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/* -*- c++ -*- */
/*
* Copyright 2015 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <gnuradio/fec/polar_encoder.h>
#include <gnuradio/io_signature.h>
#include <volk/volk.h>
#include <cmath>
#include <stdexcept>
#include <gnuradio/blocks/pack_k_bits.h>
#include <gnuradio/blocks/unpack_k_bits.h>
namespace gr {
namespace fec {
namespace code {
generic_encoder::sptr polar_encoder::make(int block_size,
int num_info_bits,
std::vector<int> frozen_bit_positions,
std::vector<uint8_t> frozen_bit_values,
bool is_packed)
{
return generic_encoder::sptr(new polar_encoder(
block_size, num_info_bits, frozen_bit_positions, frozen_bit_values, is_packed));
}
polar_encoder::polar_encoder(int block_size,
int num_info_bits,
std::vector<int>& frozen_bit_positions,
std::vector<uint8_t>& frozen_bit_values,
bool is_packed)
: polar_common(block_size, num_info_bits, frozen_bit_positions, frozen_bit_values),
d_is_packed(is_packed)
{
setup_frozen_bit_inserter();
}
void polar_encoder::setup_frozen_bit_inserter()
{
d_frozen_bit_prototype =
(unsigned char*)volk_malloc(block_size() >> 3, volk_get_alignment());
memset(d_frozen_bit_prototype, 0, block_size() >> 3);
for (unsigned int i = 0; i < d_frozen_bit_positions.size(); i++) {
int rev_pos = (int)bit_reverse((long)d_frozen_bit_positions.at(i), block_power());
unsigned char frozen_bit = (unsigned char)d_frozen_bit_values.at(i);
insert_unpacked_bit_into_packed_array_at_position(
d_frozen_bit_prototype, frozen_bit, rev_pos);
}
}
polar_encoder::~polar_encoder() { volk_free(d_frozen_bit_prototype); }
void polar_encoder::generic_work(void* in_buffer, void* out_buffer)
{
const unsigned char* in = (const unsigned char*)in_buffer;
unsigned char* out = (unsigned char*)out_buffer;
if (d_is_packed) {
insert_packed_frozen_bits_and_reverse(out, in);
encode_vector_packed(out);
} else {
volk_encode(out, in);
}
}
void polar_encoder::encode_vector_packed(unsigned char* target) const
{
encode_vector_packed_subbyte(target);
encode_vector_packed_interbyte(target);
}
void polar_encoder::encode_vector_packed_subbyte(unsigned char* target) const
{
int num_bytes_per_block = block_size() >> 3;
while (num_bytes_per_block) {
encode_packed_byte(target);
++target;
--num_bytes_per_block;
}
}
void polar_encoder::encode_packed_byte(unsigned char* target) const
{
// this method only produces correct results if block_size > 4.
// this is assumed to be the case.
*target ^= 0xaa & (*target << 1);
*target ^= 0xcc & (*target << 2);
*target ^= *target << 4;
}
void polar_encoder::encode_vector_packed_interbyte(unsigned char* target) const
{
int branch_byte_size = 1;
unsigned char* pos;
int n_branches = block_size() >> 4;
int byte = 0;
for (int stage = 3; stage < block_power(); ++stage) {
pos = target;
for (int branch = 0; branch < n_branches; ++branch) {
byte = 0;
while (byte < branch_byte_size) {
*pos ^= *(pos + branch_byte_size);
++pos;
++byte;
}
pos += branch_byte_size;
}
n_branches >>= 1;
branch_byte_size <<= 1;
}
}
void polar_encoder::insert_packed_frozen_bits_and_reverse(
unsigned char* target, const unsigned char* input) const
{
memcpy(target, d_frozen_bit_prototype, block_size() >> 3);
const int* info_bit_reversed_positions_ptr = &d_info_bit_positions_reversed[0];
int bit_num = 0;
unsigned char byte = *input;
int bit_pos;
while (bit_num < num_info_bits()) {
bit_pos = *info_bit_reversed_positions_ptr++;
insert_packet_bit_into_packed_array_at_position(
target, byte, bit_pos, bit_num % 8);
++bit_num;
if (bit_num % 8 == 0) {
++input;
byte = *input;
}
}
}
void polar_encoder::insert_unpacked_bit_into_packed_array_at_position(
unsigned char* target, const unsigned char bit, const int pos) const
{
int byte_pos = pos >> 3;
int bit_pos = pos & 0x7;
*(target + byte_pos) ^= bit << (7 - bit_pos);
}
void polar_encoder::insert_packet_bit_into_packed_array_at_position(
unsigned char* target,
const unsigned char bit,
const int target_pos,
const int bit_pos) const
{
insert_unpacked_bit_into_packed_array_at_position(
target, (bit >> (7 - bit_pos)) & 0x01, target_pos);
}
} /* namespace code */
} /* namespace fec */
} /* namespace gr */
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