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/* Copyright (c) 2007 Samuel Tesla
*
* 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.
*/
#include "encoder.h"
size_t
base32_encoder_last_quintent (const size_t bytes)
{
int quintets = bytes * 8 / 5;
int remainder = bytes % 5;
return remainder == 0 ? quintets : quintets + 1;
}
size_t
base32_encoder_output_padding_size (const size_t bytes)
{
unsigned remainder = bytes % 5;
return remainder == 0 ? 0 : (5 - remainder) * 8 / 5;
}
size_t
base32_encoder_buffer_size (const size_t bytes)
{
return base32_encoder_last_quintent (bytes) +
base32_encoder_output_padding_size (bytes);
}
static unsigned
base32_encoder_encode_bits (int position, const uint8_t *buffer)
{
unsigned offset = position / 8 * 5;
switch (position % 8)
{
case 0:
return
((buffer[offset] & 0xF8) >> 3);
case 1:
return
((buffer[offset] & 0x07) << 2) +
((buffer[offset + 1] & 0xC0) >> 6);
case 2:
return
((buffer[offset + 1] & 0x3E) >> 1);
case 3:
return
((buffer[offset + 1] & 0x01) << 4) +
((buffer[offset + 2] & 0xF0) >> 4);
case 4:
return
((buffer[offset + 2] & 0x0F) << 1) +
((buffer[offset + 3] & 0x80) >> 7);
case 5:
return
((buffer[offset + 3] & 0x7C) >> 2);
case 6:
return
((buffer[offset + 3] & 0x03) << 3) +
((buffer[offset + 4] & 0xE0) >> 5);
case 7:
return
buffer[offset + 4] & 0x1F;
default:
return 0;
}
}
static inline uint8_t
base32_encoder_encode_at_position (unsigned position, const uint8_t *buffer)
{
const char *table = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
unsigned index = base32_encoder_encode_bits (position, buffer);
return table[index];
}
void
base32_encode (uint8_t *output, const size_t outputLength,
const uint8_t *input, const size_t inputLength)
{
unsigned i;
unsigned quintets = base32_encoder_last_quintent(inputLength);
for (i = 0; i < quintets; i++)
output[i] = base32_encoder_encode_at_position (i, input);
for (i = quintets; i < outputLength; i++)
output[i] = '=';
}
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