asterisk/apps/app_fax.c

/*
 * Asterisk -- A telephony toolkit for Linux.
 *
 * Simple fax applications
 * 
 * 2007-2008, Dmitry Andrianov <asterisk@dima.spb.ru>
 *
 * Code based on original implementation by Steve Underwood <steveu@coppice.org>
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License
 *
 */

/*** MODULEINFO
	 <depend>spandsp</depend>
***/
 
#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision$")

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <pthread.h>
#include <errno.h>
#include <tiffio.h>

#include <spandsp.h>
#ifdef HAVE_SPANDSP_EXPOSE_H
#include <spandsp/expose.h>
#endif
#include <spandsp/version.h>

#include "asterisk/lock.h"
#include "asterisk/file.h"
#include "asterisk/logger.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/app.h"
#include "asterisk/dsp.h"
#include "asterisk/module.h"
#include "asterisk/manager.h"

/*** DOCUMENTATION
	<application name="SendFAX" language="en_US">
		<synopsis>
			Send a Fax
		</synopsis>
		<syntax>
			<parameter name="filename" required="true">
				<para>Filename of TIFF file to fax</para>
			</parameter>
			<parameter name="a" required="false">
				<para>Makes the application behave as the answering machine</para>
				<para>(Default behavior is as calling machine)</para>
			</parameter>
		</syntax>
		<description>
			<para>Send a given TIFF file to the channel as a FAX.</para>
			<para>This application sets the following channel variables:</para>
			<variablelist>
				<variable name="LOCALSTATIONID">
					<para>To identify itself to the remote end</para>
				</variable>
				<variable name="LOCALHEADERINFO">
					<para>To generate a header line on each page</para>
				</variable>
				<variable name="FAXSTATUS">
					<value name="SUCCESS"/>
					<value name="FAILED"/>
				</variable>
				<variable name="FAXERROR">
					<para>Cause of failure</para>
				</variable>
				<variable name="REMOTESTATIONID">
					<para>The CSID of the remote side</para>
				</variable>
				<variable name="FAXPAGES">
					<para>Number of pages sent</para>
				</variable>
				<variable name="FAXBITRATE">
					<para>Transmission rate</para>
				</variable>
				<variable name="FAXRESOLUTION">
					<para>Resolution of sent fax</para>
				</variable>
			</variablelist>
		</description>
	</application>
	<application name="ReceiveFAX" language="en_US">
		<synopsis>
			Receive a Fax
		</synopsis>
		<syntax>
			<parameter name="filename" required="true">
				<para>Filename of TIFF file save incoming fax</para>
			</parameter>
			<parameter name="c" required="false">
				<para>Makes the application behave as the calling machine</para> 
				<para>(Default behavior is as answering machine)</para>
			</parameter>
		</syntax>
		<description>
			<para>Receives a FAX from the channel into the given filename 
			overwriting the file if it already exists.</para>
			<para>File created will be in TIFF format.</para>

			<para>This application sets the following channel variables:</para>
			<variablelist>
				<variable name="LOCALSTATIONID">
					<para>To identify itself to the remote end</para>
				</variable>
				<variable name="LOCALHEADERINFO">
					<para>To generate a header line on each page</para>
				</variable>
				<variable name="FAXSTATUS">
					<value name="SUCCESS"/>
					<value name="FAILED"/>
				</variable>
				<variable name="FAXERROR">
					<para>Cause of failure</para>
				</variable>
				<variable name="REMOTESTATIONID">
					<para>The CSID of the remote side</para>
				</variable>
				<variable name="FAXPAGES">
					<para>Number of pages sent</para>
				</variable>
				<variable name="FAXBITRATE">
					<para>Transmission rate</para>
				</variable>
				<variable name="FAXRESOLUTION">
					<para>Resolution of sent fax</para>
				</variable>
			</variablelist>
		</description>
	</application>

 ***/

static const char app_sndfax_name[] = "SendFAX";
static const char app_rcvfax_name[] = "ReceiveFAX";

#define MAX_SAMPLES 240

/* Watchdog. I have seen situations when remote fax disconnects (because of poor line
   quality) while SpanDSP continues staying in T30_STATE_IV_CTC state forever.
   To avoid this, we terminate when we see that T30 state does not change for 5 minutes.
   We also terminate application when more than 30 minutes passed regardless of
   state changes. This is just a precaution measure - no fax should take that long */

#define WATCHDOG_TOTAL_TIMEOUT	30 * 60
#define WATCHDOG_STATE_TIMEOUT	5 * 60

typedef struct {
	struct ast_channel *chan;
	enum ast_t38_state t38state;	/* T38 state of the channel */
	int direction;			/* Fax direction: 0 - receiving, 1 - sending */
	int caller_mode;
	char *file_name;
	
	volatile int finished;
} fax_session;

static void span_message(int level, const char *msg)
{
	if (level == SPAN_LOG_ERROR) {
		ast_log(LOG_ERROR, "%s", msg);
	} else if (level == SPAN_LOG_WARNING) {
		ast_log(LOG_WARNING, "%s", msg);
	} else {
		ast_log(LOG_DEBUG, "%s", msg);
	}
}

static int t38_tx_packet_handler(t38_core_state_t *s, void *user_data, const uint8_t *buf, int len, int count)
{
	struct ast_channel *chan = (struct ast_channel *) user_data;

	struct ast_frame outf = {
		.frametype = AST_FRAME_MODEM,
		.subclass = AST_MODEM_T38,
		.src = __FUNCTION__,
	};

	/* TODO: Asterisk does not provide means of resending the same packet multiple
	  times so count is ignored at the moment */

	AST_FRAME_SET_BUFFER(&outf, buf, 0, len);

	if (ast_write(chan, &outf) < 0) {
		ast_log(LOG_WARNING, "Unable to write frame to channel; %s\n", strerror(errno));
		return -1;
	}

	return 0;
}

static void phase_e_handler(t30_state_t *f, void *user_data, int result)
{
	const char *local_ident;
	const char *far_ident;
	char buf[20];
	fax_session *s = (fax_session *) user_data;
	t30_stats_t stat;
	int pages_transferred;

	ast_debug(1, "Fax phase E handler. result=%d\n", result);

	t30_get_transfer_statistics(f, &stat);

	s = (fax_session *) user_data;

	if (result != T30_ERR_OK) {
		s->finished = -1;

		/* FAXSTATUS is already set to FAILED */
		pbx_builtin_setvar_helper(s->chan, "FAXERROR", t30_completion_code_to_str(result));

		ast_log(LOG_WARNING, "Error transmitting fax. result=%d: %s.\n", result, t30_completion_code_to_str(result));

		return;
	}
	
	s->finished = 1; 
	
	local_ident = t30_get_tx_ident(f);
	far_ident = t30_get_rx_ident(f);
	pbx_builtin_setvar_helper(s->chan, "FAXSTATUS", "SUCCESS"); 
	pbx_builtin_setvar_helper(s->chan, "FAXERROR", NULL); 
	pbx_builtin_setvar_helper(s->chan, "REMOTESTATIONID", far_ident);
#if SPANDSP_RELEASE_DATE >= 20090220
	pages_transferred = (s->direction) ? stat.pages_tx : stat.pages_rx;
#else
	pages_transferred = stat.pages_transferred;
#endif
	snprintf(buf, sizeof(buf), "%d", pages_transferred);
	pbx_builtin_setvar_helper(s->chan, "FAXPAGES", buf);
	snprintf(buf, sizeof(buf), "%d", stat.y_resolution);
	pbx_builtin_setvar_helper(s->chan, "FAXRESOLUTION", buf);
	snprintf(buf, sizeof(buf), "%d", stat.bit_rate);
	pbx_builtin_setvar_helper(s->chan, "FAXBITRATE", buf); 
	
	ast_debug(1, "Fax transmitted successfully.\n");
	ast_debug(1, "  Remote station ID: %s\n", far_ident);
	ast_debug(1, "  Pages transferred: %d\n", pages_transferred);
	ast_debug(1, "  Image resolution:  %d x %d\n", stat.x_resolution, stat.y_resolution);
	ast_debug(1, "  Transfer Rate:     %d\n", stat.bit_rate);
	
	manager_event(EVENT_FLAG_CALL,
		      s->direction ? "FaxSent" : "FaxReceived", 
		      "Channel: %s\r\n"
		      "Exten: %s\r\n"
		      "CallerID: %s\r\n"
		      "RemoteStationID: %s\r\n"
		      "LocalStationID: %s\r\n"
		      "PagesTransferred: %d\r\n"
		      "Resolution: %d\r\n"
		      "TransferRate: %d\r\n"
		      "FileName: %s\r\n",
		      s->chan->name,
		      s->chan->exten,
		      S_OR(s->chan->cid.cid_num, ""),
		      far_ident,
		      local_ident,
		      pages_transferred,
		      stat.y_resolution,
		      stat.bit_rate,
		      s->file_name);
}

/* === Helper functions to configure fax === */

/* Setup SPAN logging according to Asterisk debug level */
static int set_logging(logging_state_t *state)
{
	int level = SPAN_LOG_WARNING + option_debug;

	span_log_set_message_handler(state, span_message);
	span_log_set_level(state, SPAN_LOG_SHOW_SEVERITY | SPAN_LOG_SHOW_PROTOCOL | level); 

	return 0;
}

static void set_local_info(t30_state_t *state, fax_session *s)
{
	const char *x;

	x = pbx_builtin_getvar_helper(s->chan, "LOCALSTATIONID");
	if (!ast_strlen_zero(x))
		t30_set_tx_ident(state, x);

	x = pbx_builtin_getvar_helper(s->chan, "LOCALHEADERINFO");
	if (!ast_strlen_zero(x))
		t30_set_tx_page_header_info(state, x);
}

static void set_file(t30_state_t *state, fax_session *s)
{
	if (s->direction)
		t30_set_tx_file(state, s->file_name, -1, -1);
	else
		t30_set_rx_file(state, s->file_name, -1);
}

static void set_ecm(t30_state_t *state, int ecm)
{
	t30_set_ecm_capability(state, ecm);
	t30_set_supported_compressions(state, T30_SUPPORT_T4_1D_COMPRESSION | T30_SUPPORT_T4_2D_COMPRESSION | T30_SUPPORT_T6_COMPRESSION);
}

/* === Generator === */

/* This function is only needed to return passed params so
   generator_activate will save it to channel's generatordata */
static void *fax_generator_alloc(struct ast_channel *chan, void *params)
{
	return params;
}

static int fax_generator_generate(struct ast_channel *chan, void *data, int len, int samples)
{
	fax_state_t *fax = (fax_state_t*) data;
	uint8_t buffer[AST_FRIENDLY_OFFSET + MAX_SAMPLES * sizeof(uint16_t)];
	int16_t *buf = (int16_t *) (buffer + AST_FRIENDLY_OFFSET);
    
	struct ast_frame outf = {
		.frametype = AST_FRAME_VOICE,
		.subclass = AST_FORMAT_SLINEAR,
		.src = __FUNCTION__,
	};

	if (samples > MAX_SAMPLES) {
		ast_log(LOG_WARNING, "Only generating %d samples, where %d requested\n", MAX_SAMPLES, samples);
		samples = MAX_SAMPLES;
	}
	
	if ((len = fax_tx(fax, buf, samples)) > 0) {
		outf.samples = len;
		AST_FRAME_SET_BUFFER(&outf, buffer, AST_FRIENDLY_OFFSET, len * sizeof(int16_t));

		if (ast_write(chan, &outf) < 0) {
			ast_log(LOG_WARNING, "Failed to write frame to '%s': %s\n", chan->name, strerror(errno));
			return -1;
		}
	}

	return 0;
}

struct ast_generator generator = {
	alloc:		fax_generator_alloc,
	generate: 	fax_generator_generate,
};


/* === Transmission === */

static int transmit_audio(fax_session *s)
{
	int res = -1;
	int original_read_fmt = AST_FORMAT_SLINEAR;
	int original_write_fmt = AST_FORMAT_SLINEAR;
	fax_state_t fax;
	t30_state_t *t30state;
	struct ast_dsp *dsp = NULL;
	int detect_tone = 0;
	struct ast_frame *inf = NULL;
	struct ast_frame *fr;
	int last_state = 0;
	struct timeval now, start, state_change;
	enum ast_control_t38 t38control;

#if SPANDSP_RELEASE_DATE >= 20081012
        /* for spandsp shaphots 0.0.6 and higher */
        t30state = &fax.t30;
#else
        /* for spandsp release 0.0.5 */
        t30state = &fax.t30_state;
#endif

	original_read_fmt = s->chan->readformat;
	if (original_read_fmt != AST_FORMAT_SLINEAR) {
		res = ast_set_read_format(s->chan, AST_FORMAT_SLINEAR);
		if (res < 0) {
			ast_log(LOG_WARNING, "Unable to set to linear read mode, giving up\n");
			goto done;
		}
	}

	original_write_fmt = s->chan->writeformat;
	if (original_write_fmt != AST_FORMAT_SLINEAR) {
		res = ast_set_write_format(s->chan, AST_FORMAT_SLINEAR);
		if (res < 0) {
			ast_log(LOG_WARNING, "Unable to set to linear write mode, giving up\n");
			goto done;
		}
	}

	/* Initialize T30 terminal */
	fax_init(&fax, s->caller_mode);

	/* Setup logging */
	set_logging(&fax.logging);
	set_logging(&t30state->logging);

	/* Configure terminal */
	set_local_info(t30state, s);
	set_file(t30state, s);
	set_ecm(t30state, TRUE);

	fax_set_transmit_on_idle(&fax, TRUE);

	t30_set_phase_e_handler(t30state, phase_e_handler, s);

	if (s->t38state == T38_STATE_UNAVAILABLE) {
		ast_debug(1, "T38 is unavailable on %s\n", s->chan->name);
	} else if (!s->direction) {
		/* We are receiving side and this means we are the side which should
		   request T38 when the fax is detected. Use DSP to detect fax tone */
		ast_debug(1, "Setting up CNG detection on %s\n", s->chan->name);
		dsp = ast_dsp_new();
		ast_dsp_set_features(dsp, DSP_FEATURE_FAX_DETECT);
		ast_dsp_set_faxmode(dsp, DSP_FAXMODE_DETECT_CNG);
		detect_tone = 1;
	}

	start = state_change = ast_tvnow();

	ast_activate_generator(s->chan, &generator, &fax);

	while (!s->finished) {
		res = ast_waitfor(s->chan, 20);
		if (res < 0)
			break;
		else if (res > 0)
			res = 0;

		inf = ast_read(s->chan);
		if (inf == NULL) {
			ast_debug(1, "Channel hangup\n");
			res = -1;
			break;
		}

		ast_debug(10, "frame %d/%d, len=%d\n", inf->frametype, inf->subclass, inf->datalen);

		/* Detect fax tone */
		if (detect_tone && inf->frametype == AST_FRAME_VOICE) {
			/* Duplicate frame because ast_dsp_process may free the frame passed */
			fr = ast_frdup(inf);

			/* Do not pass channel to ast_dsp_process otherwise it may queue modified audio frame back */
			fr = ast_dsp_process(NULL, dsp, fr);
			if (fr && fr->frametype == AST_FRAME_DTMF && fr->subclass == 'f') {
				ast_debug(1, "Fax tone detected. Requesting T38\n");
				t38control = AST_T38_REQUEST_NEGOTIATE;
				ast_indicate_data(s->chan, AST_CONTROL_T38, &t38control, sizeof(t38control));
				detect_tone = 0;
			}

			ast_frfree(fr);
		}


		/* Check the frame type. Format also must be checked because there is a chance
		   that a frame in old format was already queued before we set chanel format
		   to slinear so it will still be received by ast_read */
		if (inf->frametype == AST_FRAME_VOICE && inf->subclass == AST_FORMAT_SLINEAR) {

			if (fax_rx(&fax, inf->data.ptr, inf->samples) < 0) {
				/* I know fax_rx never returns errors. The check here is for good style only */
				ast_log(LOG_WARNING, "fax_rx returned error\n");
				res = -1;
				break;
			}

			/* Watchdog */
			if (last_state != t30state->state) {
				state_change = ast_tvnow();
				last_state = t30state->state;
			}
		} else if (inf->frametype == AST_FRAME_CONTROL && inf->subclass == AST_CONTROL_T38 &&
				inf->datalen == sizeof(enum ast_control_t38)) {
			t38control =*((enum ast_control_t38 *) inf->data.ptr);
			if (t38control == AST_T38_NEGOTIATED) {
				/* T38 switchover completed */
				ast_debug(1, "T38 negotiated, finishing audio loop\n");
				res = 1;
				break;
			}
		}

		ast_frfree(inf);
		inf = NULL;

		/* Watchdog */
		now = ast_tvnow();
		if (ast_tvdiff_sec(now, start) > WATCHDOG_TOTAL_TIMEOUT || ast_tvdiff_sec(now, state_change) > WATCHDOG_STATE_TIMEOUT) {
			ast_log(LOG_WARNING, "It looks like we hung. Aborting.\n");
			res = -1;
			break;
		}
	}

	ast_debug(1, "Loop finished, res=%d\n", res);

	if (inf)
		ast_frfree(inf);

	if (dsp)
		ast_dsp_free(dsp);

	ast_deactivate_generator(s->chan);

	/* If we are switching to T38, remove phase E handler. Otherwise it will be executed
	   by t30_terminate, display diagnostics and set status variables although no transmittion
	   has taken place yet. */
	if (res > 0) {
		t30_set_phase_e_handler(t30state, NULL, NULL);
	}

	t30_terminate(t30state);
	fax_release(&fax);

done:
	if (original_write_fmt != AST_FORMAT_SLINEAR) {
		if (ast_set_write_format(s->chan, original_write_fmt) < 0)
			ast_log(LOG_WARNING, "Unable to restore write format on '%s'\n", s->chan->name);
	}

	if (original_read_fmt != AST_FORMAT_SLINEAR) {
		if (ast_set_read_format(s->chan, original_read_fmt) < 0)
			ast_log(LOG_WARNING, "Unable to restore read format on '%s'\n", s->chan->name);
	}

	return res;

}

static int transmit_t38(fax_session *s)
{
	int res = 0;
	t38_terminal_state_t t38;
	struct ast_frame *inf = NULL;
	int last_state = 0;
	struct timeval now, start, state_change, last_frame;
	enum ast_control_t38 t38control;

	t30_state_t *t30state;
	t38_core_state_t *t38state;

#if SPANDSP_RELEASE_DATE >= 20081012
	/* for spandsp shaphots 0.0.6 and higher */
	t30state = &t38.t30;
	t38state = &t38.t38_fe.t38;
#else
	/* for spandsp releases 0.0.5 */
	t30state = &t38.t30_state;
	t38state = &t38.t38;
#endif

	/* Initialize terminal */
	memset(&t38, 0, sizeof(t38));
	if (t38_terminal_init(&t38, s->caller_mode, t38_tx_packet_handler, s->chan) == NULL) {
		ast_log(LOG_WARNING, "Unable to start T.38 termination.\n");
		return -1;
	}

	/* Setup logging */
	set_logging(&t38.logging);
	set_logging(&t30state->logging);
	set_logging(&t38state->logging);

	/* Configure terminal */
	set_local_info(t30state, s);
	set_file(t30state, s);
	set_ecm(t30state, TRUE);

	t30_set_phase_e_handler(t30state, phase_e_handler, s);

	now = start = state_change = ast_tvnow();

	while (!s->finished) {

		res = ast_waitfor(s->chan, 20);
		if (res < 0)
			break;
		else if (res > 0)
			res = 0;

		last_frame = now;
		now = ast_tvnow();
		t38_terminal_send_timeout(&t38, ast_tvdiff_us(now, last_frame) / (1000000 / 8000));

		inf = ast_read(s->chan);
		if (inf == NULL) {
			ast_debug(1, "Channel hangup\n");
			res = -1;
			break;
		}

		ast_debug(10, "frame %d/%d, len=%d\n", inf->frametype, inf->subclass, inf->datalen);

		if (inf->frametype == AST_FRAME_MODEM && inf->subclass == AST_MODEM_T38) {
			t38_core_rx_ifp_packet(t38state, inf->data.ptr, inf->datalen, inf->seqno);

			/* Watchdog */
			if (last_state != t30state->state) {
				state_change = ast_tvnow();
				last_state = t30state->state;
			}
		} else if (inf->frametype == AST_FRAME_CONTROL && inf->subclass == AST_CONTROL_T38 &&
				inf->datalen == sizeof(enum ast_control_t38)) {

			t38control = *((enum ast_control_t38 *) inf->data.ptr);

			if (t38control == AST_T38_TERMINATED || t38control == AST_T38_REFUSED) {
				ast_debug(1, "T38 down, terminating\n");
				res = -1;
				break;
			}
		}

		ast_frfree(inf);
		inf = NULL;

		/* Watchdog */
		if (ast_tvdiff_sec(now, start) > WATCHDOG_TOTAL_TIMEOUT || ast_tvdiff_sec(now, state_change) > WATCHDOG_STATE_TIMEOUT) {
			ast_log(LOG_WARNING, "It looks like we hung. Aborting.\n");
			res = -1;
			break;
		}
	}

	ast_debug(1, "Loop finished, res=%d\n", res);

	if (inf)
		ast_frfree(inf);

	t30_terminate(t30state);
	t38_terminal_release(&t38);

	return res;
}

static int transmit(fax_session *s)
{
	int res = 0;

	/* Clear all channel variables which to be set by the application.
	   Pre-set status to error so in case of any problems we can just leave */
	pbx_builtin_setvar_helper(s->chan, "FAXSTATUS", "FAILED"); 
	pbx_builtin_setvar_helper(s->chan, "FAXERROR", "Channel problems"); 

	pbx_builtin_setvar_helper(s->chan, "FAXMODE", NULL);
	pbx_builtin_setvar_helper(s->chan, "REMOTESTATIONID", NULL);
	pbx_builtin_setvar_helper(s->chan, "FAXPAGES", NULL);
	pbx_builtin_setvar_helper(s->chan, "FAXRESOLUTION", NULL);
	pbx_builtin_setvar_helper(s->chan, "FAXBITRATE", NULL); 

	if (s->chan->_state != AST_STATE_UP) {
		/* Shouldn't need this, but checking to see if channel is already answered
		 * Theoretically asterisk should already have answered before running the app */
		res = ast_answer(s->chan);
		if (res) {
			ast_log(LOG_WARNING, "Could not answer channel '%s'\n", s->chan->name);
			return res;
		}
	}

	s->t38state = ast_channel_get_t38_state(s->chan);
	if (s->t38state != T38_STATE_NEGOTIATED) {
		/* T38 is not negotiated on the channel yet. First start regular transmission. If it switches to T38, follow */	
		pbx_builtin_setvar_helper(s->chan, "FAXMODE", "audio"); 
		res = transmit_audio(s);
		if (res > 0) {
			/* transmit_audio reports switchover to T38. Update t38state */
			s->t38state = ast_channel_get_t38_state(s->chan);
			if (s->t38state != T38_STATE_NEGOTIATED) {
				ast_log(LOG_ERROR, "Audio loop reports T38 switchover but t38state != T38_STATE_NEGOTIATED\n");
			}
		}
	}

	if (s->t38state == T38_STATE_NEGOTIATED) {
		pbx_builtin_setvar_helper(s->chan, "FAXMODE", "T38"); 
		res = transmit_t38(s);
	}

	if (res) {
		ast_log(LOG_WARNING, "Transmission error\n");
		res = -1;
	} else if (s->finished < 0) {
		ast_log(LOG_WARNING, "Transmission failed\n");
	} else if (s->finished > 0) {
		ast_debug(1, "Transmission finished Ok\n");
	}

	return res;
}

/* === Application functions === */

static int sndfax_exec(struct ast_channel *chan, const char *data)
{
	int res = 0;
	char *parse;
	fax_session session;

	AST_DECLARE_APP_ARGS(args,
		AST_APP_ARG(file_name);
		AST_APP_ARG(options);
	);

	if (chan == NULL) {
		ast_log(LOG_ERROR, "Fax channel is NULL. Giving up.\n");
		return -1;
	}

	/* The next few lines of code parse out the filename and header from the input string */
	if (ast_strlen_zero(data)) {
		/* No data implies no filename or anything is present */
		ast_log(LOG_ERROR, "SendFAX requires an argument (filename)\n");
		return -1;
	}

	parse = ast_strdupa(data);
	AST_STANDARD_APP_ARGS(args, parse);
	
	session.caller_mode = TRUE;

	if (args.options) {
		if (strchr(args.options, 'a'))
			session.caller_mode = FALSE;
	}

	/* Done parsing */
	session.direction = 1;
	session.file_name = args.file_name;
	session.chan = chan;
	session.finished = 0;

	res = transmit(&session);

	return res;
}

static int rcvfax_exec(struct ast_channel *chan, const char *data)
{
	int res = 0;
	char *parse;
	fax_session session;

	AST_DECLARE_APP_ARGS(args,
		AST_APP_ARG(file_name);
		AST_APP_ARG(options);
	);

	if (chan == NULL) {
		ast_log(LOG_ERROR, "Fax channel is NULL. Giving up.\n");
		return -1;
	}

	/* The next few lines of code parse out the filename and header from the input string */
	if (ast_strlen_zero(data)) {
		/* No data implies no filename or anything is present */
		ast_log(LOG_ERROR, "ReceiveFAX requires an argument (filename)\n");
		return -1;
	}

	parse = ast_strdupa(data);
	AST_STANDARD_APP_ARGS(args, parse);
	
	session.caller_mode = FALSE;

	if (args.options) {
		if (strchr(args.options, 'c'))
			session.caller_mode = TRUE;
	}

	/* Done parsing */
	session.direction = 0;
	session.file_name = args.file_name;
	session.chan = chan;
	session.finished = 0;

	res = transmit(&session);

	return res;
}

static int unload_module(void)
{
	int res;

	res = ast_unregister_application(app_sndfax_name);	
	res |= ast_unregister_application(app_rcvfax_name);	

	return res;
}

static int load_module(void)
{
	int res ;

	res = ast_register_application_xml(app_sndfax_name, sndfax_exec);
	res |= ast_register_application_xml(app_rcvfax_name, rcvfax_exec);

	/* The default SPAN message handler prints to stderr. It is something we do not want */
	span_set_message_handler(NULL);

	return res;
}


AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "Simple FAX Application",
		.load = load_module,
		.unload = unload_module,
		);