improve [un]marshalling of non-binder objects

this change introduces a new class LightFlattenable<> which is
a protocol to flatten simple objects that don't require
binders or file descriptors; the benefit of this protocol is that
it doesn't require the objects to have a virtual table and give us
a consitant way of doing this.

we also introduce an implementation of this protocol for
POD structures, LightFlattenablePod<>.

Parcel has been update to handle this protocol automatically.

Sensor, Rect, Point and Region now use this new protocol.

Change-Id: Icb3ce7fa1d785249eb666f39c2129f2fc143ea4a

include/binder/Parcel.h

@@ -22,10 +22,12 @@
 #include <utils/RefBase.h>
 #include <utils/String16.h>
 #include <utils/Vector.h>
+#include <utils/Flattenable.h>
 
 // ---------------------------------------------------------------------------
 namespace android {
 
+template <typename T> class LightFlattenable;
 class Flattenable;
 class IBinder;
 class IPCThreadState;
@@ -102,6 +104,10 @@ public:
     status_t            writeWeakBinder(const wp<IBinder>& val);
     status_t            write(const Flattenable& val);
 
+    template<typename T>
+    status_t            write(const LightFlattenable<T>& val);
+
+
     // Place a native_handle into the parcel (the native_handle's file-
     // descriptors are dup'ed, so it is safe to delete the native_handle
     // when this function returns). 
@@ -153,6 +159,9 @@ public:
     wp<IBinder>         readWeakBinder() const;
     status_t            read(Flattenable& val) const;
 
+    template<typename T>
+    status_t            read(LightFlattenable<T>& val) const;
+
     // Like Parcel.java's readExceptionCode().  Reads the first int32
     // off of a Parcel's header, returning 0 or the negative error
     // code on exceptions, but also deals with skipping over rich
@@ -267,6 +276,40 @@ public:
 
 // ---------------------------------------------------------------------------
 
+template<typename T>
+status_t Parcel::write(const LightFlattenable<T>& val) {
+    size_t size(val.getSize());
+    if (!val.isFixedSize()) {
+        status_t err = writeInt32(size);
+        if (err != NO_ERROR) {
+            return err;
+        }
+    }
+    void* buffer = writeInplace(size);
+    return buffer == NULL ? NO_MEMORY :
+        val.flatten(buffer);
+}
+
+template<typename T>
+status_t Parcel::read(LightFlattenable<T>& val) const {
+    size_t size;
+    if (val.isFixedSize()) {
+        size = val.getSize();
+    } else {
+        int32_t s;
+        status_t err = readInt32(&s);
+        if (err != NO_ERROR) {
+            return err;
+        }
+        size = s;
+    }
+    void const* buffer = readInplace(size);
+    return buffer == NULL ? NO_MEMORY :
+        val.unflatten(buffer, size);
+}
+
+// ---------------------------------------------------------------------------
+
 inline TextOutput& operator<<(TextOutput& to, const Parcel& parcel)
 {
     parcel.print(to);

include/gui/Sensor.h

@@ -41,7 +41,7 @@ class Parcel;
 
 // ----------------------------------------------------------------------------
 
-class Sensor : public ASensor, public Flattenable
+class Sensor : public ASensor, public LightFlattenable<Sensor>
 {
 public:
     enum {
@@ -54,7 +54,7 @@ public:
 
             Sensor();
             Sensor(struct sensor_t const* hwSensor);
-    virtual ~Sensor();
+            ~Sensor();
 
     const String8& getName() const;
     const String8& getVendor() const;
@@ -68,13 +68,11 @@ public:
     nsecs_t getMinDelayNs() const;
     int32_t getVersion() const;
 
-    // Flattenable interface
+    // LightFlattenable protocol
-    virtual size_t getFlattenedSize() const;
+    inline bool isFixedSize() const { return false; }
-    virtual size_t getFdCount() const;
+    size_t getSize() const;
-    virtual status_t flatten(void* buffer, size_t size,
+    status_t flatten(void* buffer) const;
-            int fds[], size_t count) const;
+    status_t unflatten(void const* buffer, size_t size);
-    virtual status_t unflatten(void const* buffer, size_t size,
-            int fds[], size_t count);
 
 private:
     String8 mName;

include/ui/Point.h

@@ -17,11 +17,12 @@
 #ifndef ANDROID_UI_POINT
 #define ANDROID_UI_POINT
 
+#include <utils/Flattenable.h>
 #include <utils/TypeHelpers.h>
 
 namespace android {
 
-class Point
+class Point : public LightFlattenablePod<Point>
 {
 public:
     int x;

include/ui/Rect.h

@@ -17,6 +17,7 @@
 #ifndef ANDROID_UI_RECT
 #define ANDROID_UI_RECT
 
+#include <utils/Flattenable.h>
 #include <utils/TypeHelpers.h>
 #include <ui/Point.h>
 
@@ -24,7 +25,7 @@
 
 namespace android {
 
-class Rect : public ARect
+class Rect : public ARect, public LightFlattenablePod<Rect>
 {
 public:
     typedef ARect::value_type value_type;

include/ui/Region.h

@@ -23,6 +23,7 @@
 #include <utils/Vector.h>
 
 #include <ui/Rect.h>
+#include <utils/Flattenable.h>
 
 namespace android {
 // ---------------------------------------------------------------------------
@@ -30,13 +31,12 @@ namespace android {
 class String8;
 
 // ---------------------------------------------------------------------------
-class Region
+class Region : public LightFlattenable<Region>
 {
 public:
                         Region();
                         Region(const Region& rhs);
     explicit            Region(const Rect& rhs);
-    explicit            Region(const void* buffer);
                         ~Region();
                         
         Region& operator = (const Region& rhs);
@@ -122,12 +122,10 @@ public:
             // be sorted in Y and X and must not make the region invalid.
             void        addRectUnchecked(int l, int t, int r, int b);
 
-            // flatten/unflatten a region to/from a raw buffer
+    inline  bool        isFixedSize() const { return false; }
-            ssize_t     write(void* buffer, size_t size) const;
+            size_t      getSize() const;
-    static  ssize_t     writeEmpty(void* buffer, size_t size);
+            status_t    flatten(void* buffer) const;
-
+            status_t    unflatten(void const* buffer, size_t size);
-            ssize_t     read(const void* buffer);
-    static  bool        isEmpty(void* buffer);
 
     void        dump(String8& out, const char* what, uint32_t flags=0) const;
     void        dump(const char* what, uint32_t flags=0) const;

include/utils/Flattenable.h

@@ -24,6 +24,11 @@
 
 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:
@@ -56,6 +61,73 @@ protected:
 
 };
 
+/*
+ * 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
 
 

libs/gui/ISensorServer.cpp

@@ -55,7 +55,7 @@ public:
         int32_t n = reply.readInt32();
         v.setCapacity(n);
         while (n--) {
-            reply.read(static_cast<Flattenable&>(s));
+            reply.read(s);
             v.add(s);
         }
         return v;
@@ -84,7 +84,7 @@ status_t BnSensorServer::onTransact(
             size_t n = v.size();
             reply->writeInt32(n);
             for (size_t i=0 ; i<n ; i++) {
-                reply->write(static_cast<const Flattenable&>(v[i]));
+                reply->write(v[i]);
             }
             return NO_ERROR;
         } break;

libs/gui/LayerState.cpp

@@ -26,14 +26,7 @@ status_t layer_state_t::write(Parcel& output) const
 {
     status_t err;
 
-    size_t len = transparentRegion.write(NULL, 0);
+    err = output.write(transparentRegion);
-    err = output.writeInt32(len);
-    if (err < NO_ERROR) return err;
-
-    void* buf = output.writeInplace(len);
-    if (buf == NULL) return NO_MEMORY;
-
-    err = transparentRegion.write(buf, len);
     if (err < NO_ERROR) return err;
 
     // NOTE: regions are at the end of the structure
@@ -46,11 +39,8 @@ status_t layer_state_t::write(Parcel& output) const
 status_t layer_state_t::read(const Parcel& input)
 {
     status_t err;
-    size_t len = input.readInt32();
-    void const* buf = input.readInplace(len);
-    if (buf == NULL) return NO_MEMORY;
 
-    err = transparentRegion.read(buf);
+    err = input.read(transparentRegion);
     if (err < NO_ERROR) return err;
 
     // NOTE: regions are at the end of the structure
@@ -77,8 +67,8 @@ status_t DisplayState::write(Parcel& output) const {
     output.writeInt32(what);
     output.writeInt32(layerStack);
     output.writeInt32(orientation);
-    memcpy(output.writeInplace(sizeof(Rect)), &viewport, sizeof(Rect));
+    output.write(viewport);
-    memcpy(output.writeInplace(sizeof(Rect)), &frame, sizeof(Rect));
+    output.write(frame);
     return NO_ERROR;
 }
 
@@ -88,8 +78,8 @@ status_t DisplayState::read(const Parcel& input) {
     what = input.readInt32();
     layerStack = input.readInt32();
     orientation = input.readInt32();
-    memcpy(&viewport, input.readInplace(sizeof(Rect)), sizeof(Rect));
+    input.read(viewport);
-    memcpy(&frame,    input.readInplace(sizeof(Rect)), sizeof(Rect));
+    input.read(frame);
     return NO_ERROR;
 }
 

libs/gui/Sensor.cpp

@@ -98,7 +98,7 @@ int32_t Sensor::getVersion() const {
     return mVersion;
 }
 
-size_t Sensor::getFlattenedSize() const
+size_t Sensor::getSize() const
 {
     return  sizeof(int32_t) + ((mName.length() + 3) & ~3) +
             sizeof(int32_t) + ((mVendor.length() + 3) & ~3) +
@@ -107,11 +107,6 @@ size_t Sensor::getFlattenedSize() const
             sizeof(int32_t);
 }
 
-size_t Sensor::getFdCount() const
-{
-    return 0;
-}
-
 static inline
 size_t write(void* buffer, size_t offset, const String8& value) {
     memcpy(static_cast<char*>(buffer) + offset, value.string(), value.length());
@@ -130,12 +125,8 @@ size_t write(void* buffer, size_t offset, int32_t value) {
     return sizeof(int32_t);
 }
 
-status_t Sensor::flatten(void* buffer, size_t size,
+status_t Sensor::flatten(void* buffer) const
-        int fds[], size_t count) const
 {
-    if (size < Sensor::getFlattenedSize())
-        return -ENOMEM;
-
     size_t offset = 0;
     offset += write(buffer, offset, int32_t(mName.length()));
     offset += write(buffer, offset, mName);
@@ -149,7 +140,6 @@ status_t Sensor::flatten(void* buffer, size_t size,
     offset += write(buffer, offset, mResolution);
     offset += write(buffer, offset, mPower);
     offset += write(buffer, offset, mMinDelay);
-
     return NO_ERROR;
 }
 
@@ -171,8 +161,7 @@ size_t read(void const* buffer, size_t offset, int32_t* value) {
     return sizeof(int32_t);
 }
 
-status_t Sensor::unflatten(void const* buffer, size_t size,
+status_t Sensor::unflatten(void const* buffer, size_t size)
-        int fds[], size_t count)
 {
     int32_t len;
     size_t offset = 0;
@@ -188,7 +177,6 @@ status_t Sensor::unflatten(void const* buffer, size_t size,
     offset += read(buffer, offset, &mResolution);
     offset += read(buffer, offset, &mPower);
     offset += read(buffer, offset, &mMinDelay);
-
     return NO_ERROR;
 }
 

libs/ui/Region.cpp

@@ -66,12 +66,6 @@ Region::Region(const Rect& rhs)
 {
 }
 
-Region::Region(const void* buffer)
-{
-    status_t err = read(buffer);
-    ALOGE_IF(err<0, "error %s reading Region from buffer", strerror(err));
-}
-
 Region::~Region()
 {
 }
@@ -561,55 +555,33 @@ void Region::translate(Region& dst, const Region& reg, int dx, int dy)
 
 // ----------------------------------------------------------------------------
 
-ssize_t Region::write(void* buffer, size_t size) const
+size_t Region::getSize() const {
-{
+    return (mStorage.size() + 1) * sizeof(Rect);
-#if VALIDATE_REGIONS
+}
-    validate(*this, "write(buffer)");
+
-#endif
+status_t Region::flatten(void* buffer) const {
-    const size_t count = mStorage.size();
+    Rect* rects = reinterpret_cast<Rect*>(buffer);
-    const size_t sizeNeeded = sizeof(int32_t) + (1+count)*sizeof(Rect);
+    *rects++ = mBounds;
-    if (buffer != NULL) {
+    memcpy(rects, mStorage.array(), mStorage.size() * sizeof(Rect));
-        if (sizeNeeded > size) return NO_MEMORY;
+    return NO_ERROR;
-        int32_t* const p = static_cast<int32_t*>(buffer);
+}
-        *p = count;
+
-        memcpy(p+1, &mBounds, sizeof(Rect));
+status_t Region::unflatten(void const* buffer, size_t size) {
-        if (count) {
+    mStorage.clear();
-            memcpy(p+5, mStorage.array(), count*sizeof(Rect));
+    if (size >= sizeof(Rect)) {
+        Rect const* rects = reinterpret_cast<Rect const*>(buffer);
+        mBounds = *rects++;
+        size -= sizeof(Rect);
+        size_t count = size / sizeof(Rect);
+        if (count > 0) {
+            ssize_t err = mStorage.insertAt(0, count);
+            if (err < 0) {
+                return status_t(err);
+            }
+            memcpy(mStorage.editArray(), rects, count*sizeof(Rect));
         }
     }
-    return ssize_t(sizeNeeded);
+    return NO_ERROR;
-}
-
-ssize_t Region::read(const void* buffer)
-{
-    int32_t const* const p = static_cast<int32_t const*>(buffer); 
-    const size_t count = *p;
-    memcpy(&mBounds, p+1, sizeof(Rect));
-    mStorage.clear();
-    if (count) {
-        mStorage.insertAt(0, count);
-        memcpy(mStorage.editArray(), p+5, count*sizeof(Rect));
-    }
-#if VALIDATE_REGIONS
-    validate(*this, "read(buffer)");
-#endif
-    return ssize_t(sizeof(int32_t) + (1+count)*sizeof(Rect));
-}
-
-ssize_t Region::writeEmpty(void* buffer, size_t size)
-{
-    const size_t sizeNeeded = sizeof(int32_t) + sizeof(Rect);
-    if (sizeNeeded > size) return NO_MEMORY;
-    int32_t* const p = static_cast<int32_t*>(buffer); 
-    memset(p, 0, sizeNeeded);
-    return ssize_t(sizeNeeded);
-}
-
-bool Region::isEmpty(void* buffer)
-{
-    int32_t const* const p = static_cast<int32_t const*>(buffer); 
-    Rect const* const b = reinterpret_cast<Rect const *>(p+1);
-    return b->isEmpty();
 }
 
 // ----------------------------------------------------------------------------