Make Flattenable not virtual (libutils)
Making an object Flattenable doesn't force it to
become virtual anymore. For instance, Fence and GraphicBuffer
are now non-virtual classes.
Also change Flatennable protocol a bit so that it updates
its parameters (pointers, sizes) to make it easier
to implement a flattenable in terms of other flattenables.
Change-Id: Ie81dc7637180b3c2cfcbaf644f8987ca804eb891
diff --git a/include/utils/Flattenable.h b/include/utils/Flattenable.h
index e40d289..c283ad7 100644
--- a/include/utils/Flattenable.h
+++ b/include/utils/Flattenable.h
@@ -21,30 +21,75 @@
#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*& 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);
+ }
+
+ 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 interface allows an object to serialize itself out
+ * 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.
*/
-class Flattenable
-{
+template <typename T>
+class Flattenable {
public:
// size in bytes of the flattened object
- virtual size_t getFlattenedSize() const = 0;
+ inline size_t getFlattenedSize() const;
// number of file descriptors to flatten
- virtual size_t getFdCount() const = 0;
+ 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).
- virtual status_t flatten(void* buffer, size_t size,
- int fds[], size_t count) const = 0;
+ 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
@@ -53,21 +98,34 @@
// 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;
-
+ 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.
- *
+ * 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.
- *
- * LightFlattenable doesn't require the object to be virtual.
*/
template <typename T>
class LightFlattenable {
@@ -77,10 +135,10 @@
inline bool isFixedSize() const;
// returns size in bytes of the flattened object. must be a constant.
- inline size_t getSize() const;
+ inline size_t getFlattenedSize() const;
// flattens the object into buffer.
- inline status_t flatten(void* buffer) const;
+ 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);
@@ -91,12 +149,12 @@
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();
+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) const {
- return static_cast<T const*>(this)->T::flatten(buffer);
+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) {
@@ -106,6 +164,8 @@
/*
* 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> {
@@ -114,10 +174,11 @@
return true;
}
- inline size_t getSize() const {
+ inline size_t getFlattenedSize() const {
return sizeof(T);
}
- inline status_t flatten(void* buffer) const {
+ 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;
}