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/* vim: set expandtab ts=4 sw=4: */
/*
* You may redistribute this program and/or modify it under the terms of
* the GNU General Public License as published by the Free Software Foundation,
* either version 3 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef Base32_H
#define Base32_H
#include <stdint.h>
/*
* Base32 encode or decode a byte array using the format defined in:
* http://dnscurve.org/in-implement.html
*/
/** Returned by Base32_decode() if the input is not valid base32. */
#define Base32_BAD_INPUT -1
/** Returned by Base32_decode() or Base32_encode() if the output buffer is too small. */
#define Base32_TOO_BIG -2
/**
* Decode a base32 encoded number.
*
* @param output the place to put the decoded bytes.
* This may be modified even if there is a decoding error.
* @param outLength the length of the output array, if the decoded output is longer,
* Base32_TOO_BIG will be returned.
* @param in the buffer holding the base32 encoded number.
* @param inputLength the length of the input buffer.
* @return the length of the output if all goes well, Base32_BAD_INPUT if the input
* is not valid base32, or Base32_TOO_BIG if the output buffer is not large
* enough to handle the output.
*/
static inline int Base32_decode(uint8_t* output,
const uint32_t outLength,
const uint8_t* in,
const uint32_t inputLength)
{
// Maps ascii character inputs to the numbers
// Invalid characters are represented by 99
static const uint8_t numForAscii[] =
{
99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,
99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,
99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,99,99,99,99,99,99,
99,99,10,11,12,99,13,14,15,99,16,17,18,19,20,99,
21,22,23,24,25,26,27,28,29,30,31,99,99,99,99,99,
99,99,10,11,12,99,13,14,15,99,16,17,18,19,20,99,
21,22,23,24,25,26,27,28,29,30,31,99,99,99,99,99
};
uint32_t outIndex = 0;
uint32_t inputIndex = 0;
uint32_t nextByte = 0;
uint32_t bits = 0;
while (inputIndex < inputLength) {
if (in[inputIndex] & 0x80) {
return Base32_BAD_INPUT;
}
const uint8_t b = numForAscii[in[inputIndex++]];
if (b > 31) {
return Base32_BAD_INPUT;
}
nextByte |= ((unsigned) b) << bits;
bits += 5;
if (bits >= 8) {
if (outIndex >= outLength) {
return Base32_TOO_BIG;
}
output[outIndex++] = nextByte;
bits -= 8;
nextByte >>= 8;
}
}
if (bits >= 5 || nextByte) {
return Base32_BAD_INPUT;
}
return outIndex;
}
/**
* Base32 encode a number.
*
* @param output the place to put the base32 encoded output.
* This may be modified even if there is a encoding error.
* @param outLength the length of the output array, if the encoded output is longer,
* Base32_TOO_BIG will be returned.
* @param in the buffer holding the bytes to encode.
* @param inputLength the length of the input buffer.
* @return the length of the output if all goes well,
* or Base32_TOO_BIG if the output buffer is not large enough to handle the output.
*/
static inline int Base32_encode(uint8_t* output,
const uint32_t outputLength,
const uint8_t* in,
const uint32_t inputLength)
{
uint32_t outIndex = 0;
uint32_t inIndex = 0;
uint32_t work = 0;
uint32_t bits = 0;
static const uint8_t* kChars = (uint8_t*) "0123456789bcdfghjklmnpqrstuvwxyz";
while (inIndex < inputLength) {
work |= ((unsigned) in[inIndex++]) << bits;
bits += 8;
while (bits >= 5) {
if (outIndex >= outputLength) {
return Base32_TOO_BIG;
}
output[outIndex++] = kChars[work & 31];
bits -= 5;
work >>= 5;
}
}
if (bits) {
if (outIndex >= outputLength) {
return Base32_TOO_BIG;
}
output[outIndex++] = kChars[work & 31];
bits -= 5;
work >>= 5;
}
if (outIndex < outputLength) {
output[outIndex] = '\0';
}
return outIndex;
}
#endif