llvm-6502/include/llvm/ADT/InMemoryStruct.h
Daniel Dunbar 4581dae9ea ADT/InMemoryStruct: Add an experimental helper class intended for use in
situations where on the common path an API can return a pointer to some direct
memory, but which on an exceptional path may need to return a pointer to a
temporary struct.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120201 91177308-0d34-0410-b5e6-96231b3b80d8
2010-11-27 08:11:02 +00:00

78 lines
2.1 KiB
C++

//===- InMemoryStruct.h - Indirect Struct Access Smart Pointer --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_INMEMORYSTRUCT_H
#define LLVM_ADT_INMEMORYSTRUCT_H
#include <cassert>
namespace llvm {
/// \brief Helper object for abstracting access to an in-memory structure which
/// may require some kind of temporary storage.
///
/// This class is designed to be used for accessing file data structures which
/// in the common case can be accessed from a direct pointer to a memory mapped
/// object, but which in some cases may require indirect access to a temporary
/// structure (which, for example, may have undergone endianness translation).
template<typename T>
class InMemoryStruct {
typedef T value_type;
typedef value_type &reference;
typedef value_type *pointer;
typedef const value_type &const_reference;
typedef const value_type *const_pointer;
/// \brief The smart pointer target.
value_type *Target;
/// \brief A temporary object which can be used as a target of the smart
/// pointer.
value_type Contents;
private:
public:
InMemoryStruct() : Target(0) {}
InMemoryStruct(reference Value) : Target(&Contents), Contents(Value) {}
InMemoryStruct(pointer Value) : Target(Value) {}
InMemoryStruct(const InMemoryStruct<T> &Value) { *this = Value; }
void operator=(const InMemoryStruct<T> &Value) {
if (Value.Target != &Value.Contents) {
Target = Value.Target;
} else {
Target = &Contents;
Contents = Value.Contents;
}
}
const_reference operator*() const {
assert(Target && "Cannot dereference null pointer");
return *Target;
}
reference operator*() {
assert(Target && "Cannot dereference null pointer");
return *Target;
}
const_pointer operator->() const {
return Target;
}
pointer operator->() {
return Target;
}
operator bool() const { return Target != 0; }
};
}
#endif