148 lines
5.1 KiB
C
148 lines
5.1 KiB
C
/*
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* SpanDSP - a series of DSP components for telephony
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*
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* v42bis.h
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*
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* Written by Steve Underwood <steveu@coppice.org>
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*
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* Copyright (C) 2005, 2011 Steve Underwood
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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 Lesser General Public License version 2.1,
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* as published by the Free Software Foundation.
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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 Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*! \page v42bis_page V.42bis modem data compression
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\section v42bis_page_sec_1 What does it do?
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The v.42bis specification defines a data compression scheme, to work in
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conjunction with the error correction scheme defined in V.42.
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\section v42bis_page_sec_2 How does it work?
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*/
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#include <stdint.h>
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#if !defined(_SPANDSP_V42BIS_H_)
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#define _SPANDSP_V42BIS_H_
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#define SPAN_DECLARE(x) x
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#define V42BIS_MIN_STRING_SIZE 6
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#define V42BIS_MAX_STRING_SIZE 250
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#define V42BIS_MIN_DICTIONARY_SIZE 512
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#define V42BIS_MAX_BITS 12
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#define V42BIS_MAX_CODEWORDS 4096 /* 2^V42BIS_MAX_BITS */
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#define V42BIS_MAX_OUTPUT_LENGTH 1024
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enum
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{
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V42BIS_P0_NEITHER_DIRECTION = 0,
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V42BIS_P0_INITIATOR_RESPONDER,
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V42BIS_P0_RESPONDER_INITIATOR,
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V42BIS_P0_BOTH_DIRECTIONS
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};
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enum
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{
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V42BIS_COMPRESSION_MODE_DYNAMIC = 0,
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V42BIS_COMPRESSION_MODE_ALWAYS,
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V42BIS_COMPRESSION_MODE_NEVER
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};
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typedef void (*put_msg_func_t)(void *user_data, const uint8_t *msg, int len);
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/*!
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V.42bis compression/decompression descriptor. This defines the working state for a
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single instance of V.42bis compress/decompression.
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*/
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typedef struct v42bis_state_s v42bis_state_t;
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#if defined(__cplusplus)
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extern "C"
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{
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#endif
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/*! Compress a block of octets.
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\param s The V.42bis context.
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\param buf The data to be compressed.
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\param len The length of the data buffer.
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\return 0 */
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SPAN_DECLARE(int) v42bis_compress(v42bis_state_t *s, const uint8_t buf[], int len);
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/*! Flush out any data remaining in a compression buffer.
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\param s The V.42bis context.
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\return 0 */
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SPAN_DECLARE(int) v42bis_compress_flush(v42bis_state_t *s);
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/*! Decompress a block of octets.
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\param s The V.42bis context.
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\param buf The data to be decompressed.
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\param len The length of the data buffer.
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\return 0 */
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SPAN_DECLARE(int) v42bis_decompress(v42bis_state_t *s, const uint8_t buf[], int len);
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/*! Flush out any data remaining in the decompression buffer.
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\param s The V.42bis context.
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\return 0 */
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SPAN_DECLARE(int) v42bis_decompress_flush(v42bis_state_t *s);
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/*! Set the compression mode.
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\param s The V.42bis context.
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\param mode One of the V.42bis compression modes -
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V42BIS_COMPRESSION_MODE_DYNAMIC,
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V42BIS_COMPRESSION_MODE_ALWAYS,
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V42BIS_COMPRESSION_MODE_NEVER */
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SPAN_DECLARE(void) v42bis_compression_control(v42bis_state_t *s, int mode);
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/*! Initialise a V.42bis context.
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\param s The V.42bis context.
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\param negotiated_p0 The negotiated P0 parameter, from the V.42bis spec.
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\param negotiated_p1 The negotiated P1 parameter, from the V.42bis spec.
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\param negotiated_p2 The negotiated P2 parameter, from the V.42bis spec.
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\param encode_handler Encode callback handler.
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\param encode_user_data An opaque pointer passed to the encode callback handler.
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\param max_encode_len The maximum length that should be passed to the encode handler.
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\param decode_handler Decode callback handler.
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\param decode_user_data An opaque pointer passed to the decode callback handler.
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\param max_decode_len The maximum length that should be passed to the decode handler.
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\return The V.42bis context. */
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SPAN_DECLARE(v42bis_state_t *) v42bis_init(const void *ctx,
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v42bis_state_t *s,
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int negotiated_p0,
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int negotiated_p1,
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int negotiated_p2,
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put_msg_func_t encode_handler,
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void *encode_user_data,
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int max_encode_len,
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put_msg_func_t decode_handler,
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void *decode_user_data,
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int max_decode_len);
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/*! Release a V.42bis context.
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\param s The V.42bis context.
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\return 0 if OK */
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SPAN_DECLARE(int) v42bis_release(v42bis_state_t *s);
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/*! Free a V.42bis context.
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\param s The V.42bis context.
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\return 0 if OK */
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SPAN_DECLARE(int) v42bis_free(v42bis_state_t *s);
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#if defined(__cplusplus)
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}
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#endif
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#endif
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/*- End of file ------------------------------------------------------------*/
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