--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.3/spandsp-0.0.3/src/spandsp/t38_gateway.h	Fri Jun 25 16:00:21 2010 +0200
@@ -0,0 +1,236 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * t38_gateway.h - An implementation of T.38, less the packet exchange part
+ *
+ * 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: t38_gateway.h,v 1.17 2006/12/07 13:22:26 steveu Exp $
+ */
+
+/*! \file */
+
+#if !defined(_T38_GATEWAY_H_)
+#define _T38_GATEWAY_H_
+
+/*! \page t38_gateway_page T.38 real time FAX over IP PSTN gateway
+\section t38_gateway_page_sec_1 What does it do?
+
+The T.38 gateway facility provides a robust interface between T.38 IP packet streams and
+and 8k samples/second audio streams. It provides the buffering and flow control features needed
+to maximum the tolerance of jitter and packet loss on the IP network.
+
+\section t38_gateway_page_sec_2 How does it work?
+*/
+
+#define T38_RX_BUF_LEN          2048
+#define T38_TX_BUF_LEN          16384
+
+#define T38_TX_HDLC_BUFS        256
+
+/* Make sure the HDLC frame buffers are big enough for ECM frames. */
+#define T38_MAX_HDLC_LEN        260
+
+typedef struct
+{
+    t38_core_state_t t38;
+    
+    int ecm_allowed;
+
+    /*! \brief HDLC message buffers. */
+    uint8_t hdlc_buf[T38_TX_HDLC_BUFS][T38_MAX_HDLC_LEN];
+    /*! \brief HDLC message lengths. */
+    int hdlc_len[T38_TX_HDLC_BUFS];
+    /*! \brief HDLC message status flags. */
+    int hdlc_flags[T38_TX_HDLC_BUFS];
+    /*! \brief HDLC buffer contents. */
+    int hdlc_contents[T38_TX_HDLC_BUFS];
+    /*! \brief HDLC buffer number for input. */
+    int hdlc_in;
+    /*! \brief HDLC buffer number for output. */
+    int hdlc_out;
+
+    /*! \brief Progressively calculated CRC for HDLC messaging received from a modem. */
+    uint16_t crc;
+
+    /*! \brief non-ECM modem receive data buffer */
+    uint8_t rx_data[T38_RX_BUF_LEN];
+    int rx_data_ptr;
+
+    /*! \brief non-ECM modem transmit data buffer */
+    uint8_t non_ecm_tx_data[T38_TX_BUF_LEN];
+    int non_ecm_tx_in_ptr;
+    int non_ecm_tx_out_ptr;
+
+    /*! \brief The location of the most recent EOL marker in the non-ECM data buffer */
+    int non_ecm_tx_latest_eol_ptr;
+    unsigned int bit_stream;
+    /*! \brief The non-ECM flow control fill octet (0xFF before the first data, and 0x00
+               once data has started). */
+    uint8_t non_ecm_flow_control_fill_octet;
+    /*! \brief TRUE if we are in the initial all ones part of non-ECM transmission. */
+    int non_ecm_at_initial_all_ones;
+    /*! \brief TRUE is the end of non-ECM data indication has been received. */
+    int non_ecm_data_finished;
+    /*! \brief The current octet being sent as non-ECM data. */
+    int current_non_ecm_octet;
+    /*! \brief The current bit number in the current non-ECM octet. */
+    int non_ecm_bit_no;
+    /*! \brief A count of the number of non-ECM fill octets generated for flow control control
+               purposes. */
+    int non_ecm_flow_control_fill_octets;
+
+    int current_rx_data_type;
+    int current_rx_field_type;
+    int current_rx_field_class;
+    int in_progress_rx_indicator;
+
+    /*! \brief The current T.38 data type being sent. */
+    int current_tx_data_type;
+
+    /*! \brief TRUE if we are in error correcting (ECM) mode */
+    int ecm_mode;
+    /*! \brief The current bit rate for the fast modem. */
+    int fast_bit_rate;
+    /*! \brief The current fast modem type. */
+    int fast_modem;
+    /*! \brief Use talker echo protection when transmitting. */
+    int use_tep;    
+    /*! \brief TRUE if a carrier is present. Otherwise FALSE. */
+    int rx_signal_present;
+    /*! \brief TRUE if a modem has trained correctly. */
+    int rx_trained;
+
+    /*! \brief A tone generator context used to generate supervisory tones during
+               FAX handling. */
+    tone_gen_state_t tone_gen;
+    /*! \brief An HDLC context used when receiving HDLC messages. */
+    hdlc_rx_state_t hdlcrx;
+
+    /*! \brief HDLC data used when transmitting HDLC messages. */
+    hdlc_tx_state_t hdlctx;
+
+    /*! \brief A V.21 FSK modem context used when transmitting HDLC over V.21
+               messages. */
+    fsk_tx_state_t v21tx;
+    /*! \brief A V.21 FSK modem context used when receiving HDLC over V.21
+               messages. */
+    fsk_rx_state_t v21rx;
+
+#if defined(ENABLE_V17)
+    /*! \brief A V.17 modem context used when sending FAXes at 7200bps, 9600bps
+               12000bps or 14400bps*/
+    v17_tx_state_t v17tx;
+    /*! \brief A V.29 modem context used when receiving FAXes at 7200bps, 9600bps
+               12000bps or 14400bps*/
+    v17_rx_state_t v17rx;
+#endif
+
+    /*! \brief A V.29 modem context used when sending FAXes at 7200bps or
+               9600bps */
+    v29_tx_state_t v29tx;
+    /*! \brief A V.29 modem context used when receiving FAXes at 7200bps or
+               9600bps */
+    v29_rx_state_t v29rx;
+
+    /*! \brief A V.27ter modem context used when sending FAXes at 2400bps or
+               4800bps */
+    v27ter_tx_state_t v27ter_tx;
+    /*! \brief A V.27ter modem context used when receiving FAXes at 2400bps or
+               4800bps */
+    v27ter_rx_state_t v27ter_rx;
+
+    /*! \brief Used to insert timed silences. */
+    silence_gen_state_t silence_gen;
+
+    /*! The current receive signal handler */
+    span_rx_handler_t *rx_handler;
+    void *rx_user_data;
+
+    /*! The current transmit signal handler */
+    span_tx_handler_t *tx_handler;
+    void *tx_user_data;
+    /*! The transmit signal handler to be used when the current one has finished sending. */
+    span_tx_handler_t *next_tx_handler;
+    void *next_tx_user_data;
+
+    /*! The number of octets to send in each image packet (non-ECM or ECM) at the current
+        rate and the current specified packet interval. */
+    int octets_per_data_packet;
+
+    int v21_rx_active;
+    int fast_rx_active;
+    int samples_since_last_tx_packet;
+    int octets_since_last_tx_packet;
+    int short_train;
+
+    /*! \brief TRUE if we need to corrupt the HDLC frame in progress, so the receiver cannot
+               interpret it. */
+    int corrupt_the_frame;
+    
+    int current_rx_type;
+    int current_tx_type;
+
+    logging_state_t logging;
+} t38_gateway_state_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*! \brief Initialise a gateway mode T.38 context.
+    \param s The T.38 context.
+    \param tx_packet_handler A callback routine to encapsulate and transmit T.38 packets.
+    \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler routine.
+    \return A pointer to the termination mode T.38 context, or NULL if there was a problem. */
+t38_gateway_state_t *t38_gateway_init(t38_gateway_state_t *s,
+                                      t38_tx_packet_handler_t *tx_packet_handler,
+                                      void *tx_packet_user_data);
+
+/*! Process a block of received FAX audio samples.
+    \brief Process a block of received FAX audio samples.
+    \param s The T.38 context.
+    \param amp The audio sample buffer.
+    \param len The number of samples in the buffer.
+    \return The number of samples unprocessed. */
+int t38_gateway_rx(t38_gateway_state_t *s, const int16_t *amp, int len);
+
+/*! Generate a block of FAX audio samples.
+    \brief Generate a block of FAX audio samples.
+    \param s The T.38 context.
+    \param amp The audio sample buffer.
+    \param max_len The number of samples to be generated.
+    \return The number of samples actually generated.
+*/
+int t38_gateway_tx(t38_gateway_state_t *s, int16_t *amp, int max_len);
+
+/*! Control whether error correcting mode (ECM) is allowed.
+    \brief Control whether error correcting mode (ECM) is allowed.
+    \param s The T.38 context.
+    \param ecm_allowed TRUE is ECM is to be allowed.
+*/
+void t38_gateway_ecm_control(t38_gateway_state_t *s, int ecm_allowed);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+/*- End of file ------------------------------------------------------------*/