V.42bis: add sourcecode from IAXmodem (SPANDSP)

V.42bis is a data compression method found in modems. It has also
been specified for GPRS as data compression algorithm.

The implementation has been taken from IAXmodem:

https://sourceforge.net/p/iaxmodem/code/HEAD/tree/
svn checkout svn://svn.code.sf.net/p/iaxmodem/code/ iaxmodem-code
Revision: r36

Change-Id: Iabedece9f97ca944a1e3f747bb073e532c4e9dca

1 files changed, 127 insertions, 0 deletions

diff --git a/openbsc/include/openbsc/v42bis_private.h b/openbsc/include/openbsc/v42bis_private.h
new file mode 100644
index 000000000..2c801ebe2
--- /dev/null
+++ b/openbsc/include/openbsc/v42bis_private.h
@@ -0,0 +1,127 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * private/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 Lesser General Public License version 2.1,
+ * 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#if !defined(_SPANDSP_PRIVATE_V42BIS_H_)
+#define _SPANDSP_PRIVATE_V42BIS_H_
+
+/*!
+    V.42bis dictionary node.
+    Note that 0 is not a valid node to point to (0 is always a control code), so 0 is used
+    as a "no such value" marker in this structure.
+*/
+typedef struct
+{
+    /*! \brief The value of the octet represented by the current dictionary node */
+    uint8_t node_octet;
+    /*! \brief The parent of this node */
+    uint16_t parent;
+    /*! \brief The first child of this node */
+    uint16_t child;
+    /*! \brief The next node at the same depth */
+    uint16_t next;
+} v42bis_dict_node_t;
+
+/*!
+    V.42bis compression or decompression. This defines the working state for a single instance
+    of V.42bis compression or decompression.
+*/
+typedef struct
+{
+    /*! \brief Compression enabled. */
+    int v42bis_parm_p0;
+    /*! \brief Compression mode. */
+    int compression_mode;
+    /*! \brief Callback function to handle output data. */
+    put_msg_func_t handler;
+    /*! \brief An opaque pointer passed in calls to the data handler. */
+    void *user_data;
+    /*! \brief The maximum amount to be passed to the data handler. */
+    int max_output_len;
+
+    /*! \brief TRUE if we are in transparent (i.e. uncompressable) mode */
+    int transparent;
+    /*! \brief Next empty dictionary entry */
+    uint16_t v42bis_parm_c1;
+    /*! \brief Current codeword size */
+    uint16_t v42bis_parm_c2;
+    /*! \brief Threshold for codeword size change */
+    uint16_t v42bis_parm_c3;
+    /*! \brief The current update point in the dictionary */
+    uint16_t update_at;
+    /*! \brief The last entry matched in the dictionary */
+    uint16_t last_matched;
+    /*! \brief The last entry added to the dictionary */
+    uint16_t last_added;
+    /*! \brief Total number of codewords in the dictionary */
+    int v42bis_parm_n2;
+    /*! \brief Maximum permitted string length */
+    int v42bis_parm_n7;
+    /*! \brief The dictionary */
+    v42bis_dict_node_t dict[V42BIS_MAX_CODEWORDS];
+
+    /*! \brief The octet string in progress */
+    uint8_t string[V42BIS_MAX_STRING_SIZE];
+    /*! \brief The current length of the octet string in progress */
+    int string_length;
+    /*! \brief The amount of the octet string in progress which has already
+        been flushed out of the buffer */
+    int flushed_length;
+
+    /*! \brief Compression performance metric */
+    uint16_t compression_performance;
+
+    /*! \brief Outgoing bit buffer (compression), or incoming bit buffer (decompression) */ 
+    uint32_t bit_buffer;
+    /*! \brief Outgoing bit count (compression), or incoming bit count (decompression) */ 
+    int bit_count;
+
+    /*! \brief The output composition buffer */
+    uint8_t output_buf[V42BIS_MAX_OUTPUT_LENGTH];
+    /*! \brief The length of the contents of the output composition buffer */    
+    int output_octet_count;
+
+    /*! \brief The current value of the escape code */
+    uint8_t escape_code;
+    /*! \brief TRUE if we just hit an escape code, and are waiting for the following octet */
+    int escaped;
+} v42bis_comp_state_t;
+
+/*!
+    V.42bis compression/decompression descriptor. This defines the working state for a
+    single instance of V.42bis compress/decompression.
+*/
+struct v42bis_state_s
+{
+    /*! \brief Compression state. */
+    v42bis_comp_state_t compress;
+    /*! \brief Decompression state. */
+    v42bis_comp_state_t decompress;
+
+    /*! \brief Error and flow logging control */
+    logging_state_t logging;
+};
+
+#endif
+/*- End of file ------------------------------------------------------------*/