Re-use existing Surface objects when reading them from parcels.

This change adds a process-global cache of previously deserialized Surface
objects so that if a Surface object wrapping the same ISurface gets received
again the same Surface can be used.  This is important because the 'tail'
pointer in the SharedBufferClient is stored only on the client side, and needs
to be the same for all the Surface objects wrapping an ISurface instance.  This
solves the problem by making there only be one Surface object wrapping an
ISurface per process.

Change-Id: I4bf0b8787885c56277622fca053022d2bb638902

1 files changed, 28 insertions, 7 deletions

diff --git a/libs/surfaceflinger_client/Surface.cpp b/libs/surfaceflinger_client/Surface.cpp
index dc6332c..1de3a4f 100644
--- a/libs/surfaceflinger_client/Surface.cpp
+++ b/libs/surfaceflinger_client/Surface.cpp
@@ -374,15 +374,36 @@ status_t Surface::writeToParcel(
 
 }
 
-sp<Surface> Surface::readFromParcel(
-        const Parcel& data, const sp<Surface>& other)
-{
-    sp<Surface> result(other);
+
+Mutex Surface::sCachedSurfacesLock;
+DefaultKeyedVector<wp<IBinder>, wp<Surface> > Surface::sCachedSurfaces(wp<Surface>(0));
+
+sp<Surface> Surface::readFromParcel(const Parcel& data) {
+    Mutex::Autolock _l(sCachedSurfacesLock);
     sp<IBinder> binder(data.readStrongBinder());
-    if (other==0 || binder != other->mSurface->asBinder()) {
-        result = new Surface(data, binder);
+    sp<Surface> surface = sCachedSurfaces.valueFor(binder).promote();
+    if (surface == 0) {
+       surface = new Surface(data, binder);
+       sCachedSurfaces.add(binder, surface);
+    } else {
+        LOGW("Reusing surface!");
+    }
+    if (surface->mSurface == 0) {
+      surface = 0;
+    }
+    cleanCachedSurfaces();
+    return surface;
+}
+
+// Remove the stale entries from the surface cache.  This should only be called
+// with sCachedSurfacesLock held.
+void Surface::cleanCachedSurfaces() {
+    for (int i = sCachedSurfaces.size()-1; i >= 0; --i) {
+        wp<Surface> s(sCachedSurfaces.valueAt(i));
+        if (s == 0 || s.promote() == 0) {
+            sCachedSurfaces.removeItemsAt(i);
+        }
     }
-    return result;
 }
 
 void Surface::init()