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    /*
    
     * Asterisk -- An open source telephony toolkit.
    
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     *
    
     * Copyright (C) 1999 - 2008, Digium, Inc.
    
     *
     * Mark Spencer <markster@digium.com>
    
     * Russell Bryant <russell@digium.com>
    
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     *
    
     * See http://www.asterisk.org for more information about
     * the Asterisk project. Please do not directly contact
     * any of the maintainers of this project for assistance;
     * the project provides a web site, mailing lists and IRC
     * channels for your use.
    
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     *
     * This program is free software, distributed under the terms of
    
     * the GNU General Public License Version 2. See the LICENSE file
     * at the top of the source tree.
     */
    
    
     * \brief Automatic channel service routines
    
     * \author Mark Spencer <markster@digium.com>
    
     * \author Russell Bryant <russell@digium.com>
    
    /*** MODULEINFO
    	<support_level>core</support_level>
     ***/
    
    
    #include "asterisk.h"
    
    ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
    
    
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    #include <sys/time.h>
    #include <signal.h>
    
    #include "asterisk/_private.h" /* prototype for ast_autoservice_init() */
    
    
    #include "asterisk/pbx.h"
    #include "asterisk/frame.h"
    #include "asterisk/sched.h"
    #include "asterisk/channel.h"
    #include "asterisk/file.h"
    #include "asterisk/translate.h"
    #include "asterisk/manager.h"
    #include "asterisk/chanvars.h"
    #include "asterisk/linkedlists.h"
    #include "asterisk/indications.h"
    #include "asterisk/lock.h"
    #include "asterisk/utils.h"
    
    #define MAX_AUTOMONS 1500
    
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    struct asent {
    	struct ast_channel *chan;
    
    	/*! This gets incremented each time autoservice gets started on the same
    
    	 *  channel.  It will ensure that it doesn't actually get stopped until
    
    	 *  it gets stopped for the last time. */
    	unsigned int use_count;
    
    	unsigned int orig_end_dtmf_flag:1;
    
    	unsigned int ignore_frame_types;
    
    	/*! Frames go on at the head of deferred_frames, so we have the frames
    	 *  from newest to oldest.  As we put them at the head of the readq, we'll
    	 *  end up with them in the right order for the channel's readq. */
    	AST_LIST_HEAD_NOLOCK(, ast_frame) deferred_frames;
    
    	AST_LIST_ENTRY(asent) list;
    
    static AST_LIST_HEAD_STATIC(aslist, asent);
    static ast_cond_t as_cond;
    
    static pthread_t asthread = AST_PTHREADT_NULL;
    
    static volatile int asexit = 0;
    
    static int as_chan_list_state;
    
    
    static void *autoservice_run(void *ign)
    {
    
    	struct ast_callid *callid = NULL;
    
    	struct ast_frame hangup_frame = {
    		.frametype = AST_FRAME_CONTROL,
    		.subclass.integer = AST_CONTROL_HANGUP,
    	};
    
    	while (!asexit) {
    
    		struct ast_channel *mons[MAX_AUTOMONS];
    
    		struct asent *ents[MAX_AUTOMONS];
    
    		struct ast_channel *chan;
    
    		struct asent *as;
    
    		int i, x = 0, ms = 50;
    
    		struct ast_frame *f = NULL;
    
    		struct ast_frame *defer_frame = NULL;
    
    
    		/* At this point, we know that no channels that have been removed are going
    		 * to get used again. */
    		as_chan_list_state++;
    
    
    		if (AST_LIST_EMPTY(&aslist)) {
    
    			ast_cond_wait(&as_cond, &aslist.lock);
    
    				if (x < MAX_AUTOMONS) {
    
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    					mons[x++] = as->chan;
    
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    					ast_log(LOG_WARNING, "Exceeded maximum number of automatic monitoring events.  Fix autoservice.c\n");
    
    			/* If we don't sleep, this becomes a busy loop, which causes
    			 * problems when Asterisk runs at a different priority than other
    			 * user processes.  As long as we check for new channels at least
    			 * once every 10ms, we should be fine. */
    			usleep(10000);
    
    		chan = ast_waitfor_n(mons, x, &ms);
    		if (!chan) {
    			continue;
    		}
    
    		callid = ast_channel_callid(chan);
    		ast_callid_threadassoc_change(callid);
    
    		if (callid) {
    			callid = ast_callid_unref(callid);
    		}
    
    		f = ast_read(chan);
    
    
    		if (!f) {
    			/* No frame means the channel has been hung up.
    			 * A hangup frame needs to be queued here as ast_waitfor() may
    			 * never return again for the condition to be detected outside
    			 * of autoservice.  So, we'll leave a HANGUP queued up so the
    			 * thread in charge of this channel will know. */
    
    			defer_frame = &hangup_frame;
    		} else if (ast_is_deferrable_frame(f)) {
    			defer_frame = f;
    		} else {
    			/* Can't defer. Discard and continue with next. */
    
    
    		for (i = 0; i < x; i++) {
    			struct ast_frame *dup_f;
    
    			if (mons[i] != chan) {
    				continue;
    			}
    
    			if (!f) { /* defer_frame == &hangup_frame */
    				if ((dup_f = ast_frdup(defer_frame))) {
    					AST_LIST_INSERT_HEAD(&ents[i]->deferred_frames, dup_f, frame_list);
    				}
    			} else {
    				if ((dup_f = ast_frisolate(defer_frame))) {
    					AST_LIST_INSERT_HEAD(&ents[i]->deferred_frames, dup_f, frame_list);
    				}
    				if (dup_f != defer_frame) {
    					ast_frfree(defer_frame);
    				}
    			}
    
    			break;
    		}
    		/* The ast_waitfor_n() call will only read frames from
    		 * the channels' file descriptors. If ast_waitfor_n()
    		 * returns non-NULL, then one of the channels in the
    		 * mons array must have triggered the return. It's
    		 * therefore impossible that we got here while (i >= x).
    		 * If we did, we'd need to ast_frfree(f) if (f). */
    
    	ast_callid_threadassoc_change(NULL);
    
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    	return NULL;
    }
    
    int ast_autoservice_start(struct ast_channel *chan)
    {
    
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    	struct asent *as;
    
    	AST_LIST_LOCK(&aslist);
    	AST_LIST_TRAVERSE(&aslist, as, list) {
    
    		if (as->chan == chan) {
    			as->use_count++;
    
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    			break;
    
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    	}
    
    		/* Entry exists, autoservice is already handling this channel */
    		return 0;
    
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    	}
    
    	if (!(as = ast_calloc(1, sizeof(*as))))
    		return -1;
    
    	/* New entry created */
    	as->chan = chan;
    	as->use_count = 1;
    
    	ast_channel_lock(chan);
    
    	as->orig_end_dtmf_flag = ast_test_flag(ast_channel_flags(chan), AST_FLAG_END_DTMF_ONLY) ? 1 : 0;
    
    	if (!as->orig_end_dtmf_flag)
    
    		ast_set_flag(ast_channel_flags(chan), AST_FLAG_END_DTMF_ONLY);
    
    	ast_channel_unlock(chan);
    
    
    
    	if (AST_LIST_EMPTY(&aslist) && asthread != AST_PTHREADT_NULL) {
    
    	AST_LIST_INSERT_HEAD(&aslist, as, list);
    
    	if (asthread == AST_PTHREADT_NULL) { /* need start the thread */
    		if (ast_pthread_create_background(&asthread, NULL, autoservice_run, NULL)) {
    			ast_log(LOG_WARNING, "Unable to create autoservice thread :(\n");
    			/* There will only be a single member in the list at this point,
    			   the one we just added. */
    
    			asthread = AST_PTHREADT_NULL;
    
    			pthread_kill(asthread, SIGURG);
    
    	AST_LIST_UNLOCK(&aslist);
    
    
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    	return res;
    }
    
    int ast_autoservice_stop(struct ast_channel *chan)
    {
    	int res = -1;
    
    	struct asent *as, *removed = NULL;
    
    	struct ast_frame *f;
    
    	int chan_list_state;
    
    
    	/* Save the autoservice channel list state.  We _must_ verify that the channel
    	 * list has been rebuilt before we return.  Because, after we return, the channel
    	 * could get destroyed and we don't want our poor autoservice thread to step on
    	 * it after its gone! */
    	chan_list_state = as_chan_list_state;
    
    
    	/* Find the entry, but do not free it because it still can be in the
    	   autoservice thread array */
    
    	AST_LIST_TRAVERSE_SAFE_BEGIN(&aslist, as, list) {
    
    			as->use_count--;
    
    			if (as->use_count < 1) {
    				AST_LIST_REMOVE_CURRENT(list);
    				removed = as;
    			}
    
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    			break;
    
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    	}
    
    	if (removed && asthread != AST_PTHREADT_NULL) {
    
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    		pthread_kill(asthread, SIGURG);
    
    	}
    
    	/* Wait while autoservice thread rebuilds its list. */
    	while (chan_list_state == as_chan_list_state) {
    		usleep(1000);
    	}
    
    	/* Now autoservice thread should have no references to our entry
    	   and we can safely destroy it */
    
    
    	if (!ast_channel_softhangup_internal_flag(chan)) {
    
    	if (!as->orig_end_dtmf_flag) {
    
    		ast_clear_flag(ast_channel_flags(chan), AST_FLAG_END_DTMF_ONLY);
    
    	while ((f = AST_LIST_REMOVE_HEAD(&as->deferred_frames, frame_list))) {
    		if (!((1 << f->frametype) & as->ignore_frame_types)) {
    			ast_queue_frame_head(chan, f);
    		}
    		ast_frfree(f);
    	}
    
    	ast_channel_unlock(chan);
    
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    	return res;
    }
    
    void ast_autoservice_chan_hangup_peer(struct ast_channel *chan, struct ast_channel *peer)
    {
    	if (chan && !ast_autoservice_start(chan)) {
    		ast_hangup(peer);
    		ast_autoservice_stop(chan);
    	} else {
    		ast_hangup(peer);
    	}
    }
    
    
    int ast_autoservice_ignore(struct ast_channel *chan, enum ast_frame_type ftype)
    {
    	struct asent *as;
    	int res = -1;
    
    	AST_LIST_LOCK(&aslist);
    	AST_LIST_TRAVERSE(&aslist, as, list) {
    		if (as->chan == chan) {
    			res = 0;
    			as->ignore_frame_types |= (1 << ftype);
    			break;
    		}
    	}
    	AST_LIST_UNLOCK(&aslist);
    	return res;
    }
    
    
    static void autoservice_shutdown(void)
    {
    	pthread_t th = asthread;
    	asexit = 1;
    	if (th != AST_PTHREADT_NULL) {
    		ast_cond_signal(&as_cond);
    		pthread_kill(th, SIGURG);
    		pthread_join(th, NULL);
    	}
    }
    
    
    	ast_register_cleanup(autoservice_shutdown);