| /*! \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); |
| |
| |
| /*! @} */ |