// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
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// 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
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// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
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//
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package com.google.protobuf;

import protobuf_unittest.UnittestProto.BoolMessage;
import protobuf_unittest.UnittestProto.Int32Message;
import protobuf_unittest.UnittestProto.Int64Message;
import protobuf_unittest.UnittestProto.TestAllTypes;
import protobuf_unittest.UnittestProto.TestRecursiveMessage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import junit.framework.TestCase;

/**
 * Unit test for {@link CodedInputStream}.
 *
 * @author kenton@google.com Kenton Varda
 */
public class CodedInputStreamTest extends TestCase {
  
  private static final int DEFAULT_BLOCK_SIZE = 4096; 
  
  private enum InputType {
    ARRAY {
      @Override
      CodedInputStream newDecoder(byte[] data, int blockSize) {
        return CodedInputStream.newInstance(data);
      }
    },
    NIO_HEAP {
      @Override
      CodedInputStream newDecoder(byte[] data, int blockSize) {
        return CodedInputStream.newInstance(ByteBuffer.wrap(data));
      }
    },
    NIO_DIRECT {
      @Override
      CodedInputStream newDecoder(byte[] data, int blockSize) {
        ByteBuffer buffer = ByteBuffer.allocateDirect(data.length);
        buffer.put(data);
        buffer.flip();
        return CodedInputStream.newInstance(buffer);
      }
    },
    STREAM {
      @Override
      CodedInputStream newDecoder(byte[] data, int blockSize) {
        return CodedInputStream.newInstance(new SmallBlockInputStream(data, blockSize));
      }
    },
    ITER_DIRECT {
      @Override
      CodedInputStream newDecoder(byte[] data, int blockSize) {
        if (blockSize > DEFAULT_BLOCK_SIZE) {
          blockSize = DEFAULT_BLOCK_SIZE;
        }
        ArrayList <ByteBuffer> input = new ArrayList <ByteBuffer>();
        for (int i = 0; i < data.length; i += blockSize) {
          int rl = Math.min(blockSize, data.length - i); 
          ByteBuffer rb = ByteBuffer.allocateDirect(rl); 
          rb.put(data, i, rl);
          rb.flip();
          input.add(rb);
        }
        return CodedInputStream.newInstance(input);
      }
    },
    STREAM_ITER_DIRECT {
      @Override
      CodedInputStream newDecoder(byte[] data, int blockSize) {
        if (blockSize > DEFAULT_BLOCK_SIZE) {
          blockSize = DEFAULT_BLOCK_SIZE;
        }
        ArrayList <ByteBuffer> input = new ArrayList <ByteBuffer>();
        for (int i = 0; i < data.length; i += blockSize) {
          int rl = Math.min(blockSize, data.length - i); 
          ByteBuffer rb = ByteBuffer.allocateDirect(rl); 
          rb.put(data, i, rl);
          rb.flip();
          input.add(rb);
        }
        return CodedInputStream.newInstance(new IterableByteBufferInputStream(input));
      }
    };
    
    
    CodedInputStream newDecoder(byte[] data) {
      return newDecoder(data, data.length);
    }

    abstract CodedInputStream newDecoder(byte[] data, int blockSize);
  }

  /**
   * Helper to construct a byte array from a bunch of bytes. The inputs are actually ints so that I
   * can use hex notation and not get stupid errors about precision.
   */
  private byte[] bytes(int... bytesAsInts) {
    byte[] bytes = new byte[bytesAsInts.length];
    for (int i = 0; i < bytesAsInts.length; i++) {
      bytes[i] = (byte) bytesAsInts[i];
    }
    return bytes;
  }

  /**
   * An InputStream which limits the number of bytes it reads at a time. We use this to make sure
   * that CodedInputStream doesn't screw up when reading in small blocks.
   */
  private static final class SmallBlockInputStream extends FilterInputStream {
    private final int blockSize;

    public SmallBlockInputStream(byte[] data, int blockSize) {
      super(new ByteArrayInputStream(data));
      this.blockSize = blockSize;
    }

    @Override
    public int read(byte[] b) throws IOException {
      return super.read(b, 0, Math.min(b.length, blockSize));
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
      return super.read(b, off, Math.min(len, blockSize));
    }
  }

  private void assertDataConsumed(String msg, byte[] data, CodedInputStream input)
      throws IOException {
    assertEquals(msg, data.length, input.getTotalBytesRead());
    assertTrue(msg, input.isAtEnd());
  }

  /**
   * Parses the given bytes using readRawVarint32() and readRawVarint64() and checks that the result
   * matches the given value.
   */
  private void assertReadVarint(byte[] data, long value) throws Exception {
    for (InputType inputType : InputType.values()) {
      // Try different block sizes.
      for (int blockSize = 1; blockSize <= 16; blockSize *= 2) {
        CodedInputStream input = inputType.newDecoder(data, blockSize);
        assertEquals(inputType.name(), (int) value, input.readRawVarint32());
        assertDataConsumed(inputType.name(), data, input);

        input = inputType.newDecoder(data, blockSize);
        assertEquals(inputType.name(), value, input.readRawVarint64());
        assertDataConsumed(inputType.name(), data, input);

        input = inputType.newDecoder(data, blockSize);
        assertEquals(inputType.name(), value, input.readRawVarint64SlowPath());
        assertDataConsumed(inputType.name(), data, input);

        input = inputType.newDecoder(data, blockSize);
        assertTrue(inputType.name(), input.skipField(WireFormat.WIRETYPE_VARINT));
        assertDataConsumed(inputType.name(), data, input);
      }
    }

    // Try reading direct from an InputStream.  We want to verify that it
    // doesn't read past the end of the input, so we copy to a new, bigger
    // array first.
    byte[] longerData = new byte[data.length + 1];
    System.arraycopy(data, 0, longerData, 0, data.length);
    InputStream rawInput = new ByteArrayInputStream(longerData);
    assertEquals((int) value, CodedInputStream.readRawVarint32(rawInput));
    assertEquals(1, rawInput.available());
  }

  /**
   * Parses the given bytes using readRawVarint32() and readRawVarint64() and expects them to fail
   * with an InvalidProtocolBufferException whose description matches the given one.
   */
  private void assertReadVarintFailure(InvalidProtocolBufferException expected, byte[] data)
      throws Exception {
    for (InputType inputType : InputType.values()) {
      try {
        CodedInputStream input = inputType.newDecoder(data);
        input.readRawVarint32();
        fail(inputType.name() + ": Should have thrown an exception.");
      } catch (InvalidProtocolBufferException e) {
        assertEquals(inputType.name(), expected.getMessage(), e.getMessage());
      }
      try {
        CodedInputStream input = inputType.newDecoder(data);
        input.readRawVarint64();
        fail(inputType.name() + ": Should have thrown an exception.");
      } catch (InvalidProtocolBufferException e) {
        assertEquals(inputType.name(), expected.getMessage(), e.getMessage());
      }
    }

    // Make sure we get the same error when reading direct from an InputStream.
    try {
      CodedInputStream.readRawVarint32(new ByteArrayInputStream(data));
      fail("Should have thrown an exception.");
    } catch (InvalidProtocolBufferException e) {
      assertEquals(expected.getMessage(), e.getMessage());
    }
  }

  /** Tests readRawVarint32() and readRawVarint64(). */
  public void testReadVarint() throws Exception {
    assertReadVarint(bytes(0x00), 0);
    assertReadVarint(bytes(0x01), 1);
    assertReadVarint(bytes(0x7f), 127);
    // 14882
    assertReadVarint(bytes(0xa2, 0x74), (0x22 << 0) | (0x74 << 7));
    // 2961488830
    assertReadVarint(
        bytes(0xbe, 0xf7, 0x92, 0x84, 0x0b),
        (0x3e << 0) | (0x77 << 7) | (0x12 << 14) | (0x04 << 21) | (0x0bL << 28));

    // 64-bit
    // 7256456126
    assertReadVarint(
        bytes(0xbe, 0xf7, 0x92, 0x84, 0x1b),
        (0x3e << 0) | (0x77 << 7) | (0x12 << 14) | (0x04 << 21) | (0x1bL << 28));
    // 41256202580718336
    assertReadVarint(
        bytes(0x80, 0xe6, 0xeb, 0x9c, 0xc3, 0xc9, 0xa4, 0x49),
        (0x00 << 0)
            | (0x66 << 7)
            | (0x6b << 14)
            | (0x1c << 21)
            | (0x43L << 28)
            | (0x49L << 35)
            | (0x24L << 42)
            | (0x49L << 49));
    // 11964378330978735131
    assertReadVarint(
        bytes(0x9b, 0xa8, 0xf9, 0xc2, 0xbb, 0xd6, 0x80, 0x85, 0xa6, 0x01),
        (0x1b << 0)
            | (0x28 << 7)
            | (0x79 << 14)
            | (0x42 << 21)
            | (0x3bL << 28)
            | (0x56L << 35)
            | (0x00L << 42)
            | (0x05L << 49)
            | (0x26L << 56)
            | (0x01L << 63));

    // Failures
    assertReadVarintFailure(
        InvalidProtocolBufferException.malformedVarint(),
        bytes(0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x00));
    assertReadVarintFailure(InvalidProtocolBufferException.truncatedMessage(), bytes(0x80));
  }

  /**
   * Parses the given bytes using readRawLittleEndian32() and checks that the result matches the
   * given value.
   */
  private void assertReadLittleEndian32(byte[] data, int value) throws Exception {
    for (InputType inputType : InputType.values()) {
      // Try different block sizes.
      for (int blockSize = 1; blockSize <= 16; blockSize *= 2) {
        CodedInputStream input = inputType.newDecoder(data, blockSize);
        assertEquals(inputType.name(), value, input.readRawLittleEndian32());
        assertTrue(inputType.name(), input.isAtEnd());
      }
    }
  }

  /**
   * Parses the given bytes using readRawLittleEndian64() and checks that the result matches the
   * given value.
   */
  private void assertReadLittleEndian64(byte[] data, long value) throws Exception {
    for (InputType inputType : InputType.values()) {
      // Try different block sizes.
      for (int blockSize = 1; blockSize <= 16; blockSize *= 2) {
        CodedInputStream input = inputType.newDecoder(data, blockSize);
        assertEquals(inputType.name(), value, input.readRawLittleEndian64());
        assertTrue(inputType.name(), input.isAtEnd());
      }
    }
  }

  /** Tests readRawLittleEndian32() and readRawLittleEndian64(). */
  public void testReadLittleEndian() throws Exception {
    assertReadLittleEndian32(bytes(0x78, 0x56, 0x34, 0x12), 0x12345678);
    assertReadLittleEndian32(bytes(0xf0, 0xde, 0xbc, 0x9a), 0x9abcdef0);

    assertReadLittleEndian64(
        bytes(0xf0, 0xde, 0xbc, 0x9a, 0x78, 0x56, 0x34, 0x12), 0x123456789abcdef0L);
    assertReadLittleEndian64(
        bytes(0x78, 0x56, 0x34, 0x12, 0xf0, 0xde, 0xbc, 0x9a), 0x9abcdef012345678L);
  }

  /** Test decodeZigZag32() and decodeZigZag64(). */
  public void testDecodeZigZag() throws Exception {
    assertEquals(0, CodedInputStream.decodeZigZag32(0));
    assertEquals(-1, CodedInputStream.decodeZigZag32(1));
    assertEquals(1, CodedInputStream.decodeZigZag32(2));
    assertEquals(-2, CodedInputStream.decodeZigZag32(3));
    assertEquals(0x3FFFFFFF, CodedInputStream.decodeZigZag32(0x7FFFFFFE));
    assertEquals(0xC0000000, CodedInputStream.decodeZigZag32(0x7FFFFFFF));
    assertEquals(0x7FFFFFFF, CodedInputStream.decodeZigZag32(0xFFFFFFFE));
    assertEquals(0x80000000, CodedInputStream.decodeZigZag32(0xFFFFFFFF));

    assertEquals(0, CodedInputStream.decodeZigZag64(0));
    assertEquals(-1, CodedInputStream.decodeZigZag64(1));
    assertEquals(1, CodedInputStream.decodeZigZag64(2));
    assertEquals(-2, CodedInputStream.decodeZigZag64(3));
    assertEquals(0x000000003FFFFFFFL, CodedInputStream.decodeZigZag64(0x000000007FFFFFFEL));
    assertEquals(0xFFFFFFFFC0000000L, CodedInputStream.decodeZigZag64(0x000000007FFFFFFFL));
    assertEquals(0x000000007FFFFFFFL, CodedInputStream.decodeZigZag64(0x00000000FFFFFFFEL));
    assertEquals(0xFFFFFFFF80000000L, CodedInputStream.decodeZigZag64(0x00000000FFFFFFFFL));
    assertEquals(0x7FFFFFFFFFFFFFFFL, CodedInputStream.decodeZigZag64(0xFFFFFFFFFFFFFFFEL));
    assertEquals(0x8000000000000000L, CodedInputStream.decodeZigZag64(0xFFFFFFFFFFFFFFFFL));
  }

  /** Tests reading and parsing a whole message with every field type. */
  public void testReadWholeMessage() throws Exception {
    TestAllTypes message = TestUtil.getAllSet();

    byte[] rawBytes = message.toByteArray();
    assertEquals(rawBytes.length, message.getSerializedSize());

    for (InputType inputType : InputType.values()) {
      // Try different block sizes.
      for (int blockSize = 1; blockSize < 256; blockSize *= 2) {
        TestAllTypes message2 = TestAllTypes.parseFrom(inputType.newDecoder(rawBytes, blockSize));
        TestUtil.assertAllFieldsSet(message2);
      }
    }
  }

  /** Tests skipField(). */
  public void testSkipWholeMessage() throws Exception {
    TestAllTypes message = TestUtil.getAllSet();
    byte[] rawBytes = message.toByteArray();

    InputType[] inputTypes = InputType.values();
    CodedInputStream[] inputs = new CodedInputStream[inputTypes.length];
    for (int i = 0; i < inputs.length; ++i) {
      inputs[i] = inputTypes[i].newDecoder(rawBytes);
    }
    UnknownFieldSet.Builder unknownFields = UnknownFieldSet.newBuilder();

    while (true) {
      CodedInputStream input1 = inputs[0];
      int tag = input1.readTag();
      // Ensure that the rest match.
      for (int i = 1; i < inputs.length; ++i) {
        assertEquals(inputTypes[i].name(), tag, inputs[i].readTag());
      }
      if (tag == 0) {
        break;
      }
      unknownFields.mergeFieldFrom(tag, input1);
      // Skip the field for the rest of the inputs.
      for (int i = 1; i < inputs.length; ++i) {
        inputs[i].skipField(tag);
      }
    }
  }


  /**
   * Test that a bug in skipRawBytes() has been fixed: if the skip skips exactly up to a limit, this
   * should not break things.
   */
  public void testSkipRawBytesBug() throws Exception {
    byte[] rawBytes = new byte[] {1, 2};
    for (InputType inputType : InputType.values()) {
      CodedInputStream input = inputType.newDecoder(rawBytes);
      int limit = input.pushLimit(1);
      input.skipRawBytes(1);
      input.popLimit(limit);
      assertEquals(inputType.name(), 2, input.readRawByte());
    }
  }

  /**
   * Test that a bug in skipRawBytes() has been fixed: if the skip skips past the end of a buffer
   * with a limit that has been set past the end of that buffer, this should not break things.
   */
  public void testSkipRawBytesPastEndOfBufferWithLimit() throws Exception {
    byte[] rawBytes = new byte[] {1, 2, 3, 4, 5};
    for (InputType inputType : InputType.values()) {
      CodedInputStream input = inputType.newDecoder(rawBytes);
      int limit = input.pushLimit(4);
      // In order to expose the bug we need to read at least one byte to prime the
      // buffer inside the CodedInputStream.
      assertEquals(inputType.name(), 1, input.readRawByte());
      // Skip to the end of the limit.
      input.skipRawBytes(3);
      assertTrue(inputType.name(), input.isAtEnd());
      input.popLimit(limit);
      assertEquals(inputType.name(), 5, input.readRawByte());
    }
  }

  public void testReadHugeBlob() throws Exception {
    // Allocate and initialize a 1MB blob.
    byte[] blob = new byte[1 << 20];
    for (int i = 0; i < blob.length; i++) {
      blob[i] = (byte) i;
    }

    // Make a message containing it.
    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
    TestUtil.setAllFields(builder);
    builder.setOptionalBytes(ByteString.copyFrom(blob));
    TestAllTypes message = builder.build();

    byte[] data = message.toByteArray();
    for (InputType inputType : InputType.values()) {
      // Serialize and parse it.  Make sure to parse from an InputStream, not
      // directly from a ByteString, so that CodedInputStream uses buffered
      // reading.
      TestAllTypes message2 = TestAllTypes.parseFrom(inputType.newDecoder(data));

      assertEquals(inputType.name(), message.getOptionalBytes(), message2.getOptionalBytes());

      // Make sure all the other fields were parsed correctly.
      TestAllTypes message3 =
          TestAllTypes.newBuilder(message2)
              .setOptionalBytes(TestUtil.getAllSet().getOptionalBytes())
              .build();
      TestUtil.assertAllFieldsSet(message3);
    }
  }

  public void testReadMaliciouslyLargeBlob() throws Exception {
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);

    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
    output.writeRawVarint32(tag);
    output.writeRawVarint32(0x7FFFFFFF);
    output.writeRawBytes(new byte[32]); // Pad with a few random bytes.
    output.flush();

    byte[] data = rawOutput.toByteString().toByteArray();
    for (InputType inputType : InputType.values()) {
      CodedInputStream input = inputType.newDecoder(data);
      assertEquals(tag, input.readTag());
      try {
        input.readBytes();
        fail(inputType.name() + ": Should have thrown an exception!");
      } catch (InvalidProtocolBufferException e) {
        // success.
      }
    }
  }

  /**
   * Test we can do messages that are up to CodedInputStream#DEFAULT_SIZE_LIMIT
   * in size (2G or Integer#MAX_SIZE).
   * @throws IOException
   */
  public void testParseMessagesCloseTo2G() throws IOException {
    byte[] serializedMessage = getBigSerializedMessage();
    // How many of these big messages do we need to take us near our 2G limit?
    int count = Integer.MAX_VALUE / serializedMessage.length;
    // Now make an inputstream that will fake a near 2G message of messages
    // returning our big serialized message 'count' times.
    InputStream is = new RepeatingInputStream(serializedMessage, count);
    // Parse should succeed!
    TestAllTypes.parseFrom(is);
  }

  /**
   * Test there is an exception if a message exceeds
   * CodedInputStream#DEFAULT_SIZE_LIMIT in size (2G or Integer#MAX_SIZE).
   * @throws IOException
   */
  public void testParseMessagesOver2G() throws IOException {
    byte[] serializedMessage = getBigSerializedMessage();
    // How many of these big messages do we need to take us near our 2G limit?
    int count = Integer.MAX_VALUE / serializedMessage.length;
    // Now add one to take us over the limit
    count++;
    // Now make an inputstream that will fake a near 2G message of messages
    // returning our big serialized message 'count' times.
    InputStream is = new RepeatingInputStream(serializedMessage, count);
    try {
      TestAllTypes.parseFrom(is);
      fail("Should have thrown an exception!");
    } catch (InvalidProtocolBufferException e) {
      assertTrue(e.getMessage().contains("too large"));
    }
  }

  /*
   * @return A serialized big message.
   */
  private static byte[] getBigSerializedMessage() {
    byte[] value = new byte[16 * 1024 * 1024]; 
    ByteString bsValue = ByteString.wrap(value);
    return TestAllTypes.newBuilder().setOptionalBytes(bsValue).build().toByteArray();
  }

  /*
   * An input stream that repeats a byte arrays' content a number of times.
   * Simulates really large input without consuming loads of memory. Used above
   * to test the parsing behavior when the input size exceeds 2G or close to it.
   */
  private static class RepeatingInputStream extends InputStream {
    private final byte[] serializedMessage;
    private final int count;
    private int index = 0;
    private int offset = 0;

    RepeatingInputStream(byte[] serializedMessage, int count) {
      this.serializedMessage = serializedMessage;
      this.count = count;
    }

    @Override
    public int read() throws IOException {
      if (this.offset == this.serializedMessage.length) {
        this.index++;
        this.offset = 0;
      }
      if (this.index == this.count) {
        return -1;
      }
      return this.serializedMessage[offset++];
    }
  }

  private TestRecursiveMessage makeRecursiveMessage(int depth) {
    if (depth == 0) {
      return TestRecursiveMessage.newBuilder().setI(5).build();
    } else {
      return TestRecursiveMessage.newBuilder().setA(makeRecursiveMessage(depth - 1)).build();
    }
  }

  private void assertMessageDepth(String msg, TestRecursiveMessage message, int depth) {
    if (depth == 0) {
      assertFalse(msg, message.hasA());
      assertEquals(msg, 5, message.getI());
    } else {
      assertTrue(msg, message.hasA());
      assertMessageDepth(msg, message.getA(), depth - 1);
    }
  }

  public void testMaliciousRecursion() throws Exception {
    byte[] data100 = makeRecursiveMessage(100).toByteArray();
    byte[] data101 = makeRecursiveMessage(101).toByteArray();

    for (InputType inputType : InputType.values()) {
      assertMessageDepth(
          inputType.name(), TestRecursiveMessage.parseFrom(inputType.newDecoder(data100)), 100);

      try {
        TestRecursiveMessage.parseFrom(inputType.newDecoder(data101));
        fail("Should have thrown an exception!");
      } catch (InvalidProtocolBufferException e) {
        // success.
      }

      CodedInputStream input = inputType.newDecoder(data100);
      input.setRecursionLimit(8);
      try {
        TestRecursiveMessage.parseFrom(input);
        fail(inputType.name() + ": Should have thrown an exception!");
      } catch (InvalidProtocolBufferException e) {
        // success.
      }
    }
  }

  private void checkSizeLimitExceeded(InvalidProtocolBufferException e) {
    assertEquals(InvalidProtocolBufferException.sizeLimitExceeded().getMessage(), e.getMessage());
  }

  public void testSizeLimit() throws Exception {
    // NOTE: Size limit only applies to the stream-backed CIS.
    CodedInputStream input =
        CodedInputStream.newInstance(
            new SmallBlockInputStream(TestUtil.getAllSet().toByteArray(), 16));
    input.setSizeLimit(16);

    try {
      TestAllTypes.parseFrom(input);
      fail("Should have thrown an exception!");
    } catch (InvalidProtocolBufferException expected) {
      checkSizeLimitExceeded(expected);
    }
  }

  public void testResetSizeCounter() throws Exception {
    // NOTE: Size limit only applies to the stream-backed CIS.
    CodedInputStream input =
        CodedInputStream.newInstance(new SmallBlockInputStream(new byte[256], 8));
    input.setSizeLimit(16);
    input.readRawBytes(16);
    assertEquals(16, input.getTotalBytesRead());

    try {
      input.readRawByte();
      fail("Should have thrown an exception!");
    } catch (InvalidProtocolBufferException expected) {
      checkSizeLimitExceeded(expected);
    }

    input.resetSizeCounter();
    assertEquals(0, input.getTotalBytesRead());
    input.readRawByte(); // No exception thrown.
    input.resetSizeCounter();
    assertEquals(0, input.getTotalBytesRead());
    input.readRawBytes(16);
    assertEquals(16, input.getTotalBytesRead());
    input.resetSizeCounter();

    try {
      input.readRawBytes(17); // Hits limit again.
      fail("Should have thrown an exception!");
    } catch (InvalidProtocolBufferException expected) {
      checkSizeLimitExceeded(expected);
    }
  }
  
  public void testRefillBufferWithCorrectSize() throws Exception {
    // NOTE: refillBuffer only applies to the stream-backed CIS.
    byte[] bytes = "123456789".getBytes("UTF-8");
    ByteArrayOutputStream rawOutput = new ByteArrayOutputStream();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput, bytes.length);

    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
    output.writeRawVarint32(tag);
    output.writeRawVarint32(bytes.length);
    output.writeRawBytes(bytes);
    output.writeRawVarint32(tag);
    output.writeRawVarint32(bytes.length);
    output.writeRawBytes(bytes);
    output.writeRawByte(4);
    output.flush();

    // Input is two string with length 9 and one raw byte.
    byte[] rawInput = rawOutput.toByteArray(); 
    for (int inputStreamBufferLength = 8; 
        inputStreamBufferLength <= rawInput.length + 1; inputStreamBufferLength++) {
      CodedInputStream input = CodedInputStream.newInstance(
              new ByteArrayInputStream(rawInput), inputStreamBufferLength);
      input.setSizeLimit(rawInput.length - 1);
      input.readString();
      input.readString(); 
      try {
        input.readRawByte(); // Hits limit.
        fail("Should have thrown an exception!");
      } catch (InvalidProtocolBufferException expected) {
        checkSizeLimitExceeded(expected);
      }
    }
  }

  public void testIsAtEnd() throws Exception {
    CodedInputStream input = CodedInputStream.newInstance(
        new ByteArrayInputStream(new byte[5]));
    try {   
      for (int i = 0; i < 5; i++) {
        assertEquals(false, input.isAtEnd());
        input.readRawByte();
      }
      assertEquals(true, input.isAtEnd());
    } catch (Exception e) {
      fail("Catch exception in the testIsAtEnd");
    }
  }

  public void testCurrentLimitExceeded() throws Exception {
    byte[] bytes = "123456789".getBytes("UTF-8");
    ByteArrayOutputStream rawOutput = new ByteArrayOutputStream();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput, bytes.length);

    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
    output.writeRawVarint32(tag);
    output.writeRawVarint32(bytes.length);
    output.writeRawBytes(bytes);
    output.flush();

    byte[] rawInput = rawOutput.toByteArray();
    CodedInputStream input = CodedInputStream.newInstance(
              new ByteArrayInputStream(rawInput));
    // The length of the whole rawInput
    input.setSizeLimit(11);
    // Some number that is smaller than the rawInput's length
    // but larger than 2 
    input.pushLimit(5);
    try {
      input.readString();
      fail("Should have thrown an exception");
    } catch (InvalidProtocolBufferException expected) {
      assertEquals(expected.getMessage(), 
          InvalidProtocolBufferException.truncatedMessage().getMessage());
    }
  }

  public void testSizeLimitMultipleMessages() throws Exception {
    // NOTE: Size limit only applies to the stream-backed CIS.
    byte[] bytes = new byte[256];
    for (int i = 0; i < bytes.length; i++) {
      bytes[i] = (byte) i;
    }
    CodedInputStream input = CodedInputStream.newInstance(new SmallBlockInputStream(bytes, 7));
    input.setSizeLimit(16);
    for (int i = 0; i < 256 / 16; i++) {
      byte[] message = input.readRawBytes(16);
      for (int j = 0; j < message.length; j++) {
        assertEquals(i * 16 + j, message[j] & 0xff);
      }
      assertEquals(16, input.getTotalBytesRead());
      input.resetSizeCounter();
      assertEquals(0, input.getTotalBytesRead());
    }
  }

  public void testReadString() throws Exception {
    String lorem = "Lorem ipsum dolor sit amet ";
    StringBuilder builder = new StringBuilder();
    for (int i = 0; i < 4096; i += lorem.length()) {
      builder.append(lorem);
    }
    lorem = builder.toString().substring(0, 4096);
    byte[] bytes = lorem.getBytes("UTF-8");
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput, bytes.length);

    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
    output.writeRawVarint32(tag);
    output.writeRawVarint32(bytes.length);
    output.writeRawBytes(bytes);
    output.flush();

    byte[] rawInput = rawOutput.toByteString().toByteArray();
    for (InputType inputType : InputType.values()) {
      CodedInputStream input = inputType.newDecoder(rawInput);
      assertEquals(inputType.name(), tag, input.readTag());
      String text = input.readString();
      assertEquals(inputType.name(), lorem, text);
    }
  }

  public void testReadStringRequireUtf8() throws Exception {
    String lorem = "Lorem ipsum dolor sit amet ";
    StringBuilder builder = new StringBuilder();
    for (int i = 0; i < 4096; i += lorem.length()) {
      builder.append(lorem);
    }
    lorem = builder.toString().substring(0, 4096);
    byte[] bytes = lorem.getBytes("UTF-8");
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput, bytes.length);

    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
    output.writeRawVarint32(tag);
    output.writeRawVarint32(bytes.length);
    output.writeRawBytes(bytes);
    output.flush();

    byte[] rawInput = rawOutput.toByteString().toByteArray();
    for (InputType inputType : InputType.values()) {
      CodedInputStream input = inputType.newDecoder(rawInput);
      assertEquals(inputType.name(), tag, input.readTag());
      String text = input.readStringRequireUtf8();
      assertEquals(inputType.name(), lorem, text);
    }
  }

  /**
   * Tests that if we readString invalid UTF-8 bytes, no exception is thrown. Instead, the invalid
   * bytes are replaced with the Unicode "replacement character" U+FFFD.
   */
  public void testReadStringInvalidUtf8() throws Exception {
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);

    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
    output.writeRawVarint32(tag);
    output.writeRawVarint32(1);
    output.writeRawBytes(new byte[] {(byte) 0x80});
    output.flush();

    byte[] rawInput = rawOutput.toByteString().toByteArray();
    for (InputType inputType : InputType.values()) {
      CodedInputStream input = inputType.newDecoder(rawInput);
      assertEquals(inputType.name(), tag, input.readTag());
      String text = input.readString();
      assertEquals(inputType.name(), 0xfffd, text.charAt(0));
    }
  }

  /**
   * Tests that if we readStringRequireUtf8 invalid UTF-8 bytes, an InvalidProtocolBufferException
   * is thrown.
   */
  public void testReadStringRequireUtf8InvalidUtf8() throws Exception {
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);

    int tag = WireFormat.makeTag(1, WireFormat.WIRETYPE_LENGTH_DELIMITED);
    output.writeRawVarint32(tag);
    output.writeRawVarint32(1);
    output.writeRawBytes(new byte[] {(byte) 0x80});
    output.flush();

    byte[] rawInput = rawOutput.toByteString().toByteArray();
    for (InputType inputType : InputType.values()) {
      CodedInputStream input = inputType.newDecoder(rawInput);
      assertEquals(tag, input.readTag());
      try {
        input.readStringRequireUtf8();
        fail(inputType.name() + ": Expected invalid UTF-8 exception.");
      } catch (InvalidProtocolBufferException exception) {
        assertEquals(
            inputType.name(), "Protocol message had invalid UTF-8.", exception.getMessage());
      }
    }
  }

  public void testReadFromSlice() throws Exception {
    byte[] bytes = bytes(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
    CodedInputStream in = CodedInputStream.newInstance(bytes, 3, 5);
    assertEquals(0, in.getTotalBytesRead());
    for (int i = 3; i < 8; i++) {
      assertEquals(i, in.readRawByte());
      assertEquals(i - 2, in.getTotalBytesRead());
    }
    // eof
    assertEquals(0, in.readTag());
    assertEquals(5, in.getTotalBytesRead());
  }

  public void testInvalidTag() throws Exception {
    // Any tag number which corresponds to field number zero is invalid and
    // should throw InvalidProtocolBufferException.
    for (InputType inputType : InputType.values()) {
      for (int i = 0; i < 8; i++) {
        try {
          inputType.newDecoder(bytes(i)).readTag();
          fail(inputType.name() + ": Should have thrown an exception.");
        } catch (InvalidProtocolBufferException e) {
          assertEquals(
              inputType.name(),
              InvalidProtocolBufferException.invalidTag().getMessage(),
              e.getMessage());
        }
      }
    }
  }

  public void testReadByteArray() throws Exception {
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);
    // Zero-sized bytes field.
    output.writeRawVarint32(0);
    // One one-byte bytes field
    output.writeRawVarint32(1);
    output.writeRawBytes(new byte[] {(byte) 23});
    // Another one-byte bytes field
    output.writeRawVarint32(1);
    output.writeRawBytes(new byte[] {(byte) 45});
    // A bytes field large enough that won't fit into the 4K buffer.
    final int bytesLength = 16 * 1024;
    byte[] bytes = new byte[bytesLength];
    bytes[0] = (byte) 67;
    bytes[bytesLength - 1] = (byte) 89;
    output.writeRawVarint32(bytesLength);
    output.writeRawBytes(bytes);

    output.flush();

    byte[] rawInput = rawOutput.toByteString().toByteArray();
    for (InputType inputType : InputType.values()) {
      CodedInputStream inputStream = inputType.newDecoder(rawInput);

      byte[] result = inputStream.readByteArray();
      assertEquals(inputType.name(), 0, result.length);
      result = inputStream.readByteArray();
      assertEquals(inputType.name(), 1, result.length);
      assertEquals(inputType.name(), (byte) 23, result[0]);
      result = inputStream.readByteArray();
      assertEquals(inputType.name(), 1, result.length);
      assertEquals(inputType.name(), (byte) 45, result[0]);
      result = inputStream.readByteArray();
      assertEquals(inputType.name(), bytesLength, result.length);
      assertEquals(inputType.name(), (byte) 67, result[0]);
      assertEquals(inputType.name(), (byte) 89, result[bytesLength - 1]);
    }
  }

  public void testReadLargeByteStringFromInputStream() throws Exception {
    byte[] bytes = new byte[1024 * 1024];
    for (int i = 0; i < bytes.length; i++) {
      bytes[i] = (byte) (i & 0xFF);
    }
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);
    output.writeRawVarint32(bytes.length);
    output.writeRawBytes(bytes);
    output.flush();
    byte[] data = rawOutput.toByteString().toByteArray();

    CodedInputStream input = CodedInputStream.newInstance(
        new ByteArrayInputStream(data) {
          @Override
          public synchronized int available() {
            return 0;
          }
        });
    ByteString result = input.readBytes();
    assertEquals(ByteString.copyFrom(bytes), result);
  }

  public void testReadLargeByteArrayFromInputStream() throws Exception {
    byte[] bytes = new byte[1024 * 1024];
    for (int i = 0; i < bytes.length; i++) {
      bytes[i] = (byte) (i & 0xFF);
    }
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);
    output.writeRawVarint32(bytes.length);
    output.writeRawBytes(bytes);
    output.flush();
    byte[] data = rawOutput.toByteString().toByteArray();

    CodedInputStream input = CodedInputStream.newInstance(
        new ByteArrayInputStream(data) {
          @Override
          public synchronized int available() {
            return 0;
          }
        });
    byte[] result = input.readByteArray();
    assertTrue(Arrays.equals(bytes, result));
  }

  public void testReadByteBuffer() throws Exception {
    ByteString.Output rawOutput = ByteString.newOutput();
    CodedOutputStream output = CodedOutputStream.newInstance(rawOutput);
    // Zero-sized bytes field.
    output.writeRawVarint32(0);
    // One one-byte bytes field
    output.writeRawVarint32(1);
    output.writeRawBytes(new byte[] {(byte) 23});
    // Another one-byte bytes field
    output.writeRawVarint32(1);
    output.writeRawBytes(new byte[] {(byte) 45});
    // A bytes field large enough that won't fit into the 4K buffer.
    final int bytesLength = 16 * 1024;
    byte[] bytes = new byte[bytesLength];
    bytes[0] = (byte) 67;
    bytes[bytesLength - 1] = (byte) 89;
    output.writeRawVarint32(bytesLength);
    output.writeRawBytes(bytes);

    output.flush();

    byte[] rawInput = rawOutput.toByteString().toByteArray();
    for (InputType inputType : InputType.values()) {
      CodedInputStream inputStream = inputType.newDecoder(rawInput);

      ByteBuffer result = inputStream.readByteBuffer();
      assertEquals(inputType.name(), 0, result.capacity());
      result = inputStream.readByteBuffer();
      assertEquals(inputType.name(), 1, result.capacity());
      assertEquals(inputType.name(), (byte) 23, result.get());
      result = inputStream.readByteBuffer();
      assertEquals(inputType.name(), 1, result.capacity());
      assertEquals(inputType.name(), (byte) 45, result.get());
      result = inputStream.readByteBuffer();
      assertEquals(inputType.name(), bytesLength, result.capacity());
      assertEquals(inputType.name(), (byte) 67, result.get());
      result.position(bytesLength - 1);
      assertEquals(inputType.name(), (byte) 89, result.get());
    }
  }

  public void testReadByteBufferAliasing() throws Exception {
    ByteArrayOutputStream byteArrayStream = new ByteArrayOutputStream();
    CodedOutputStream output = CodedOutputStream.newInstance(byteArrayStream);
    // Zero-sized bytes field.
    output.writeRawVarint32(0);
    // One one-byte bytes field
    output.writeRawVarint32(1);
    output.writeRawBytes(new byte[] {(byte) 23});
    // Another one-byte bytes field
    output.writeRawVarint32(1);
    output.writeRawBytes(new byte[] {(byte) 45});
    // A bytes field large enough that won't fit into the 4K buffer.
    final int bytesLength = 16 * 1024;
    byte[] bytes = new byte[bytesLength];
    bytes[0] = (byte) 67;
    bytes[bytesLength - 1] = (byte) 89;
    output.writeRawVarint32(bytesLength);
    output.writeRawBytes(bytes);
    output.flush();

    byte[] data = byteArrayStream.toByteArray();

    for (InputType inputType : InputType.values()) {
      if (inputType == InputType.STREAM 
          || inputType == InputType.STREAM_ITER_DIRECT 
          || inputType == InputType.ITER_DIRECT) {
        // Aliasing doesn't apply to stream-backed CIS.
        continue;
      }

      // Without aliasing
      CodedInputStream inputStream = inputType.newDecoder(data);
      ByteBuffer result = inputStream.readByteBuffer();
      assertEquals(inputType.name(), 0, result.capacity());
      result = inputStream.readByteBuffer();
      assertTrue(inputType.name(), result.array() != data);
      assertEquals(inputType.name(), 1, result.capacity());
      assertEquals(inputType.name(), (byte) 23, result.get());
      result = inputStream.readByteBuffer();
      assertTrue(inputType.name(), result.array() != data);
      assertEquals(inputType.name(), 1, result.capacity());
      assertEquals(inputType.name(), (byte) 45, result.get());
      result = inputStream.readByteBuffer();
      assertTrue(inputType.name(), result.array() != data);
      assertEquals(inputType.name(), bytesLength, result.capacity());
      assertEquals(inputType.name(), (byte) 67, result.get());
      result.position(bytesLength - 1);
      assertEquals(inputType.name(), (byte) 89, result.get());

      // Enable aliasing
      inputStream = inputType.newDecoder(data, data.length);
      inputStream.enableAliasing(true);
      result = inputStream.readByteBuffer();
      assertEquals(inputType.name(), 0, result.capacity());
      result = inputStream.readByteBuffer();
      if (result.hasArray()) {
        assertTrue(inputType.name(), result.array() == data);
      }
      assertEquals(inputType.name(), 1, result.capacity());
      assertEquals(inputType.name(), (byte) 23, result.get());
      result = inputStream.readByteBuffer();
      if (result.hasArray()) {
        assertTrue(inputType.name(), result.array() == data);
      }
      assertEquals(inputType.name(), 1, result.capacity());
      assertEquals(inputType.name(), (byte) 45, result.get());
      result = inputStream.readByteBuffer();
      if (result.hasArray()) {
        assertTrue(inputType.name(), result.array() == data);
      }
      assertEquals(inputType.name(), bytesLength, result.capacity());
      assertEquals(inputType.name(), (byte) 67, result.get());
      result.position(bytesLength - 1);
      assertEquals(inputType.name(), (byte) 89, result.get());
    }
  }

  public void testCompatibleTypes() throws Exception {
    long data = 0x100000000L;
    Int64Message message = Int64Message.newBuilder().setData(data).build();
    byte[] serialized = message.toByteArray();
    for (InputType inputType : InputType.values()) {
      CodedInputStream inputStream = inputType.newDecoder(serialized);

      // Test int64(long) is compatible with bool(boolean)
      BoolMessage msg2 = BoolMessage.parseFrom(inputStream);
      assertTrue(msg2.getData());

      // Test int64(long) is compatible with int32(int)
      inputStream = inputType.newDecoder(serialized);
      Int32Message msg3 = Int32Message.parseFrom(inputStream);
      assertEquals((int) data, msg3.getData());
    }
  }

  public void testSkipInvalidVarint_FastPath() throws Exception {
    // Fast path: We have >= 10 bytes available. Ensure we properly recognize a non-ending varint.
    byte[] data = new byte[] {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0};
    for (InputType inputType : InputType.values()) {
      try {
        CodedInputStream input = inputType.newDecoder(data);
        input.skipField(WireFormat.makeTag(1, WireFormat.WIRETYPE_VARINT));
        fail(inputType.name() + ": Should have thrown an exception.");
      } catch (InvalidProtocolBufferException e) {
        // Expected
      }
    }
  }

  public void testSkipInvalidVarint_SlowPath() throws Exception {
    // Slow path: < 10 bytes available. Ensure we properly recognize a non-ending varint.
    byte[] data = new byte[] {-1, -1, -1, -1, -1, -1, -1, -1, -1};
    for (InputType inputType : InputType.values()) {
      try {
        CodedInputStream input = inputType.newDecoder(data);
        input.skipField(WireFormat.makeTag(1, WireFormat.WIRETYPE_VARINT));
        fail(inputType.name() + ": Should have thrown an exception.");
      } catch (InvalidProtocolBufferException e) {
        // Expected
      }
    }
  }
}