| #ifndef BASE32_H |
| #define BASE32_H |
| |
| /* |
| * |
| * Copyright (c) 2002 Bryce "Zooko" Wilcox-O'Hearn Permission is hereby |
| * granted, free of charge, to any person obtaining a copy of this software to |
| * deal in this software without restriction, including without limitation the |
| * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or |
| * sell copies of this software, and to permit persons to whom this software |
| * is furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be included in |
| * all copies or substantial portions of this software. |
| * |
| * THIS SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
| * FROM, OUT OF OR IN CONNECTION WITH THIS SOFTWARE OR THE USE OR OTHER |
| * DEALINGS IN THIS SOFTWARE. |
| * |
| * Converted to C++ by: |
| * @author Werner Dittmann <Werner.Dittmann@t-online.de> |
| */ |
| |
| /** |
| * @file Base32.h |
| * @brief C++ implmentation of the Base32 encoding and decoding |
| * |
| * ZRTP uses the base 32 encoding and decoding to generate the Short |
| * Authentication String (SAS). |
| * |
| * @ingroup GNU_ZRTP |
| * @{ |
| */ |
| |
| #include <iostream> |
| #include <cstdlib> |
| |
| #include <string.h> |
| #include <assert.h> |
| #include <stddef.h> |
| |
| using namespace std; |
| |
| extern int divceil(int a, int b); |
| |
| class Base32 { |
| |
| public: |
| |
| /** |
| * A Constructor that decodes from base32 into binary. |
| * |
| * The constructor decodes the base32 encoded data back into binary |
| * data. Use <code>getDecoded(...)</code> to get the binary data. |
| * |
| * @param encoded |
| * The string that contains the base32 encoded data. |
| */ |
| Base32(const string encoded); |
| |
| /** |
| * A Constructor that decodes from base32 into binary. |
| * |
| * This constructor decodes the base32 encoded data back into |
| * binary data. Only the specified number of bits are decoded |
| * (should be a multiple of 5). Use |
| * <code>getDecoded(...)</code> to get the binary data. |
| * |
| * @param encoded |
| * The string that contains the base32 encoded data. |
| * @param noOfBits |
| * How many bits to decode into binary data. |
| */ |
| Base32(const string encoded, int noOfBits); |
| |
| /** |
| * A Constructor that encodes binary data. |
| * |
| * The constructor converts the first specified number of bits of |
| * the binary data into a base32 presentation. Use |
| * <code>getEncoded</code> to get the encoded data. |
| * |
| * @param data |
| * A pointer to the first bits (byte) of binary data |
| * @param noOfBits |
| * How many bits to use for encoding. Should be a |
| * multiple of 5. |
| */ |
| Base32(const unsigned char* data, int noOfBits); |
| |
| ~Base32(); |
| |
| /** |
| * Get the decoded binary data and its length. |
| * |
| * The method returns the decoded binary data if the appropriate |
| * Constructor was used. Otherwise we return <code>NULL</code> |
| * pointer and length zero. |
| * |
| * <em>Note:</em> This method returns a pointer to the decoded |
| * binary data. The Base32 object manages this pointer, thus you |
| * may need to copy the data to a save place before deleting this |
| * object. If the object is deleted this pointer is no longer |
| * valid. |
| * |
| * @param length |
| * A reference to an integer. |
| * @return |
| * A pointer to the decoded binary data. |
| */ |
| const unsigned char* getDecoded(int &length); |
| |
| /** |
| * Get the encoded base32 string. |
| * |
| * The method returns a string that contains the base32 encoded |
| * data if the appropriate constructor was used. Otherwise we |
| * return an empty string. |
| * |
| * @return |
| * The string containing the base32 encoded data. |
| */ |
| const string getEncoded() { return encoded; }; |
| |
| /** |
| * Compute the number of base32 encoded characters given the |
| * number of bits. |
| * |
| * @param lengthInBits |
| * The length of the data in bits |
| * @return |
| * The length of the base-32 encoding of the data in characters |
| */ |
| static size_t const b2alen(const size_t lengthInBits) { |
| return divceil(lengthInBits, 5); }; |
| |
| private: |
| |
| /** |
| * Decodes a string with base32 presentation into binary data. |
| * |
| * a2b_l() will return a result big enough to hold lengthinbits bits. So |
| * for example if cs is 4 characters long (encoding at least 15 and up to |
| * 20 bits) and lengthinbits is 16, then a2b_l() will return a string of |
| * length 2 (since 2 bytes is sufficient to store 16 bits). If cs is 4 |
| * characters long and lengthinbits is 20, then a2b_l() will return a |
| * string of length 3 (since 3 bytes is sufficient to store 20 bits). Note |
| * that `b2a_l()' does not mask off unused least-significant bits, so for |
| * example if cs is 4 characters long and lengthinbits is 17, then you |
| * must ensure that all three of the unused least-significant bits of cs |
| * are zero bits or you will get the wrong result. This precondition is |
| * tested by assertions if assertions are enabled. (Generally you just |
| * require the encoder to ensure this consistency property between the |
| * least significant zero bits and value of `lengthinbits', and reject |
| * strings that have a length-in-bits which isn't a multiple of 8 and yet |
| * don't have trailing zero bits, as improperly encoded.) |
| * |
| * @param cs |
| * The data to be decoded |
| * @param size |
| * The length of the input data buffer. Usually divceil(length in bits, 5). |
| * @param lengthinbits |
| * The number of bits of data in <code>cs</code> to be decoded |
| */ |
| void a2b_l(const string cs, size_t size, const size_t lengthinbits); |
| |
| /** |
| * Encodes binary to to base32 presentation. |
| * |
| * b2a_l() will generate a base-32 encoded string big enough to encode |
| * lengthinbits bits. So for example if os is 2 bytes long and |
| * lengthinbits is 15, then b2a_l() will generate a 3-character- long |
| * base-32 encoded string (since 3 quintets is sufficient to encode 15 |
| * bits). If os is 2 bytes long and lengthinbits is 16 (or None), then |
| * b2a_l() will generate a 4-character string. Note that `b2a_l()' does |
| * not mask off unused least-significant bits, so for example if os is 2 |
| * bytes long and lengthinbits is 15, then you must ensure that the unused |
| * least-significant bit of os is a zero bit or you will get the wrong |
| * result. This precondition is tested by assertions if assertions are |
| * enabled. |
| * |
| * Warning: if you generate a base-32 encoded string with `b2a_l()', and |
| * then someone else tries to decode it by calling `a2b()' instead of |
| * `a2b_l()', then they will (probably) get a different string than the |
| * one you encoded! So only use `b2a_l()' when you are sure that the |
| * encoding and decoding sides know exactly which `lengthinbits' to use. |
| * If you do not have a way for the encoder and the decoder to agree upon |
| * the lengthinbits, then it is best to use `b2a()' and `a2b()'. The only |
| * drawback to using `b2a()' over `b2a_l()' is that when you have a number |
| * of bits to encode that is not a multiple of 8, `b2a()' can sometimes |
| * generate a base-32 encoded string that is one or two characters longer |
| * than necessary. |
| * |
| * @param cs |
| * Pointer to binary data. |
| * @param len |
| * Length of the binary data buffer. Usually (noOfBits+7)/8. |
| * @param noOfBits |
| * The number of bits of data in encoded into `cs' |
| */ |
| void b2a_l(const unsigned char* cs, int len, const size_t noOfBits); |
| |
| /** |
| * Holds the pointer to decoded binary data |
| */ |
| unsigned char *binaryResult; |
| |
| /** |
| * Length of decoding result |
| */ |
| int resultLength; |
| |
| /** |
| * The string containing the base32 encoded data. |
| */ |
| string encoded; |
| |
| unsigned char smallBuffer[128]; |
| }; |
| |
| /** |
| * @} |
| */ |
| #endif |