Copyright 2015 Red Hat, Inc.

All rights reserved. This program and the accompanying materials
are made available under the terms of the Eclipse Public License v1.0
and Apache License v2.0 which accompanies this distribution.

The Eclipse Public License is available at
http://www.eclipse.org/legal/epl-v10.html

The Apache License v2.0 is available at
http://www.opensource.org/licenses/apache2.0.php

You may elect to redistribute this code under either of these licenses.
/**
 * Copyright 2015 Red Hat, Inc.
 * <p>
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Apache License v2.0 which accompanies this distribution.
 * <p>
 * The Eclipse Public License is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * <p>
 * The Apache License v2.0 is available at
 * http://www.opensource.org/licenses/apache2.0.php
 * <p>
 * You may elect to redistribute this code under either of these licenses.
 */
package io.vertx.redis.impl;

This is how Redis escapes char codes:
DEC      HEX    REDIS
07       07     \a
08       08     \b
09       09     \t
10       0a     \n
13       0d     \r
Otherwise:
00-32    00-20  \xXX
32-127   20-7f  ASCII char
127-256  7f-ff  \xXX
Author:
Marko Strukelj/**
 * This is how Redis escapes char codes:
 *
 * DEC      HEX    REDIS
 * 07       07     \a
 * 08       08     \b
 * 09       09     \t
 * 10       0a     \n
 * 13       0d     \r
 *
 * Otherwise:
 * 00-32    00-20  \xXX
 * 32-127   20-7f  ASCII char
 * 127-256  7f-ff  \xXX
 *
 * @author <a href="mailto:marko.strukelj@gmail.com">Marko Strukelj</a>
 */
public class RedisEncoding {

  private static final char[] NUMERALS = "0123456789abcdef".toCharArray();

  
Encode characters in input string using \\xXX syntax.
Only lower byte of every character is used when encoding.
Params:
value – Input string with characters between 0 and 255
Returns:
Encoded string that can be pasted into redis-cli shell/**
   * Encode characters in input string using \\xXX syntax.
   * Only lower byte of every character is used when encoding.
   *
   * @param value Input string with characters between 0 and 255
   * @return Encoded string that can be pasted into redis-cli shell
   */
  public static String encode(String value) {
    StringBuilder sb = new StringBuilder();
    int len = value.length();
    for (int i = 0; i < len; i++) {
      char c = value.charAt(i);
      int lo = 0xFF & c;
      if (lo >= 32 && lo < 127) {
        sb.append((char) lo);
        continue;
      }
      switch (lo) {
        case 7:
          sb.append("\\a");
          continue;
        case 8:
          sb.append("\\b");
          continue;
        case 9:
          sb.append("\\t");
          continue;
        case 10:
          sb.append("\\n");
          continue;
        case 13:
          sb.append("\\r");
          continue;
      }

      int ma = lo / 16;
      int mi = lo % 16;
      sb.append("\\x").append(NUMERALS[ma]).append(NUMERALS[mi]);
    }
    return sb.toString();
  }

  
Decode characters in input string from \\xXX syntax.
Result can be passed to setBinary(), and restore()
Params:
value – Input string with characters between 0 and 255
Returns:
Encoded string that can be pasted into redis-cli shell/**
   * Decode characters in input string from \\xXX syntax.
   * Result can be passed to setBinary(), and restore()
   *
   * @param value Input string with characters between 0 and 255
   * @return Encoded string that can be pasted into redis-cli shell
   */
  public static String decode(String value) {
    StringBuilder sb = new StringBuilder();
    int len = value.length();

    int decoding = -1;
    int d = 0;

    for (int i = 0; i < len; i++) {
      char c = value.charAt(i);

      if (decoding > -1) {
        int df = i - decoding;
        if (df == 1) {
          if (c == 'x') {
            continue;
          }
          switch (c) {
            case 'a':
              sb.append('\u0007');
              break;
            case 'b':
              sb.append('\u0008');
              break;
            case 't':
              sb.append('\u0009');
              break;
            case 'n':
              sb.append('\n');
              break;
            case 'r':
              sb.append('\r');
              break;
            case '\\':
              sb.append('\\');
              break;
            default:
              throw new RuntimeException("Invalid escape sequence: \\" + c + " at pos " + i);
          }
          decoding = -1;
          d = 0;
          continue;
        }

        int val = c >= 48 && c < 58 ? (c - 48)
          : c >= 65 && c < 71 ? (10 + c - 65)
          : c >= 97 && c < 103 ? (10 + c - 97)
          : -1;
        if (val == -1) {
          throw new RuntimeException("Invalid escape sequence: " + value.substring(decoding, i + 1) + " at pos: " + i);
        }

        d += df == 2 ? 16 * val : val;

        if (df == 3) {
          sb.append((char) d);
          decoding = -1;
          d = 0;
        }
      } else if (c == '\\') {
        decoding = i;
      } else {
        sb.append(c);
      }
    }
    return sb.toString();
  }
}