java/core/src/main/java/com/google/protobuf/TextFormatEscaper.java

// 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
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package com.google.protobuf;

/** Provide text format escaping support for proto2 instances. */
final class TextFormatEscaper {
  private TextFormatEscaper() {}

  private interface ByteSequence {
    int size();

    byte byteAt(int offset);
  }

  /**
   * Escapes bytes in the format used in protocol buffer text format, which is the same as the
   * format used for C string literals. All bytes that are not printable 7-bit ASCII characters are
   * escaped, as well as backslash, single-quote, and double-quote characters. Characters for which
   * no defined short-hand escape sequence is defined will be escaped using 3-digit octal sequences.
   */
  static String escapeBytes(final ByteSequence input) {
    final StringBuilder builder = new StringBuilder(input.size());
    for (int i = 0; i < input.size(); i++) {
      final byte b = input.byteAt(i);
      switch (b) {
          // Java does not recognize \a or \v, apparently.
        case 0x07:
          builder.append("\\a");
          break;
        case '\b':
          builder.append("\\b");
          break;
        case '\f':
          builder.append("\\f");
          break;
        case '\n':
          builder.append("\\n");
          break;
        case '\r':
          builder.append("\\r");
          break;
        case '\t':
          builder.append("\\t");
          break;
        case 0x0b:
          builder.append("\\v");
          break;
        case '\\':
          builder.append("\\\\");
          break;
        case '\'':
          builder.append("\\\'");
          break;
        case '"':
          builder.append("\\\"");
          break;
        default:
          // Only ASCII characters between 0x20 (space) and 0x7e (tilde) are
          // printable.  Other byte values must be escaped.
          if (b >= 0x20 && b <= 0x7e) {
            builder.append((char) b);
          } else {
            builder.append('\\');
            builder.append((char) ('0' + ((b >>> 6) & 3)));
            builder.append((char) ('0' + ((b >>> 3) & 7)));
            builder.append((char) ('0' + (b & 7)));
          }
          break;
      }
    }
    return builder.toString();
  }

  /**
   * Escapes bytes in the format used in protocol buffer text format, which is the same as the
   * format used for C string literals. All bytes that are not printable 7-bit ASCII characters are
   * escaped, as well as backslash, single-quote, and double-quote characters. Characters for which
   * no defined short-hand escape sequence is defined will be escaped using 3-digit octal sequences.
   */
  static String escapeBytes(final ByteString input) {
    return escapeBytes(
        new ByteSequence() {
          @Override
          public int size() {
            return input.size();
          }

          @Override
          public byte byteAt(int offset) {
            return input.byteAt(offset);
          }
        });
  }

  /** Like {@link #escapeBytes(ByteString)}, but used for byte array. */
  static String escapeBytes(final byte[] input) {
    return escapeBytes(
        new ByteSequence() {
          @Override
          public int size() {
            return input.length;
          }

          @Override
          public byte byteAt(int offset) {
            return input[offset];
          }
        });
  }

  /**
   * Like {@link #escapeBytes(ByteString)}, but escapes a text string. Non-ASCII characters are
   * first encoded as UTF-8, then each byte is escaped individually as a 3-digit octal escape. Yes,
   * it's weird.
   */
  static String escapeText(final String input) {
    return escapeBytes(ByteString.copyFromUtf8(input));
  }

  /** Escape double quotes and backslashes in a String for unicode output of a message. */
  static String escapeDoubleQuotesAndBackslashes(final String input) {
    return input.replace("\\", "\\\\").replace("\"", "\\\"");
  }
}