TextFormat.java

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// 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 com.google.protobuf.Descriptors.Descriptor;
import com.google.protobuf.Descriptors.EnumDescriptor;
import com.google.protobuf.Descriptors.EnumValueDescriptor;
import com.google.protobuf.Descriptors.FieldDescriptor;
import java.io.IOException;
import java.math.BigInteger;
import java.nio.CharBuffer;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.logging.Logger;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public final class TextFormat {
  private TextFormat() {}
 
  private static final Logger logger = Logger.getLogger(TextFormat.class.getName());
 
  @Deprecated
  public static void print(final MessageOrBuilder message, final Appendable output)
      throws IOException {
    printer().print(message, output);
  }
 
  @Deprecated
  public static void print(final UnknownFieldSet fields, final Appendable output)
      throws IOException {
    printer().print(fields, output);
  }
 
  @Deprecated
  public static void printUnicode(final MessageOrBuilder message, final Appendable output)
      throws IOException {
    printer().escapingNonAscii(false).print(message, output);
  }
 
  @Deprecated
  public static void printUnicode(final UnknownFieldSet fields, final Appendable output)
      throws IOException {
    printer().escapingNonAscii(false).print(fields, output);
  }
 
  public static String shortDebugString(final MessageOrBuilder message) {
    return printer().shortDebugString(message);
  }
 
  @Deprecated
  public static String shortDebugString(final FieldDescriptor field, final Object value) {
    return printer().shortDebugString(field, value);
  }
 
  @Deprecated
  public static String shortDebugString(final UnknownFieldSet fields) {
    return printer().shortDebugString(fields);
  }
 
  @Deprecated
  public static String printToString(final MessageOrBuilder message) {
    return printer().printToString(message);
  }
 
  @Deprecated
  public static String printToString(final UnknownFieldSet fields) {
    return printer().printToString(fields);
  }
 
  @Deprecated
  public static String printToUnicodeString(final MessageOrBuilder message) {
    return printer().escapingNonAscii(false).printToString(message);
  }
 
  @Deprecated
  public static String printToUnicodeString(final UnknownFieldSet fields) {
    return printer().escapingNonAscii(false).printToString(fields);
  }
 
  @Deprecated
  public static void printField(
      final FieldDescriptor field, final Object value, final Appendable output) throws IOException {
    printer().printField(field, value, output);
  }
 
  @Deprecated
  public static String printFieldToString(final FieldDescriptor field, final Object value) {
    return printer().printFieldToString(field, value);
  }
 
  @Deprecated
  public static void printUnicodeFieldValue(
      final FieldDescriptor field, final Object value, final Appendable output) throws IOException {
    printer().escapingNonAscii(false).printFieldValue(field, value, output);
  }
 
  @Deprecated
  public static void printFieldValue(
      final FieldDescriptor field, final Object value, final Appendable output) throws IOException {
    printer().printFieldValue(field, value, output);
  }
 
  public static void printUnknownFieldValue(
      final int tag, final Object value, final Appendable output) throws IOException {
    printUnknownFieldValue(tag, value, multiLineOutput(output));
  }
 
  private static void printUnknownFieldValue(
      final int tag, final Object value, final TextGenerator generator) throws IOException {
    switch (WireFormat.getTagWireType(tag)) {
      case WireFormat.WIRETYPE_VARINT:
        generator.print(unsignedToString((Long) value));
        break;
      case WireFormat.WIRETYPE_FIXED32:
        generator.print(String.format((Locale) null, "0x%08x", (Integer) value));
        break;
      case WireFormat.WIRETYPE_FIXED64:
        generator.print(String.format((Locale) null, "0x%016x", (Long) value));
        break;
      case WireFormat.WIRETYPE_LENGTH_DELIMITED:
        try {
          // Try to parse and print the field as an embedded message
          UnknownFieldSet message = UnknownFieldSet.parseFrom((ByteString) value);
          generator.print("{");
          generator.eol();
          generator.indent();
          Printer.printUnknownFields(message, generator);
          generator.outdent();
          generator.print("}");
        } catch (InvalidProtocolBufferException e) {
          // If not parseable as a message, print as a String
          generator.print("\"");
          generator.print(escapeBytes((ByteString) value));
          generator.print("\"");
        }
        break;
      case WireFormat.WIRETYPE_START_GROUP:
        Printer.printUnknownFields((UnknownFieldSet) value, generator);
        break;
      default:
        throw new IllegalArgumentException("Bad tag: " + tag);
    }
  }
 
  public static Printer printer() {
    return Printer.DEFAULT;
  }
 
  public static final class Printer {
 
    // Printer instance which escapes non-ASCII characters.
    private static final Printer DEFAULT = new Printer(true);
 
    private final boolean escapeNonAscii;
 
    private Printer(boolean escapeNonAscii) {
      this.escapeNonAscii = escapeNonAscii;
    }
 
    public Printer escapingNonAscii(boolean escapeNonAscii) {
      return new Printer(escapeNonAscii);
    }
 
    public void print(final MessageOrBuilder message, final Appendable output) throws IOException {
      print(message, multiLineOutput(output));
    }
 
    public void print(final UnknownFieldSet fields, final Appendable output) throws IOException {
      printUnknownFields(fields, multiLineOutput(output));
    }
 
    private void print(final MessageOrBuilder message, final TextGenerator generator)
        throws IOException {
      printMessage(message, generator);
    }
 
    public String printFieldToString(final FieldDescriptor field, final Object value) {
      try {
        final StringBuilder text = new StringBuilder();
        printField(field, value, text);
        return text.toString();
      } catch (IOException e) {
        throw new IllegalStateException(e);
      }
    }
 
    public void printField(final FieldDescriptor field, final Object value, final Appendable output)
        throws IOException {
      printField(field, value, multiLineOutput(output));
    }
 
    private void printField(
        final FieldDescriptor field, final Object value, final TextGenerator generator)
        throws IOException {
      if (field.isRepeated()) {
        // Repeated field.  Print each element.
        for (Object element : (List<?>) value) {
          printSingleField(field, element, generator);
        }
      } else {
        printSingleField(field, value, generator);
      }
    }
 
    public void printFieldValue(
        final FieldDescriptor field, final Object value, final Appendable output)
        throws IOException {
      printFieldValue(field, value, multiLineOutput(output));
    }
 
    private void printFieldValue(
        final FieldDescriptor field, final Object value, final TextGenerator generator)
        throws IOException {
      switch (field.getType()) {
        case INT32:
        case SINT32:
        case SFIXED32:
          generator.print(((Integer) value).toString());
          break;
 
        case INT64:
        case SINT64:
        case SFIXED64:
          generator.print(((Long) value).toString());
          break;
 
        case BOOL:
          generator.print(((Boolean) value).toString());
          break;
 
        case FLOAT:
          generator.print(((Float) value).toString());
          break;
 
        case DOUBLE:
          generator.print(((Double) value).toString());
          break;
 
        case UINT32:
        case FIXED32:
          generator.print(unsignedToString((Integer) value));
          break;
 
        case UINT64:
        case FIXED64:
          generator.print(unsignedToString((Long) value));
          break;
 
        case STRING:
          generator.print("\"");
          generator.print(
              escapeNonAscii
                  ? TextFormatEscaper.escapeText((String) value)
                  : escapeDoubleQuotesAndBackslashes((String) value).replace("\n", "\\n"));
          generator.print("\"");
          break;
 
        case BYTES:
          generator.print("\"");
          if (value instanceof ByteString) {
            generator.print(escapeBytes((ByteString) value));
          } else {
            generator.print(escapeBytes((byte[]) value));
          }
          generator.print("\"");
          break;
 
        case ENUM:
          generator.print(((EnumValueDescriptor) value).getName());
          break;
 
        case MESSAGE:
        case GROUP:
          print((Message) value, generator);
          break;
      }
    }
 
    public String printToString(final MessageOrBuilder message) {
      try {
        final StringBuilder text = new StringBuilder();
        print(message, text);
        return text.toString();
      } catch (IOException e) {
        throw new IllegalStateException(e);
      }
    }
    public String printToString(final UnknownFieldSet fields) {
      try {
        final StringBuilder text = new StringBuilder();
        print(fields, text);
        return text.toString();
      } catch (IOException e) {
        throw new IllegalStateException(e);
      }
    }
 
    public String shortDebugString(final MessageOrBuilder message) {
      try {
        final StringBuilder text = new StringBuilder();
        print(message, singleLineOutput(text));
        return text.toString();
      } catch (IOException e) {
        throw new IllegalStateException(e);
      }
    }
 
    public String shortDebugString(final FieldDescriptor field, final Object value) {
      try {
        final StringBuilder text = new StringBuilder();
        printField(field, value, singleLineOutput(text));
        return text.toString();
      } catch (IOException e) {
        throw new IllegalStateException(e);
      }
    }
 
    public String shortDebugString(final UnknownFieldSet fields) {
      try {
        final StringBuilder text = new StringBuilder();
        printUnknownFields(fields, singleLineOutput(text));
        return text.toString();
      } catch (IOException e) {
        throw new IllegalStateException(e);
      }
    }
 
    private static void printUnknownFieldValue(
        final int tag, final Object value, final TextGenerator generator) throws IOException {
      switch (WireFormat.getTagWireType(tag)) {
        case WireFormat.WIRETYPE_VARINT:
          generator.print(unsignedToString((Long) value));
          break;
        case WireFormat.WIRETYPE_FIXED32:
          generator.print(String.format((Locale) null, "0x%08x", (Integer) value));
          break;
        case WireFormat.WIRETYPE_FIXED64:
          generator.print(String.format((Locale) null, "0x%016x", (Long) value));
          break;
        case WireFormat.WIRETYPE_LENGTH_DELIMITED:
          try {
            // Try to parse and print the field as an embedded message
            UnknownFieldSet message = UnknownFieldSet.parseFrom((ByteString) value);
            generator.print("{");
            generator.eol();
            generator.indent();
            printUnknownFields(message, generator);
            generator.outdent();
            generator.print("}");
          } catch (InvalidProtocolBufferException e) {
            // If not parseable as a message, print as a String
            generator.print("\"");
            generator.print(escapeBytes((ByteString) value));
            generator.print("\"");
          }
          break;
        case WireFormat.WIRETYPE_START_GROUP:
          printUnknownFields((UnknownFieldSet) value, generator);
          break;
        default:
          throw new IllegalArgumentException("Bad tag: " + tag);
      }
    }
 
    private void printMessage(final MessageOrBuilder message, final TextGenerator generator)
        throws IOException {
      for (Map.Entry<FieldDescriptor, Object> field : message.getAllFields().entrySet()) {
        printField(field.getKey(), field.getValue(), generator);
      }
      printUnknownFields(message.getUnknownFields(), generator);
    }
 
    private void printSingleField(
        final FieldDescriptor field, final Object value, final TextGenerator generator)
        throws IOException {
      if (field.isExtension()) {
        generator.print("[");
        // We special-case MessageSet elements for compatibility with proto1.
        if (field.getContainingType().getOptions().getMessageSetWireFormat()
            && (field.getType() == FieldDescriptor.Type.MESSAGE)
            && (field.isOptional())
            // object equality
            && (field.getExtensionScope() == field.getMessageType())) {
          generator.print(field.getMessageType().getFullName());
        } else {
          generator.print(field.getFullName());
        }
        generator.print("]");
      } else {
        if (field.getType() == FieldDescriptor.Type.GROUP) {
          // Groups must be serialized with their original capitalization.
          generator.print(field.getMessageType().getName());
        } else {
          generator.print(field.getName());
        }
      }
 
      if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
        generator.print(" {");
        generator.eol();
        generator.indent();
      } else {
        generator.print(": ");
      }
 
      printFieldValue(field, value, generator);
 
      if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
        generator.outdent();
        generator.print("}");
      }
      generator.eol();
    }
 
    private static void printUnknownFields(
        final UnknownFieldSet unknownFields, final TextGenerator generator) throws IOException {
      for (Map.Entry<Integer, UnknownFieldSet.Field> entry : unknownFields.asMap().entrySet()) {
        final int number = entry.getKey();
        final UnknownFieldSet.Field field = entry.getValue();
        printUnknownField(number, WireFormat.WIRETYPE_VARINT, field.getVarintList(), generator);
        printUnknownField(number, WireFormat.WIRETYPE_FIXED32, field.getFixed32List(), generator);
        printUnknownField(number, WireFormat.WIRETYPE_FIXED64, field.getFixed64List(), generator);
        printUnknownField(
            number,
            WireFormat.WIRETYPE_LENGTH_DELIMITED,
            field.getLengthDelimitedList(),
            generator);
        for (final UnknownFieldSet value : field.getGroupList()) {
          generator.print(entry.getKey().toString());
          generator.print(" {");
          generator.eol();
          generator.indent();
          printUnknownFields(value, generator);
          generator.outdent();
          generator.print("}");
          generator.eol();
        }
      }
    }
 
    private static void printUnknownField(
        final int number, final int wireType, final List<?> values, final TextGenerator generator)
        throws IOException {
      for (final Object value : values) {
        generator.print(String.valueOf(number));
        generator.print(": ");
        printUnknownFieldValue(wireType, value, generator);
        generator.eol();
      }
    }
  }
 
  public static String unsignedToString(final int value) {
    if (value >= 0) {
      return Integer.toString(value);
    } else {
      return Long.toString(value & 0x00000000FFFFFFFFL);
    }
  }
 
  public static String unsignedToString(final long value) {
    if (value >= 0) {
      return Long.toString(value);
    } else {
      // Pull off the most-significant bit so that BigInteger doesn't think
      // the number is negative, then set it again using setBit().
      return BigInteger.valueOf(value & 0x7FFFFFFFFFFFFFFFL).setBit(63).toString();
    }
  }
 
  private static TextGenerator multiLineOutput(Appendable output) {
    return new TextGenerator(output, false);
  }
 
  private static TextGenerator singleLineOutput(Appendable output) {
    return new TextGenerator(output, true);
  }
 
  private static final class TextGenerator {
    private final Appendable output;
    private final StringBuilder indent = new StringBuilder();
    private final boolean singleLineMode;
    // While technically we are "at the start of a line" at the very beginning of the output, all
    // we would do in response to this is emit the (zero length) indentation, so it has no effect.
    // Setting it false here does however suppress an unwanted leading space in single-line mode.
    private boolean atStartOfLine = false;
 
    private TextGenerator(final Appendable output, boolean singleLineMode) {
      this.output = output;
      this.singleLineMode = singleLineMode;
    }
 
    public void indent() {
      indent.append("  ");
    }
 
    public void outdent() {
      final int length = indent.length();
      if (length == 0) {
        throw new IllegalArgumentException(" Outdent() without matching Indent().");
      }
      indent.setLength(length - 2);
    }
 
    public void print(final CharSequence text) throws IOException {
      if (atStartOfLine) {
        atStartOfLine = false;
        output.append(singleLineMode ? " " : indent);
      }
      output.append(text);
    }
 
    public void eol() throws IOException {
      if (!singleLineMode) {
        output.append("\n");
      }
      atStartOfLine = true;
    }
  }
 
  // =================================================================
  // Parsing
 
  private static final class Tokenizer {
    private final CharSequence text;
    private final Matcher matcher;
    private String currentToken;
 
    // The character index within this.text at which the current token begins.
    private int pos = 0;
 
    // The line and column numbers of the current token.
    private int line = 0;
    private int column = 0;
 
    // The line and column numbers of the previous token (allows throwing
    // errors *after* consuming).
    private int previousLine = 0;
    private int previousColumn = 0;
 
    // We use possessive quantifiers (*+ and ++) because otherwise the Java
    // regex matcher has stack overflows on large inputs.
    private static final Pattern WHITESPACE = Pattern.compile("(\\s|(#.*$))++", Pattern.MULTILINE);
    private static final Pattern TOKEN =
        Pattern.compile(
            "[a-zA-Z_][0-9a-zA-Z_+-]*+|" // an identifier
                + "[.]?[0-9+-][0-9a-zA-Z_.+-]*+|" // a number
                + "\"([^\"\n\\\\]|\\\\.)*+(\"|\\\\?$)|" // a double-quoted string
                + "\'([^\'\n\\\\]|\\\\.)*+(\'|\\\\?$)", // a single-quoted string
            Pattern.MULTILINE);
 
    private static final Pattern DOUBLE_INFINITY =
        Pattern.compile("-?inf(inity)?", Pattern.CASE_INSENSITIVE);
    private static final Pattern FLOAT_INFINITY =
        Pattern.compile("-?inf(inity)?f?", Pattern.CASE_INSENSITIVE);
    private static final Pattern FLOAT_NAN = Pattern.compile("nanf?", Pattern.CASE_INSENSITIVE);
 
    private Tokenizer(final CharSequence text) {
      this.text = text;
      this.matcher = WHITESPACE.matcher(text);
      skipWhitespace();
      nextToken();
    }
 
    int getPreviousLine() {
      return previousLine;
    }
 
    int getPreviousColumn() {
      return previousColumn;
    }
 
    int getLine() {
      return line;
    }
 
    int getColumn() {
      return column;
    }
 
    public boolean atEnd() {
      return currentToken.length() == 0;
    }
 
    public void nextToken() {
      previousLine = line;
      previousColumn = column;
 
      // Advance the line counter to the current position.
      while (pos < matcher.regionStart()) {
        if (text.charAt(pos) == '\n') {
          ++line;
          column = 0;
        } else {
          ++column;
        }
        ++pos;
      }
 
      // Match the next token.
      if (matcher.regionStart() == matcher.regionEnd()) {
        // EOF
        currentToken = "";
      } else {
        matcher.usePattern(TOKEN);
        if (matcher.lookingAt()) {
          currentToken = matcher.group();
          matcher.region(matcher.end(), matcher.regionEnd());
        } else {
          // Take one character.
          currentToken = String.valueOf(text.charAt(pos));
          matcher.region(pos + 1, matcher.regionEnd());
        }
 
        skipWhitespace();
      }
    }
 
    private void skipWhitespace() {
      matcher.usePattern(WHITESPACE);
      if (matcher.lookingAt()) {
        matcher.region(matcher.end(), matcher.regionEnd());
      }
    }
 
    public boolean tryConsume(final String token) {
      if (currentToken.equals(token)) {
        nextToken();
        return true;
      } else {
        return false;
      }
    }
 
    public void consume(final String token) throws ParseException {
      if (!tryConsume(token)) {
        throw parseException("Expected \"" + token + "\".");
      }
    }
 
    public boolean lookingAtInteger() {
      if (currentToken.length() == 0) {
        return false;
      }
 
      final char c = currentToken.charAt(0);
      return ('0' <= c && c <= '9') || c == '-' || c == '+';
    }
 
    public boolean lookingAt(String text) {
      return currentToken.equals(text);
    }
 
    public String consumeIdentifier() throws ParseException {
      for (int i = 0; i < currentToken.length(); i++) {
        final char c = currentToken.charAt(i);
        if (('a' <= c && c <= 'z')
            || ('A' <= c && c <= 'Z')
            || ('0' <= c && c <= '9')
            || (c == '_')
            || (c == '.')) {
          // OK
        } else {
          throw parseException("Expected identifier. Found '" + currentToken + "'");
        }
      }
 
      final String result = currentToken;
      nextToken();
      return result;
    }
 
    public boolean tryConsumeIdentifier() {
      try {
        consumeIdentifier();
        return true;
      } catch (ParseException e) {
        return false;
      }
    }
 
    public int consumeInt32() throws ParseException {
      try {
        final int result = parseInt32(currentToken);
        nextToken();
        return result;
      } catch (NumberFormatException e) {
        throw integerParseException(e);
      }
    }
 
    public int consumeUInt32() throws ParseException {
      try {
        final int result = parseUInt32(currentToken);
        nextToken();
        return result;
      } catch (NumberFormatException e) {
        throw integerParseException(e);
      }
    }
 
    public long consumeInt64() throws ParseException {
      try {
        final long result = parseInt64(currentToken);
        nextToken();
        return result;
      } catch (NumberFormatException e) {
        throw integerParseException(e);
      }
    }
 
    public boolean tryConsumeInt64() {
      try {
        consumeInt64();
        return true;
      } catch (ParseException e) {
        return false;
      }
    }
 
    public long consumeUInt64() throws ParseException {
      try {
        final long result = parseUInt64(currentToken);
        nextToken();
        return result;
      } catch (NumberFormatException e) {
        throw integerParseException(e);
      }
    }
 
    public boolean tryConsumeUInt64() {
      try {
        consumeUInt64();
        return true;
      } catch (ParseException e) {
        return false;
      }
    }
 
    public double consumeDouble() throws ParseException {
      // We need to parse infinity and nan separately because
      // Double.parseDouble() does not accept "inf", "infinity", or "nan".
      if (DOUBLE_INFINITY.matcher(currentToken).matches()) {
        final boolean negative = currentToken.startsWith("-");
        nextToken();
        return negative ? Double.NEGATIVE_INFINITY : Double.POSITIVE_INFINITY;
      }
      if (currentToken.equalsIgnoreCase("nan")) {
        nextToken();
        return Double.NaN;
      }
      try {
        final double result = Double.parseDouble(currentToken);
        nextToken();
        return result;
      } catch (NumberFormatException e) {
        throw floatParseException(e);
      }
    }
 
    public boolean tryConsumeDouble() {
      try {
        consumeDouble();
        return true;
      } catch (ParseException e) {
        return false;
      }
    }
 
    public float consumeFloat() throws ParseException {
      // We need to parse infinity and nan separately because
      // Float.parseFloat() does not accept "inf", "infinity", or "nan".
      if (FLOAT_INFINITY.matcher(currentToken).matches()) {
        final boolean negative = currentToken.startsWith("-");
        nextToken();
        return negative ? Float.NEGATIVE_INFINITY : Float.POSITIVE_INFINITY;
      }
      if (FLOAT_NAN.matcher(currentToken).matches()) {
        nextToken();
        return Float.NaN;
      }
      try {
        final float result = Float.parseFloat(currentToken);
        nextToken();
        return result;
      } catch (NumberFormatException e) {
        throw floatParseException(e);
      }
    }
 
    public boolean tryConsumeFloat() {
      try {
        consumeFloat();
        return true;
      } catch (ParseException e) {
        return false;
      }
    }
 
    public boolean consumeBoolean() throws ParseException {
      if (currentToken.equals("true")
          || currentToken.equals("True")
          || currentToken.equals("t")
          || currentToken.equals("1")) {
        nextToken();
        return true;
      } else if (currentToken.equals("false")
          || currentToken.equals("False")
          || currentToken.equals("f")
          || currentToken.equals("0")) {
        nextToken();
        return false;
      } else {
        throw parseException("Expected \"true\" or \"false\". Found \"" + currentToken + "\".");
      }
    }
 
    public String consumeString() throws ParseException {
      return consumeByteString().toStringUtf8();
    }
 
    public boolean tryConsumeString() {
      try {
        consumeString();
        return true;
      } catch (ParseException e) {
        return false;
      }
    }
 
    public ByteString consumeByteString() throws ParseException {
      List<ByteString> list = new ArrayList<ByteString>();
      consumeByteString(list);
      while (currentToken.startsWith("'") || currentToken.startsWith("\"")) {
        consumeByteString(list);
      }
      return ByteString.copyFrom(list);
    }
 
    private void consumeByteString(List<ByteString> list) throws ParseException {
      final char quote = currentToken.length() > 0 ? currentToken.charAt(0) : '\0';
      if (quote != '\"' && quote != '\'') {
        throw parseException("Expected string.");
      }
 
      if (currentToken.length() < 2 || currentToken.charAt(currentToken.length() - 1) != quote) {
        throw parseException("String missing ending quote.");
      }
 
      try {
        final String escaped = currentToken.substring(1, currentToken.length() - 1);
        final ByteString result = unescapeBytes(escaped);
        nextToken();
        list.add(result);
      } catch (InvalidEscapeSequenceException e) {
        throw parseException(e.getMessage());
      }
    }
 
    public ParseException parseException(final String description) {
      // Note:  People generally prefer one-based line and column numbers.
      return new ParseException(line + 1, column + 1, description);
    }
 
    public ParseException parseExceptionPreviousToken(final String description) {
      // Note:  People generally prefer one-based line and column numbers.
      return new ParseException(previousLine + 1, previousColumn + 1, description);
    }
 
    private ParseException integerParseException(final NumberFormatException e) {
      return parseException("Couldn't parse integer: " + e.getMessage());
    }
 
    private ParseException floatParseException(final NumberFormatException e) {
      return parseException("Couldn't parse number: " + e.getMessage());
    }
 
    public UnknownFieldParseException unknownFieldParseExceptionPreviousToken(
        final String unknownField, final String description) {
      // Note:  People generally prefer one-based line and column numbers.
      return new UnknownFieldParseException(
          previousLine + 1, previousColumn + 1, unknownField, description);
    }
  }
 
  public static class ParseException extends IOException {
    private static final long serialVersionUID = 3196188060225107702L;
 
    private final int line;
    private final int column;
 
    public ParseException(final String message) {
      this(-1, -1, message);
    }
 
    public ParseException(final int line, final int column, final String message) {
      super(Integer.toString(line) + ":" + column + ": " + message);
      this.line = line;
      this.column = column;
    }
 
    public int getLine() {
      return line;
    }
 
    public int getColumn() {
      return column;
    }
  }
 
  public static class UnknownFieldParseException extends ParseException {
    private final String unknownField;
 
    public UnknownFieldParseException(final String message) {
      this(-1, -1, "", message);
    }
 
    public UnknownFieldParseException(
        final int line, final int column, final String unknownField, final String message) {
      super(line, column, message);
      this.unknownField = unknownField;
    }
 
    public String getUnknownField() {
      return unknownField;
    }
  }
 
  private static final Parser PARSER = Parser.newBuilder().build();
 
  public static Parser getParser() {
    return PARSER;
  }
 
  public static void merge(final Readable input, final Message.Builder builder) throws IOException {
    PARSER.merge(input, builder);
  }
 
  public static void merge(final CharSequence input, final Message.Builder builder)
      throws ParseException {
    PARSER.merge(input, builder);
  }
 
  public static <T extends Message> T parse(final CharSequence input, final Class<T> protoClass)
      throws ParseException {
    Message.Builder builder = Internal.getDefaultInstance(protoClass).newBuilderForType();
    merge(input, builder);
    @SuppressWarnings("unchecked")
    T output = (T) builder.build();
    return output;
  }
 
  public static void merge(
      final Readable input,
      final ExtensionRegistry extensionRegistry,
      final Message.Builder builder)
      throws IOException {
    PARSER.merge(input, extensionRegistry, builder);
  }
 
 
  public static void merge(
      final CharSequence input,
      final ExtensionRegistry extensionRegistry,
      final Message.Builder builder)
      throws ParseException {
    PARSER.merge(input, extensionRegistry, builder);
  }
 
  public static <T extends Message> T parse(
      final CharSequence input,
      final ExtensionRegistry extensionRegistry,
      final Class<T> protoClass)
      throws ParseException {
    Message.Builder builder = Internal.getDefaultInstance(protoClass).newBuilderForType();
    merge(input, extensionRegistry, builder);
    @SuppressWarnings("unchecked")
    T output = (T) builder.build();
    return output;
  }
 
 
  public static class Parser {
    public enum SingularOverwritePolicy {
      ALLOW_SINGULAR_OVERWRITES,
      FORBID_SINGULAR_OVERWRITES
    }
 
    private final boolean allowUnknownFields;
    private final boolean allowUnknownEnumValues;
    private final boolean allowUnknownExtensions;
    private final SingularOverwritePolicy singularOverwritePolicy;
    private TextFormatParseInfoTree.Builder parseInfoTreeBuilder;
 
    private Parser(
        boolean allowUnknownFields,
        boolean allowUnknownEnumValues,
        boolean allowUnknownExtensions,
        SingularOverwritePolicy singularOverwritePolicy,
        TextFormatParseInfoTree.Builder parseInfoTreeBuilder) {
      this.allowUnknownFields = allowUnknownFields;
      this.allowUnknownEnumValues = allowUnknownEnumValues;
      this.allowUnknownExtensions = allowUnknownExtensions;
      this.singularOverwritePolicy = singularOverwritePolicy;
      this.parseInfoTreeBuilder = parseInfoTreeBuilder;
    }
 
    public static Builder newBuilder() {
      return new Builder();
    }
 
    public static class Builder {
      private boolean allowUnknownFields = false;
      private boolean allowUnknownEnumValues = false;
      private boolean allowUnknownExtensions = false;
      private SingularOverwritePolicy singularOverwritePolicy =
          SingularOverwritePolicy.ALLOW_SINGULAR_OVERWRITES;
      private TextFormatParseInfoTree.Builder parseInfoTreeBuilder = null;
 
      public Builder setAllowUnknownFields(boolean allowUnknownFields) {
        this.allowUnknownFields = allowUnknownFields;
        return this;
      }
 
      public Builder setAllowUnknownExtensions(boolean allowUnknownExtensions) {
        this.allowUnknownExtensions = allowUnknownExtensions;
        return this;
      }
 
      public Builder setSingularOverwritePolicy(SingularOverwritePolicy p) {
        this.singularOverwritePolicy = p;
        return this;
      }
 
      public Builder setParseInfoTreeBuilder(TextFormatParseInfoTree.Builder parseInfoTreeBuilder) {
        this.parseInfoTreeBuilder = parseInfoTreeBuilder;
        return this;
      }
 
      public Parser build() {
        return new Parser(
            allowUnknownFields,
            allowUnknownEnumValues,
            allowUnknownExtensions,
            singularOverwritePolicy,
            parseInfoTreeBuilder);
      }
    }
 
    public void merge(final Readable input, final Message.Builder builder) throws IOException {
      merge(input, ExtensionRegistry.getEmptyRegistry(), builder);
    }
 
    public void merge(final CharSequence input, final Message.Builder builder)
        throws ParseException {
      merge(input, ExtensionRegistry.getEmptyRegistry(), builder);
    }
 
    public void merge(
        final Readable input,
        final ExtensionRegistry extensionRegistry,
        final Message.Builder builder)
        throws IOException {
      // Read the entire input to a String then parse that.
 
      // If StreamTokenizer were not quite so crippled, or if there were a kind
      // of Reader that could read in chunks that match some particular regex,
      // or if we wanted to write a custom Reader to tokenize our stream, then
      // we would not have to read to one big String.  Alas, none of these is
      // the case.  Oh well.
 
      merge(toStringBuilder(input), extensionRegistry, builder);
    }
 
 
    private static final int BUFFER_SIZE = 4096;
 
    // TODO(chrisn): See if working around java.io.Reader#read(CharBuffer)
    // overhead is worthwhile
    private static StringBuilder toStringBuilder(final Readable input) throws IOException {
      final StringBuilder text = new StringBuilder();
      final CharBuffer buffer = CharBuffer.allocate(BUFFER_SIZE);
      while (true) {
        final int n = input.read(buffer);
        if (n == -1) {
          break;
        }
        buffer.flip();
        text.append(buffer, 0, n);
      }
      return text;
    }
 
    static final class UnknownField {
      static enum Type {
        FIELD, EXTENSION;
      }
 
      final String message;
      final Type type;
 
      UnknownField(String message, Type type) {
        this.message = message;
        this.type = type;
      }
    }
 
    // Check both unknown fields and unknown extensions and log warning messages
    // or throw exceptions according to the flag.
    private void checkUnknownFields(final List<UnknownField> unknownFields) throws ParseException {
      if (unknownFields.isEmpty()) {
        return;
      }
 
      StringBuilder msg = new StringBuilder("Input contains unknown fields and/or extensions:");
      for (UnknownField field : unknownFields) {
        msg.append('\n').append(field.message);
      }
 
      if (allowUnknownFields) {
        logger.warning(msg.toString());
        return;
      }
 
      int firstErrorIndex = 0;
      if (allowUnknownExtensions) {
        boolean allUnknownExtensions = true;
        for (UnknownField field : unknownFields) {
          if (field.type == UnknownField.Type.FIELD) {
            allUnknownExtensions = false;
            break;
          }
          ++firstErrorIndex;
        }
        if (allUnknownExtensions) {
          logger.warning(msg.toString());
          return;
        }
      }
 
      String[] lineColumn = unknownFields.get(firstErrorIndex).message.split(":");
      throw new ParseException(
          Integer.parseInt(lineColumn[0]), Integer.parseInt(lineColumn[1]), msg.toString());
    }
 
    public void merge(
        final CharSequence input,
        final ExtensionRegistry extensionRegistry,
        final Message.Builder builder)
        throws ParseException {
      final Tokenizer tokenizer = new Tokenizer(input);
      MessageReflection.BuilderAdapter target = new MessageReflection.BuilderAdapter(builder);
 
      List<UnknownField> unknownFields = new ArrayList<UnknownField>();
 
      while (!tokenizer.atEnd()) {
        mergeField(tokenizer, extensionRegistry, target, unknownFields);
      }
 
      checkUnknownFields(unknownFields);
    }
 
 
    private void mergeField(
        final Tokenizer tokenizer,
        final ExtensionRegistry extensionRegistry,
        final MessageReflection.MergeTarget target,
        List<UnknownField> unknownFields)
        throws ParseException {
      mergeField(
          tokenizer,
          extensionRegistry,
          target,
          parseInfoTreeBuilder,
          unknownFields);
    }
 
    private void mergeField(
        final Tokenizer tokenizer,
        final ExtensionRegistry extensionRegistry,
        final MessageReflection.MergeTarget target,
        TextFormatParseInfoTree.Builder parseTreeBuilder,
        List<UnknownField> unknownFields)
        throws ParseException {
      FieldDescriptor field = null;
      int startLine = tokenizer.getLine();
      int startColumn = tokenizer.getColumn();
      final Descriptor type = target.getDescriptorForType();
      ExtensionRegistry.ExtensionInfo extension = null;
 
      if (tokenizer.tryConsume("[")) {
        // An extension.
        final StringBuilder name = new StringBuilder(tokenizer.consumeIdentifier());
        while (tokenizer.tryConsume(".")) {
          name.append('.');
          name.append(tokenizer.consumeIdentifier());
        }
 
        extension = target.findExtensionByName(extensionRegistry, name.toString());
 
        if (extension == null) {
          String message =
              (tokenizer.getPreviousLine() + 1)
                  + ":"
                  + (tokenizer.getPreviousColumn() + 1)
                  + ":\t"
                  + type.getFullName()
                  + ".["
                  + name
                  + "]";
          unknownFields.add(new UnknownField(message, UnknownField.Type.EXTENSION));
        } else {
          if (extension.descriptor.getContainingType() != type) {
            throw tokenizer.parseExceptionPreviousToken(
                "Extension \""
                    + name
                    + "\" does not extend message type \""
                    + type.getFullName()
                    + "\".");
          }
          field = extension.descriptor;
        }
 
        tokenizer.consume("]");
      } else {
        final String name = tokenizer.consumeIdentifier();
        field = type.findFieldByName(name);
 
        // Group names are expected to be capitalized as they appear in the
        // .proto file, which actually matches their type names, not their field
        // names.
        if (field == null) {
          // Explicitly specify US locale so that this code does not break when
          // executing in Turkey.
          final String lowerName = name.toLowerCase(Locale.US);
          field = type.findFieldByName(lowerName);
          // If the case-insensitive match worked but the field is NOT a group,
          if (field != null && field.getType() != FieldDescriptor.Type.GROUP) {
            field = null;
          }
        }
        // Again, special-case group names as described above.
        if (field != null
            && field.getType() == FieldDescriptor.Type.GROUP
            && !field.getMessageType().getName().equals(name)) {
          field = null;
        }
 
        if (field == null) {
          String message = (tokenizer.getPreviousLine() + 1)
                           + ":"
                           + (tokenizer.getPreviousColumn() + 1)
                           + ":\t"
                           + type.getFullName()
                           + "."
                           + name;
          unknownFields.add(new UnknownField(message, UnknownField.Type.FIELD));
        }
      }
 
      // Skips unknown fields.
      if (field == null) {
        // Try to guess the type of this field.
        // If this field is not a message, there should be a ":" between the
        // field name and the field value and also the field value should not
        // start with "{" or "<" which indicates the beginning of a message body.
        // If there is no ":" or there is a "{" or "<" after ":", this field has
        // to be a message or the input is ill-formed.
        if (tokenizer.tryConsume(":") && !tokenizer.lookingAt("{") && !tokenizer.lookingAt("<")) {
          skipFieldValue(tokenizer);
        } else {
          skipFieldMessage(tokenizer);
        }
        return;
      }
 
      // Handle potential ':'.
      if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
        tokenizer.tryConsume(":"); // optional
        if (parseTreeBuilder != null) {
          TextFormatParseInfoTree.Builder childParseTreeBuilder =
              parseTreeBuilder.getBuilderForSubMessageField(field);
          consumeFieldValues(
              tokenizer,
              extensionRegistry,
              target,
              field,
              extension,
              childParseTreeBuilder,
              unknownFields);
        } else {
          consumeFieldValues(
              tokenizer,
              extensionRegistry,
              target,
              field,
              extension,
              parseTreeBuilder,
              unknownFields);
        }
      } else {
        tokenizer.consume(":"); // required
        consumeFieldValues(
            tokenizer,
            extensionRegistry,
            target,
            field,
            extension,
            parseTreeBuilder,
            unknownFields);
      }
 
      if (parseTreeBuilder != null) {
        parseTreeBuilder.setLocation(field, TextFormatParseLocation.create(startLine, startColumn));
      }
 
      // For historical reasons, fields may optionally be separated by commas or
      // semicolons.
      if (!tokenizer.tryConsume(";")) {
        tokenizer.tryConsume(",");
      }
    }
 
    private void consumeFieldValues(
        final Tokenizer tokenizer,
        final ExtensionRegistry extensionRegistry,
        final MessageReflection.MergeTarget target,
        final FieldDescriptor field,
        final ExtensionRegistry.ExtensionInfo extension,
        final TextFormatParseInfoTree.Builder parseTreeBuilder,
        List<UnknownField> unknownFields)
        throws ParseException {
      // Support specifying repeated field values as a comma-separated list.
      // Ex."foo: [1, 2, 3]"
      if (field.isRepeated() && tokenizer.tryConsume("[")) {
        if (!tokenizer.tryConsume("]")) { // Allow "foo: []" to be treated as empty.
          while (true) {
            consumeFieldValue(
                tokenizer,
                extensionRegistry,
                target,
                field,
                extension,
                parseTreeBuilder,
                unknownFields);
            if (tokenizer.tryConsume("]")) {
              // End of list.
              break;
            }
            tokenizer.consume(",");
          }
        }
      } else {
        consumeFieldValue(
            tokenizer,
            extensionRegistry,
            target,
            field,
            extension,
            parseTreeBuilder,
            unknownFields);
      }
    }
 
    private void consumeFieldValue(
        final Tokenizer tokenizer,
        final ExtensionRegistry extensionRegistry,
        final MessageReflection.MergeTarget target,
        final FieldDescriptor field,
        final ExtensionRegistry.ExtensionInfo extension,
        final TextFormatParseInfoTree.Builder parseTreeBuilder,
        List<UnknownField> unknownFields)
        throws ParseException {
      if (singularOverwritePolicy == SingularOverwritePolicy.FORBID_SINGULAR_OVERWRITES
          && !field.isRepeated()) {
        if (target.hasField(field)) {
          throw tokenizer.parseExceptionPreviousToken(
              "Non-repeated field \"" + field.getFullName() + "\" cannot be overwritten.");
        } else if (field.getContainingOneof() != null
            && target.hasOneof(field.getContainingOneof())) {
          Descriptors.OneofDescriptor oneof = field.getContainingOneof();
          throw tokenizer.parseExceptionPreviousToken(
              "Field \""
                  + field.getFullName()
                  + "\" is specified along with field \""
                  + target.getOneofFieldDescriptor(oneof).getFullName()
                  + "\", another member of oneof \""
                  + oneof.getName()
                  + "\".");
        }
      }
 
      Object value = null;
 
      if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
        final String endToken;
        if (tokenizer.tryConsume("<")) {
          endToken = ">";
        } else {
          tokenizer.consume("{");
          endToken = "}";
        }
 
          Message defaultInstance = (extension == null) ? null : extension.defaultInstance;
          MessageReflection.MergeTarget subField =
              target.newMergeTargetForField(field, defaultInstance);
 
          while (!tokenizer.tryConsume(endToken)) {
            if (tokenizer.atEnd()) {
              throw tokenizer.parseException("Expected \"" + endToken + "\".");
            }
            mergeField(tokenizer, extensionRegistry, subField, parseTreeBuilder, unknownFields);
          }
 
          value = subField.finish();
      } else {
        switch (field.getType()) {
          case INT32:
          case SINT32:
          case SFIXED32:
            value = tokenizer.consumeInt32();
            break;
 
          case INT64:
          case SINT64:
          case SFIXED64:
            value = tokenizer.consumeInt64();
            break;
 
          case UINT32:
          case FIXED32:
            value = tokenizer.consumeUInt32();
            break;
 
          case UINT64:
          case FIXED64:
            value = tokenizer.consumeUInt64();
            break;
 
          case FLOAT:
            value = tokenizer.consumeFloat();
            break;
 
          case DOUBLE:
            value = tokenizer.consumeDouble();
            break;
 
          case BOOL:
            value = tokenizer.consumeBoolean();
            break;
 
          case STRING:
            value = tokenizer.consumeString();
            break;
 
          case BYTES:
            value = tokenizer.consumeByteString();
            break;
 
          case ENUM:
            final EnumDescriptor enumType = field.getEnumType();
 
            if (tokenizer.lookingAtInteger()) {
              final int number = tokenizer.consumeInt32();
              value = enumType.findValueByNumber(number);
              if (value == null) {
                String unknownValueMsg =
                    "Enum type \""
                        + enumType.getFullName()
                        + "\" has no value with number "
                        + number
                        + '.';
                if (allowUnknownEnumValues) {
                  logger.warning(unknownValueMsg);
                  return;
                } else {
                  throw tokenizer.parseExceptionPreviousToken(
                      "Enum type \""
                          + enumType.getFullName()
                          + "\" has no value with number "
                          + number
                          + '.');
                }
              }
            } else {
              final String id = tokenizer.consumeIdentifier();
              value = enumType.findValueByName(id);
              if (value == null) {
                String unknownValueMsg =
                    "Enum type \""
                        + enumType.getFullName()
                        + "\" has no value named \""
                        + id
                        + "\".";
                if (allowUnknownEnumValues) {
                  logger.warning(unknownValueMsg);
                  return;
                } else {
                  throw tokenizer.parseExceptionPreviousToken(unknownValueMsg);
                }
              }
            }
 
            break;
 
          case MESSAGE:
          case GROUP:
            throw new RuntimeException("Can't get here.");
        }
      }
 
      if (field.isRepeated()) {
        // TODO(b/29122459): If field.isMapField() and FORBID_SINGULAR_OVERWRITES mode,
        //     check for duplicate map keys here.
        target.addRepeatedField(field, value);
      } else {
        target.setField(field, value);
      }
    }
 
 
    private void skipField(Tokenizer tokenizer) throws ParseException {
      if (tokenizer.tryConsume("[")) {
        // Extension name.
        do {
          tokenizer.consumeIdentifier();
        } while (tokenizer.tryConsume("."));
        tokenizer.consume("]");
      } else {
        tokenizer.consumeIdentifier();
      }
 
      // Try to guess the type of this field.
      // If this field is not a message, there should be a ":" between the
      // field name and the field value and also the field value should not
      // start with "{" or "<" which indicates the beginning of a message body.
      // If there is no ":" or there is a "{" or "<" after ":", this field has
      // to be a message or the input is ill-formed.
      if (tokenizer.tryConsume(":") && !tokenizer.lookingAt("<") && !tokenizer.lookingAt("{")) {
        skipFieldValue(tokenizer);
      } else {
        skipFieldMessage(tokenizer);
      }
      // For historical reasons, fields may optionally be separated by commas or
      // semicolons.
      if (!tokenizer.tryConsume(";")) {
        tokenizer.tryConsume(",");
      }
    }
 
    private void skipFieldMessage(Tokenizer tokenizer) throws ParseException {
      final String delimiter;
      if (tokenizer.tryConsume("<")) {
        delimiter = ">";
      } else {
        tokenizer.consume("{");
        delimiter = "}";
      }
      while (!tokenizer.lookingAt(">") && !tokenizer.lookingAt("}")) {
        skipField(tokenizer);
      }
      tokenizer.consume(delimiter);
    }
 
    private void skipFieldValue(Tokenizer tokenizer) throws ParseException {
      if (tokenizer.tryConsumeString()) {
        while (tokenizer.tryConsumeString()) {}
        return;
      }
      if (!tokenizer.tryConsumeIdentifier() // includes enum & boolean
          && !tokenizer.tryConsumeInt64() // includes int32
          && !tokenizer.tryConsumeUInt64() // includes uint32
          && !tokenizer.tryConsumeDouble()
          && !tokenizer.tryConsumeFloat()) {
        throw tokenizer.parseException("Invalid field value: " + tokenizer.currentToken);
      }
    }
  }
 
  // =================================================================
  // Utility functions
  //
  // Some of these methods are package-private because Descriptors.java uses
  // them.
 
  public static String escapeBytes(ByteString input) {
    return TextFormatEscaper.escapeBytes(input);
  }
 
  public static String escapeBytes(byte[] input) {
    return TextFormatEscaper.escapeBytes(input);
  }
 
  public static ByteString unescapeBytes(final CharSequence charString)
      throws InvalidEscapeSequenceException {
    // First convert the Java character sequence to UTF-8 bytes.
    ByteString input = ByteString.copyFromUtf8(charString.toString());
    // Then unescape certain byte sequences introduced by ASCII '\\'.  The valid
    // escapes can all be expressed with ASCII characters, so it is safe to
    // operate on bytes here.
    //
    // Unescaping the input byte array will result in a byte sequence that's no
    // longer than the input.  That's because each escape sequence is between
    // two and four bytes long and stands for a single byte.
    final byte[] result = new byte[input.size()];
    int pos = 0;
    for (int i = 0; i < input.size(); i++) {
      byte c = input.byteAt(i);
      if (c == '\\') {
        if (i + 1 < input.size()) {
          ++i;
          c = input.byteAt(i);
          if (isOctal(c)) {
            // Octal escape.
            int code = digitValue(c);
            if (i + 1 < input.size() && isOctal(input.byteAt(i + 1))) {
              ++i;
              code = code * 8 + digitValue(input.byteAt(i));
            }
            if (i + 1 < input.size() && isOctal(input.byteAt(i + 1))) {
              ++i;
              code = code * 8 + digitValue(input.byteAt(i));
            }
            // TODO: Check that 0 <= code && code <= 0xFF.
            result[pos++] = (byte) code;
          } else {
            switch (c) {
              case 'a':
                result[pos++] = 0x07;
                break;
              case 'b':
                result[pos++] = '\b';
                break;
              case 'f':
                result[pos++] = '\f';
                break;
              case 'n':
                result[pos++] = '\n';
                break;
              case 'r':
                result[pos++] = '\r';
                break;
              case 't':
                result[pos++] = '\t';
                break;
              case 'v':
                result[pos++] = 0x0b;
                break;
              case '\\':
                result[pos++] = '\\';
                break;
              case '\'':
                result[pos++] = '\'';
                break;
              case '"':
                result[pos++] = '\"';
                break;
 
              case 'x':
                // hex escape
                int code = 0;
                if (i + 1 < input.size() && isHex(input.byteAt(i + 1))) {
                  ++i;
                  code = digitValue(input.byteAt(i));
                } else {
                  throw new InvalidEscapeSequenceException(
                      "Invalid escape sequence: '\\x' with no digits");
                }
                if (i + 1 < input.size() && isHex(input.byteAt(i + 1))) {
                  ++i;
                  code = code * 16 + digitValue(input.byteAt(i));
                }
                result[pos++] = (byte) code;
                break;
 
              default:
                throw new InvalidEscapeSequenceException(
                    "Invalid escape sequence: '\\" + (char) c + '\'');
            }
          }
        } else {
          throw new InvalidEscapeSequenceException(
              "Invalid escape sequence: '\\' at end of string.");
        }
      } else {
        result[pos++] = c;
      }
    }
 
    return result.length == pos
        ? ByteString.wrap(result) // This reference has not been out of our control.
        : ByteString.copyFrom(result, 0, pos);
  }
 
  public static class InvalidEscapeSequenceException extends IOException {
    private static final long serialVersionUID = -8164033650142593304L;
 
    InvalidEscapeSequenceException(final String description) {
      super(description);
    }
  }
 
  static String escapeText(final String input) {
    return escapeBytes(ByteString.copyFromUtf8(input));
  }
 
  public static String escapeDoubleQuotesAndBackslashes(final String input) {
    return TextFormatEscaper.escapeDoubleQuotesAndBackslashes(input);
  }
 
  static String unescapeText(final String input) throws InvalidEscapeSequenceException {
    return unescapeBytes(input).toStringUtf8();
  }
 
  private static boolean isOctal(final byte c) {
    return '0' <= c && c <= '7';
  }
 
  private static boolean isHex(final byte c) {
    return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F');
  }
 
  private static int digitValue(final byte c) {
    if ('0' <= c && c <= '9') {
      return c - '0';
    } else if ('a' <= c && c <= 'z') {
      return c - 'a' + 10;
    } else {
      return c - 'A' + 10;
    }
  }
 
  static int parseInt32(final String text) throws NumberFormatException {
    return (int) parseInteger(text, true, false);
  }
 
  static int parseUInt32(final String text) throws NumberFormatException {
    return (int) parseInteger(text, false, false);
  }
 
  static long parseInt64(final String text) throws NumberFormatException {
    return parseInteger(text, true, true);
  }
 
  static long parseUInt64(final String text) throws NumberFormatException {
    return parseInteger(text, false, true);
  }
 
  private static long parseInteger(final String text, final boolean isSigned, final boolean isLong)
      throws NumberFormatException {
    int pos = 0;
 
    boolean negative = false;
    if (text.startsWith("-", pos)) {
      if (!isSigned) {
        throw new NumberFormatException("Number must be positive: " + text);
      }
      ++pos;
      negative = true;
    }
 
    int radix = 10;
    if (text.startsWith("0x", pos)) {
      pos += 2;
      radix = 16;
    } else if (text.startsWith("0", pos)) {
      radix = 8;
    }
 
    final String numberText = text.substring(pos);
 
    long result = 0;
    if (numberText.length() < 16) {
      // Can safely assume no overflow.
      result = Long.parseLong(numberText, radix);
      if (negative) {
        result = -result;
      }
 
      // Check bounds.
      // No need to check for 64-bit numbers since they'd have to be 16 chars
      // or longer to overflow.
      if (!isLong) {
        if (isSigned) {
          if (result > Integer.MAX_VALUE || result < Integer.MIN_VALUE) {
            throw new NumberFormatException(
                "Number out of range for 32-bit signed integer: " + text);
          }
        } else {
          if (result >= (1L << 32) || result < 0) {
            throw new NumberFormatException(
                "Number out of range for 32-bit unsigned integer: " + text);
          }
        }
      }
    } else {
      BigInteger bigValue = new BigInteger(numberText, radix);
      if (negative) {
        bigValue = bigValue.negate();
      }
 
      // Check bounds.
      if (!isLong) {
        if (isSigned) {
          if (bigValue.bitLength() > 31) {
            throw new NumberFormatException(
                "Number out of range for 32-bit signed integer: " + text);
          }
        } else {
          if (bigValue.bitLength() > 32) {
            throw new NumberFormatException(
                "Number out of range for 32-bit unsigned integer: " + text);
          }
        }
      } else {
        if (isSigned) {
          if (bigValue.bitLength() > 63) {
            throw new NumberFormatException(
                "Number out of range for 64-bit signed integer: " + text);
          }
        } else {
          if (bigValue.bitLength() > 64) {
            throw new NumberFormatException(
                "Number out of range for 64-bit unsigned integer: " + text);
          }
        }
      }
 
      result = bigValue.longValue();
    }
 
    return result;
  }
}