The struct.
StructDecl *const Target;
StructMetadataLayout(IRGenModule &IGM, StructDecl *target)
: super(IGM), Target(target) {}
public:
void layout() {
// Metadata header.
super::layout();
// StructMetadata header.
asImpl().addNominalTypeDescriptor();
asImpl().addParentMetadataRef();
// If changing this layout, you must update the magic number in
// emitParentMetadataRef.
// Struct field offsets.
asImpl().noteStartOfFieldOffsets();
for (VarDecl *prop : Target->getStoredProperties())
asImpl().addFieldOffset(prop);
// Instantiation-specific.
if (auto generics = Target->getGenericParamsOfContext()) {
asImpl().addGenericFields(*generics);
}
}
// Note the start of the field offset vector.
void noteStartOfFieldOffsets() {}
};
/// An "implementation" of StructMetadataLayout that just scans through
/// the metadata layout, maintaining the offset of the next field.
template <class Impl>
class StructMetadataScanner : public StructMetadataLayout<Impl> {
typedef StructMetadataLayout<Impl> super;
protected:
Size NextOffset = Size(0);
StructMetadataScanner(IRGenModule &IGM, StructDecl *target)
: super(IGM, target) {}
public:
void addMetadataFlags() { addPointer(); }
void addValueWitnessTable() { addPointer(); }
void addNominalTypeDescriptor() { addPointer(); }
void addParentMetadataRef() { addPointer(); }
void addFieldOffset(VarDecl*) { addPointer(); }
void addGenericArgument(ArchetypeType *argument) { addPointer(); }
void addGenericWitnessTable(ArchetypeType *argument,
ProtocolDecl *protocol) {
addPointer();
}
private:
void addPointer() {
NextOffset += super::IGM.getPointerSize();
}
};
} // end namespace irgen
} // end namespace swift
#endif