Use Ashmem to reduce buffer copies

Use android.os.MemoryFile to allocate Ashmem and use gsid.setAshmem and
gsid.commitGsiChunkFromAshmem to submit data.

Bug: 138976291
Test: adb shell am start-activity \
    -n com.android.dynsystem/com.android.dynsystem.VerificationActivity \
    -a android.os.image.action.START_INSTALL \
    -d file:///storage/emulated/0/Download/system.raw.gz \
    --el KEY_SYSTEM_SIZE $(du -b system.raw|cut -f1) \
    --el KEY_USERDATA_SIZE 8589934592

Change-Id: I6df718a8cc3f4e5835c9d20d0bf5bf8bb0daee22

core/java/android/os/image/DynamicSystemManager.java

@@ -20,6 +20,7 @@ import android.annotation.RequiresPermission;
 import android.annotation.SystemService;
 import android.content.Context;
 import android.gsi.GsiProgress;
+import android.os.ParcelFileDescriptor;
 import android.os.RemoteException;
 
 /**
@@ -52,21 +53,38 @@ public class DynamicSystemManager {
     /** The DynamicSystemManager.Session represents a started session for the installation. */
     public class Session {
         private Session() {}
+
         /**
-         * Write a chunk of the DynamicSystem system image
+         * Set the file descriptor that points to a ashmem which will be used
+         * to fetch data during the submitFromAshmem.
          *
-         * @return {@code true} if the call succeeds. {@code false} if there is any native runtime
-         *     error.
+         * @param ashmem fd that points to a ashmem
+         * @param size size of the ashmem file
          */
         @RequiresPermission(android.Manifest.permission.MANAGE_DYNAMIC_SYSTEM)
-        public boolean write(byte[] buf) {
+        public boolean setAshmem(ParcelFileDescriptor ashmem, long size) {
             try {
-                return mService.write(buf);
+                return mService.setAshmem(ashmem, size);
             } catch (RemoteException e) {
                 throw new RuntimeException(e.toString());
             }
         }
 
+        /**
+         * Submit bytes to the DSU partition from the ashmem previously set with
+         * setAshmem.
+         *
+         * @param size Number of bytes
+         * @return true on success, false otherwise.
+         */
+        @RequiresPermission(android.Manifest.permission.MANAGE_DYNAMIC_SYSTEM)
+        public boolean submitFromAshmem(int size) {
+            try {
+                return mService.submitFromAshmem(size);
+            } catch (RemoteException e) {
+                throw new RuntimeException(e.toString());
+            }
+        }
         /**
          * Finish write and make device to boot into the it after reboot.
          *

core/java/android/os/image/IDynamicSystemService.aidl

@@ -79,10 +79,20 @@ interface IDynamicSystemService
     boolean setEnable(boolean enable, boolean oneShot);
 
     /**
-     * Write a chunk of the DynamicSystem system image
+     * Set the file descriptor that points to a ashmem which will be used
+     * to fetch data during the submitFromAshmem.
      *
-     * @return true if the call succeeds
+     * @param fd            fd that points to a ashmem
+     * @param size          size of the ashmem file
      */
-    boolean write(in byte[] buf);
+    boolean setAshmem(in ParcelFileDescriptor fd, long size);
 
+    /**
+     * Submit bytes to the DSU partition from the ashmem previously set with
+     * setAshmem.
+     *
+     * @param bytes         number of bytes that can be read from stream.
+     * @return              true on success, false otherwise.
+     */
+    boolean submitFromAshmem(long bytes);
 }