Alexandre Lision | 51140e1 | 2013-12-02 10:54:09 -0500 | [diff] [blame] | 1 | #ifndef BASE32_H |
| 2 | #define BASE32_H |
| 3 | |
| 4 | /* |
| 5 | * |
| 6 | * Copyright (c) 2002 Bryce "Zooko" Wilcox-O'Hearn Permission is hereby |
| 7 | * granted, free of charge, to any person obtaining a copy of this software to |
| 8 | * deal in this software without restriction, including without limitation the |
| 9 | * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or |
| 10 | * sell copies of this software, and to permit persons to whom this software |
| 11 | * is furnished to do so, subject to the following conditions: |
| 12 | * |
| 13 | * The above copyright notice and this permission notice shall be included in |
| 14 | * all copies or substantial portions of this software. |
| 15 | * |
| 16 | * THIS SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| 19 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 20 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
| 21 | * FROM, OUT OF OR IN CONNECTION WITH THIS SOFTWARE OR THE USE OR OTHER |
| 22 | * DEALINGS IN THIS SOFTWARE. |
| 23 | * |
| 24 | * Converted to C++ by: |
| 25 | * @author Werner Dittmann <Werner.Dittmann@t-online.de> |
| 26 | */ |
| 27 | |
| 28 | /** |
| 29 | * @file Base32.h |
| 30 | * @brief C++ implmentation of the Base32 encoding and decoding |
| 31 | * |
| 32 | * ZRTP uses the base 32 encoding and decoding to generate the Short |
| 33 | * Authentication String (SAS). |
| 34 | * |
| 35 | * @ingroup GNU_ZRTP |
| 36 | * @{ |
| 37 | */ |
| 38 | |
| 39 | #include <iostream> |
| 40 | #include <cstdlib> |
| 41 | |
| 42 | #include <string.h> |
| 43 | #include <assert.h> |
| 44 | #include <stddef.h> |
| 45 | |
| 46 | using namespace std; |
| 47 | |
| 48 | extern int divceil(int a, int b); |
| 49 | |
| 50 | class Base32 { |
| 51 | |
| 52 | public: |
| 53 | |
| 54 | /** |
| 55 | * A Constructor that decodes from base32 into binary. |
| 56 | * |
| 57 | * The constructor decodes the base32 encoded data back into binary |
| 58 | * data. Use <code>getDecoded(...)</code> to get the binary data. |
| 59 | * |
| 60 | * @param encoded |
| 61 | * The string that contains the base32 encoded data. |
| 62 | */ |
| 63 | Base32(const string encoded); |
| 64 | |
| 65 | /** |
| 66 | * A Constructor that decodes from base32 into binary. |
| 67 | * |
| 68 | * This constructor decodes the base32 encoded data back into |
| 69 | * binary data. Only the specified number of bits are decoded |
| 70 | * (should be a multiple of 5). Use |
| 71 | * <code>getDecoded(...)</code> to get the binary data. |
| 72 | * |
| 73 | * @param encoded |
| 74 | * The string that contains the base32 encoded data. |
| 75 | * @param noOfBits |
| 76 | * How many bits to decode into binary data. |
| 77 | */ |
| 78 | Base32(const string encoded, int noOfBits); |
| 79 | |
| 80 | /** |
| 81 | * A Constructor that encodes binary data. |
| 82 | * |
| 83 | * The constructor converts the first specified number of bits of |
| 84 | * the binary data into a base32 presentation. Use |
| 85 | * <code>getEncoded</code> to get the encoded data. |
| 86 | * |
| 87 | * @param data |
| 88 | * A pointer to the first bits (byte) of binary data |
| 89 | * @param noOfBits |
| 90 | * How many bits to use for encoding. Should be a |
| 91 | * multiple of 5. |
| 92 | */ |
| 93 | Base32(const unsigned char* data, int noOfBits); |
| 94 | |
| 95 | ~Base32(); |
| 96 | |
| 97 | /** |
| 98 | * Get the decoded binary data and its length. |
| 99 | * |
| 100 | * The method returns the decoded binary data if the appropriate |
| 101 | * Constructor was used. Otherwise we return <code>NULL</code> |
| 102 | * pointer and length zero. |
| 103 | * |
| 104 | * <em>Note:</em> This method returns a pointer to the decoded |
| 105 | * binary data. The Base32 object manages this pointer, thus you |
| 106 | * may need to copy the data to a save place before deleting this |
| 107 | * object. If the object is deleted this pointer is no longer |
| 108 | * valid. |
| 109 | * |
| 110 | * @param length |
| 111 | * A reference to an integer. |
| 112 | * @return |
| 113 | * A pointer to the decoded binary data. |
| 114 | */ |
| 115 | const unsigned char* getDecoded(int &length); |
| 116 | |
| 117 | /** |
| 118 | * Get the encoded base32 string. |
| 119 | * |
| 120 | * The method returns a string that contains the base32 encoded |
| 121 | * data if the appropriate constructor was used. Otherwise we |
| 122 | * return an empty string. |
| 123 | * |
| 124 | * @return |
| 125 | * The string containing the base32 encoded data. |
| 126 | */ |
| 127 | const string getEncoded() { return encoded; }; |
| 128 | |
| 129 | /** |
| 130 | * Compute the number of base32 encoded characters given the |
| 131 | * number of bits. |
| 132 | * |
| 133 | * @param lengthInBits |
| 134 | * The length of the data in bits |
| 135 | * @return |
| 136 | * The length of the base-32 encoding of the data in characters |
| 137 | */ |
| 138 | static size_t const b2alen(const size_t lengthInBits) { |
| 139 | return divceil(lengthInBits, 5); }; |
| 140 | |
| 141 | private: |
| 142 | |
| 143 | /** |
| 144 | * Decodes a string with base32 presentation into binary data. |
| 145 | * |
| 146 | * a2b_l() will return a result big enough to hold lengthinbits bits. So |
| 147 | * for example if cs is 4 characters long (encoding at least 15 and up to |
| 148 | * 20 bits) and lengthinbits is 16, then a2b_l() will return a string of |
| 149 | * length 2 (since 2 bytes is sufficient to store 16 bits). If cs is 4 |
| 150 | * characters long and lengthinbits is 20, then a2b_l() will return a |
| 151 | * string of length 3 (since 3 bytes is sufficient to store 20 bits). Note |
| 152 | * that `b2a_l()' does not mask off unused least-significant bits, so for |
| 153 | * example if cs is 4 characters long and lengthinbits is 17, then you |
| 154 | * must ensure that all three of the unused least-significant bits of cs |
| 155 | * are zero bits or you will get the wrong result. This precondition is |
| 156 | * tested by assertions if assertions are enabled. (Generally you just |
| 157 | * require the encoder to ensure this consistency property between the |
| 158 | * least significant zero bits and value of `lengthinbits', and reject |
| 159 | * strings that have a length-in-bits which isn't a multiple of 8 and yet |
| 160 | * don't have trailing zero bits, as improperly encoded.) |
| 161 | * |
| 162 | * @param cs |
| 163 | * The data to be decoded |
| 164 | * @param size |
| 165 | * The length of the input data buffer. Usually divceil(length in bits, 5). |
| 166 | * @param lengthinbits |
| 167 | * The number of bits of data in <code>cs</code> to be decoded |
| 168 | */ |
| 169 | void a2b_l(const string cs, size_t size, const size_t lengthinbits); |
| 170 | |
| 171 | /** |
| 172 | * Encodes binary to to base32 presentation. |
| 173 | * |
| 174 | * b2a_l() will generate a base-32 encoded string big enough to encode |
| 175 | * lengthinbits bits. So for example if os is 2 bytes long and |
| 176 | * lengthinbits is 15, then b2a_l() will generate a 3-character- long |
| 177 | * base-32 encoded string (since 3 quintets is sufficient to encode 15 |
| 178 | * bits). If os is 2 bytes long and lengthinbits is 16 (or None), then |
| 179 | * b2a_l() will generate a 4-character string. Note that `b2a_l()' does |
| 180 | * not mask off unused least-significant bits, so for example if os is 2 |
| 181 | * bytes long and lengthinbits is 15, then you must ensure that the unused |
| 182 | * least-significant bit of os is a zero bit or you will get the wrong |
| 183 | * result. This precondition is tested by assertions if assertions are |
| 184 | * enabled. |
| 185 | * |
| 186 | * Warning: if you generate a base-32 encoded string with `b2a_l()', and |
| 187 | * then someone else tries to decode it by calling `a2b()' instead of |
| 188 | * `a2b_l()', then they will (probably) get a different string than the |
| 189 | * one you encoded! So only use `b2a_l()' when you are sure that the |
| 190 | * encoding and decoding sides know exactly which `lengthinbits' to use. |
| 191 | * If you do not have a way for the encoder and the decoder to agree upon |
| 192 | * the lengthinbits, then it is best to use `b2a()' and `a2b()'. The only |
| 193 | * drawback to using `b2a()' over `b2a_l()' is that when you have a number |
| 194 | * of bits to encode that is not a multiple of 8, `b2a()' can sometimes |
| 195 | * generate a base-32 encoded string that is one or two characters longer |
| 196 | * than necessary. |
| 197 | * |
| 198 | * @param cs |
| 199 | * Pointer to binary data. |
| 200 | * @param len |
| 201 | * Length of the binary data buffer. Usually (noOfBits+7)/8. |
| 202 | * @param noOfBits |
| 203 | * The number of bits of data in encoded into `cs' |
| 204 | */ |
| 205 | void b2a_l(const unsigned char* cs, int len, const size_t noOfBits); |
| 206 | |
| 207 | /** |
| 208 | * Holds the pointer to decoded binary data |
| 209 | */ |
| 210 | unsigned char *binaryResult; |
| 211 | |
| 212 | /** |
| 213 | * Length of decoding result |
| 214 | */ |
| 215 | int resultLength; |
| 216 | |
| 217 | /** |
| 218 | * The string containing the base32 encoded data. |
| 219 | */ |
| 220 | string encoded; |
| 221 | |
| 222 | unsigned char smallBuffer[128]; |
| 223 | }; |
| 224 | |
| 225 | /** |
| 226 | * @} |
| 227 | */ |
| 228 | #endif |