base32.h
/**
 * base32 (de)coder implementation as specified by RFC4648.
 *
 * Copyright (c) 2010 Adrien Kunysz
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the 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 the Software.
 *
 * THE 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 THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 **/

#ifndef __BASE32_H_
#define __BASE32_H_

#include <stddef.h>   // size_t

/**
 * Returns the length of the output buffer required to encode len bytes of
 * data into base32. This is a macro to allow users to define buffer size at
 * compilation time.
 */
#define BASE32_LEN(len)  (((len)/5)*8 + ((len) % 5 ? 8 : 0))

/**
 * Returns the length of the output buffer required to decode a base32 string
 * of len characters. Please note that len must be a multiple of 8 as per
 * definition of a base32 string. This is a macro to allow users to define
 * buffer size at compilation time.
 */
#define UNBASE32_LEN(len)  (((len)/8)*5)

/**
 * Encode the data pointed to by plain into base32 and store the
 * result at the address pointed to by coded. The "coded" argument
 * must point to a location that has enough available space
 * to store the whole coded string. The resulting string will only
 * contain characters from the [A-Z2-7=] set. The "len" arguments
 * define how many bytes will be read from the "plain" buffer.
 **/
void base32_encode(const unsigned char *plain, size_t len, unsigned char *coded);

/**
 * Decode the null terminated string pointed to by coded and write
 * the decoded data into the location pointed to by plain. The
 * "plain" argument must point to a location that has enough available
 * space to store the whole decoded string.
 * Returns the length of the decoded string. This may be less than
 * expected due to padding. If an invalid base32 character is found
 * in the coded string, decoding will stop at that point.
 **/
size_t base32_decode(const unsigned char *coded, unsigned char *plain);

#endif
