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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 <string.h>
#include <sys/types.h>
#include <utils/Errors.h>
#include <utils/Debug.h>
#include <type_traits>
namespace android {
class FlattenableUtils {
public:
template<size_t N>
static size_t align(size_t size) {
COMPILE_TIME_ASSERT_FUNCTION_SCOPE( !(N & (N-1)) );
return (size + (N-1)) & ~(N-1);
}
template<size_t N>
static size_t align(void const*& buffer) {
COMPILE_TIME_ASSERT_FUNCTION_SCOPE( !(N & (N-1)) );
uintptr_t b = uintptr_t(buffer);
buffer = reinterpret_cast<void*>((uintptr_t(buffer) + (N-1)) & ~(N-1));
return size_t(uintptr_t(buffer) - b);
}
template<size_t N>
static size_t align(void*& buffer) {
return align<N>( const_cast<void const*&>(buffer) );
}
static void advance(void*& buffer, size_t& size, size_t offset) {
buffer = reinterpret_cast<void*>( uintptr_t(buffer) + offset );
size -= offset;
}
static void advance(void const*& buffer, size_t& size, size_t offset) {
buffer = reinterpret_cast<void const*>( uintptr_t(buffer) + offset );
size -= offset;
}
// write a POD structure
template<typename T>
static void write(void*& buffer, size_t& size, const T& value) {
static_assert(std::is_trivially_copyable<T>::value,
"Cannot flatten a non-trivially-copyable type");
memcpy(buffer, &value, sizeof(T));
advance(buffer, size, sizeof(T));
}
// read a POD structure
template<typename T>
static void read(void const*& buffer, size_t& size, T& value) {
static_assert(std::is_trivially_copyable<T>::value,
"Cannot unflatten a non-trivially-copyable type");
memcpy(&value, buffer, sizeof(T));
advance(buffer, size, sizeof(T));
}
};
/*
* The Flattenable protocol allows an object to serialize itself out
* to a byte-buffer and an array of file descriptors.
* Flattenable objects must implement this protocol.
*/
template <typename T>
class Flattenable {
public:
// size in bytes of the flattened object
inline size_t getFlattenedSize() const;
// number of file descriptors to flatten
inline size_t getFdCount() const;
// 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).
inline status_t flatten(void*& buffer, size_t& size, int*& fds, size_t& count) const;
// 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.
inline status_t unflatten(void const*& buffer, size_t& size, int const*& fds, size_t& count);
};
template<typename T>
inline size_t Flattenable<T>::getFlattenedSize() const {
return static_cast<T const*>(this)->T::getFlattenedSize();
}
template<typename T>
inline size_t Flattenable<T>::getFdCount() const {
return static_cast<T const*>(this)->T::getFdCount();
}
template<typename T>
inline status_t Flattenable<T>::flatten(
void*& buffer, size_t& size, int*& fds, size_t& count) const {
return static_cast<T const*>(this)->T::flatten(buffer, size, fds, count);
}
template<typename T>
inline status_t Flattenable<T>::unflatten(
void const*& buffer, size_t& size, int const*& fds, size_t& count) {
return static_cast<T*>(this)->T::unflatten(buffer, size, fds, count);
}
/*
* LightFlattenable is a protocol allowing object to serialize themselves out
* to a byte-buffer. Because it doesn't handle file-descriptors,
* LightFlattenable is usually more size efficient than Flattenable.
* LightFlattenable objects must implement this protocol.
*/
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 getFlattenedSize() const;
// flattens the object into buffer.
inline status_t flatten(void* buffer, size_t size) 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>::getFlattenedSize() const {
return static_cast<T const*>(this)->T::getFlattenedSize();
}
template <typename T>
inline status_t LightFlattenable<T>::flatten(void* buffer, size_t size) const {
return static_cast<T const*>(this)->T::flatten(buffer, size);
}
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.
* Simply derive from LightFlattenablePod<Foo> to make Foo flattenable; no
* need to implement any methods; obviously Foo must be a POD structure.
*/
template <typename T>
class LightFlattenablePod : public LightFlattenable<T> {
public:
inline bool isFixedSize() const {
return true;
}
inline size_t getFlattenedSize() const {
return sizeof(T);
}
inline status_t flatten(void* buffer, size_t size) const {
if (size < sizeof(T)) return NO_MEMORY;
*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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