Pivot network statistics to use DataInput/Output.

Using these generalized interfaces is more flexible, since it enables
us to pivot the implementation being used internally.  In particular,
an upcoming CL will pivot them to use a more efficient alternative.

This is a no-op refactoring.

Bug: 176777285
Test: atest FrameworksNetTests CtsNetTestCases
Change-Id: Ibd4717174cf1f136e9d5d80172ecb6e493265306

services/core/java/com/android/server/net/NetworkIdentitySet.java

@@ -20,8 +20,8 @@ import android.net.NetworkIdentity;
 import android.service.NetworkIdentitySetProto;
 import android.util.proto.ProtoOutputStream;
 
-import java.io.DataInputStream;
-import java.io.DataOutputStream;
+import java.io.DataInput;
+import java.io.DataOutput;
 import java.io.IOException;
 import java.util.HashSet;
 
@@ -44,7 +44,7 @@ public class NetworkIdentitySet extends HashSet<NetworkIdentity> implements
     public NetworkIdentitySet() {
     }
 
-    public NetworkIdentitySet(DataInputStream in) throws IOException {
+    public NetworkIdentitySet(DataInput in) throws IOException {
         final int version = in.readInt();
         final int size = in.readInt();
         for (int i = 0; i < size; i++) {
@@ -89,7 +89,7 @@ public class NetworkIdentitySet extends HashSet<NetworkIdentity> implements
         }
     }
 
-    public void writeToStream(DataOutputStream out) throws IOException {
+    public void writeToStream(DataOutput out) throws IOException {
         out.writeInt(VERSION_ADD_DEFAULT_NETWORK);
         out.writeInt(size());
         for (NetworkIdentity ident : this) {
@@ -143,7 +143,7 @@ public class NetworkIdentitySet extends HashSet<NetworkIdentity> implements
         return true;
     }
 
-    private static void writeOptionalString(DataOutputStream out, String value) throws IOException {
+    private static void writeOptionalString(DataOutput out, String value) throws IOException {
         if (value != null) {
             out.writeByte(1);
             out.writeUTF(value);
@@ -152,7 +152,7 @@ public class NetworkIdentitySet extends HashSet<NetworkIdentity> implements
         }
     }
 
-    private static String readOptionalString(DataInputStream in) throws IOException {
+    private static String readOptionalString(DataInput in) throws IOException {
         if (in.readByte() != 0) {
             return in.readUTF();
         } else {

services/core/java/com/android/server/net/NetworkStatsCollection.java

@@ -63,12 +63,15 @@ import com.google.android.collect.Lists;
 import com.google.android.collect.Maps;
 
 import java.io.BufferedInputStream;
+import java.io.DataInput;
 import java.io.DataInputStream;
+import java.io.DataOutput;
 import java.io.DataOutputStream;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
 import java.io.PrintWriter;
 import java.net.ProtocolException;
 import java.time.ZonedDateTime;
@@ -82,7 +85,7 @@ import java.util.Objects;
  * Collection of {@link NetworkStatsHistory}, stored based on combined key of
  * {@link NetworkIdentitySet}, UID, set, and tag. Knows how to persist itself.
  */
-public class NetworkStatsCollection implements FileRotator.Reader {
+public class NetworkStatsCollection implements FileRotator.Reader, FileRotator.Writer {
     /** File header magic number: "ANET" */
     private static final int FILE_MAGIC = 0x414E4554;
 
@@ -431,10 +434,10 @@ public class NetworkStatsCollection implements FileRotator.Reader {
 
     @Override
     public void read(InputStream in) throws IOException {
-        read(new DataInputStream(in));
+        read((DataInput) new DataInputStream(in));
     }
 
-    public void read(DataInputStream in) throws IOException {
+    private void read(DataInput in) throws IOException {
         // verify file magic header intact
         final int magic = in.readInt();
         if (magic != FILE_MAGIC) {
@@ -468,7 +471,13 @@ public class NetworkStatsCollection implements FileRotator.Reader {
         }
     }
 
-    public void write(DataOutputStream out) throws IOException {
+    @Override
+    public void write(OutputStream out) throws IOException {
+        write((DataOutput) new DataOutputStream(out));
+        out.flush();
+    }
+
+    private void write(DataOutput out) throws IOException {
         // cluster key lists grouped by ident
         final HashMap<NetworkIdentitySet, ArrayList<Key>> keysByIdent = Maps.newHashMap();
         for (Key key : mStats.keySet()) {
@@ -497,8 +506,6 @@ public class NetworkStatsCollection implements FileRotator.Reader {
                 history.writeToStream(out);
             }
         }
-
-        out.flush();
     }
 
     @Deprecated

services/core/java/com/android/server/net/NetworkStatsRecorder.java

@@ -42,7 +42,6 @@ import com.google.android.collect.Sets;
 import libcore.io.IoUtils;
 
 import java.io.ByteArrayOutputStream;
-import java.io.DataOutputStream;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
@@ -375,7 +374,7 @@ public class NetworkStatsRecorder {
 
         @Override
         public void write(OutputStream out) throws IOException {
-            mCollection.write(new DataOutputStream(out));
+            mCollection.write(out);
             mCollection.reset();
         }
     }
@@ -412,7 +411,7 @@ public class NetworkStatsRecorder {
 
         @Override
         public void write(OutputStream out) throws IOException {
-            mTemp.write(new DataOutputStream(out));
+            mTemp.write(out);
         }
     }