Update //third_party/protobuf to version 3.

third_party/protobuf/java/src/main/java/com/google/protobuf/ByteString.java

Index: third_party/protobuf/java/src/main/java/com/google/protobuf/ByteString.java
diff --git a/third_party/protobuf/java/src/main/java/com/google/protobuf/ByteString.java b/third_party/protobuf/java/src/main/java/com/google/protobuf/ByteString.java
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@@ -0,0 +1,1152 @@
+// 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,
+// 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;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.Serializable;
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
+import java.nio.charset.UnsupportedCharsetException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+/**
+ * Immutable sequence of bytes.  Substring is supported by sharing the reference
+ * to the immutable underlying bytes, as with {@link String}.  Concatenation is
+ * likewise supported without copying (long strings) by building a tree of
+ * pieces in {@link RopeByteString}.
+ * <p>
+ * Like {@link String}, the contents of a {@link ByteString} can never be
+ * observed to change, not even in the presence of a data race or incorrect
+ * API usage in the client code.
+ *
+ * @author crazybob@google.com Bob Lee
+ * @author kenton@google.com Kenton Varda
+ * @author carlanton@google.com Carl Haverl
+ * @author martinrb@google.com Martin Buchholz
+ */
+public abstract class ByteString implements Iterable<Byte>, Serializable {
+
+  /**
+   * When two strings to be concatenated have a combined length shorter than
+   * this, we just copy their bytes on {@link #concat(ByteString)}.
+   * The trade-off is copy size versus the overhead of creating tree nodes
+   * in {@link RopeByteString}.
+   */
+  static final int CONCATENATE_BY_COPY_SIZE = 128;
+
+  /**
+   * When copying an InputStream into a ByteString with .readFrom(),
+   * the chunks in the underlying rope start at 256 bytes, but double
+   * each iteration up to 8192 bytes.
+   */
+  static final int MIN_READ_FROM_CHUNK_SIZE = 0x100;  // 256b
+  static final int MAX_READ_FROM_CHUNK_SIZE = 0x2000;  // 8k
+
+  /**
+   * Empty {@code ByteString}.
+   */
+  public static final ByteString EMPTY = new LiteralByteString(new byte[0]);
+
+  /**
+   * Cached hash value. Intentionally accessed via a data race, which
+   * is safe because of the Java Memory Model's "no out-of-thin-air values"
+   * guarantees for ints. A value of 0 implies that the hash has not been set.
+   */
+  private int hash = 0;
+
+  // This constructor is here to prevent subclassing outside of this package,
+  ByteString() {}
+
+  /**
+   * Gets the byte at the given index. This method should be used only for
+   * random access to individual bytes. To access bytes sequentially, use the
+   * {@link ByteIterator} returned by {@link #iterator()}, and call {@link
+   * #substring(int, int)} first if necessary.
+   *
+   * @param index index of byte
+   * @return the value
+   * @throws ArrayIndexOutOfBoundsException {@code index < 0 or index >= size}
+   */
+  public abstract byte byteAt(int index);
+
+  /**
+   * Return a {@link ByteString.ByteIterator} over the bytes in the ByteString.
+   * To avoid auto-boxing, you may get the iterator manually and call
+   * {@link ByteIterator#nextByte()}.
+   *
+   * @return the iterator
+   */
+  @Override
+  public final ByteIterator iterator() {
+    return new ByteIterator() {
+      private int position = 0;
+      private final int limit = size();
+
+      @Override
+      public boolean hasNext() {
+        return position < limit;
+      }
+
+      @Override
+      public Byte next() {
+        // Boxing calls Byte.valueOf(byte), which does not instantiate.
+        return nextByte();
+      }
+
+      @Override
+      public byte nextByte() {
+        try {
+          return byteAt(position++);
+        } catch (ArrayIndexOutOfBoundsException e) {
+          throw new NoSuchElementException(e.getMessage());
+        }
+      }
+
+      @Override
+      public void remove() {
+        throw new UnsupportedOperationException();
+      }
+    };
+  }
+
+  /**
+   * This interface extends {@code Iterator<Byte>}, so that we can return an
+   * unboxed {@code byte}.
+   */
+  public interface ByteIterator extends Iterator<Byte> {
+    /**
+     * An alternative to {@link Iterator#next()} that returns an
+     * unboxed primitive {@code byte}.
+     *
+     * @return the next {@code byte} in the iteration
+     * @throws NoSuchElementException if the iteration has no more elements
+     */
+    byte nextByte();
+  }
+
+  /**
+   * Gets the number of bytes.
+   *
+   * @return size in bytes
+   */
+  public abstract int size();
+
+  /**
+   * Returns {@code true} if the size is {@code 0}, {@code false} otherwise.
+   *
+   * @return true if this is zero bytes long
+   */
+  public final boolean isEmpty() {
+    return size() == 0;
+  }
+
+  // =================================================================
+  // ByteString -> substring
+
+  /**
+   * Return the substring from {@code beginIndex}, inclusive, to the end of the
+   * string.
+   *
+   * @param beginIndex start at this index
+   * @return substring sharing underlying data
+   * @throws IndexOutOfBoundsException if {@code beginIndex < 0} or
+   *     {@code beginIndex > size()}.
+   */
+  public final ByteString substring(int beginIndex) {
+    return substring(beginIndex, size());
+  }
+
+  /**
+   * Return the substring from {@code beginIndex}, inclusive, to {@code
+   * endIndex}, exclusive.
+   *
+   * @param beginIndex start at this index
+   * @param endIndex   the last character is the one before this index
+   * @return substring sharing underlying data
+   * @throws IndexOutOfBoundsException if {@code beginIndex < 0},
+   *     {@code endIndex > size()}, or {@code beginIndex > endIndex}.
+   */
+  public abstract ByteString substring(int beginIndex, int endIndex);
+
+  /**
+   * Tests if this bytestring starts with the specified prefix.
+   * Similar to {@link String#startsWith(String)}
+   *
+   * @param prefix the prefix.
+   * @return <code>true</code> if the byte sequence represented by the
+   *         argument is a prefix of the byte sequence represented by
+   *         this string; <code>false</code> otherwise.
+   */
+  public final boolean startsWith(ByteString prefix) {
+    return size() >= prefix.size() &&
+           substring(0, prefix.size()).equals(prefix);
+  }
+
+  /**
+   * Tests if this bytestring ends with the specified suffix.
+   * Similar to {@link String#endsWith(String)}
+   *
+   * @param suffix the suffix.
+   * @return <code>true</code> if the byte sequence represented by the
+   *         argument is a suffix of the byte sequence represented by
+   *         this string; <code>false</code> otherwise.
+   */
+  public final boolean endsWith(ByteString suffix) {
+    return size() >= suffix.size() &&
+        substring(size() - suffix.size()).equals(suffix);
+  }
+
+  // =================================================================
+  // byte[] -> ByteString
+
+  /**
+   * Copies the given bytes into a {@code ByteString}.
+   *
+   * @param bytes source array
+   * @param offset offset in source array
+   * @param size number of bytes to copy
+   * @return new {@code ByteString}
+   */
+  public static ByteString copyFrom(byte[] bytes, int offset, int size) {
+    byte[] copy = new byte[size];
+    System.arraycopy(bytes, offset, copy, 0, size);
+    return new LiteralByteString(copy);
+  }
+
+  /**
+   * Copies the given bytes into a {@code ByteString}.
+   *
+   * @param bytes to copy
+   * @return new {@code ByteString}
+   */
+  public static ByteString copyFrom(byte[] bytes) {
+    return copyFrom(bytes, 0, bytes.length);
+  }
+
+  /**
+   * Copies the next {@code size} bytes from a {@code java.nio.ByteBuffer} into
+   * a {@code ByteString}.
+   *
+   * @param bytes source buffer
+   * @param size number of bytes to copy
+   * @return new {@code ByteString}
+   */
+  public static ByteString copyFrom(ByteBuffer bytes, int size) {
+    byte[] copy = new byte[size];
+    bytes.get(copy);
+    return new LiteralByteString(copy);
+  }
+
+  /**
+   * Copies the remaining bytes from a {@code java.nio.ByteBuffer} into
+   * a {@code ByteString}.
+   *
+   * @param bytes sourceBuffer
+   * @return new {@code ByteString}
+   */
+  public static ByteString copyFrom(ByteBuffer bytes) {
+    return copyFrom(bytes, bytes.remaining());
+  }
+
+  /**
+   * Encodes {@code text} into a sequence of bytes using the named charset
+   * and returns the result as a {@code ByteString}.
+   *
+   * @param text source string
+   * @param charsetName encoding to use
+   * @return new {@code ByteString}
+   * @throws UnsupportedEncodingException if the encoding isn't found
+   */
+  public static ByteString copyFrom(String text, String charsetName)
+      throws UnsupportedEncodingException {
+    return new LiteralByteString(text.getBytes(charsetName));
+  }
+
+  /**
+   * Encodes {@code text} into a sequence of bytes using the named charset
+   * and returns the result as a {@code ByteString}.
+   *
+   * @param text source string
+   * @param charset encode using this charset
+   * @return new {@code ByteString}
+   */
+  public static ByteString copyFrom(String text, Charset charset) {
+    return new LiteralByteString(text.getBytes(charset));
+  }
+
+  /**
+   * Encodes {@code text} into a sequence of UTF-8 bytes and returns the
+   * result as a {@code ByteString}.
+   *
+   * @param text source string
+   * @return new {@code ByteString}
+   */
+  public static ByteString copyFromUtf8(String text) {
+    return new LiteralByteString(text.getBytes(Internal.UTF_8));
+  }
+
+  // =================================================================
+  // InputStream -> ByteString
+
+  /**
+   * Completely reads the given stream's bytes into a
+   * {@code ByteString}, blocking if necessary until all bytes are
+   * read through to the end of the stream.
+   *
+   * <b>Performance notes:</b> The returned {@code ByteString} is an
+   * immutable tree of byte arrays ("chunks") of the stream data.  The
+   * first chunk is small, with subsequent chunks each being double
+   * the size, up to 8K.
+   * 
+   * <p>Each byte read from the input stream will be copied twice to ensure
+   * that the resulting ByteString is truly immutable.
+   *
+   * @param streamToDrain The source stream, which is read completely
+   *     but not closed.
+   * @return A new {@code ByteString} which is made up of chunks of
+   *     various sizes, depending on the behavior of the underlying
+   *     stream.
+   * @throws IOException IOException is thrown if there is a problem
+   *     reading the underlying stream.
+   */
+  public static ByteString readFrom(InputStream streamToDrain)
+      throws IOException {
+    return readFrom(streamToDrain, MIN_READ_FROM_CHUNK_SIZE, MAX_READ_FROM_CHUNK_SIZE);
+  }
+
+  /**
+   * Completely reads the given stream's bytes into a
+   * {@code ByteString}, blocking if necessary until all bytes are
+   * read through to the end of the stream.
+   *
+   * <b>Performance notes:</b> The returned {@code ByteString} is an
+   * immutable tree of byte arrays ("chunks") of the stream data.  The
+   * chunkSize parameter sets the size of these byte arrays.
+   *
+   * <p>Each byte read from the input stream will be copied twice to ensure
+   * that the resulting ByteString is truly immutable.
+   *
+   * @param streamToDrain The source stream, which is read completely
+   *     but not closed.
+   * @param chunkSize The size of the chunks in which to read the
+   *     stream.
+   * @return A new {@code ByteString} which is made up of chunks of
+   *     the given size.
+   * @throws IOException IOException is thrown if there is a problem
+   *     reading the underlying stream.
+   */
+  public static ByteString readFrom(InputStream streamToDrain, int chunkSize)
+      throws IOException {
+    return readFrom(streamToDrain, chunkSize, chunkSize);
+  }
+
+  // Helper method that takes the chunk size range as a parameter.
+  public static ByteString readFrom(InputStream streamToDrain, int minChunkSize,
+      int maxChunkSize) throws IOException {
+    Collection<ByteString> results = new ArrayList<ByteString>();
+
+    // copy the inbound bytes into a list of chunks; the chunk size
+    // grows exponentially to support both short and long streams.
+    int chunkSize = minChunkSize;
+    while (true) {
+      ByteString chunk = readChunk(streamToDrain, chunkSize);
+      if (chunk == null) {
+        break;
+      }
+      results.add(chunk);
+      chunkSize = Math.min(chunkSize * 2, maxChunkSize);
+    }
+
+    return ByteString.copyFrom(results);
+  }
+
+  /**
+   * Blocks until a chunk of the given size can be made from the
+   * stream, or EOF is reached.  Calls read() repeatedly in case the
+   * given stream implementation doesn't completely fill the given
+   * buffer in one read() call.
+   *
+   * @return A chunk of the desired size, or else a chunk as large as
+   * was available when end of stream was reached. Returns null if the
+   * given stream had no more data in it.
+   */
+  private static ByteString readChunk(InputStream in, final int chunkSize)
+      throws IOException {
+      final byte[] buf = new byte[chunkSize];
+      int bytesRead = 0;
+      while (bytesRead < chunkSize) {
+        final int count = in.read(buf, bytesRead, chunkSize - bytesRead);
+        if (count == -1) {
+          break;
+        }
+        bytesRead += count;
+      }
+
+      if (bytesRead == 0) {
+        return null;
+      }
+
+      // Always make a copy since InputStream could steal a reference to buf.
+      return ByteString.copyFrom(buf, 0, bytesRead);
+  }
+
+  // =================================================================
+  // Multiple ByteStrings -> One ByteString
+
+  /**
+   * Concatenate the given {@code ByteString} to this one. Short concatenations,
+   * of total size smaller than {@link ByteString#CONCATENATE_BY_COPY_SIZE}, are
+   * produced by copying the underlying bytes (as per Rope.java, <a
+   * href="http://www.cs.ubc.ca/local/reading/proceedings/spe91-95/spe/vol25/issue12/spe986.pdf">
+   * BAP95 </a>. In general, the concatenate involves no copying.
+   *
+   * @param other string to concatenate
+   * @return a new {@code ByteString} instance
+   */
+  public final ByteString concat(ByteString other) {
+    if (Integer.MAX_VALUE - size() < other.size()) {
+      throw new IllegalArgumentException("ByteString would be too long: " +
+          size() + "+" + other.size());
+    }
+
+    return RopeByteString.concatenate(this, other);
+  }
+
+  /**
+   * Concatenates all byte strings in the iterable and returns the result.
+   * This is designed to run in O(list size), not O(total bytes).
+   *
+   * <p>The returned {@code ByteString} is not necessarily a unique object.
+   * If the list is empty, the returned object is the singleton empty
+   * {@code ByteString}.  If the list has only one element, that
+   * {@code ByteString} will be returned without copying.
+   *
+   * @param byteStrings strings to be concatenated
+   * @return new {@code ByteString}
+   */
+  public static ByteString copyFrom(Iterable<ByteString> byteStrings) {
+    // Determine the size;
+    final int size;
+    if (!(byteStrings instanceof Collection)) {
+      int tempSize = 0;
+      for (Iterator<ByteString> iter = byteStrings.iterator(); iter.hasNext();
+          iter.next(), ++tempSize) {
+      }
+      size = tempSize;
+    } else {
+      size = ((Collection<ByteString>) byteStrings).size();
+    }
+
+    if (size == 0) {
+      return EMPTY;
+    }
+
+    return balancedConcat(byteStrings.iterator(), size);
+  }
+
+  // Internal function used by copyFrom(Iterable<ByteString>).
+  // Create a balanced concatenation of the next "length" elements from the
+  // iterable.
+  private static ByteString balancedConcat(Iterator<ByteString> iterator, int length) {
+    assert length >= 1;
+    ByteString result;
+    if (length == 1) {
+      result = iterator.next();
+    } else {
+      int halfLength = length >>> 1;
+      ByteString left = balancedConcat(iterator, halfLength);
+      ByteString right = balancedConcat(iterator, length - halfLength);
+      result = left.concat(right);
+    }
+    return result;
+  }
+
+  // =================================================================
+  // ByteString -> byte[]
+
+  /**
+   * Copies bytes into a buffer at the given offset.
+   *
+   * @param target buffer to copy into
+   * @param offset in the target buffer
+   * @throws IndexOutOfBoundsException if the offset is negative or too large
+   */
+  public void copyTo(byte[] target, int offset) {
+    copyTo(target, 0, offset, size());
+  }
+
+  /**
+   * Copies bytes into a buffer.
+   *
+   * @param target       buffer to copy into
+   * @param sourceOffset offset within these bytes
+   * @param targetOffset offset within the target buffer
+   * @param numberToCopy number of bytes to copy
+   * @throws IndexOutOfBoundsException if an offset or size is negative or too
+   *     large
+   */
+  public final void copyTo(byte[] target, int sourceOffset, int targetOffset,
+      int numberToCopy) {
+    checkRange(sourceOffset, sourceOffset + numberToCopy, size());
+    checkRange(targetOffset, targetOffset + numberToCopy, target.length);
+    if (numberToCopy > 0) {
+      copyToInternal(target, sourceOffset, targetOffset, numberToCopy);
+    }
+  }
+
+  /**
+   * Internal (package private) implementation of
+   * {@link #copyTo(byte[],int,int,int)}.
+   * It assumes that all error checking has already been performed and that
+   * {@code numberToCopy > 0}.
+   */
+  protected abstract void copyToInternal(byte[] target, int sourceOffset,
+      int targetOffset, int numberToCopy);
+
+  /**
+   * Copies bytes into a ByteBuffer.
+   *
+   * @param target ByteBuffer to copy into.
+   * @throws java.nio.ReadOnlyBufferException if the {@code target} is read-only
+   * @throws java.nio.BufferOverflowException if the {@code target}'s
+   *     remaining() space is not large enough to hold the data.
+   */
+  public abstract void copyTo(ByteBuffer target);
+
+  /**
+   * Copies bytes to a {@code byte[]}.
+   *
+   * @return copied bytes
+   */
+  public final byte[] toByteArray() {
+    final int size = size();
+    if (size == 0) {
+      return Internal.EMPTY_BYTE_ARRAY;
+    }
+    byte[] result = new byte[size];
+    copyToInternal(result, 0, 0, size);
+    return result;
+  }
+
+  /**
+   * Writes the complete contents of this byte string to
+   * the specified output stream argument.
+   *
+   * <p>It is assumed that the {@link OutputStream} will not modify the contents passed it
+   * it. It may be possible for a malicious {@link OutputStream} to corrupt
+   * the data underlying the {@link ByteString}.
+   *
+   * @param  out  the output stream to which to write the data.
+   * @throws IOException  if an I/O error occurs.
+   */
+  public abstract void writeTo(OutputStream out) throws IOException;
+
+  /**
+   * Writes a specified part of this byte string to an output stream.
+   *
+   * @param  out  the output stream to which to write the data.
+   * @param  sourceOffset offset within these bytes
+   * @param  numberToWrite number of bytes to write
+   * @throws IOException  if an I/O error occurs.
+   * @throws IndexOutOfBoundsException if an offset or size is negative or too
+   *     large
+   */
+  final void writeTo(OutputStream out, int sourceOffset, int numberToWrite)
+      throws IOException {
+    checkRange(sourceOffset, sourceOffset + numberToWrite, size());
+    if (numberToWrite > 0) {
+      writeToInternal(out, sourceOffset, numberToWrite);
+    }
+  }
+
+  /**
+   * Internal version of {@link #writeTo(OutputStream,int,int)} that assumes
+   * all error checking has already been done.
+   */
+  abstract void writeToInternal(OutputStream out, int sourceOffset, int numberToWrite)
+      throws IOException;
+
+  /**
+   * Constructs a read-only {@code java.nio.ByteBuffer} whose content
+   * is equal to the contents of this byte string.
+   * The result uses the same backing array as the byte string, if possible.
+   *
+   * @return wrapped bytes
+   */
+  public abstract ByteBuffer asReadOnlyByteBuffer();
+
+  /**
+   * Constructs a list of read-only {@code java.nio.ByteBuffer} objects
+   * such that the concatenation of their contents is equal to the contents
+   * of this byte string.  The result uses the same backing arrays as the
+   * byte string.
+   * <p>
+   * By returning a list, implementations of this method may be able to avoid
+   * copying even when there are multiple backing arrays.
+   *
+   * @return a list of wrapped bytes
+   */
+  public abstract List<ByteBuffer> asReadOnlyByteBufferList();
+
+  /**
+   * Constructs a new {@code String} by decoding the bytes using the
+   * specified charset.
+   *
+   * @param charsetName encode using this charset
+   * @return new string
+   * @throws UnsupportedEncodingException if charset isn't recognized
+   */
+  public final String toString(String charsetName)
+      throws UnsupportedEncodingException {
+    try {
+      return toString(Charset.forName(charsetName));
+    } catch (UnsupportedCharsetException e) {
+      UnsupportedEncodingException exception = new UnsupportedEncodingException(charsetName);
+      exception.initCause(e);
+      throw exception;
+    }
+  }
+
+  /**
+   * Constructs a new {@code String} by decoding the bytes using the
+   * specified charset. Returns the same empty String if empty.
+   *
+   * @param charset encode using this charset
+   * @return new string
+   */
+  public final String toString(Charset charset) {
+    return size() == 0 ? "" : toStringInternal(charset);
+  }
+
+  /**
+   * Constructs a new {@code String} by decoding the bytes using the
+   * specified charset.
+   *
+   * @param charset encode using this charset
+   * @return new string
+   */
+  protected abstract String toStringInternal(Charset charset);
+
+  // =================================================================
+  // UTF-8 decoding
+
+  /**
+   * Constructs a new {@code String} by decoding the bytes as UTF-8.
+   *
+   * @return new string using UTF-8 encoding
+   */
+  public final String toStringUtf8() {
+    return toString(Internal.UTF_8);
+  }
+
+  /**
+   * Tells whether this {@code ByteString} represents a well-formed UTF-8
+   * byte sequence, such that the original bytes can be converted to a
+   * String object and then round tripped back to bytes without loss.
+   *
+   * <p>More precisely, returns {@code true} whenever: <pre> {@code
+   * Arrays.equals(byteString.toByteArray(),
+   *     new String(byteString.toByteArray(), "UTF-8").getBytes("UTF-8"))
+   * }</pre>
+   *
+   * <p>This method returns {@code false} for "overlong" byte sequences,
+   * as well as for 3-byte sequences that would map to a surrogate
+   * character, in accordance with the restricted definition of UTF-8
+   * introduced in Unicode 3.1.  Note that the UTF-8 decoder included in
+   * Oracle's JDK has been modified to also reject "overlong" byte
+   * sequences, but (as of 2011) still accepts 3-byte surrogate
+   * character byte sequences.
+   *
+   * <p>See the Unicode Standard,<br>
+   * Table 3-6. <em>UTF-8 Bit Distribution</em>,<br>
+   * Table 3-7. <em>Well Formed UTF-8 Byte Sequences</em>.
+   *
+   * @return whether the bytes in this {@code ByteString} are a
+   * well-formed UTF-8 byte sequence
+   */
+  public abstract boolean isValidUtf8();
+
+  /**
+   * Tells whether the given byte sequence is a well-formed, malformed, or
+   * incomplete UTF-8 byte sequence.  This method accepts and returns a partial
+   * state result, allowing the bytes for a complete UTF-8 byte sequence to be
+   * composed from multiple {@code ByteString} segments.
+   *
+   * @param state either {@code 0} (if this is the initial decoding operation)
+   *     or the value returned from a call to a partial decoding method for the
+   *     previous bytes
+   * @param offset offset of the first byte to check
+   * @param length number of bytes to check
+   *
+   * @return {@code -1} if the partial byte sequence is definitely malformed,
+   * {@code 0} if it is well-formed (no additional input needed), or, if the
+   * byte sequence is "incomplete", i.e. apparently terminated in the middle of
+   * a character, an opaque integer "state" value containing enough information
+   * to decode the character when passed to a subsequent invocation of a
+   * partial decoding method.
+   */
+  protected abstract int partialIsValidUtf8(int state, int offset, int length);
+
+  // =================================================================
+  // equals() and hashCode()
+
+  @Override
+  public abstract boolean equals(Object o);
+
+  /**
+   * Base class for leaf {@link ByteString}s (i.e. non-ropes).
+   */
+  abstract static class LeafByteString extends ByteString {
+    @Override
+    protected final int getTreeDepth() {
+      return 0;
+    }
+
+    @Override
+    protected final boolean isBalanced() {
+      return true;
+    }
+
+    /**
+     * Check equality of the substring of given length of this object starting at
+     * zero with another {@code ByteString} substring starting at offset.
+     *
+     * @param other  what to compare a substring in
+     * @param offset offset into other
+     * @param length number of bytes to compare
+     * @return true for equality of substrings, else false.
+     */
+    abstract boolean equalsRange(ByteString other, int offset, int length);
+  }
+
+  /**
+   * Compute the hashCode using the traditional algorithm from {@link
+   * ByteString}.
+   *
+   * @return hashCode value
+   */
+  @Override
+  public final int hashCode() {
+    int h = hash;
+
+    if (h == 0) {
+      int size = size();
+      h = partialHash(size, 0, size);
+      if (h == 0) {
+        h = 1;
+      }
+      hash = h;
+    }
+    return h;
+  }
+
+  // =================================================================
+  // Input stream
+
+  /**
+   * Creates an {@code InputStream} which can be used to read the bytes.
+   * <p>
+   * The {@link InputStream} returned by this method is guaranteed to be
+   * completely non-blocking.  The method {@link InputStream#available()}
+   * returns the number of bytes remaining in the stream. The methods
+   * {@link InputStream#read(byte[])}, {@link InputStream#read(byte[],int,int)}
+   * and {@link InputStream#skip(long)} will read/skip as many bytes as are
+   * available.  The method {@link InputStream#markSupported()} returns
+   * {@code true}.
+   * <p>
+   * The methods in the returned {@link InputStream} might <b>not</b> be
+   * thread safe.
+   *
+   * @return an input stream that returns the bytes of this byte string.
+   */
+  public abstract InputStream newInput();
+
+  /**
+   * Creates a {@link CodedInputStream} which can be used to read the bytes.
+   * Using this is often more efficient than creating a {@link CodedInputStream}
+   * that wraps the result of {@link #newInput()}.
+   *
+   * @return stream based on wrapped data
+   */
+  public abstract CodedInputStream newCodedInput();
+
+  // =================================================================
+  // Output stream
+
+  /**
+   * Creates a new {@link Output} with the given initial capacity. Call {@link
+   * Output#toByteString()} to create the {@code ByteString} instance.
+   * <p>
+   * A {@link ByteString.Output} offers the same functionality as a
+   * {@link ByteArrayOutputStream}, except that it returns a {@link ByteString}
+   * rather than a {@code byte} array.
+   *
+   * @param initialCapacity estimate of number of bytes to be written
+   * @return {@code OutputStream} for building a {@code ByteString}
+   */
+  public static Output newOutput(int initialCapacity) {
+    return new Output(initialCapacity);
+  }
+
+  /**
+   * Creates a new {@link Output}. Call {@link Output#toByteString()} to create
+   * the {@code ByteString} instance.
+   * <p>
+   * A {@link ByteString.Output} offers the same functionality as a
+   * {@link ByteArrayOutputStream}, except that it returns a {@link ByteString}
+   * rather than a {@code byte array}.
+   *
+   * @return {@code OutputStream} for building a {@code ByteString}
+   */
+  public static Output newOutput() {
+    return new Output(CONCATENATE_BY_COPY_SIZE);
+  }
+
+  /**
+   * Outputs to a {@code ByteString} instance. Call {@link #toByteString()} to
+   * create the {@code ByteString} instance.
+   */
+  public static final class Output extends OutputStream {
+    // Implementation note.
+    // The public methods of this class must be synchronized.  ByteStrings
+    // are guaranteed to be immutable.  Without some sort of locking, it could
+    // be possible for one thread to call toByteSring(), while another thread
+    // is still modifying the underlying byte array.
+
+    private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
+    // argument passed by user, indicating initial capacity.
+    private final int initialCapacity;
+    // ByteStrings to be concatenated to create the result
+    private final ArrayList<ByteString> flushedBuffers;
+    // Total number of bytes in the ByteStrings of flushedBuffers
+    private int flushedBuffersTotalBytes;
+    // Current buffer to which we are writing
+    private byte[] buffer;
+    // Location in buffer[] to which we write the next byte.
+    private int bufferPos;
+
+    /**
+     * Creates a new ByteString output stream with the specified
+     * initial capacity.
+     *
+     * @param initialCapacity  the initial capacity of the output stream.
+     */
+    Output(int initialCapacity) {
+      if (initialCapacity < 0) {
+        throw new IllegalArgumentException("Buffer size < 0");
+      }
+      this.initialCapacity = initialCapacity;
+      this.flushedBuffers = new ArrayList<ByteString>();
+      this.buffer = new byte[initialCapacity];
+    }
+
+    @Override
+    public synchronized void write(int b) {
+      if (bufferPos == buffer.length) {
+        flushFullBuffer(1);
+      }
+      buffer[bufferPos++] = (byte)b;
+    }
+
+    @Override
+    public synchronized void write(byte[] b, int offset, int length)  {
+      if (length <= buffer.length - bufferPos) {
+        // The bytes can fit into the current buffer.
+        System.arraycopy(b, offset, buffer, bufferPos, length);
+        bufferPos += length;
+      } else {
+        // Use up the current buffer
+        int copySize  = buffer.length - bufferPos;
+        System.arraycopy(b, offset, buffer, bufferPos, copySize);
+        offset += copySize;
+        length -= copySize;
+        // Flush the buffer, and get a new buffer at least big enough to cover
+        // what we still need to output
+        flushFullBuffer(length);
+        System.arraycopy(b, offset, buffer, 0 /* count */, length);
+        bufferPos = length;
+      }
+    }
+
+    /**
+     * Creates a byte string. Its size is the current size of this output
+     * stream and its output has been copied to it.
+     *
+     * @return  the current contents of this output stream, as a byte string.
+     */
+    public synchronized ByteString toByteString() {
+      flushLastBuffer();
+      return ByteString.copyFrom(flushedBuffers);
+    }
+
+    /**
+     * Implement java.util.Arrays.copyOf() for jdk 1.5.
+     */
+    private byte[] copyArray(byte[] buffer, int length) {
+      byte[] result = new byte[length];
+      System.arraycopy(buffer, 0, result, 0, Math.min(buffer.length, length));
+      return result;
+    }
+
+    /**
+     * Writes the complete contents of this byte array output stream to
+     * the specified output stream argument.
+     *
+     * @param out the output stream to which to write the data.
+     * @throws IOException  if an I/O error occurs.
+     */
+    public void writeTo(OutputStream out) throws IOException {
+      ByteString[] cachedFlushBuffers;
+      byte[] cachedBuffer;
+      int cachedBufferPos;
+      synchronized (this) {
+        // Copy the information we need into local variables so as to hold
+        // the lock for as short a time as possible.
+        cachedFlushBuffers =
+            flushedBuffers.toArray(new ByteString[flushedBuffers.size()]);
+        cachedBuffer = buffer;
+        cachedBufferPos = bufferPos;
+      }
+      for (ByteString byteString : cachedFlushBuffers) {
+        byteString.writeTo(out);
+      }
+
+      out.write(copyArray(cachedBuffer, cachedBufferPos));
+    }
+
+    /**
+     * Returns the current size of the output stream.
+     *
+     * @return  the current size of the output stream
+     */
+    public synchronized int size() {
+      return flushedBuffersTotalBytes + bufferPos;
+    }
+
+    /**
+     * Resets this stream, so that all currently accumulated output in the
+     * output stream is discarded. The output stream can be used again,
+     * reusing the already allocated buffer space.
+     */
+    public synchronized void reset() {
+      flushedBuffers.clear();
+      flushedBuffersTotalBytes = 0;
+      bufferPos = 0;
+    }
+
+    @Override
+    public String toString() {
+      return String.format("<ByteString.Output@%s size=%d>",
+          Integer.toHexString(System.identityHashCode(this)), size());
+    }
+
+    /**
+     * Internal function used by writers.  The current buffer is full, and the
+     * writer needs a new buffer whose size is at least the specified minimum
+     * size.
+     */
+    private void flushFullBuffer(int minSize)  {
+      flushedBuffers.add(new LiteralByteString(buffer));
+      flushedBuffersTotalBytes += buffer.length;
+      // We want to increase our total capacity by 50%, but as a minimum,
+      // the new buffer should also at least be >= minSize and
+      // >= initial Capacity.
+      int newSize = Math.max(initialCapacity,
+          Math.max(minSize, flushedBuffersTotalBytes >>> 1));
+      buffer = new byte[newSize];
+      bufferPos = 0;
+    }
+
+    /**
+     * Internal function used by {@link #toByteString()}. The current buffer may
+     * or may not be full, but it needs to be flushed.
+     */
+    private void flushLastBuffer()  {
+      if (bufferPos < buffer.length) {
+        if (bufferPos > 0) {
+          byte[] bufferCopy = copyArray(buffer, bufferPos);
+          flushedBuffers.add(new LiteralByteString(bufferCopy));
+        }
+        // We reuse this buffer for further writes.
+      } else {
+        // Buffer is completely full.  Huzzah.
+        flushedBuffers.add(new LiteralByteString(buffer));
+        // 99% of the time, we're not going to use this OutputStream again.
+        // We set buffer to an empty byte stream so that we're handling this
+        // case without wasting space.  In the rare case that more writes
+        // *do* occur, this empty buffer will be flushed and an appropriately
+        // sized new buffer will be created.
+        buffer = EMPTY_BYTE_ARRAY;
+      }
+      flushedBuffersTotalBytes += bufferPos;
+      bufferPos = 0;
+    }
+  }
+
+  /**
+   * Constructs a new {@code ByteString} builder, which allows you to
+   * efficiently construct a {@code ByteString} by writing to a {@link
+   * CodedOutputStream}. Using this is much more efficient than calling {@code
+   * newOutput()} and wrapping that in a {@code CodedOutputStream}.
+   *
+   * <p>This is package-private because it's a somewhat confusing interface.
+   * Users can call {@link Message#toByteString()} instead of calling this
+   * directly.
+   *
+   * @param size The target byte size of the {@code ByteString}.  You must write
+   *     exactly this many bytes before building the result.
+   * @return the builder
+   */
+  static CodedBuilder newCodedBuilder(int size) {
+    return new CodedBuilder(size);
+  }
+
+  /** See {@link ByteString#newCodedBuilder(int)}. */
+  static final class CodedBuilder {
+    private final CodedOutputStream output;
+    private final byte[] buffer;
+
+    private CodedBuilder(int size) {
+      buffer = new byte[size];
+      output = CodedOutputStream.newInstance(buffer);
+    }
+
+    public ByteString build() {
+      output.checkNoSpaceLeft();
+
+      // We can be confident that the CodedOutputStream will not modify the
+      // underlying bytes anymore because it already wrote all of them.  So,
+      // no need to make a copy.
+      return new LiteralByteString(buffer);
+    }
+
+    public CodedOutputStream getCodedOutput() {
+      return output;
+    }
+  }
+
+  // =================================================================
+  // Methods {@link RopeByteString} needs on instances, which aren't part of the
+  // public API.
+
+  /**
+   * Return the depth of the tree representing this {@code ByteString}, if any,
+   * whose root is this node. If this is a leaf node, return 0.
+   *
+   * @return tree depth or zero
+   */
+  protected abstract int getTreeDepth();
+
+  /**
+   * Return {@code true} if this ByteString is literal (a leaf node) or a
+   * flat-enough tree in the sense of {@link RopeByteString}.
+   *
+   * @return true if the tree is flat enough
+   */
+  protected abstract boolean isBalanced();
+
+  /**
+   * Return the cached hash code if available.
+   *
+   * @return value of cached hash code or 0 if not computed yet
+   */
+  protected final int peekCachedHashCode() {
+    return hash;
+  }
+
+  /**
+   * Compute the hash across the value bytes starting with the given hash, and
+   * return the result.  This is used to compute the hash across strings
+   * represented as a set of pieces by allowing the hash computation to be
+   * continued from piece to piece.
+   *
+   * @param h starting hash value
+   * @param offset offset into this value to start looking at data values
+   * @param length number of data values to include in the hash computation
+   * @return ending hash value
+   */
+  protected abstract int partialHash(int h, int offset, int length);
+
+  /**
+   * Checks that the given index falls within the specified array size.
+   *
+   * @param index the index position to be tested
+   * @param size the length of the array
+   * @throws ArrayIndexOutOfBoundsException if the index does not fall within the array.
+   */
+  static void checkIndex(int index, int size) {
+    if ((index | (size - (index + 1))) < 0) {
+      if (index < 0) {
+        throw new ArrayIndexOutOfBoundsException("Index < 0: " + index);
+      }
+      throw new ArrayIndexOutOfBoundsException("Index > length: " + index + ", " + size);
+    }
+  }
+
+  /**
+   * Checks that the given range falls within the bounds of an array
+   *
+   * @param startIndex the start index of the range (inclusive)
+   * @param endIndex the end index of the range (exclusive)
+   * @param size the size of the array.
+   * @return the length of the range.
+   * @throws ArrayIndexOutOfBoundsException some or all of the range falls outside of the array.
+   */
+  static int checkRange(int startIndex, int endIndex, int size) {
+    final int length = endIndex - startIndex;
+    if ((startIndex | endIndex | length | (size - endIndex)) < 0) {
+      if (startIndex < 0) {
+        throw new IndexOutOfBoundsException("Beginning index: " + startIndex + " < 0");
+      }
+      if (endIndex < startIndex) {
+        throw new IndexOutOfBoundsException(
+            "Beginning index larger than ending index: " + startIndex + ", " + endIndex);
+      }
+      // endIndex >= size
+      throw new IndexOutOfBoundsException("End index: " + endIndex + " >= " + size);
+    }
+    return length;
+  }
+
+  @Override
+  public final String toString() {
+    return String.format("<ByteString@%s size=%d>",
+        Integer.toHexString(System.identityHashCode(this)), size());
+  }
+}