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/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ANDROID_UTILS_FLATTENABLE_H
#define ANDROID_UTILS_FLATTENABLE_H
#include <stdint.h>
#include <sys/types.h>
#include <utils/Errors.h>
namespace android {
/*
* The Flattenable interface allows an object to serialize itself out
* to a byte-buffer and an array of file descriptors.
*/
class Flattenable
{
public:
// size in bytes of the flattened object
virtual size_t getFlattenedSize() const = 0;
// number of file descriptors to flatten
virtual size_t getFdCount() const = 0;
// flattens the object into buffer.
// size should be at least of getFlattenedSize()
// file descriptors are written in the fds[] array but ownership is
// not transfered (ie: they must be dupped by the caller of
// flatten() if needed).
virtual status_t flatten(void* buffer, size_t size,
int fds[], size_t count) const = 0;
// unflattens the object from buffer.
// size should be equal to the value of getFlattenedSize() when the
// object was flattened.
// unflattened file descriptors are found in the fds[] array and
// don't need to be dupped(). ie: the caller of unflatten doesn't
// keep ownership. If a fd is not retained by unflatten() it must be
// explicitly closed.
virtual status_t unflatten(void const* buffer, size_t size,
int fds[], size_t count) = 0;
protected:
virtual ~Flattenable() = 0;
};
/*
* LightFlattenable is a protocol allowing object to serialize themselves out
* to a byte-buffer.
*
* LightFlattenable objects must implement this protocol.
*
* LightFlattenable doesn't require the object to be virtual.
*/
template <typename T>
class LightFlattenable {
public:
// returns whether this object always flatten into the same size.
// for efficiency, this should always be inline.
inline bool isFixedSize() const;
// returns size in bytes of the flattened object. must be a constant.
inline size_t getSize() const;
// flattens the object into buffer.
inline status_t flatten(void* buffer) const;
// unflattens the object from buffer of given size.
inline status_t unflatten(void const* buffer, size_t size);
};
template <typename T>
inline bool LightFlattenable<T>::isFixedSize() const {
return static_cast<T const*>(this)->T::isFixedSize();
}
template <typename T>
inline size_t LightFlattenable<T>::getSize() const {
return static_cast<T const*>(this)->T::getSize();
}
template <typename T>
inline status_t LightFlattenable<T>::flatten(void* buffer) const {
return static_cast<T const*>(this)->T::flatten(buffer);
}
template <typename T>
inline status_t LightFlattenable<T>::unflatten(void const* buffer, size_t size) {
return static_cast<T*>(this)->T::unflatten(buffer, size);
}
/*
* LightFlattenablePod is an implementation of the LightFlattenable protocol
* for POD (plain-old-data) objects.
*/
template <typename T>
class LightFlattenablePod : public LightFlattenable<T> {
public:
inline bool isFixedSize() const {
return true;
}
inline size_t getSize() const {
return sizeof(T);
}
inline status_t flatten(void* buffer) const {
*reinterpret_cast<T*>(buffer) = *static_cast<T const*>(this);
return NO_ERROR;
}
inline status_t unflatten(void const* buffer, size_t) {
*static_cast<T*>(this) = *reinterpret_cast<T const*>(buffer);
return NO_ERROR;
}
};
}; // namespace android
#endif /* ANDROID_UTILS_FLATTENABLE_H */
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