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