From aca4e2287939b4ce3d9e9aced64c5c9641333503 Mon Sep 17 00:00:00 2001
From: Jamie Gennis <jgennis@google.com>
Date: Thu, 15 Jul 2010 17:29:15 -0700
Subject: [PATCH] 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
---
 include/surfaceflinger/Surface.h       | 10 ++++++--
 libs/surfaceflinger_client/Surface.cpp | 35 ++++++++++++++++++++------
 2 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/include/surfaceflinger/Surface.h b/include/surfaceflinger/Surface.h
index 4fd068159..294c867c3 100644
--- a/include/surfaceflinger/Surface.h
+++ b/include/surfaceflinger/Surface.h
@@ -20,6 +20,7 @@
 #include <stdint.h>
 #include <sys/types.h>
 
+#include <utils/KeyedVector.h>
 #include <utils/RefBase.h>
 #include <utils/threads.h>
 
@@ -147,8 +148,7 @@ public:
     static status_t writeToParcel(
             const sp<Surface>& control, Parcel* parcel);
 
-    static sp<Surface> readFromParcel(
-            const Parcel& data, const sp<Surface>& other);
+    static sp<Surface> readFromParcel(const Parcel& data);
 
     static bool isValid(const sp<Surface>& surface) {
         return (surface != 0) && surface->isValid();
@@ -244,6 +244,8 @@ private:
             uint32_t *pWidth, uint32_t *pHeight,
             uint32_t *pFormat, uint32_t *pUsage) const;
 
+    static void cleanCachedSurfaces();
+
     class BufferInfo {
         uint32_t mWidth;
         uint32_t mHeight;
@@ -298,6 +300,10 @@ private:
     // Inherently thread-safe
     mutable Mutex               mSurfaceLock;
     mutable Mutex               mApiLock;
+
+    // A cache of Surface objects that have been deserialized into this process.
+    static Mutex sCachedSurfacesLock;
+    static DefaultKeyedVector<wp<IBinder>, wp<Surface> > sCachedSurfaces;
 };
 
 }; // namespace android
diff --git a/libs/surfaceflinger_client/Surface.cpp b/libs/surfaceflinger_client/Surface.cpp
index dc6332cb6..1de3a4fb7 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()