channel.h

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/*
 * Asterisk -- A telephony toolkit for Linux.
 *
 * General Asterisk channel definitions.
 * 
 * Copyright (C) 1999, Mark Spencer
 *
 * Mark Spencer <markster@linux-support.net>
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License
 */

#ifndef _ASTERISK_CHANNEL_H
#define _ASTERISK_CHANNEL_H

#include <asterisk/frame.h>
#include <asterisk/sched.h>
#include <asterisk/chanvars.h>
#include <unistd.h>
#include <setjmp.h>
#include <pthread.h>
#include <sys/poll.h>

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

#include <asterisk/lock.h>

//! Max length of an extension
#define AST_MAX_EXTENSION 80

#include <asterisk/cdr.h>
#include <asterisk/monitor.h>


#define AST_CHANNEL_NAME 80
#define AST_CHANNEL_MAX_STACK 32

#define MAX_LANGUAGE 20


#define AST_MAX_FDS 8

struct ast_generator {
   void *(*alloc)(struct ast_channel *chan, void *params);
   void (*release)(struct ast_channel *chan, void *data);
   int (*generate)(struct ast_channel *chan, void *data, int len, int samples);
};

//! Main Channel structure associated with a channel.
/*! 
 * This is the side of it mostly used by the pbx and call management.
 */
struct ast_channel {
   /*! ASCII Description of channel name */
   char name[AST_CHANNEL_NAME];     
   /*! Language requested */
   char language[MAX_LANGUAGE];     
   /*! Type of channel */
   char *type;          
   /*! File descriptor for channel -- Drivers will poll on these file descriptors, so at least one must be non -1.  */
   int fds[AST_MAX_FDS];         

   /*! Default music class */
   char musicclass[MAX_LANGUAGE];

   /*! Current generator data if there is any */
   void *generatordata;
   /*! Current active data generator */
   struct ast_generator *generator;
   /*! Whether or not the generator should be interrupted by write */
   int writeinterrupt;

   /*! Who are we bridged to, if we're bridged */
   struct ast_channel *bridge;
   /*! Who did we call? */
   struct ast_channel *dialed;
   /*! Who called us? */
   struct ast_channel *dialing;
   /*! Reverse the dialed link (0 false, 1 true) */
   int reversedialed;
   /*! Channel that will masquerade as us */
   struct ast_channel *masq;     
   /*! Who we are masquerading as */
   struct ast_channel *masqr;    
   /*! Call Detail Record Flags */
   int cdrflags;                                
   /*! Whether or not we're blocking */
   int blocking;           
   /*! Whether or not we have been hung up...  Do not set this value
       directly, use ast_softhangup */
   int _softhangup;           
   /*! Non-zero if this is a zombie channel */
   int zombie;             
   /*! Non-zero, set to actual time when channel is to be hung up */
   time_t   whentohangup;
   /*! If anyone is blocking, this is them */
   pthread_t blocker;         
   /*! Lock, can be used to lock a channel for some operations */
   ast_mutex_t lock;       
   /*! Procedure causing blocking */
   char *blockproc;        

   /*! Current application */
   char *appl;          
   /*! Data passed to current application */
   char *data;          
   
   /*! Has an exception been detected */
   int exception;          
   /*! Which fd had an event detected on */
   int fdno;            
   /*! Schedule context */
   struct sched_context *sched;     
   /*! For streaming playback, the schedule ID */
   int streamid;           
   /*! Stream itself. */
   struct ast_filestream *stream;      
   /*! For streaming playback, the schedule ID */
   int vstreamid;          
   /*! Stream itself. */
   struct ast_filestream *vstream;     
   /*! Original writer format */
   int oldwriteformat;        
   
   /*! Timing fd */
   int timingfd;
   int (*timingfunc)(void *data);
   void *timingdata;

   /*! State of line -- Don't write directly, use ast_setstate */
   int _state;          
   /*! Number of rings so far */
   int rings;           
   /*! Current level of application */
   int stack;


   /*! Kinds of data this channel can natively handle */
   int nativeformats;         
   /*! Requested read format */
   int readformat;            
   /*! Requested write format */
   int writeformat;        

   
   /*! Malloc'd Dialed Number Identifier */
   char *dnid;          
   /*! Malloc'd Caller ID */
   char *callerid;            
   /*! Malloc'd ANI */
   char *ani;        
   /*! Malloc'd RDNIS */
   char *rdnis;
   /*! Hide callerid from user */
   int restrictcid;
   /*! Callerid presentation/screening */
   int callingpres;

   
   /*! Current extension context */
   char context[AST_MAX_EXTENSION]; 
   /*! Current non-macro context */
   char macrocontext[AST_MAX_EXTENSION];  
   /*! Current non-macro extension */
   char macroexten[AST_MAX_EXTENSION];
   /*! Current non-macro priority */
   int macropriority;
   /*! Current extension number */
   char exten[AST_MAX_EXTENSION];      
   /* Current extension priority */
   int priority;                 
   /*! Application information -- see assigned numbers */
   void *app[AST_CHANNEL_MAX_STACK];   
   /*! Any/all queued DTMF characters */
   char dtmfq[AST_MAX_EXTENSION];      
   /*! Are DTMF digits being deferred */
   int deferdtmf;          
   /*! DTMF frame */
   struct ast_frame dtmff;       
   /*! Private channel implementation details */
   struct ast_channel_pvt *pvt;

                  
   /*! Jump buffer used for returning from applications */
   jmp_buf jmp[AST_CHANNEL_MAX_STACK]; 

   struct ast_pbx *pbx;
   /*! Set BEFORE PBX is started to determine AMA flags */
   int   amaflags;         
   /*! Account code for billing */
   char  accountcode[20];     
   /*! Call Detail Record */
   struct ast_cdr *cdr;       
   /*! Whether or not ADSI is detected on CPE */
   int   adsicpe;
   /*! Where to forward to if asked to dial on this interface */
   char call_forward[AST_MAX_EXTENSION];

   /*! Tone zone */
   struct tone_zone *zone;

   /* Channel monitoring */
   struct ast_channel_monitor *monitor;

   /*! Track the read/written samples for monitor use */
   unsigned long insmpl;
   unsigned long outsmpl;

   /* Frames in/out counters */
   unsigned int fin;
   unsigned int fout;

   /* Unique Channel Identifier */
   char uniqueid[32];

   /* Why is the channel hanged up */
   int hangupcause;
   
   /* A linked list for variables */
   struct ast_var_t *vars; 
   AST_LIST_HEAD(varshead,ast_var_t) varshead;

   unsigned int callgroup;
   unsigned int pickupgroup;

   /*! channel flags of AST_FLAG_ type */
   int flag;
   
   /*! For easy linking */
   struct ast_channel *next;

};

#define AST_FLAG_DIGITAL   1  /* if the call is a digital ISDN call */

static inline int ast_test_flag(struct ast_channel *chan, int mode)
{
   return chan->flag & mode;
}

static inline void ast_set_flag(struct ast_channel *chan, int mode)
{
   chan->flag |= mode;
}

static inline void ast_clear_flag(struct ast_channel *chan, int mode)
{
   chan->flag &= ~mode;
}

static inline void ast_set2_flag(struct ast_channel *chan, int value, int mode)
{
   if (value)
      ast_set_flag(chan, mode);
   else
      ast_clear_flag(chan, mode);
}

static inline void ast_dup_flag(struct ast_channel *dstchan, struct ast_channel *srcchan, int mode)
{
   if (ast_test_flag(srcchan, mode))
      ast_set_flag(dstchan, mode);
   else
      ast_clear_flag(dstchan, mode);
}  

struct ast_bridge_config {
   int play_to_caller;
   int play_to_callee;
   int allowredirect_in;
   int allowredirect_out;
   int allowdisconnect;
   long timelimit;
   long play_warning;
   long warning_freq;
   char *warning_sound;
   char *end_sound;
   char *start_sound;
};

struct chanmon;

#define LOAD_OH(oh) {   \
   oh.context = context; \
   oh.exten = exten; \
   oh.priority = priority; \
   oh.callerid = callerid; \
   oh.variable = variable; \
   oh.account = account; \
} 

struct outgoing_helper {
   char *context;
   char *exten;
   int priority;
   char *callerid;
   char *variable;
   char *account;
};

#define AST_CDR_TRANSFER   (1 << 0)
#define AST_CDR_FORWARD    (1 << 1)
#define AST_CDR_CALLWAIT   (1 << 2)
#define AST_CDR_CONFERENCE (1 << 3)

#define AST_ADSI_UNKNOWN   (0)
#define AST_ADSI_AVAILABLE (1)
#define AST_ADSI_UNAVAILABLE  (2)
#define AST_ADSI_OFFHOOKONLY  (3)

#define AST_SOFTHANGUP_DEV       (1 << 0) /* Soft hangup by device */
#define AST_SOFTHANGUP_ASYNCGOTO (1 << 1) /* Soft hangup for async goto */
#define AST_SOFTHANGUP_SHUTDOWN     (1 << 2)
#define AST_SOFTHANGUP_TIMEOUT      (1 << 3)
#define AST_SOFTHANGUP_APPUNLOAD (1 << 4)
#define AST_SOFTHANGUP_EXPLICIT     (1 << 5)

/* Bits 0-15 of state are reserved for the state (up/down) of the line */
/*! Channel is down and available */
#define AST_STATE_DOWN     0     
/*! Channel is down, but reserved */
#define AST_STATE_RESERVED 1     
/*! Channel is off hook */
#define AST_STATE_OFFHOOK  2     
/*! Digits (or equivalent) have been dialed */
#define AST_STATE_DIALING  3     
/*! Line is ringing */
#define AST_STATE_RING     4     
/*! Remote end is ringing */
#define AST_STATE_RINGING  5     
/*! Line is up */
#define AST_STATE_UP    6     
/*! Line is busy */
#define AST_STATE_BUSY     7     
/*! Digits (or equivalent) have been dialed while offhook */
#define AST_STATE_DIALING_OFFHOOK   8

/* Bits 16-32 of state are reserved for flags */
/*! Do not transmit voice data */
#define AST_STATE_MUTE     (1 << 16)   

/*! Device is valid but channel didn't know state */
#define AST_DEVICE_UNKNOWN 0
/*! Device is not used */
#define AST_DEVICE_NOT_INUSE  1
/*! Device is in use */
#define AST_DEVICE_INUSE   2
/*! Device is busy */
#define AST_DEVICE_BUSY    3
/*! Device is invalid */
#define AST_DEVICE_INVALID 4
/*! Device is unavailable */
#define AST_DEVICE_UNAVAILABLE   5

//! Requests a channel
/*! 
 * \param type type of channel to request
 * \param format requested channel format
 * \param data data to pass to the channel requester
 * Request a channel of a given type, with data as optional information used 
 * by the low level module
 * Returns an ast_channel on success, NULL on failure.
 */
struct ast_channel *ast_request(char *type, int format, void *data);

//! Search the Channels by Name
/*!
 * \param device like a dialstring
 * Search the Device in active channels by compare the channelname against 
 * the devicename. Compared are only the first chars to the first '-' char.
 * Returns an AST_DEVICE_UNKNOWN if no channel found or
 * AST_DEVICE_INUSE if a channel is found
 */
int ast_parse_device_state(char *device);

//! Asks a channel for device state
/*!
 * \param device like a dialstring
 * Asks a channel for device state, data is  normaly a number from dialstring
 * used by the low level module
 * Trys the channel devicestate callback if not supported search in the
 * active channels list for the device.
 * Returns an AST_DEVICE_??? state -1 on failure
 */
int ast_device_state(char *device);

/*!
 * \param type type of channel to request
 * \param format requested channel format
 * \param data data to pass to the channel requester
 * \param timeout maximum amount of time to wait for an answer
 * \param why unsuccessful (if unsuceessful)
 * Request a channel of a given type, with data as optional information used 
 * by the low level module and attempt to place a call on it
 * Returns an ast_channel on success or no answer, NULL on failure.  Check the value of chan->_state
 * to know if the call was answered or not.
 */
struct ast_channel *ast_request_and_dial(char *type, int format, void *data, int timeout, int *reason, char *callerid);

struct ast_channel *__ast_request_and_dial(char *type, int format, void *data, int timeout, int *reason, char *callerid, struct outgoing_helper *oh);

//! Registers a channel
/*! 
 * \param type type of channel you are registering
 * \param description short description of the channel
 * \param capabilities a bit mask of the capabilities of the channel
 * \param requester a function pointer that properly responds to a call.  See one of the channel drivers for details.
 * Called by a channel module to register the kind of channels it supports.
 * It supplies a brief type, a longer, but still short description, and a
 * routine that creates a channel
 * Returns 0 on success, -1 on failure.
 */
int ast_channel_register(char *type, char *description, int capabilities, 
         struct ast_channel* (*requester)(char *type, int format, void *data));

/* Same like the upper function but with support for devicestate */
int ast_channel_register_ex(char *type, char *description, int capabilities,
      struct ast_channel *(*requester)(char *type, int format, void *data),
      int (*devicestate)(void *data));

//! Unregister a channel class
/*
 * \param type the character string that corresponds to the channel you wish to unregister
 * Basically just unregisters the channel with the asterisk channel system
 * No return value.
 */
void ast_channel_unregister(char *type);

//! Hang up a channel 
/*! 
 * \param chan channel to hang up
 * This function performs a hard hangup on a channel.  Unlike the soft-hangup, this function
 * performs all stream stopping, etc, on the channel that needs to end.
 * chan is no longer valid after this call.
 * Returns 0 on success, -1 on failure.
 */
int ast_hangup(struct ast_channel *chan);

//! Softly hangup up a channel
/*! 
 * \param chan channel to be soft-hung-up
 * Call the protocol layer, but don't destroy the channel structure (use this if you are trying to
 * safely hangup a channel managed by another thread.
 * Returns 0 regardless
 */
int ast_softhangup(struct ast_channel *chan, int cause);
int ast_softhangup_nolock(struct ast_channel *chan, int cause);

//! Check to see if a channel is needing hang up
/*! 
 * \param chan channel on which to check for hang up
 * This function determines if the channel is being requested to be hung up.
 * Returns 0 if not, or 1 if hang up is requested (including time-out).
 */
int ast_check_hangup(struct ast_channel *chan);

//! Set when to hang a channel up
/*! 
 * \param chan channel on which to check for hang up
 * \param offset offset in seconds from current time of when to hang up
 * This function sets the absolute time out on a channel (when to hang up).
 */
void ast_channel_setwhentohangup(struct ast_channel *chan, time_t offset);

//! Answer a ringing call
/*!
 * \param chan channel to answer
 * This function answers a channel and handles all necessary call
 * setup functions.
 * Returns 0 on success, -1 on failure
 */
int ast_answer(struct ast_channel *chan);

//! Make a call
/*! 
 * \param chan which channel to make the call on
 * \param addr destination of the call
 * \param timeout time to wait on for connect
 * Place a call, take no longer than timeout ms.  Returns -1 on failure, 
   0 on not enough time (does not auto matically stop ringing), and  
   the number of seconds the connect took otherwise.
   Returns 0 on success, -1 on failure
   */
int ast_call(struct ast_channel *chan, char *addr, int timeout);

//! Indicates condition of channel
/*! 
 * \param chan channel to change the indication
 * \param condition which condition to indicate on the channel
 * Indicate a condition such as AST_CONTROL_BUSY, AST_CONTROL_RINGING, or AST_CONTROL_CONGESTION on a channel
 * Returns 0 on success, -1 on failure
 */
int ast_indicate(struct ast_channel *chan, int condition);

/* Misc stuff */

//! Wait for input on a channel
/*! 
 * \param chan channel to wait on
 * \param ms length of time to wait on the channel
 * Wait for input on a channel for a given # of milliseconds (<0 for indefinite). 
  Returns < 0 on  failure, 0 if nothing ever arrived, and the # of ms remaining otherwise */
int ast_waitfor(struct ast_channel *chan, int ms);

//! Wait for a specied amount of time, looking for hangups
/*!
 * \param chan channel to wait for
 * \param ms length of time in milliseconds to sleep
 * Waits for a specified amount of time, servicing the channel as required.
 * returns -1 on hangup, otherwise 0.
 */
int ast_safe_sleep(struct ast_channel *chan, int ms);

//! Wait for a specied amount of time, looking for hangups and a condition argument
/*!
 * \param chan channel to wait for
 * \param ms length of time in milliseconds to sleep
 * \param cond a function pointer for testing continue condition
 * \param data argument to be passed to the condition test function
 * Waits for a specified amount of time, servicing the channel as required. If cond
 * returns 0, this function returns.
 * returns -1 on hangup, otherwise 0.
 */
int ast_safe_sleep_conditional(struct ast_channel *chan, int ms, int (*cond)(void*), void *data );

//! Waits for activity on a group of channels
/*! 
 * \param chan an array of pointers to channels
 * \param n number of channels that are to be waited upon
 * \param fds an array of fds to wait upon
 * \param nfds the number of fds to wait upon
 * \param exception exception flag
 * \param outfd fd that had activity on it
 * \param ms how long the wait was
 * Big momma function here.  Wait for activity on any of the n channels, or any of the nfds
   file descriptors.  Returns the channel with activity, or NULL on error or if an FD
   came first.  If the FD came first, it will be returned in outfd, otherwise, outfd
   will be -1 */
struct ast_channel *ast_waitfor_nandfds(struct ast_channel **chan, int n, int *fds, int nfds, int *exception, int *outfd, int *ms);

//! Waits for input on a group of channels
/*! Wait for input on an array of channels for a given # of milliseconds. Return channel
   with activity, or NULL if none has activity.  time "ms" is modified in-place, if applicable */
struct ast_channel *ast_waitfor_n(struct ast_channel **chan, int n, int *ms);

//! Waits for input on an fd
/*! This version works on fd's only.  Be careful with it. */
int ast_waitfor_n_fd(int *fds, int n, int *ms, int *exception);


//! Reads a frame
/*!
 * \param chan channel to read a frame from
 * Read a frame.  Returns a frame, or NULL on error.  If it returns NULL, you
   best just stop reading frames and assume the channel has been
   disconnected. */
struct ast_frame *ast_read(struct ast_channel *chan);

//! Write a frame to a channel
/*!
 * \param chan destination channel of the frame
 * \param frame frame that will be written
 * This function writes the given frame to the indicated channel.
 * It returns 0 on success, -1 on failure.
 */
int ast_write(struct ast_channel *chan, struct ast_frame *frame);

//! Write video frame to a channel
/*!
 * \param chan destination channel of the frame
 * \param frame frame that will be written
 * This function writes the given frame to the indicated channel.
 * It returns 1 on success, 0 if not implemented, and -1 on failure.
 */
int ast_write_video(struct ast_channel *chan, struct ast_frame *frame);

/* Send empty audio to prime a channel driver */
int ast_prod(struct ast_channel *chan);

//! Sets read format on channel chan
/*! 
 * \param chan channel to change
 * \param format format to change to
 * Set read format for channel to whichever component of "format" is best. 
 * Returns 0 on success, -1 on failure
 */
int ast_set_read_format(struct ast_channel *chan, int format);

//! Sets write format on channel chan
/*! 
 * \param chan channel to change
 * \param format new format for writing
 * Set write format for channel to whichever compoent of "format" is best. 
 * Returns 0 on success, -1 on failure
 */
int ast_set_write_format(struct ast_channel *chan, int format);

//! Sends text to a channel
/*! 
 * \param chan channel to act upon
 * \param text string of text to send on the channel
 * Write text to a display on a channel
 * Returns 0 on success, -1 on failure
 */
int ast_sendtext(struct ast_channel *chan, char *text);

//! Receives a text character from a channel
/*! 
 * \param chan channel to act upon
 * \param timeout timeout in milliseconds (0 for infinite wait)
 * Read a char of text from a channel
 * Returns 0 on success, -1 on failure
 */

int ast_senddigit(struct ast_channel *chan, char digit);

int ast_recvchar(struct ast_channel *chan, int timeout);

//! Browse channels in use
/*! 
 * \param prev where you want to start in the channel list
 * Browse the channels currently in use 
 * Returns the next channel in the list, NULL on end.
 * If it returns a channel, that channel *has been locked*!
 */
struct ast_channel *ast_channel_walk_locked(struct ast_channel *prev);

//! Get channel by name (locks channel)
struct ast_channel *ast_get_channel_by_name_locked(char *channame);

//! Waits for a digit
/*! 
 * \param c channel to wait for a digit on
 * \param ms how many milliseconds to wait
 * Wait for a digit.  Returns <0 on error, 0 on no entry, and the digit on success. */
char ast_waitfordigit(struct ast_channel *c, int ms);

/* Same as above with audio fd for outputing read audio and ctrlfd to monitor for
   reading. Returns 1 if ctrlfd becomes available */
char ast_waitfordigit_full(struct ast_channel *c, int ms, int audiofd, int ctrlfd);

//! Reads multiple digits
/*! 
 * \param c channel to read from
 * \param s string to read in to.  Must be at least the size of your length
 * \param len how many digits to read (maximum)
 * \param timeout how long to timeout between digits
 * \param rtimeout timeout to wait on the first digit
 * \param enders digits to end the string
 * Read in a digit string "s", max length "len", maximum timeout between 
   digits "timeout" (-1 for none), terminated by anything in "enders".  Give them rtimeout
   for the first digit.  Returns 0 on normal return, or 1 on a timeout.  In the case of
   a timeout, any digits that were read before the timeout will still be available in s.  
   RETURNS 2 in full version when ctrlfd is available, NOT 1*/
int ast_readstring(struct ast_channel *c, char *s, int len, int timeout, int rtimeout, char *enders);
int ast_readstring_full(struct ast_channel *c, char *s, int len, int timeout, int rtimeout, char *enders, int audiofd, int ctrlfd);

/*! Report DTMF on channel 0 */
#define AST_BRIDGE_DTMF_CHANNEL_0      (1 << 0)    
/*! Report DTMF on channel 1 */
#define AST_BRIDGE_DTMF_CHANNEL_1      (1 << 1)    
/*! Return all voice frames on channel 0 */
#define AST_BRIDGE_REC_CHANNEL_0    (1 << 2)    
/*! Return all voice frames on channel 1 */
#define AST_BRIDGE_REC_CHANNEL_1    (1 << 3)    
/*! Ignore all signal frames except NULL */
#define AST_BRIDGE_IGNORE_SIGS         (1 << 4)    


//! Makes two channel formats compatible
/*! 
 * \param c0 first channel to make compatible
 * \param c1 other channel to make compatible
 * Set two channels to compatible formats -- call before ast_channel_bridge in general .  Returns 0 on success
   and -1 if it could not be done */
int ast_channel_make_compatible(struct ast_channel *c0, struct ast_channel *c1);

//! Bridge two channels together
/*! 
 * \param c0 first channel to bridge
 * \param c1 second channel to bridge
 * \param flags for the channels
 * \param fo destination frame(?)
 * \param rc destination channel(?)
 * Bridge two channels (c0 and c1) together.  If an important frame occurs, we return that frame in
   *rf (remember, it could be NULL) and which channel (0 or 1) in rc */
//int ast_channel_bridge(struct ast_channel *c0, struct ast_channel *c1, int flags, struct ast_frame **fo, struct ast_channel **rc);
int ast_channel_bridge(struct ast_channel *c0,struct ast_channel *c1,struct ast_bridge_config *config, struct ast_frame **fo, struct ast_channel **rc);

//! Weird function made for call transfers
/*! 
 * \param original channel to make a copy of
 * \param clone copy of the original channel
 * This is a very strange and freaky function used primarily for transfer.  Suppose that
   "original" and "clone" are two channels in random situations.  This function takes
   the guts out of "clone" and puts them into the "original" channel, then alerts the
   channel driver of the change, asking it to fixup any private information (like the
   p->owner pointer) that is affected by the change.  The physical layer of the original
   channel is hung up.  */
int ast_channel_masquerade(struct ast_channel *original, struct ast_channel *clone);

//! Gives the string form of a given state
/*! 
 * \param state state to get the name of
 * Give a name to a state 
 * Pretty self explanatory.
 * Returns the text form of the binary state given
 */
char *ast_state2str(int state);

/* Options: Some low-level drivers may implement "options" allowing fine tuning of the
   low level channel.  See frame.h for options.  Note that many channel drivers may support
   none or a subset of those features, and you should not count on this if you want your
   asterisk application to be portable.  They're mainly useful for tweaking performance */

//! Sets an option on a channel
/*! 
 * \param channel channel to set options on
 * \param option option to change
 * \param data data specific to option
 * \param datalen length of the data
 * \param block blocking or not
 * Set an option on a channel (see frame.h), optionally blocking awaiting the reply 
 * Returns 0 on success and -1 on failure
 */
int ast_channel_setoption(struct ast_channel *channel, int option, void *data, int datalen, int block);

//! Checks the value of an option
/*! 
 * Query the value of an option, optionally blocking until a reply is received
 * Works similarly to setoption except only reads the options.
 */
struct ast_frame *ast_channel_queryoption(struct ast_channel *channel, int option, void *data, int *datalen, int block);

//! Checks for HTML support on a channel
/*! Returns 0 if channel does not support HTML or non-zero if it does */
int ast_channel_supports_html(struct ast_channel *channel);

//! Sends HTML on given channel
/*! Send HTML or URL on link.  Returns 0 on success or -1 on failure */
int ast_channel_sendhtml(struct ast_channel *channel, int subclass, char *data, int datalen);

//! Sends a URL on a given link
/*! Send URL on link.  Returns 0 on success or -1 on failure */
int ast_channel_sendurl(struct ast_channel *channel, char *url);

//! Defers DTMF
/*! Defer DTMF so that you only read things like hangups and audio.  Returns
   non-zero if channel was already DTMF-deferred or 0 if channel is just now
   being DTMF-deferred */
int ast_channel_defer_dtmf(struct ast_channel *chan);

//! Undeos a defer
/*! Undo defer.  ast_read will return any dtmf characters that were queued */
void ast_channel_undefer_dtmf(struct ast_channel *chan);

/*! Initiate system shutdown -- prevents new channels from being allocated.
    If "hangup" is non-zero, all existing channels will receive soft
     hangups */
void ast_begin_shutdown(int hangup);

/*! Cancels an existing shutdown and returns to normal operation */
void ast_cancel_shutdown(void);

/*! Returns number of active/allocated channels */
int ast_active_channels(void);

/*! Returns non-zero if Asterisk is being shut down */
int ast_shutting_down(void);

/*! Activate a given generator */
int ast_activate_generator(struct ast_channel *chan, struct ast_generator *gen, void *params);

/*! Deactive an active generator */
void ast_deactivate_generator(struct ast_channel *chan);

void ast_set_callerid(struct ast_channel *chan, char *callerid, int  anitoo);

/*! Start a tone going */
int ast_tonepair_start(struct ast_channel *chan, int freq1, int freq2, int duration, int vol);
/*! Stop a tone from playing */
void ast_tonepair_stop(struct ast_channel *chan);
/*! Play a tone pair for a given amount of time */
int ast_tonepair(struct ast_channel *chan, int freq1, int freq2, int duration, int vol);

/*! Automatically service a channel for us... */
int ast_autoservice_start(struct ast_channel *chan);

/*! Stop servicing a channel for us...  Returns -1 on error or if channel has been hungup */
int ast_autoservice_stop(struct ast_channel *chan);

/* If built with zaptel optimizations, force a scheduled expiration on the
   timer fd, at which point we call the callback function / data */
int ast_settimeout(struct ast_channel *c, int samples, int (*func)(void *data), void *data);

/* Transfer a channel (if supported).  Returns -1 on error, 0 if not supported
   and 1 if supported and requested */
int ast_transfer(struct ast_channel *chan, char *dest);

int ast_do_masquerade(struct ast_channel *chan);

/* Misc. functions below */

/* Helper function for migrating select to poll */
static inline int ast_fdisset(struct pollfd *pfds, int fd, int max, int *start)
{
   int x;
   for (x=start ? *start : 0;x<max;x++)
      if (pfds[x].fd == fd) {
         if (start) {
            if (x==*start)
               (*start)++;
         }
         return pfds[x].revents;
      }
   return 0;
}

//! Waits for activity on a group of channels
/*! 
 * \param nfds the maximum number of file descriptors in the sets
 * \param rfds file descriptors to check for read availability
 * \param wfds file descriptors to check for write availability
 * \param efds file descriptors to check for exceptions (OOB data)
 * \param tvp timeout while waiting for events
 * This is the same as a standard select(), except it guarantees the
 * behaviour where the passed struct timeval is updated with how much
 * time was not slept while waiting for the specified events
 */
static inline int ast_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeval *tvp)
{
#ifdef __linux__
   return select(nfds, rfds, wfds, efds, tvp);
#else
   if (tvp) {
      struct timeval tv, tvstart, tvend, tvlen;
      int res;

      tv = *tvp;
      gettimeofday(&tvstart, NULL);
      res = select(nfds, rfds, wfds, efds, tvp);
      gettimeofday(&tvend, NULL);
      timersub(&tvend, &tvstart, &tvlen);
      timersub(&tv, &tvlen, tvp);
      if (tvp->tv_sec < 0 || (tvp->tv_sec == 0 && tvp->tv_usec < 0)) {
         tvp->tv_sec = 0;
         tvp->tv_usec = 0;
      }
      return res;
   }
   else
      return select(nfds, rfds, wfds, efds, NULL);
#endif
}

#if !defined(ast_strdupa) && defined(__GNUC__)
# define ast_strdupa(s)                         \
  (__extension__                             \
    ({                                       \
      __const char *__old = (s);                \
      size_t __len = strlen (__old) + 1;           \
      char *__new = (char *) __builtin_alloca (__len);   \
      (char *) memcpy (__new, __old, __len);       \
    }))
#endif

#ifdef DO_CRASH
#define CRASH do { fprintf(stderr, "!! Forcing immediate crash a-la abort !!\n"); *((int *)0) = 0; } while(0)
#else
#define CRASH do { } while(0)
#endif

#define CHECK_BLOCKING(c) {    \
                     if ((c)->blocking) {\
                        ast_log(LOG_WARNING, "Thread %ld Blocking '%s', already blocked by thread %ld in procedure %s\n", (long) pthread_self(), (c)->name, (long) (c)->blocker, (c)->blockproc); \
                        CRASH; \
                     } else { \
                        (c)->blocker = pthread_self(); \
                        (c)->blockproc = __PRETTY_FUNCTION__; \
                           c->blocking = -1; \
                           } }

extern unsigned int ast_get_group(char *s);

#if defined(__cplusplus) || defined(c_plusplus)
}
#endif


#endif

---