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Last updated: Sat Feb 3 05:00:47 2007

Asterisk developer's documentation :: Codename Pineapple

---

dial.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2007, Digium, Inc.
 *
 * Joshua Colp <jcolp@digium.com>
 *
 * 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.
 *
 * 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.
 */

/*! \file
 *
 * \brief Dialing API
 *
 * \author Joshua Colp <jcolp@digium.com>
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 52331 $")

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <signal.h>
#include <errno.h>
#include <unistd.h>

#include "asterisk/logger.h"
#include "asterisk/channel.h"
#include "asterisk/options.h"
#include "asterisk/utils.h"
#include "asterisk/lock.h"
#include "asterisk/linkedlists.h"
#include "asterisk/dial.h"
#include "asterisk/pbx.h"

/*! \brief Main dialing structure. Contains global options, channels being dialed, and more! */
struct ast_dial {
   int num;                                           /*! Current number to give to next dialed channel */
   enum ast_dial_result status;                       /*! Status of dial */
   void *options[AST_DIAL_OPTION_MAX];                /*! Global options */
   AST_LIST_HEAD_NOLOCK(, ast_dial_channel) channels; /*! Channels being dialed */
   pthread_t thread;                                  /*! Thread (if running in async) */
};

/*! \brief Dialing channel structure. Contains per-channel dialing options, asterisk channel, and more! */
struct ast_dial_channel {
   int num;                               /*! Unique number for dialed channel */
   const char *tech;                      /*! Technology being dialed */
   const char *device;                    /*! Device being dialed */
   void *options[AST_DIAL_OPTION_MAX];    /*! Channel specific options */
   int cause;                             /*! Cause code in case of failure */
   struct ast_channel *owner;             /*! Asterisk channel */
   AST_LIST_ENTRY(ast_dial_channel) list; /*! Linked list information */
};

/*! \brief Typedef for dial option enable */
typedef void *(*ast_dial_option_cb_enable)(void *data);

/*! \brief Typedef for dial option disable */
typedef int (*ast_dial_option_cb_disable)(void *data);

/* Structure for 'ANSWER_EXEC' option */
struct answer_exec_struct {
   char app[AST_MAX_APP]; /* Application name */
   char *args;            /* Application arguments */
};

/* Enable function for 'ANSWER_EXEC' option */
static void *answer_exec_enable(void *data)
{
   struct answer_exec_struct *answer_exec = NULL;
   char *app = ast_strdupa((char*)data), *args = NULL;

   /* Not giving any data to this option is bad, mmmk? */
   if (ast_strlen_zero(app))
      return NULL;

   /* Create new data structure */
   if (!(answer_exec = ast_calloc(1, sizeof(*answer_exec))))
      return NULL;
   
   /* Parse out application and arguments */
   if ((args = strchr(app, '|'))) {
      *args++ = '\0';
      answer_exec->args = ast_strdup(args);
   }

   /* Copy application name */
   ast_copy_string(answer_exec->app, app, sizeof(answer_exec->app));

   return answer_exec;
}

/* Disable function for 'ANSWER_EXEC' option */
static int answer_exec_disable(void *data)
{
   struct answer_exec_struct *answer_exec = data;

   /* Make sure we have a value */
   if (!answer_exec)
      return -1;

   /* If arguments are present, free them too */
   if (answer_exec->args)
      free(answer_exec->args);

   /* This is simple - just free the structure */
   free(answer_exec);

   return 0;
}

/* Application execution function for 'ANSWER_EXEC' option */
static void answer_exec_run(struct ast_channel *chan, char *app, char *args)
{
   struct ast_app *ast_app = pbx_findapp(app);

   /* If the application was not found, return immediately */
   if (!ast_app)
      return;

   /* All is well... execute the application */
   pbx_exec(chan, ast_app, args);

   return;
}

/*! \brief Options structure - maps options to respective handlers (enable/disable). This list MUST be perfectly kept in order, or else madness will happen. */
static const struct ast_option_types {
   enum ast_dial_option option;
   ast_dial_option_cb_enable enable;
   ast_dial_option_cb_disable disable;
} option_types[] = {
   { AST_DIAL_OPTION_RINGING, NULL, NULL },                                  /*! Always indicate ringing to caller */
   { AST_DIAL_OPTION_ANSWER_EXEC, answer_exec_enable, answer_exec_disable }, /*! Execute application upon answer in async mode */
   { AST_DIAL_OPTION_MAX, NULL, NULL },                                      /*! Terminator of list */
};

/* free the buffer if allocated, and set the pointer to the second arg */
#define S_REPLACE(s, new_val)           \
        do {                            \
                if (s)                  \
                        free(s);        \
                s = (new_val);          \
        } while (0)

/*! \brief Maximum number of channels we can watch at a time */
#define AST_MAX_WATCHERS 256

/*! \brief Macro for finding the option structure to use on a dialed channel */
#define FIND_RELATIVE_OPTION(dial, dial_channel, ast_dial_option) (dial_channel->options[ast_dial_option] ? dial_channel->options[ast_dial_option] : dial->options[ast_dial_option])

/*! \brief Macro that determines whether a channel is the caller or not */
#define IS_CALLER(chan, owner) (chan == owner ? 1 : 0)

/*! \brief New dialing structure
 * \note Create a dialing structure
 * \return Returns a calloc'd ast_dial structure, NULL on failure
 */
struct ast_dial *ast_dial_create(void)
{
   struct ast_dial *dial = NULL;

   /* Allocate new memory for structure */
   if (!(dial = ast_calloc(1, sizeof(*dial))))
      return NULL;

   /* Initialize list of channels */
   AST_LIST_HEAD_INIT_NOLOCK(&dial->channels);

   /* Initialize thread to NULL */
   dial->thread = AST_PTHREADT_NULL;

   return dial;
}

/*! \brief Append a channel
 * \note Appends a channel to a dialing structure
 * \return Returns channel reference number on success, -1 on failure
 */
int ast_dial_append(struct ast_dial *dial, const char *tech, const char *device)
{
   struct ast_dial_channel *channel = NULL;

   /* Make sure we have required arguments */
   if (!dial || !tech || !device)
      return -1;

   /* Allocate new memory for dialed channel structure */
   if (!(channel = ast_calloc(1, sizeof(*channel))))
      return -1;

   /* Record technology and device for when we actually dial */
   channel->tech = tech;
   channel->device = device;

   /* Grab reference number from dial structure */
   channel->num = ast_atomic_fetchadd_int(&dial->num, +1);

   /* Insert into channels list */
   AST_LIST_INSERT_TAIL(&dial->channels, channel, list);

   return channel->num;
}

/*! \brief Helper function that does the beginning dialing */
static int begin_dial(struct ast_dial *dial, struct ast_channel *chan)
{
   struct ast_dial_channel *channel = NULL;
   int success = 0, res = 0;

   /* Iterate through channel list, requesting and calling each one */
   AST_LIST_TRAVERSE(&dial->channels, channel, list) {
      char numsubst[AST_MAX_EXTENSION];

      /* Copy device string over */
      ast_copy_string(numsubst, channel->device, sizeof(numsubst));

      /* Request that the channel be created */
      if (!(channel->owner = ast_request(channel->tech, chan->nativeformats, numsubst, &channel->cause)))
         continue;

      channel->owner->appl = "AppDial2";
                channel->owner->data = "(Outgoing Line)";
                channel->owner->whentohangup = 0;

      /* Inherit everything from he who spawned this Dial */
      ast_channel_inherit_variables(chan, channel->owner);

      /* Copy over callerid information */
      S_REPLACE(channel->owner->cid.cid_num, ast_strdup(chan->cid.cid_num));
      S_REPLACE(channel->owner->cid.cid_name, ast_strdup(chan->cid.cid_name));
      S_REPLACE(channel->owner->cid.cid_ani, ast_strdup(chan->cid.cid_ani));
      S_REPLACE(channel->owner->cid.cid_rdnis, ast_strdup(chan->cid.cid_rdnis));

      ast_string_field_set(channel->owner, language, chan->language);
      ast_string_field_set(channel->owner, accountcode, chan->accountcode);
      channel->owner->cdrflags = chan->cdrflags;
      if (ast_strlen_zero(channel->owner->musicclass))
         ast_string_field_set(channel->owner, musicclass, chan->musicclass);

      channel->owner->cid.cid_pres = chan->cid.cid_pres;
      channel->owner->cid.cid_ton = chan->cid.cid_ton;
      channel->owner->cid.cid_tns = chan->cid.cid_tns;
      channel->owner->adsicpe = chan->adsicpe;
      channel->owner->transfercapability = chan->transfercapability;

      /* Actually call the device */
      if ((res = ast_call(channel->owner, numsubst, 0))) {
         ast_hangup(channel->owner);
         channel->owner = NULL;
      } else {
         success++;
         if (option_verbose > 2)
            ast_verbose(VERBOSE_PREFIX_3 "Called %s\n", numsubst);
      }
   }

   /* If number of failures matches the number of channels, then this truly failed */
   return success;
}

/*! \brief Helper function that finds the dialed channel based on owner */
static struct ast_dial_channel *find_relative_dial_channel(struct ast_dial *dial, struct ast_channel *owner)
{
   struct ast_dial_channel *channel = NULL;

   AST_LIST_TRAVERSE(&dial->channels, channel, list) {
      if (channel->owner == owner)
         break;
   }

   return channel;
}

/*! \brief Helper function that handles control frames WITH owner */
static void handle_frame(struct ast_dial *dial, struct ast_dial_channel *channel, struct ast_frame *fr, struct ast_channel *chan)
{
   if (fr->frametype == AST_FRAME_CONTROL) {
      switch (fr->subclass) {
      case AST_CONTROL_ANSWER:
         if (option_verbose > 2)
            ast_verbose( VERBOSE_PREFIX_3 "%s answered %s\n", channel->owner->name, chan->name);
         AST_LIST_REMOVE(&dial->channels, channel, list);
         AST_LIST_INSERT_HEAD(&dial->channels, channel, list);
         dial->status = AST_DIAL_RESULT_ANSWERED;
         break;
      case AST_CONTROL_BUSY:
         if (option_verbose > 2)
            ast_verbose(VERBOSE_PREFIX_3 "%s is busy\n", channel->owner->name);
         ast_hangup(channel->owner);
         channel->owner = NULL;
         break;
      case AST_CONTROL_CONGESTION:
         if (option_verbose > 2)
            ast_verbose(VERBOSE_PREFIX_3 "%s is circuit-busy\n", channel->owner->name);
         ast_hangup(channel->owner);
         channel->owner = NULL;
         break;
      case AST_CONTROL_RINGING:
         if (option_verbose > 2)
            ast_verbose(VERBOSE_PREFIX_3 "%s is ringing\n", channel->owner->name);
         ast_indicate(chan, AST_CONTROL_RINGING);
         break;
      case AST_CONTROL_PROGRESS:
         if (option_verbose > 2)
            ast_verbose (VERBOSE_PREFIX_3 "%s is making progress, passing it to %s\n", channel->owner->name, chan->name);
         ast_indicate(chan, AST_CONTROL_PROGRESS);
         break;
      case AST_CONTROL_VIDUPDATE:
         if (option_verbose > 2)
            ast_verbose (VERBOSE_PREFIX_3 "%s requested a video update, passing it to %s\n", channel->owner->name, chan->name);
         ast_indicate(chan, AST_CONTROL_VIDUPDATE);
         break;
      case AST_CONTROL_PROCEEDING:
         if (option_verbose > 2)
            ast_verbose (VERBOSE_PREFIX_3 "%s is proceeding, passing it to %s\n", channel->owner->name, chan->name);
         ast_indicate(chan, AST_CONTROL_PROCEEDING);
         break;
      case AST_CONTROL_HOLD:
         if (option_verbose > 2)
            ast_verbose(VERBOSE_PREFIX_3 "Call on %s placed on hold\n", chan->name);
         ast_indicate(chan, AST_CONTROL_HOLD);
         break;
      case AST_CONTROL_UNHOLD:
         if (option_verbose > 2)
            ast_verbose(VERBOSE_PREFIX_3 "Call on %s left from hold\n", chan->name);
         ast_indicate(chan, AST_CONTROL_UNHOLD);
         break;
      case AST_CONTROL_OFFHOOK:
      case AST_CONTROL_FLASH:
         break;
      case -1:
         /* Prod the channel */
         ast_indicate(chan, -1);
         break;
      default:
         break;
      }
   }

   return;
}

/*! \brief Helper function that handles control frames WITHOUT owner */
static void handle_frame_ownerless(struct ast_dial *dial, struct ast_dial_channel *channel, struct ast_frame *fr)
{
   /* If we have no owner we can only update the status of the dial structure, so only look at control frames */
   if (fr->frametype != AST_FRAME_CONTROL)
      return;

   switch (fr->subclass) {
   case AST_CONTROL_ANSWER:
      if (option_verbose > 2)
         ast_verbose( VERBOSE_PREFIX_3 "%s answered\n", channel->owner->name);
      AST_LIST_REMOVE(&dial->channels, channel, list);
      AST_LIST_INSERT_HEAD(&dial->channels, channel, list);
      dial->status = AST_DIAL_RESULT_ANSWERED;
      break;
   case AST_CONTROL_BUSY:
      if (option_verbose > 2)
         ast_verbose(VERBOSE_PREFIX_3 "%s is busy\n", channel->owner->name);
      ast_hangup(channel->owner);
      channel->owner = NULL;
      break;
   case AST_CONTROL_CONGESTION:
      if (option_verbose > 2)
         ast_verbose(VERBOSE_PREFIX_3 "%s is circuit-busy\n", channel->owner->name);
      ast_hangup(channel->owner);
      channel->owner = NULL;
      break;
   case AST_CONTROL_RINGING:
      if (option_verbose > 2)
         ast_verbose(VERBOSE_PREFIX_3 "%s is ringing\n", channel->owner->name);
      dial->status = AST_DIAL_RESULT_RINGING;
      break;
   case AST_CONTROL_PROGRESS:
      if (option_verbose > 2)
         ast_verbose (VERBOSE_PREFIX_3 "%s is making progress\n", channel->owner->name);
      dial->status = AST_DIAL_RESULT_PROGRESS;
      break;
   case AST_CONTROL_PROCEEDING:
      if (option_verbose > 2)
         ast_verbose (VERBOSE_PREFIX_3 "%s is proceeding\n", channel->owner->name);
      dial->status = AST_DIAL_RESULT_PROCEEDING;
      break;
   default:
      break;
   }

   return;
}

/*! \brief Helper function that basically keeps tabs on dialing attempts */
static enum ast_dial_result monitor_dial(struct ast_dial *dial, struct ast_channel *chan)
{
   int timeout = -1, count = 0;
   struct ast_channel *cs[AST_MAX_WATCHERS], *who = NULL;
   struct ast_dial_channel *channel = NULL;
   struct answer_exec_struct *answer_exec = NULL;

   /* Switch dialing status to trying */
   dial->status = AST_DIAL_RESULT_TRYING;

   /* If the "always indicate ringing" option is set, change status to ringing and indicate to the owner if present */
   if (dial->options[AST_DIAL_OPTION_RINGING]) {
      dial->status = AST_DIAL_RESULT_RINGING;
      if (chan)
         ast_indicate(chan, AST_CONTROL_RINGING);
   }

   /* Go into an infinite loop while we are trying */
   while ((dial->status != AST_DIAL_RESULT_UNANSWERED) && (dial->status != AST_DIAL_RESULT_ANSWERED) && (dial->status != AST_DIAL_RESULT_HANGUP) && (dial->status != AST_DIAL_RESULT_TIMEOUT)) {
      int pos = 0;
      struct ast_frame *fr = NULL;

      /* Set up channel structure array */
      pos = count = 0;
      if (chan)
         cs[pos++] = chan;

      /* Add channels we are attempting to dial */
      AST_LIST_TRAVERSE(&dial->channels, channel, list) {
         if (channel->owner) {
            cs[pos++] = channel->owner;
            count++;
         }
      }

      /* If we have no outbound channels in progress, switch status to unanswered and stop */
      if (!count) {
         dial->status = AST_DIAL_RESULT_UNANSWERED;
         break;
      }

      /* Just to be safe... */
      if (dial->thread == AST_PTHREADT_STOP)
         break;

      /* Wait for frames from channels */
      who = ast_waitfor_n(cs, pos, &timeout);

      /* Check to see if our thread is being cancelled */
      if (dial->thread == AST_PTHREADT_STOP)
         break;

      /* If we are not being cancelled and we have no channel, then timeout was tripped */
      if (!who)
         continue;

      /* Find relative dial channel */
      if (!chan || !IS_CALLER(chan, who))
         channel = find_relative_dial_channel(dial, who);

      /* Attempt to read in a frame */
      if (!(fr = ast_read(who))) {
         /* If this is the caller then we switch status to hangup and stop */
         if (chan && IS_CALLER(chan, who)) {
            dial->status = AST_DIAL_RESULT_HANGUP;
            break;
         }
         ast_hangup(who);
         channel->owner = NULL;
         continue;
      }

      /* Process the frame */
      if (chan)
         handle_frame(dial, channel, fr, chan);
      else
         handle_frame_ownerless(dial, channel, fr);

      /* Free the received frame and start all over */
      ast_frfree(fr);
   }

   /* Do post-processing from loop */
   if (dial->status == AST_DIAL_RESULT_ANSWERED) {
      /* Hangup everything except that which answered */
      AST_LIST_TRAVERSE(&dial->channels, channel, list) {
         if (!channel->owner || channel->owner == who)
            continue;
         ast_hangup(channel->owner);
         channel->owner = NULL;
      }
      /* If ANSWER_EXEC is enabled as an option, execute application on answered channel */
      if ((channel = find_relative_dial_channel(dial, who)) && (answer_exec = FIND_RELATIVE_OPTION(dial, channel, AST_DIAL_OPTION_ANSWER_EXEC)))
         answer_exec_run(who, answer_exec->app, answer_exec->args);
   } else if (dial->status == AST_DIAL_RESULT_HANGUP) {
      /* Hangup everything */
      AST_LIST_TRAVERSE(&dial->channels, channel, list) {
         if (!channel->owner)
            continue;
         ast_hangup(channel->owner);
         channel->owner = NULL;
      }
   }

   return dial->status;
}

/*! \brief Dial async thread function */
static void *async_dial(void *data)
{
   struct ast_dial *dial = data;

   /* This is really really simple... we basically pass monitor_dial a NULL owner and it changes it's behavior */
   monitor_dial(dial, NULL);

   return NULL;
}

/*! \brief Execute dialing synchronously or asynchronously
 * \note Dials channels in a dial structure.
 * \return Returns dial result code. (TRYING/INVALID/FAILED/ANSWERED/TIMEOUT/UNANSWERED).
 */
enum ast_dial_result ast_dial_run(struct ast_dial *dial, struct ast_channel *chan, int async)
{
   enum ast_dial_result res = AST_DIAL_RESULT_TRYING;

   /* Ensure required arguments are passed */
   if (!dial || !chan)
      return AST_DIAL_RESULT_INVALID;

   /* If there are no channels to dial we can't very well try to dial them */
   if (AST_LIST_EMPTY(&dial->channels))
      return AST_DIAL_RESULT_INVALID;

   /* Dial each requested channel */
   if (!begin_dial(dial, chan))
      return AST_DIAL_RESULT_FAILED;

   /* If we are running async spawn a thread and send it away... otherwise block here */
   if (async) {
      /* Try to create a thread */
      if (ast_pthread_create(&dial->thread, NULL, async_dial, dial)) {
         /* Failed to create the thread - hangup all dialed channels and return failed */
         ast_dial_hangup(dial);
         res = AST_DIAL_RESULT_FAILED;
      }
   } else {
      res = monitor_dial(dial, chan);
   }

   return res;
}

/*! \brief Return channel that answered
 * \note Returns the Asterisk channel that answered
 * \param dial Dialing structure
 */
struct ast_channel *ast_dial_answered(struct ast_dial *dial)
{
   if (!dial)
      return NULL;

   return ((dial->status == AST_DIAL_RESULT_ANSWERED) ? AST_LIST_FIRST(&dial->channels)->owner : NULL);
}

/*! \brief Return status of dial
 * \note Returns the status of the dial attempt
 * \param dial Dialing structure
 */
enum ast_dial_result ast_dial_status(struct ast_dial *dial)
{
   return dial->status;
}

/*! \brief Cancel async thread
 * \note Cancel a running async thread
 * \param dial Dialing structure
 */
enum ast_dial_result ast_dial_join(struct ast_dial *dial)
{
   pthread_t thread;

   /* If the dial structure is not running in async, return failed */
   if (dial->thread == AST_PTHREADT_NULL)
      return AST_DIAL_RESULT_FAILED;

   /* Record thread */
   thread = dial->thread;

   /* Stop the thread */
   dial->thread = AST_PTHREADT_STOP;

   /* Now we signal it with SIGURG so it will break out of it's waitfor */
   pthread_kill(thread, SIGURG);

   /* Finally wait for the thread to exit */
   pthread_join(thread, NULL);

   /* Yay thread is all gone */
   dial->thread = AST_PTHREADT_NULL;

   return dial->status;
}

/*! \brief Hangup channels
 * \note Hangup all active channels
 * \param dial Dialing structure
 */
void ast_dial_hangup(struct ast_dial *dial)
{
   struct ast_dial_channel *channel = NULL;

   if (!dial)
      return;
   
   AST_LIST_TRAVERSE(&dial->channels, channel, list) {
      if (channel->owner) {
         ast_hangup(channel->owner);
         channel->owner = NULL;
      }
   }

   return;
}

/*! \brief Destroys a dialing structure
 * \note Destroys (free's) the given ast_dial structure
 * \param dial Dialing structure to free
 * \return Returns 0 on success, -1 on failure
 */
int ast_dial_destroy(struct ast_dial *dial)
{
   int i = 0;
   struct ast_dial_channel *channel = NULL;

   if (!dial)
      return -1;
   
   /* Hangup and deallocate all the dialed channels */
   AST_LIST_TRAVERSE(&dial->channels, channel, list) {
      /* Disable any enabled options */
      for (i = 0; i < AST_DIAL_OPTION_MAX; i++) {
         if (!channel->options[i])
            continue;
         if (option_types[i].disable)
            option_types[i].disable(channel->options[i]);
         channel->options[i] = NULL;
      }
      /* Hang up channel if need be */
      if (channel->owner) {
         ast_hangup(channel->owner);
         channel->owner = NULL;
      }
      /* Free structure */
      free(channel);
   }
       
   /* Disable any enabled options globally */
   for (i = 0; i < AST_DIAL_OPTION_MAX; i++) {
      if (!dial->options[i])
         continue;
      if (option_types[i].disable)
         option_types[i].disable(dial->options[i]);
      dial->options[i] = NULL;
   }

   /* Free structure */
   free(dial);

   return 0;
}

/*! \brief Enables an option globally
 * \param dial Dial structure to enable option on
 * \param option Option to enable
 * \param data Data to pass to this option (not always needed)
 * \return Returns 0 on success, -1 on failure
 */
int ast_dial_option_global_enable(struct ast_dial *dial, enum ast_dial_option option, void *data)
{
   /* If the option is already enabled, return failure */
   if (dial->options[option])
      return -1;

   /* Execute enable callback if it exists, if not simply make sure the value is set */
   if (option_types[option].enable)
      dial->options[option] = option_types[option].enable(data);
   else
      dial->options[option] = (void*)1;

   return 0;
}

/*! \brief Enables an option per channel
 * \param dial Dial structure
 * \param num Channel number to enable option on
 * \param option Option to enable
 * \param data Data to pass to this option (not always needed)
 * \return Returns 0 on success, -1 on failure
 */
int ast_dial_option_enable(struct ast_dial *dial, int num, enum ast_dial_option option, void *data)
{
   struct ast_dial_channel *channel = NULL;

   /* Ensure we have required arguments */
   if (!dial || AST_LIST_EMPTY(&dial->channels))
      return -1;
   
   /* Look for channel, we can sort of cheat and predict things - the last channel in the list will probably be what they want */
   if (AST_LIST_LAST(&dial->channels)->num != num) {
      AST_LIST_TRAVERSE(&dial->channels, channel, list) {
         if (channel->num == num)
            break;
      }
   } else {
      channel = AST_LIST_LAST(&dial->channels);
   }

   /* If none found, return failure */
   if (!channel)
      return -1;

   /* If the option is already enabled, return failure */
   if (channel->options[option])
      return -1;

        /* Execute enable callback if it exists, if not simply make sure the value is set */
   if (option_types[option].enable)
      channel->options[option] = option_types[option].enable(data);
   else
      channel->options[option] = (void*)1;

   return 0;
}

/*! \brief Disables an option globally
 * \param dial Dial structure to disable option on
 * \param option Option to disable
 * \return Returns 0 on success, -1 on failure
 */
int ast_dial_option_global_disable(struct ast_dial *dial, enum ast_dial_option option)
{
        /* If the option is not enabled, return failure */
        if (!dial->options[option])
                return -1;

   /* Execute callback of option to disable if it exists */
   if (option_types[option].disable)
      option_types[option].disable(dial->options[option]);

   /* Finally disable option on the structure */
   dial->options[option] = NULL;

        return 0;
}

/*! \brief Disables an option per channel
 * \param dial Dial structure
 * \param num Channel number to disable option on
 * \param option Option to disable
 * \return Returns 0 on success, -1 on failure
 */
int ast_dial_option_disable(struct ast_dial *dial, int num, enum ast_dial_option option)
{
   struct ast_dial_channel *channel = NULL;

   /* Ensure we have required arguments */
   if (!dial || AST_LIST_EMPTY(&dial->channels))
      return -1;

   /* Look for channel, we can sort of cheat and predict things - the last channel in the list will probably be what they want */
   if (AST_LIST_LAST(&dial->channels)->num != num) {
      AST_LIST_TRAVERSE(&dial->channels, channel, list) {
         if (channel->num == num)
            break;
      }
   } else {
      channel = AST_LIST_LAST(&dial->channels);
   }

   /* If none found, return failure */
   if (!channel)
      return -1;

   /* If the option is not enabled, return failure */
   if (!channel->options[option])
      return -1;

   /* Execute callback of option to disable it if it exists */
   if (option_types[option].disable)
      option_types[option].disable(channel->options[option]);

   /* Finally disable the option on the structure */
   channel->options[option] = NULL;

   return 0;
}

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