content: // Protocol Buffers - Google's data interchange format
  // Copyright 2014 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf.nano;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  
  /**
   * Stores unknown fields. These might be extensions or fields that the generated API doesn't
   * know about yet.
   */
  class FieldData {
      private Extension<?, ?> cachedExtension;
      private Object value;
      /** The serialised values for this object. Will be cleared if getValue is called */
      private List<UnknownFieldData> unknownFieldData;
  
      <T> FieldData(Extension<?, T> extension, T newValue) {
          cachedExtension = extension;
          value = newValue;
      }
  
      FieldData() {
          unknownFieldData = new ArrayList<UnknownFieldData>();
      }
  
      void addUnknownField(UnknownFieldData unknownField) {
          unknownFieldData.add(unknownField);
      }
  
      UnknownFieldData getUnknownField(int index) {
          if (unknownFieldData == null) {
              return null;
          }
          if (index < unknownFieldData.size()) {
              return unknownFieldData.get(index);
          }
          return null;
      }
  
      int getUnknownFieldSize() {
          if (unknownFieldData == null) {
              return 0;
          }
          return unknownFieldData.size();
      }
  
      <T> T getValue(Extension<?, T> extension) {
          if (value != null){
              if (cachedExtension != extension) {  // Extension objects are singletons.
                  throw new IllegalStateException(
                          "Tried to getExtension with a differernt Extension.");
              }
          } else {
              cachedExtension = extension;
              value = extension.getValueFrom(unknownFieldData);
              unknownFieldData = null;
          }
          return (T) value;
      }
  
      <T> void setValue(Extension<?, T> extension, T newValue) {
          cachedExtension = extension;
          value = newValue;
          unknownFieldData = null;
      }
  
      int computeSerializedSize() {
          int size = 0;
          if (value != null) {
              size = cachedExtension.computeSerializedSize(value);
          } else {
              for (UnknownFieldData unknownField : unknownFieldData) {
                  size += unknownField.computeSerializedSize();
              }
          }
          return size;
      }
  
      void writeTo(CodedOutputByteBufferNano output) throws IOException {
          if (value != null) {
              cachedExtension.writeTo(value, output);
          } else {
              for (UnknownFieldData unknownField : unknownFieldData) {
                  unknownField.writeTo(output);
              }
          }
      }
  
      @Override
      public boolean equals(Object o) {
          if (o == this) {
              return true;
          }
          if (!(o instanceof FieldData)) {
              return false;
          }
  
          FieldData other = (FieldData) o;
          if (value != null && other.value != null) {
              // If both objects have deserialized values, compare those.
              // Since unknown fields are only compared if messages have generated equals methods
              // we know this will be a meaningful comparison (not identity) for all values.
              if (cachedExtension != other.cachedExtension) {  // Extension objects are singletons.
                  return false;
              }
              if (!cachedExtension.clazz.isArray()) {
                  // Can't test (!cachedExtension.repeated) due to 'bytes' -> 'byte[]'
                  return value.equals(other.value);
              }
              if (value instanceof byte[]) {
                  return Arrays.equals((byte[]) value, (byte[]) other.value);
              } else if (value instanceof int[]) {
                  return Arrays.equals((int[]) value, (int[]) other.value);
              } else if (value instanceof long[]) {
                  return Arrays.equals((long[]) value, (long[]) other.value);
              } else if (value instanceof float[]) {
                  return Arrays.equals((float[]) value, (float[]) other.value);
              } else if (value instanceof double[]) {
                  return Arrays.equals((double[]) value, (double[]) other.value);
              } else if (value instanceof boolean[]) {
                  return Arrays.equals((boolean[]) value, (boolean[]) other.value);
              } else {
                  return Arrays.deepEquals((Object[]) value, (Object[]) other.value);
              }
          }
          if (unknownFieldData != null && other.unknownFieldData != null) {
              // If both objects have byte arrays compare those directly.
              return unknownFieldData.equals(other.unknownFieldData);
          }
          try {
              // As a last resort, serialize and compare the resulting byte arrays.
              return Arrays.equals(toByteArray(), other.toByteArray());
          } catch (IOException e) {
              // Should not happen.
              throw new IllegalStateException(e);
          }
      }
  
      @Override
      public int hashCode() {
          int result = 17;
          try {
              // The only way to generate a consistent hash is to use the serialized form.
              result = 31 * result + Arrays.hashCode(toByteArray());
          } catch (IOException e) {
              // Should not happen.
              throw new IllegalStateException(e);
          }
          return result;
      }
  
      private byte[] toByteArray() throws IOException {
          byte[] result = new byte[computeSerializedSize()];
          CodedOutputByteBufferNano output = CodedOutputByteBufferNano.newInstance(result);
          writeTo(output);
          return result;
      }
  
  }
  