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#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
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