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/*! \file conv.h
* Osmocom convolutional encoder and decoder. */
/*
* Copyright (C) 2011 Sylvain Munaut <tnt@246tNt.com>
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 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, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/*! \defgroup conv Convolutional encoding and decoding routines
* @{
* \file conv.h */
#pragma once
#include <stdint.h>
#include <osmocom/core/bits.h>
/*! possibe termination types
*
* The termination type will determine which state the encoder/decoder
* can start/end with. This is mostly taken care of in the high level API
* call. So if you use the low level API, you must take care of making the
* proper calls yourself.
*/
enum osmo_conv_term {
CONV_TERM_FLUSH = 0, /*!< Flush encoder state */
CONV_TERM_TRUNCATION, /*!< Direct truncation */
CONV_TERM_TAIL_BITING, /*!< Tail biting */
};
/*! structure describing a given convolutional code
*
* The only required fields are N,K and the next_output/next_state arrays. The
* other can be left to default value of zero depending on what the code does.
* If 'len' is left at 0 then only the low level API can be used.
*/
struct osmo_conv_code {
int N; /*!< Inverse of code rate */
int K; /*!< Constraint length */
int len; /*!< # of data bits */
enum osmo_conv_term term; /*!< Termination type */
const uint8_t (*next_output)[2];/*!< Next output array */
const uint8_t (*next_state)[2]; /*!< Next state array */
const uint8_t *next_term_output;/*!< Flush termination output */
const uint8_t *next_term_state; /*!< Flush termination state */
const int *puncture; /*!< Punctured bits indexes */
};
/* Common */
int osmo_conv_get_input_length(const struct osmo_conv_code *code, int len);
int osmo_conv_get_output_length(const struct osmo_conv_code *code, int len);
/* Encoding */
/* Low level API */
/*! convolutional encoder state */
struct osmo_conv_encoder {
const struct osmo_conv_code *code; /*!< for which code? */
int i_idx; /*!< Next input bit index */
int p_idx; /*!< Current puncture index */
uint8_t state; /*!< Current state */
};
void osmo_conv_encode_init(struct osmo_conv_encoder *encoder,
const struct osmo_conv_code *code);
void osmo_conv_encode_load_state(struct osmo_conv_encoder *encoder,
const ubit_t *input);
int osmo_conv_encode_raw(struct osmo_conv_encoder *encoder,
const ubit_t *input, ubit_t *output, int n);
int osmo_conv_encode_flush(struct osmo_conv_encoder *encoder, ubit_t *output);
/* All-in-one */
int osmo_conv_encode(const struct osmo_conv_code *code,
const ubit_t *input, ubit_t *output);
/* Decoding */
/* Low level API */
/*! convolutional decoder state */
struct osmo_conv_decoder {
const struct osmo_conv_code *code; /*!< for which code? */
int n_states; /*!< number of states */
int len; /*!< Max o_idx (excl. termination) */
int o_idx; /*!< output index */
int p_idx; /*!< puncture index */
unsigned int *ae; /*!< accumulated error */
unsigned int *ae_next; /*!< next accumulated error (tmp in scan) */
uint8_t *state_history; /*!< state history [len][n_states] */
};
void osmo_conv_decode_init(struct osmo_conv_decoder *decoder,
const struct osmo_conv_code *code,
int len, int start_state);
void osmo_conv_decode_reset(struct osmo_conv_decoder *decoder, int start_state);
void osmo_conv_decode_rewind(struct osmo_conv_decoder *decoder);
void osmo_conv_decode_deinit(struct osmo_conv_decoder *decoder);
int osmo_conv_decode_scan(struct osmo_conv_decoder *decoder,
const sbit_t *input, int n);
int osmo_conv_decode_flush(struct osmo_conv_decoder *decoder,
const sbit_t *input);
int osmo_conv_decode_get_output(struct osmo_conv_decoder *decoder,
ubit_t *output, int has_flush, int end_state);
/* All-in-one */
int osmo_conv_decode(const struct osmo_conv_code *code,
const sbit_t *input, ubit_t *output);
/*! @} */
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