General tidy up of android.system

This commit changes StructIcmpHdr to the byte[] factory that it
effectively already is. StructIcmpHdr is not referenced by anything in
android.system.Os so is not the same as other Struct classes.

It also add toString() to structs / containers where missing and makes
a field final.

Bug: 135660232
Test: build / boot
Test: atest CtsLibcoreTestCases:libcore.android.system.OsTest
Change-Id: I84985c817234aadc2380a08a6afa71400366a6f6

7 files changed, 42 insertions, 25 deletions

diff --git a/luni/src/main/java/android/system/StructIcmpHdr.java b/luni/src/main/java/android/system/IcmpHeaders.java
index 87ae679da6..2203d4095d 100644
--- a/luni/src/main/java/android/system/StructIcmpHdr.java
+++ b/luni/src/main/java/android/system/IcmpHeaders.java
@@ -19,22 +19,26 @@ package android.system;
 import static android.system.OsConstants.ICMP6_ECHO_REQUEST;
 import static android.system.OsConstants.ICMP_ECHO;
 
+import java.io.FileDescriptor;
+import java.net.SocketAddress;
+
 /**
- * Corresponds to C's {@code struct icmphdr} from linux/icmp.h and {@code struct icmp6hdr} from
- * linux/icmpv6.h
+ * A utility class that can create ICMP header bytes corresponding to C's {@code struct icmphdr}
+ * from linux/icmp.h and {@code struct icmp6hdr} from linux/icmpv6.h. The bytes can be passed to
+ * methods like {@link Os#sendto(FileDescriptor, byte[], int, int, int, SocketAddress)}.
  *
  * @hide
  */
-public final class StructIcmpHdr {
-    private byte[] packet;
+public final class IcmpHeaders {
 
-    private StructIcmpHdr() {
-        packet =  new byte[8];
-    }
+    private IcmpHeaders() {}
 
-    /*
-     * Echo or Echo Reply Message
+    /**
+     * Creates the header bytes for an {@link OsConstants#ICMP_ECHO} or
+     * {@link OsConstants#ICMP6_ECHO_REQUEST} message. Code, checksum and identifier are left as
+     * zeros.
      *
+     * <pre>
      * 0                   1                   2                   3
      * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
@@ -42,21 +46,16 @@ public final class StructIcmpHdr {
      * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      * |           Identifier          |        Sequence Number        |
      * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-     * |     Data ...
-     * +-+-+-+-+-
+     * </pre>
      */
-    public static StructIcmpHdr IcmpEchoHdr(boolean ipv4, int seq) {
-        StructIcmpHdr hdr = new StructIcmpHdr();
-        hdr.packet[0] = ipv4 ? (byte) ICMP_ECHO : (byte) ICMP6_ECHO_REQUEST;
+    public static byte[] createIcmpEchoHdr(boolean ipv4, int seq) {
+        byte[] bytes = new byte[8];
+        bytes[0] = ipv4 ? (byte) ICMP_ECHO : (byte) ICMP6_ECHO_REQUEST;
         // packet[1]: Code is always zero.
         // packet[2,3]: Checksum is computed by kernel.
         // packet[4,5]: ID (= port) inserted by kernel.
-        hdr.packet[6] = (byte) (seq >> 8);
-        hdr.packet[7] = (byte) seq;
-        return hdr;
-    }
-
-    public byte[] getBytes() {
-        return packet.clone();
+        bytes[6] = (byte) (seq >> 8);
+        bytes[7] = (byte) seq;
+        return bytes;
     }
 }
diff --git a/luni/src/main/java/android/system/Int32Ref.java b/luni/src/main/java/android/system/Int32Ref.java
index 8f4a9496ef..8ffcfc5f25 100644
--- a/luni/src/main/java/android/system/Int32Ref.java
+++ b/luni/src/main/java/android/system/Int32Ref.java
@@ -16,6 +16,8 @@
 
 package android.system;
 
+import libcore.util.Objects;
+
 import dalvik.annotation.compat.UnsupportedAppUsage;
 
 /**
@@ -32,4 +34,8 @@ public class Int32Ref {
     public Int32Ref(int value) {
         this.value = value;
     }
+
+    @Override public String toString() {
+        return Objects.toString(this);
+    }
 }
diff --git a/luni/src/main/java/android/system/Int64Ref.java b/luni/src/main/java/android/system/Int64Ref.java
index f42450d868..77edaf0876 100644
--- a/luni/src/main/java/android/system/Int64Ref.java
+++ b/luni/src/main/java/android/system/Int64Ref.java
@@ -16,6 +16,8 @@
 
 package android.system;
 
+import libcore.util.Objects;
+
 /**
  * A signed 64bit integer reference suitable for passing to lower-level system calls.
  */
@@ -25,4 +27,8 @@ public class Int64Ref {
     public Int64Ref(long value) {
         this.value = value;
     }
+
+    @Override public String toString() {
+        return Objects.toString(this);
+    }
 }
diff --git a/luni/src/main/java/android/system/StructIfaddrs.java b/luni/src/main/java/android/system/StructIfaddrs.java
index 7769f282a2..81d180abf5 100644
--- a/luni/src/main/java/android/system/StructIfaddrs.java
+++ b/luni/src/main/java/android/system/StructIfaddrs.java
@@ -16,6 +16,8 @@
 
 package android.system;
 
+import libcore.util.Objects;
+
 import java.net.InetAddress;
 
 /**
@@ -44,4 +46,8 @@ public final class StructIfaddrs {
         this.ifa_broadaddr = ifa_broadaddr;
         this.hwaddr = hwaddr;
     }
+
+    @Override public String toString() {
+        return Objects.toString(this);
+    }
 }
diff --git a/luni/src/main/java/android/system/UnixSocketAddress.java b/luni/src/main/java/android/system/UnixSocketAddress.java
index be689b36de..bd211eff4a 100644
--- a/luni/src/main/java/android/system/UnixSocketAddress.java
+++ b/luni/src/main/java/android/system/UnixSocketAddress.java
@@ -35,7 +35,7 @@ public final class UnixSocketAddress extends SocketAddress {
     // 1) pathname: 0 < sun_path.length <= NAMED_PATH_LENGTH, sun_path[0] != 0.
     // 2) unnamed: sun_path = [].
     // 3) abstract: 0 < sun_path.length <= NAMED_PATH_LENGTH, sun_path[0] == 0.
-    private byte[] sun_path;
+    private final byte[] sun_path;
 
     /** This constructor is also used from JNI. */
     private UnixSocketAddress(byte[] sun_path) {
diff --git a/non_openjdk_java_files.bp b/non_openjdk_java_files.bp
index 1952687571..27fabecf6f 100644
--- a/non_openjdk_java_files.bp
+++ b/non_openjdk_java_files.bp
@@ -3,6 +3,7 @@ filegroup {
     srcs: [
         "luni/src/main/java/android/system/ErrnoException.java",
         "luni/src/main/java/android/system/GaiException.java",
+        "luni/src/main/java/android/system/IcmpHeaders.java",
         "luni/src/main/java/android/system/Int32Ref.java",
         "luni/src/main/java/android/system/Int64Ref.java",
         "luni/src/main/java/android/system/NetlinkSocketAddress.java",
@@ -14,7 +15,6 @@ filegroup {
         "luni/src/main/java/android/system/StructCapUserHeader.java",
         "luni/src/main/java/android/system/StructFlock.java",
         "luni/src/main/java/android/system/StructGroupReq.java",
-        "luni/src/main/java/android/system/StructIcmpHdr.java",
         "luni/src/main/java/android/system/StructIfaddrs.java",
         "luni/src/main/java/android/system/StructLinger.java",
         "luni/src/main/java/android/system/StructPasswd.java",
diff --git a/ojluni/src/main/java/java/net/Inet6AddressImpl.java b/ojluni/src/main/java/java/net/Inet6AddressImpl.java
index bb722f3df2..29ccda2a54 100644
--- a/ojluni/src/main/java/java/net/Inet6AddressImpl.java
+++ b/ojluni/src/main/java/java/net/Inet6AddressImpl.java
@@ -27,7 +27,7 @@ package java.net;
 import android.system.ErrnoException;
 import android.system.GaiException;
 import android.system.StructAddrinfo;
-import android.system.StructIcmpHdr;
+import android.system.IcmpHeaders;
 
 import dalvik.system.BlockGuard;
 
@@ -263,7 +263,7 @@ class Inet6AddressImpl implements InetAddressImpl {
 
                 IoBridge.setSocketOption(fd, SocketOptions.SO_TIMEOUT, sockTo);
 
-                packet = StructIcmpHdr.IcmpEchoHdr(isIPv4, seq).getBytes();
+                packet = IcmpHeaders.createIcmpEchoHdr(isIPv4, seq);
                 IoBridge.sendto(fd, packet, 0, packet.length, 0, addr, 0);
                 final int icmpId = IoBridge.getLocalInetSocketAddress(fd).getPort();