Implement hashCode() and equals() behind a generator option.

The option is only called 'generate_equals' because:
- equals() is the main thing; hashCode() is there only to
  complement equals();
- it's shorter;
- toString() should not be included in this option because
  it's more for debugging and it's more likely to stop
  ProGuard from working well.

Also shortened the "has bit" expression; was
((bitField & mask) == mask), now ((bitField & mask) != 0).
Both the Java code and the bytecode are slightly shorter.

Change-Id: Ic309a08a60883bf454eb6612679aa99611620e76

4 files changed, 459 insertions, 8 deletions

diff --git a/java/pom.xml b/java/pom.xml
index dcc1cfa..cfa35a5 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -133,7 +133,7 @@
                 </exec>
 		<!-- java nano -->
                 <exec executable="../src/protoc">
-                  <arg value="--javanano_out=java_package=google/protobuf/unittest_import_nano.proto|com.google.protobuf.nano,java_outer_classname=google/protobuf/unittest_import_nano.proto|UnittestImportNano:target/generated-test-sources" />
+                  <arg value="--javanano_out=java_package=google/protobuf/unittest_import_nano.proto|com.google.protobuf.nano,java_outer_classname=google/protobuf/unittest_import_nano.proto|UnittestImportNano,generate_equals=true:target/generated-test-sources" />
                   <arg value="--proto_path=../src" />
                   <arg value="--proto_path=src/test/java" />
                   <arg value="../src/google/protobuf/unittest_nano.proto" />
@@ -154,13 +154,13 @@
                   <arg value="../src/google/protobuf/unittest_extension_nano.proto" />
                 </exec>
                 <exec executable="../src/protoc">
-                  <arg value="--javanano_out=java_nano_generate_has=true:target/generated-test-sources" />
+                  <arg value="--javanano_out=java_nano_generate_has=true,generate_equals=true:target/generated-test-sources" />
                   <arg value="--proto_path=../src" />
                   <arg value="--proto_path=src/test/java" />
                   <arg value="../src/google/protobuf/unittest_has_nano.proto" />
                 </exec>
                 <exec executable="../src/protoc">
-                  <arg value="--javanano_out=optional_field_style=accessors:target/generated-test-sources" />
+                  <arg value="--javanano_out=optional_field_style=accessors,generate_equals=true:target/generated-test-sources" />
                   <arg value="--proto_path=../src" />
                   <arg value="--proto_path=src/test/java" />
                   <arg value="../src/google/protobuf/unittest_accessors_nano.proto" />
@@ -173,7 +173,7 @@
                   <arg value="../src/google/protobuf/unittest_enum_class_multiple_nano.proto" />
                 </exec>
                 <exec executable="../src/protoc">
-                  <arg value="--javanano_out=optional_field_style=reftypes:target/generated-test-sources" />
+                  <arg value="--javanano_out=optional_field_style=reftypes,generate_equals=true:target/generated-test-sources" />
                   <arg value="--proto_path=../src" />
                   <arg value="--proto_path=src/test/java" />
                   <arg value="../src/google/protobuf/unittest_reference_types_nano.proto" />
diff --git a/java/src/main/java/com/google/protobuf/nano/InternalNano.java b/java/src/main/java/com/google/protobuf/nano/InternalNano.java
index 4930951..ce4a206 100644
--- a/java/src/main/java/com/google/protobuf/nano/InternalNano.java
+++ b/java/src/main/java/com/google/protobuf/nano/InternalNano.java
@@ -31,6 +31,7 @@
 package com.google.protobuf.nano;
 
 import java.io.UnsupportedEncodingException;
+import java.util.Arrays;
 
 /**
  * The classes contained within are used internally by the Protocol Buffer
@@ -40,7 +41,10 @@ import java.io.UnsupportedEncodingException;
  *
  * @author kenton@google.com (Kenton Varda)
  */
-public class InternalNano {
+public final class InternalNano {
+
+  private InternalNano() {}
+
   /**
    * Helper called by generated code to construct default values for string
    * fields.
@@ -69,7 +73,7 @@ public class InternalNano {
    * converts from the generated string to the string we actually want.  The
    * generated code calls this automatically.
    */
-  public static final String stringDefaultValue(String bytes) {
+  public static String stringDefaultValue(String bytes) {
     try {
       return new String(bytes.getBytes("ISO-8859-1"), "UTF-8");
     } catch (UnsupportedEncodingException e) {
@@ -88,7 +92,7 @@ public class InternalNano {
    * In this case we only need the second of the two hacks -- allowing us to
    * embed raw bytes as a string literal with ISO-8859-1 encoding.
    */
-  public static final byte[] bytesDefaultValue(String bytes) {
+  public static byte[] bytesDefaultValue(String bytes) {
     try {
       return bytes.getBytes("ISO-8859-1");
     } catch (UnsupportedEncodingException e) {
@@ -103,11 +107,215 @@ public class InternalNano {
    * Helper function to convert a string into UTF-8 while turning the
    * UnsupportedEncodingException to a RuntimeException.
    */
-  public static final byte[] copyFromUtf8(final String text) {
+  public static byte[] copyFromUtf8(final String text) {
     try {
       return text.getBytes("UTF-8");
     } catch (UnsupportedEncodingException e) {
       throw new RuntimeException("UTF-8 not supported?");
     }
   }
+
+  /**
+   * Checks repeated int field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(int[] field1, int[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated long field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(long[] field1, long[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated float field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(float[] field1, float[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated double field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(double[] field1, double[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated boolean field equality; null-value and 0-length fields are
+   * considered equal.
+   */
+  public static boolean equals(boolean[] field1, boolean[] field2) {
+    if (field1 == null || field1.length == 0) {
+      return field2 == null || field2.length == 0;
+    } else {
+      return Arrays.equals(field1, field2);
+    }
+  }
+
+  /**
+   * Checks repeated bytes field equality. Only non-null elements are tested.
+   * Returns true if the two fields have the same sequence of non-null
+   * elements. Null-value fields and fields of any length with only null
+   * elements are considered equal.
+   */
+  public static boolean equals(byte[][] field1, byte[][] field2) {
+    int index1 = 0;
+    int length1 = field1 == null ? 0 : field1.length;
+    int index2 = 0;
+    int length2 = field2 == null ? 0 : field2.length;
+    while (true) {
+      while (index1 < length1 && field1[index1] == null) {
+        index1++;
+      }
+      while (index2 < length2 && field2[index2] == null) {
+        index2++;
+      }
+      boolean atEndOf1 = index1 >= length1;
+      boolean atEndOf2 = index2 >= length2;
+      if (atEndOf1 && atEndOf2) {
+        // no more non-null elements to test in both arrays
+        return true;
+      } else if (atEndOf1 != atEndOf2) {
+        // one of the arrays have extra non-null elements
+        return false;
+      } else if (!Arrays.equals(field1[index1], field2[index2])) {
+        // element mismatch
+        return false;
+      }
+      index1++;
+      index2++;
+    }
+  }
+
+  /**
+   * Checks repeated string/message field equality. Only non-null elements are
+   * tested. Returns true if the two fields have the same sequence of non-null
+   * elements. Null-value fields and fields of any length with only null
+   * elements are considered equal.
+   */
+  public static boolean equals(Object[] field1, Object[] field2) {
+    int index1 = 0;
+    int length1 = field1 == null ? 0 : field1.length;
+    int index2 = 0;
+    int length2 = field2 == null ? 0 : field2.length;
+    while (true) {
+      while (index1 < length1 && field1[index1] == null) {
+        index1++;
+      }
+      while (index2 < length2 && field2[index2] == null) {
+        index2++;
+      }
+      boolean atEndOf1 = index1 >= length1;
+      boolean atEndOf2 = index2 >= length2;
+      if (atEndOf1 && atEndOf2) {
+        // no more non-null elements to test in both arrays
+        return true;
+      } else if (atEndOf1 != atEndOf2) {
+        // one of the arrays have extra non-null elements
+        return false;
+      } else if (!field1[index1].equals(field2[index2])) {
+        // element mismatch
+        return false;
+      }
+      index1++;
+      index2++;
+    }
+  }
+
+  /**
+   * Computes the hash code of a repeated int field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(int[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated long field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(long[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated float field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(float[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated double field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(double[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated boolean field. Null-value and 0-length
+   * fields have the same hash code.
+   */
+  public static int hashCode(boolean[] field) {
+    return field == null || field.length == 0 ? 0 : Arrays.hashCode(field);
+  }
+
+  /**
+   * Computes the hash code of a repeated bytes field. Only the sequence of all
+   * non-null elements are used in the computation. Null-value fields and fields
+   * of any length with only null elements have the same hash code.
+   */
+  public static int hashCode(byte[][] field) {
+    int result = 0;
+    for (int i = 0, size = field == null ? 0 : field.length; i < size; i++) {
+      byte[] element = field[i];
+      if (element != null) {
+        result = 31 * result + Arrays.hashCode(element);
+      }
+    }
+    return result;
+  }
+
+  /**
+   * Computes the hash code of a repeated string/message field. Only the
+   * sequence of all non-null elements are used in the computation. Null-value
+   * fields and fields of any length with only null elements have the same hash
+   * code.
+   */
+  public static int hashCode(Object[] field) {
+    int result = 0;
+    for (int i = 0, size = field == null ? 0 : field.length; i < size; i++) {
+      Object element = field[i];
+      if (element != null) {
+        result = 31 * result + element.hashCode();
+      }
+    }
+    return result;
+  }
+
 }
diff --git a/java/src/main/java/com/google/protobuf/nano/UnknownFieldData.java b/java/src/main/java/com/google/protobuf/nano/UnknownFieldData.java
index 0db2a83..833ed2a 100644
--- a/java/src/main/java/com/google/protobuf/nano/UnknownFieldData.java
+++ b/java/src/main/java/com/google/protobuf/nano/UnknownFieldData.java
@@ -30,6 +30,8 @@
 
 package com.google.protobuf.nano;
 
+import java.util.Arrays;
+
 /**
  * Stores unknown fields. These might be extensions or fields that the generated API doesn't
  * know about yet.
@@ -37,6 +39,7 @@ package com.google.protobuf.nano;
  * @author bduff@google.com (Brian Duff)
  */
 public final class UnknownFieldData {
+
   final int tag;
   final byte[] bytes;
 
@@ -44,4 +47,25 @@ public final class UnknownFieldData {
     this.tag = tag;
     this.bytes = bytes;
   }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o == this) {
+      return true;
+    }
+    if (!(o instanceof UnknownFieldData)) {
+      return false;
+    }
+
+    UnknownFieldData other = (UnknownFieldData) o;
+    return tag == other.tag && Arrays.equals(bytes, other.bytes);
+  }
+
+  @Override
+  public int hashCode() {
+    int result = 17;
+    result = 31 * result + tag;
+    result = 31 * result + Arrays.hashCode(bytes);
+    return result;
+  }
 }
diff --git a/java/src/test/java/com/google/protobuf/NanoTest.java b/java/src/test/java/com/google/protobuf/NanoTest.java
index 1149c40..b9061e9 100644
--- a/java/src/test/java/com/google/protobuf/NanoTest.java
+++ b/java/src/test/java/com/google/protobuf/NanoTest.java
@@ -60,6 +60,7 @@ import junit.framework.TestCase;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.List;
 
 /**
@@ -2684,6 +2685,224 @@ public class NanoTest extends TestCase {
     assertHasWireData(message, false);
   }
 
+  public void testHashCodeEquals() throws Exception {
+    // Complete equality:
+    TestAllTypesNano a = createMessageForHashCodeEqualsTest();
+    TestAllTypesNano aEquivalent = createMessageForHashCodeEqualsTest();
+
+    // Null and empty array for repeated fields equality:
+    TestAllTypesNano b = createMessageForHashCodeEqualsTest();
+    b.repeatedBool = null;
+    b.repeatedFloat = new float[0];
+    TestAllTypesNano bEquivalent = createMessageForHashCodeEqualsTest();
+    bEquivalent.repeatedBool = new boolean[0];
+    bEquivalent.repeatedFloat = null;
+
+    // Ref-element-type repeated fields use non-null subsequence equality:
+    TestAllTypesNano c = createMessageForHashCodeEqualsTest();
+    c.repeatedString = null;
+    c.repeatedStringPiece = new String[] {null, "one", null, "two"};
+    c.repeatedBytes = new byte[][] {{3, 4}, null};
+    TestAllTypesNano cEquivalent = createMessageForHashCodeEqualsTest();
+    cEquivalent.repeatedString = new String[3];
+    cEquivalent.repeatedStringPiece = new String[] {"one", "two", null};
+    cEquivalent.repeatedBytes = new byte[][] {{3, 4}};
+
+    // Complete equality for messages with has fields:
+    TestAllTypesNanoHas d = createMessageWithHasForHashCodeEqualsTest();
+    TestAllTypesNanoHas dEquivalent = createMessageWithHasForHashCodeEqualsTest();
+
+    // If has-fields exist, fields with the same default values but
+    // different has-field values are different.
+    TestAllTypesNanoHas e = createMessageWithHasForHashCodeEqualsTest();
+    e.optionalInt32++; // make different from d
+    e.hasDefaultString = false;
+    TestAllTypesNanoHas eDifferent = createMessageWithHasForHashCodeEqualsTest();
+    eDifferent.optionalInt32 = e.optionalInt32;
+    eDifferent.hasDefaultString = true;
+
+    // Complete equality for messages with accessors:
+    TestNanoAccessors f = createMessageWithAccessorsForHashCodeEqualsTest();
+    TestNanoAccessors fEquivalent = createMessageWithAccessorsForHashCodeEqualsTest();
+    System.out.println("equals: " + f.equals(fEquivalent));
+    System.out.println("hashCode: " + f.hashCode() + " vs " + fEquivalent.hashCode());
+
+    // If using accessors, explicitly setting a field to its default value
+    // should make the message different.
+    TestNanoAccessors g = createMessageWithAccessorsForHashCodeEqualsTest();
+    g.setOptionalInt32(g.getOptionalInt32() + 1); // make different from f
+    g.clearDefaultString();
+    TestNanoAccessors gDifferent = createMessageWithAccessorsForHashCodeEqualsTest();
+    gDifferent.setOptionalInt32(g.getOptionalInt32());
+    gDifferent.setDefaultString(g.getDefaultString());
+
+    // Complete equality for reference typed messages:
+    NanoReferenceTypes.TestAllTypesNano h = createRefTypedMessageForHashCodeEqualsTest();
+    NanoReferenceTypes.TestAllTypesNano hEquivalent = createRefTypedMessageForHashCodeEqualsTest();
+
+    // Inequality of null and default value for reference typed messages:
+    NanoReferenceTypes.TestAllTypesNano i = createRefTypedMessageForHashCodeEqualsTest();
+    i.optionalInt32 = 1; // make different from h
+    i.optionalFloat = null;
+    NanoReferenceTypes.TestAllTypesNano iDifferent = createRefTypedMessageForHashCodeEqualsTest();
+    iDifferent.optionalInt32 = i.optionalInt32;
+    iDifferent.optionalFloat = 0.0f;
+
+    HashMap<MessageNano, String> hashMap = new HashMap<MessageNano, String>();
+    hashMap.put(a, "a");
+    hashMap.put(b, "b");
+    hashMap.put(c, "c");
+    hashMap.put(d, "d");
+    hashMap.put(e, "e");
+    hashMap.put(f, "f");
+    hashMap.put(g, "g");
+    hashMap.put(h, "h");
+    hashMap.put(i, "i");
+
+    assertEquals(9, hashMap.size()); // a-i should be different from each other.
+
+    assertEquals("a", hashMap.get(a));
+    assertEquals("a", hashMap.get(aEquivalent));
+
+    assertEquals("b", hashMap.get(b));
+    assertEquals("b", hashMap.get(bEquivalent));
+
+    assertEquals("c", hashMap.get(c));
+    assertEquals("c", hashMap.get(cEquivalent));
+
+    assertEquals("d", hashMap.get(d));
+    assertEquals("d", hashMap.get(dEquivalent));
+
+    assertEquals("e", hashMap.get(e));
+    assertNull(hashMap.get(eDifferent));
+
+    assertEquals("f", hashMap.get(f));
+    assertEquals("f", hashMap.get(fEquivalent));
+
+    assertEquals("g", hashMap.get(g));
+    assertNull(hashMap.get(gDifferent));
+
+    assertEquals("h", hashMap.get(h));
+    assertEquals("h", hashMap.get(hEquivalent));
+
+    assertEquals("i", hashMap.get(i));
+    assertNull(hashMap.get(iDifferent));
+  }
+
+  private TestAllTypesNano createMessageForHashCodeEqualsTest() {
+    TestAllTypesNano message = new TestAllTypesNano();
+    message.optionalInt32 = 5;
+    message.optionalInt64 = 777;
+    message.optionalFloat = 1.0f;
+    message.optionalDouble = 2.0;
+    message.optionalBool = true;
+    message.optionalString = "Hello";
+    message.optionalBytes = new byte[] { 1, 2, 3 };
+    message.optionalNestedMessage = new TestAllTypesNano.NestedMessage();
+    message.optionalNestedMessage.bb = 27;
+    message.optionalNestedEnum = TestAllTypesNano.BAR;
+    message.repeatedInt32 = new int[] { 5, 6, 7, 8 };
+    message.repeatedInt64 = new long[] { 27L, 28L, 29L };
+    message.repeatedFloat = new float[] { 5.0f, 6.0f };
+    message.repeatedDouble = new double[] { 99.1, 22.5 };
+    message.repeatedBool = new boolean[] { true, false, true };
+    message.repeatedString = new String[] { "One", "Two" };
+    message.repeatedBytes = new byte[][] { { 2, 7 }, { 2, 7 } };
+    message.repeatedNestedMessage = new TestAllTypesNano.NestedMessage[] {
+      message.optionalNestedMessage,
+      message.optionalNestedMessage
+    };
+    message.repeatedNestedEnum = new int[] {
+      TestAllTypesNano.BAR,
+      TestAllTypesNano.BAZ
+    };
+    // We set the _nan fields to something other than nan, because equality
+    // is defined for nan such that Float.NaN != Float.NaN, which makes any
+    // instance of TestAllTypesNano unequal to any other instance unless
+    // these fields are set. This is also the behavior of the regular java
+    // generator when the value of a field is NaN.
+    message.defaultFloatNan = 1.0f;
+    message.defaultDoubleNan = 1.0;
+    return message;
+  }
+
+  private TestAllTypesNanoHas createMessageWithHasForHashCodeEqualsTest() {
+    TestAllTypesNanoHas message = new TestAllTypesNanoHas();
+    message.optionalInt32 = 5;
+    message.optionalString = "Hello";
+    message.optionalBytes = new byte[] { 1, 2, 3 };
+    message.optionalNestedMessage = new TestAllTypesNanoHas.NestedMessage();
+    message.optionalNestedMessage.bb = 27;
+    message.optionalNestedEnum = TestAllTypesNano.BAR;
+    message.repeatedInt32 = new int[] { 5, 6, 7, 8 };
+    message.repeatedString = new String[] { "One", "Two" };
+    message.repeatedBytes = new byte[][] { { 2, 7 }, { 2, 7 } };
+    message.repeatedNestedMessage = new TestAllTypesNanoHas.NestedMessage[] {
+      message.optionalNestedMessage,
+      message.optionalNestedMessage
+    };
+    message.repeatedNestedEnum = new int[] {
+      TestAllTypesNano.BAR,
+      TestAllTypesNano.BAZ
+    };
+    message.defaultFloatNan = 1.0f;
+    return message;
+  }
+
+  private TestNanoAccessors createMessageWithAccessorsForHashCodeEqualsTest() {
+    TestNanoAccessors message = new TestNanoAccessors()
+        .setOptionalInt32(5)
+        .setOptionalString("Hello")
+        .setOptionalBytes(new byte[] {1, 2, 3})
+        .setOptionalNestedMessage(new TestNanoAccessors.NestedMessage().setBb(27))
+        .setOptionalNestedEnum(TestNanoAccessors.BAR)
+        .setDefaultFloatNan(1.0f);
+    message.repeatedInt32 = new int[] { 5, 6, 7, 8 };
+    message.repeatedString = new String[] { "One", "Two" };
+    message.repeatedBytes = new byte[][] { { 2, 7 }, { 2, 7 } };
+    message.repeatedNestedMessage = new TestNanoAccessors.NestedMessage[] {
+      message.getOptionalNestedMessage(),
+      message.getOptionalNestedMessage()
+    };
+    message.repeatedNestedEnum = new int[] {
+      TestAllTypesNano.BAR,
+      TestAllTypesNano.BAZ
+    };
+    return message;
+  }
+
+  private NanoReferenceTypes.TestAllTypesNano createRefTypedMessageForHashCodeEqualsTest() {
+    NanoReferenceTypes.TestAllTypesNano message = new NanoReferenceTypes.TestAllTypesNano();
+    message.optionalInt32 = 5;
+    message.optionalInt64 = 777L;
+    message.optionalFloat = 1.0f;
+    message.optionalDouble = 2.0;
+    message.optionalBool = true;
+    message.optionalString = "Hello";
+    message.optionalBytes = new byte[] { 1, 2, 3 };
+    message.optionalNestedMessage =
+        new NanoReferenceTypes.TestAllTypesNano.NestedMessage();
+    message.optionalNestedMessage.foo = 27;
+    message.optionalNestedEnum = NanoReferenceTypes.TestAllTypesNano.BAR;
+    message.repeatedInt32 = new int[] { 5, 6, 7, 8 };
+    message.repeatedInt64 = new long[] { 27L, 28L, 29L };
+    message.repeatedFloat = new float[] { 5.0f, 6.0f };
+    message.repeatedDouble = new double[] { 99.1, 22.5 };
+    message.repeatedBool = new boolean[] { true, false, true };
+    message.repeatedString = new String[] { "One", "Two" };
+    message.repeatedBytes = new byte[][] { { 2, 7 }, { 2, 7 } };
+    message.repeatedNestedMessage =
+        new NanoReferenceTypes.TestAllTypesNano.NestedMessage[] {
+          message.optionalNestedMessage,
+          message.optionalNestedMessage
+        };
+    message.repeatedNestedEnum = new int[] {
+      NanoReferenceTypes.TestAllTypesNano.BAR,
+      NanoReferenceTypes.TestAllTypesNano.BAZ
+    };
+    return message;
+  }
+
   public void testNullRepeatedFields() throws Exception {
     // Check that serialization after explicitly setting a repeated field
     // to null doesn't NPE.