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view spandsp-0.0.3/spandsp-0.0.3/src/spandsp/v42bis.h @ 5:f762bf195c4b
import spandsp-0.0.3
author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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date | Fri, 25 Jun 2010 16:00:21 +0200 |
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/* * SpanDSP - a series of DSP components for telephony * * v42bis.h * * Written by Steve Underwood <steveu@coppice.org> * * Copyright (C) 2005 Steve Underwood * * 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 version 2, as * published by the Free Software Foundation. * * 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., 675 Mass Ave, Cambridge, MA 02139, USA. * * $Id: v42bis.h,v 1.15 2006/11/30 15:41:47 steveu Exp $ */ /*! \page v42bis_page V.42bis modem data compression \section v42bis_page_sec_1 What does it do? The v.42bis specification defines a data compression scheme, to work in conjunction with the error correction scheme defined in V.42. \section v42bis_page_sec_2 How does it work? */ #if !defined(_V42BIS_H_) #define _V42BIS_H_ #define V42BIS_MAX_BITS 12 #define V42BIS_MAX_CODEWORDS 4096 /* 2^V42BIS_MAX_BITS */ #define V42BIS_TABLE_SIZE 5021 /* This should be a prime >(2^V42BIS_MAX_BITS) */ #define V42BIS_MAX_STRING_SIZE 250 enum { V42BIS_P0_NEITHER_DIRECTION = 0, V42BIS_P0_INITIATOR_RESPONDER, V42BIS_P0_RESPONDER_INITIATOR, V42BIS_P0_BOTH_DIRECTIONS }; enum { V42BIS_COMPRESSION_MODE_DYNAMIC = 0, V42BIS_COMPRESSION_MODE_ALWAYS, V42BIS_COMPRESSION_MODE_NEVER }; typedef void (*v42bis_frame_handler_t)(void *user_data, const uint8_t *pkt, int len); typedef void (*v42bis_data_handler_t)(void *user_data, const uint8_t *buf, int len); typedef struct { /*! \brief The prior code for each defined code. */ uint16_t parent_code; /*! \brief The number of leaf nodes this node has */ int16_t leaves; /*! \brief This leaf octet for each defined code. */ uint8_t node_octet; /*! \brief Bit map of the children which exist */ uint32_t children[8]; } v42bis_dict_node_t; typedef struct { /*! \brief Compression mode. */ int compression_mode; /*! \brief Callback function to handle received frames. */ v42bis_frame_handler_t handler; /*! \brief An opaque pointer passed in calls to frame_handler. */ void *user_data; /*! \brief The maximum frame length allowed */ int max_len; uint32_t string_code; uint32_t latest_code; int string_length; uint32_t output_bit_buffer; int output_bit_count; int output_octet_count; uint8_t output_buf[1024]; v42bis_dict_node_t dict[V42BIS_MAX_CODEWORDS]; /*! \brief TRUE if we are in transparent (i.e. uncompressable) mode */ int transparent; int change_transparency; int compressibility_filter; int compressibility_persistence; /*! \brief Next empty dictionary entry */ uint32_t v42bis_parm_c1; /*! \brief Current codeword size */ int v42bis_parm_c2; /*! \brief Threshold for codeword size change */ uint32_t v42bis_parm_c3; /*! \brief Mark that this is the first octet/code to be processed */ int first; uint8_t escape_code; } v42bis_compress_state_t; typedef struct { /*! \brief Callback function to handle decompressed data. */ v42bis_data_handler_t handler; /*! \brief An opaque pointer passed in calls to data_handler. */ void *user_data; /*! \brief The maximum decompressed data block length allowed */ int max_len; uint32_t old_code; uint32_t last_old_code; uint32_t input_bit_buffer; int input_bit_count; int octet; int last_length; int output_octet_count; uint8_t output_buf[1024]; v42bis_dict_node_t dict[V42BIS_MAX_CODEWORDS]; /*! \brief TRUE if we are in transparent (i.e. uncompressable) mode */ int transparent; int last_extra_octet; /*! \brief Next empty dictionary entry */ int v42bis_parm_c1; /*! \brief Current codeword size */ int v42bis_parm_c2; /*! \brief Threshold for codeword size change */ int v42bis_parm_c3; /*! \brief Mark that this is the first octet/code to be processed */ int first; uint8_t escape_code; int escaped; } v42bis_decompress_state_t; /*! V.42bis compression/decompression descriptor. This defines the working state for a single instance of V.42bis compress/decompression. */ typedef struct { /*! \brief V.42bis data compression directions. */ int v42bis_parm_p0; v42bis_compress_state_t compress; v42bis_decompress_state_t decompress; /*! \brief Maximum codeword size (bits) */ int v42bis_parm_n1; /*! \brief Total number of codewords */ uint32_t v42bis_parm_n2; /*! \brief Maximum string length */ int v42bis_parm_n7; } v42bis_state_t; #ifdef __cplusplus extern "C" { #endif /*! Compress a block of octets. \param s The V.42bis context. \param buf The data to be compressed. \param len The length of the data buffer. \return 0 */ int v42bis_compress(v42bis_state_t *s, const uint8_t *buf, int len); /*! Flush out any data remaining in a compression buffer. \param s The V.42bis context. \return 0 */ int v42bis_compress_flush(v42bis_state_t *s); /*! Decompress a block of octets. \param s The V.42bis context. \param buf The data to be decompressed. \param len The length of the data buffer. \return 0 */ int v42bis_decompress(v42bis_state_t *s, const uint8_t *buf, int len); /*! Flush out any data remaining in the decompression buffer. \param s The V.42bis context. \return 0 */ int v42bis_decompress_flush(v42bis_state_t *s); /*! Initialise a V.42bis context. \param s The V.42bis context. \param negotiated_p0 The negotiated P0 parameter, from the V.42bis spec. \param negotiated_p1 The negotiated P1 parameter, from the V.42bis spec. \param negotiated_p2 The negotiated P2 parameter, from the V.42bis spec. \param frame_handler . \param frame_user_data . \param max_frame_len The maximum length that should be passed to the frame handler. \param data_handler . \param data_user_data . \param max_data_len The maximum length that should be passed to the data handler. \return The V.42bis context. */ v42bis_state_t *v42bis_init(v42bis_state_t *s, int negotiated_p0, int negotiated_p1, int negotiated_p2, v42bis_frame_handler_t frame_handler, void *frame_user_data, int max_frame_len, v42bis_data_handler_t data_handler, void *data_user_data, int max_data_len); /*! Set the compression mode. \param s The V.42bis context. \param mode One of the V.42bis compression modes - V42BIS_COMPRESSION_MODE_DYNAMIC, V42BIS_COMPRESSION_MODE_ALWAYS, V42BIS_COMPRESSION_MODE_NEVER */ void v42bis_compression_control(v42bis_state_t *s, int mode); /*! Release a V.42bis context. \param s The V.42bis context. \return 0 if OK */ int v42bis_release(v42bis_state_t *s); #ifdef __cplusplus } #endif #endif /*- End of file ------------------------------------------------------------*/