content: // Protocol Buffers - Google's data interchange format
  // Copyright 2008 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,
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  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.Map;
  
  /** A reader of fields from a serialized protobuf message. */
  // TODO(nathanmittler): Refactor to allow the reader to allocate properly sized lists.
  @ExperimentalApi
  interface Reader {
    /** Value used to indicate that the end of input has been reached. */
    int READ_DONE = Integer.MAX_VALUE;
  
    /** Value used to indicate that the reader does not know the tag about the field. */
    int TAG_UNKNOWN = 0;
  
    boolean shouldDiscardUnknownFields();
  
    /**
     * Gets the field number for the current field being read.
     *
     * <p>TODO(liujisi): Rename it to make it more explicit about the side effect on the underlying
     * buffer.
     *
     * @return the current field number or {@link #READ_DONE} if the end of input has been reached.
     */
    int getFieldNumber() throws IOException;
  
    /**
     * Gets the wire tag of the current field.
     *
     * @return the current wire tag or {@link #TAG_UNKNOWN} if the reader does not know the tag of the
     *     current field.
     */
    int getTag();
  
    /**
     * Skips the current field and advances the reader to the next field.
     *
     * @return {@code true} if there are more fields or {@code false} if the end of input has been
     *     reached.
     */
    boolean skipField() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code DOUBLE} and advances the reader to the next
     * field.
     */
    double readDouble() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code FLOAT} and advances the reader to the next
     * field.
     */
    float readFloat() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code UINT64} and advances the reader to the next
     * field.
     */
    long readUInt64() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code INT64} and advances the reader to the next
     * field.
     */
    long readInt64() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code INT32} and advances the reader to the next
     * field.
     */
    int readInt32() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code FIXED64} and advances the reader to the next
     * field.
     */
    long readFixed64() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code FIXED32} and advances the reader to the next
     * field.
     */
    int readFixed32() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code BOOL} and advances the reader to the next
     * field.
     */
    boolean readBool() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code STRING} and advances the reader to the next
     * field. If the stream contains malformed UTF-8, replace the offending bytes with the standard
     * UTF-8 replacement character.
     */
    String readString() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code STRING} and advances the reader to the next
     * field. If the stream contains malformed UTF-8, throw exception {@link
     * InvalidProtocolBufferException}.
     */
    String readStringRequireUtf8() throws IOException;
  
    // TODO(yilunchong): the lack of other opinions for whether to expose this on the interface
    <T> T readMessageBySchemaWithCheck(Schema<T> schema, ExtensionRegistryLite extensionRegistry)
        throws IOException;
  
    /**
     * Reads and returns the next field of type {@code MESSAGE} and advances the reader to the next
     * field.
     */
    <T> T readMessage(Class<T> clazz, ExtensionRegistryLite extensionRegistry) throws IOException;
  
    /**
     * Reads and returns the next field of type {@code GROUP} and advances the reader to the next
     * field.
     *
     * @deprecated groups fields are deprecated.
     */
    @Deprecated
    <T> T readGroup(Class<T> clazz, ExtensionRegistryLite extensionRegistry) throws IOException;
  
    // TODO(yilunchong): the lack of other opinions for whether to expose this on the interface
    @Deprecated
    <T> T readGroupBySchemaWithCheck(Schema<T> schema, ExtensionRegistryLite extensionRegistry)
        throws IOException;
  
    /**
     * Reads and returns the next field of type {@code BYTES} and advances the reader to the next
     * field.
     */
    ByteString readBytes() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code UINT32} and advances the reader to the next
     * field.
     */
    int readUInt32() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code ENUM} and advances the reader to the next
     * field.
     */
    int readEnum() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code SFIXED32} and advances the reader to the next
     * field.
     */
    int readSFixed32() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code SFIXED64} and advances the reader to the next
     * field.
     */
    long readSFixed64() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code SINT32} and advances the reader to the next
     * field.
     */
    int readSInt32() throws IOException;
  
    /**
     * Reads and returns the next field of type {@code SINT64} and advances the reader to the next
     * field.
     */
    long readSInt64() throws IOException;
  
    /**
     * Reads the next field of type {@code DOUBLE_LIST} or {@code DOUBLE_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readDoubleList(List<Double> target) throws IOException;
  
    /**
     * Reads the next field of type {@code FLOAT_LIST} or {@code FLOAT_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readFloatList(List<Float> target) throws IOException;
  
    /**
     * Reads the next field of type {@code UINT64_LIST} or {@code UINT64_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readUInt64List(List<Long> target) throws IOException;
  
    /**
     * Reads the next field of type {@code INT64_LIST} or {@code INT64_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readInt64List(List<Long> target) throws IOException;
  
    /**
     * Reads the next field of type {@code INT32_LIST} or {@code INT32_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readInt32List(List<Integer> target) throws IOException;
  
    /**
     * Reads the next field of type {@code FIXED64_LIST} or {@code FIXED64_LIST_PACKED} and advances
     * the reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readFixed64List(List<Long> target) throws IOException;
  
    /**
     * Reads the next field of type {@code FIXED32_LIST} or {@code FIXED32_LIST_PACKED} and advances
     * the reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readFixed32List(List<Integer> target) throws IOException;
  
    /**
     * Reads the next field of type {@code BOOL_LIST} or {@code BOOL_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readBoolList(List<Boolean> target) throws IOException;
  
    /**
     * Reads the next field of type {@code STRING_LIST} and advances the reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readStringList(List<String> target) throws IOException;
  
    /**
     * Reads the next field of type {@code STRING_LIST} and advances the reader to the next field. If
     * the stream contains malformed UTF-8, throw exception {@link InvalidProtocolBufferException}.
     *
     * @param target the list that will receive the read values.
     */
    void readStringListRequireUtf8(List<String> target) throws IOException;
  
    /**
     * Reads the next field of type {@code MESSAGE_LIST} and advances the reader to the next field.
     *
     * @param target the list that will receive the read values.
     * @param targetType the type of the elements stored in the {@code target} list.
     */
    <T> void readMessageList(
        List<T> target, Schema<T> schema, ExtensionRegistryLite extensionRegistry) throws IOException;
  
    <T> void readMessageList(
        List<T> target, Class<T> targetType, ExtensionRegistryLite extensionRegistry)
        throws IOException;
  
    /**
     * Reads the next field of type {@code GROUP_LIST} and advances the reader to the next field.
     *
     * @param target the list that will receive the read values.
     * @param targetType the type of the elements stored in the {@code target} list.
     * @deprecated groups fields are deprecated.
     */
    @Deprecated
    <T> void readGroupList(
        List<T> target, Class<T> targetType, ExtensionRegistryLite extensionRegistry)
        throws IOException;
  
    @Deprecated
    <T> void readGroupList(
        List<T> target, Schema<T> targetType, ExtensionRegistryLite extensionRegistry)
        throws IOException;
  
    /**
     * Reads the next field of type {@code BYTES_LIST} and advances the reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readBytesList(List<ByteString> target) throws IOException;
  
    /**
     * Reads the next field of type {@code UINT32_LIST} or {@code UINT32_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readUInt32List(List<Integer> target) throws IOException;
  
    /**
     * Reads the next field of type {@code ENUM_LIST} or {@code ENUM_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readEnumList(List<Integer> target) throws IOException;
  
    /**
     * Reads the next field of type {@code SFIXED32_LIST} or {@code SFIXED32_LIST_PACKED} and advances
     * the reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readSFixed32List(List<Integer> target) throws IOException;
  
    /**
     * Reads the next field of type {@code SFIXED64_LIST} or {@code SFIXED64_LIST_PACKED} and advances
     * the reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readSFixed64List(List<Long> target) throws IOException;
  
    /**
     * Reads the next field of type {@code SINT32_LIST} or {@code SINT32_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readSInt32List(List<Integer> target) throws IOException;
  
    /**
     * Reads the next field of type {@code SINT64_LIST} or {@code SINT64_LIST_PACKED} and advances the
     * reader to the next field.
     *
     * @param target the list that will receive the read values.
     */
    void readSInt64List(List<Long> target) throws IOException;
  
    /**
     * Reads the next field of type {@code MAP} and advances the reader to the next field.
     *
     * @param target the mutable map that will receive the read values.
     * @param mapDefaultEntry the default entry of the map field.
     * @param extensionRegistry the extension registry for parsing message value fields.
     */
    <K, V> void readMap(
        Map<K, V> target,
        MapEntryLite.Metadata<K, V> mapDefaultEntry,
        ExtensionRegistryLite extensionRegistry)
        throws IOException;
  }
  