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

2 files changed, 92 insertions, 39 deletions

diff --git a/include/utils/BlobCache.h b/include/utils/BlobCache.h
index 4f342a2..7d621e4 100644
--- a/include/utils/BlobCache.h
+++ b/include/utils/BlobCache.h
@@ -33,7 +33,8 @@ namespace android {
 // and then reloaded in a subsequent execution of the program.  This
 // serialization is non-portable and the data should only be used by the device
 // that generated it.
-class BlobCache : public RefBase, public Flattenable {
+class BlobCache : public RefBase {
+
 public:
 
     // Create an empty blob cache. The blob cache will cache key/value pairs
@@ -78,14 +79,10 @@ public:
     //   0 <= valueSize
     size_t get(const void* key, size_t keySize, void* value, size_t valueSize);
 
+
     // getFlattenedSize returns the number of bytes needed to store the entire
     // serialized cache.
-    virtual size_t getFlattenedSize() const;
-
-    // getFdCount returns the number of file descriptors that will result from
-    // flattening the cache.  This will always return 0 so as to allow the
-    // flattened cache to be saved to disk and then later restored.
-    virtual size_t getFdCount() const;
+    size_t getFlattenedSize() const;
 
     // flatten serializes the current contents of the cache into the memory
     // pointed to by 'buffer'.  The serialized cache contents can later be
@@ -94,9 +91,7 @@ public:
     //
     // Preconditions:
     //   size >= this.getFlattenedSize()
-    //   count == 0
-    virtual status_t flatten(void* buffer, size_t size, int fds[],
-            size_t count) const;
+    status_t flatten(void* buffer, size_t size) const;
 
     // unflatten replaces the contents of the cache with the serialized cache
     // contents in the memory pointed to by 'buffer'.  The previous contents of
@@ -104,10 +99,7 @@ public:
     // unflattening the serialized cache contents then the BlobCache will be
     // left in an empty state.
     //
-    // Preconditions:
-    //   count == 0
-    virtual status_t unflatten(void const* buffer, size_t size, int fds[],
-            size_t count);
+    status_t unflatten(void const* buffer, size_t size);
 
 private:
     // Copying is disallowed.
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 @@ public:
     // 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 @@ public:
     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 @@ 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();
+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 @@ inline status_t LightFlattenable<T>::unflatten(void const* buffer, size_t 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> {
@@ -114,10 +174,11 @@ public:
         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;
     }