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/*
* Base Encoding and Decoding
* (C) 2018 Erwan Chaussy
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_BASE_CODEC_H_
#define BOTAN_BASE_CODEC_H_
#include <botan/secmem.h>
#include <vector>
#include <string>
namespace Botan {
/**
* Perform encoding using the base provided
* @param base object giving access to the encodings specifications
* @param output an array of at least base.encode_max_output bytes
* @param input is some binary data
* @param input_length length of input in bytes
* @param input_consumed is an output parameter which says how many
* bytes of input were actually consumed. If less than
* input_length, then the range input[consumed:length]
* should be passed in later along with more input.
* @param final_inputs true iff this is the last input, in which case
padding chars will be applied if needed
* @return number of bytes written to output
*/
template <class Base>
size_t base_encode(Base&& base,
char output[],
const uint8_t input[],
size_t input_length,
size_t& input_consumed,
bool final_inputs)
{
input_consumed = 0;
const size_t encoding_bytes_in = base.encoding_bytes_in();
const size_t encoding_bytes_out = base.encoding_bytes_out();
size_t input_remaining = input_length;
size_t output_produced = 0;
while(input_remaining >= encoding_bytes_in)
{
base.encode(output + output_produced, input + input_consumed);
input_consumed += encoding_bytes_in;
output_produced += encoding_bytes_out;
input_remaining -= encoding_bytes_in;
}
if(final_inputs && input_remaining)
{
std::vector<uint8_t> remainder(encoding_bytes_in, 0);
for(size_t i = 0; i != input_remaining; ++i)
{ remainder[i] = input[input_consumed + i]; }
base.encode(output + output_produced, remainder.data());
const size_t bits_consumed = base.bits_consumed();
const size_t remaining_bits_before_padding = base.remaining_bits_before_padding();
size_t empty_bits = 8 * (encoding_bytes_in - input_remaining);
size_t index = output_produced + encoding_bytes_out - 1;
while(empty_bits >= remaining_bits_before_padding)
{
output[index--] = '=';
empty_bits -= bits_consumed;
}
input_consumed += input_remaining;
output_produced += encoding_bytes_out;
}
return output_produced;
}
/**
* Perform decoding using the base provided
* @param base object giving access to the encodings specifications
* @param output an array of at least base.decode_max_output bytes
* @param input some base input
* @param input_length length of input in bytes
* @param input_consumed is an output parameter which says how many
* bytes of input were actually consumed. If less than
* input_length, then the range input[consumed:length]
* should be passed in later along with more input.
* @param final_inputs true iff this is the last input, in which case
padding is allowed
* @param ignore_ws ignore whitespace on input; if false, throw an
exception if whitespace is encountered
* @return number of bytes written to output
*/
template <typename Base>
size_t base_decode(Base&& base,
uint8_t output[],
const char input[],
size_t input_length,
size_t& input_consumed,
bool final_inputs,
bool ignore_ws = true)
{
const size_t decoding_bytes_in = base.decoding_bytes_in();
const size_t decoding_bytes_out = base.decoding_bytes_out();
uint8_t* out_ptr = output;
std::vector<uint8_t> decode_buf(decoding_bytes_in, 0);
size_t decode_buf_pos = 0;
size_t final_truncate = 0;
clear_mem(output, base.decode_max_output(input_length));
for(size_t i = 0; i != input_length; ++i)
{
const uint8_t bin = base.lookup_binary_value(input[i]);
if(base.check_bad_char(bin, input[i], ignore_ws)) // May throw Invalid_Argument
{
decode_buf[decode_buf_pos] = bin;
++decode_buf_pos;
}
/*
* If we're at the end of the input, pad with 0s and truncate
*/
if(final_inputs && (i == input_length - 1))
{
if(decode_buf_pos)
{
for(size_t j = decode_buf_pos; j < decoding_bytes_in; ++j)
{ decode_buf[j] = 0; }
final_truncate = decoding_bytes_in - decode_buf_pos;
decode_buf_pos = decoding_bytes_in;
}
}
if(decode_buf_pos == decoding_bytes_in)
{
base.decode(out_ptr, decode_buf.data());
out_ptr += decoding_bytes_out;
decode_buf_pos = 0;
input_consumed = i+1;
}
}
while(input_consumed < input_length &&
base.lookup_binary_value(input[input_consumed]) == 0x80)
{
++input_consumed;
}
size_t written = (out_ptr - output) - base.bytes_to_remove(final_truncate);
return written;
}
}
#endif
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