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Diffstat (limited to 'include/utils/Flattenable.h')
| -rw-r--r-- | include/utils/Flattenable.h | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/include/utils/Flattenable.h b/include/utils/Flattenable.h new file mode 100644 index 0000000..882a8b2 --- /dev/null +++ b/include/utils/Flattenable.h @@ -0,0 +1,198 @@ +/* + * 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> +#include <utils/Debug.h> + +namespace android { + + +class FlattenableUtils { +public: + template<int N> + static size_t align(size_t size) { + COMPILE_TIME_ASSERT_FUNCTION_SCOPE( !(N & (N-1)) ); + return (size + (N-1)) & ~(N-1); + } + + template<int N> + static size_t align(void const*& buffer) { + COMPILE_TIME_ASSERT_FUNCTION_SCOPE( !(N & (N-1)) ); + intptr_t b = intptr_t(buffer); + buffer = (void*)((intptr_t(buffer) + (N-1)) & ~(N-1)); + return size_t(intptr_t(buffer) - b); + } + + template<int 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*>( intptr_t(buffer) + offset ); + size -= offset; + } + + static void advance(void const*& buffer, size_t& size, size_t offset) { + buffer = reinterpret_cast<void const*>( intptr_t(buffer) + offset ); + size -= offset; + } + + // write a POD structure + template<typename T> + static void write(void*& buffer, size_t& size, const T& value) { + *static_cast<T*>(buffer) = value; + advance(buffer, size, sizeof(T)); + } + + // read a POD structure + template<typename T> + static void read(void const*& buffer, size_t& size, T& value) { + value = *static_cast<T const*>(buffer); + 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 */ |