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Start the documentation of the timer API functions and macros. About 50% done so far.

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Richard Barry 14 years ago
parent a9558864b7
commit 553a8389cc
1 changed files with 579 additions and 4 deletions
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Source/include/timers.h
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@ -66,7 +66,9 @@
extern "C" {
#endif
/* IDs for commands that can be sent/received on the timer queue. */
/* IDs for commands that can be sent/received on the timer queue. These are to
be used solely through the macros that make up the public software timer API,
as defined below. */
#define tmrCOMMAND_START 0
#define tmrCOMMAND_STOP 1
#define tmrCOMMAND_CHANGE_PERIOD 2
@ -76,28 +78,601 @@ extern "C" {
* MACROS AND DEFINITIONS
*----------------------------------------------------------*/
/**
* Type by which software timers are referenced. For example, a call to
* xTimerCreate() returns an xTimerHandle variable that can then be used to
* reference the subject timer in calls to other software timer API functions
* (for example, xTimerStart(), xTimerReset(), etc.).
*/
typedef void * xTimerHandle;
/* Define the prototype to which timer callback functions must conform. */
typedef void (*tmrTIMER_CALLBACK)( xTimerHandle xTimer );
portBASE_TYPE xTimerCreateTimerTask( void ) PRIVILEGED_FUNCTION;
/**
* xTimerHandle xTimerCreate( const signed char *pcTimerName,
* portTickType xTimerPeriod,
* unsigned portBASE_TYPE uxAutoReload,
* void * pvTimerID,
* tmrTIMER_CALLBACK pxCallbackFunction );
*
* Creates a new software timer instance. This allocates the storage required
* by the new timer, initialises the new timers internal state, and returns a
* handle by which the new timer can be referenced.
*
* Timers are created in the dormant state. The xTimerStart(), xTimerReset(),
* xTimerStartFromISR(), xTimerResetFromISR(), xTimerChangePeriod() and
* xTimerChangePeriodFromISR() can all be used to transition a timer into the
* active state.
*
* @param pcTimerName A text name that is assigned to the timer. This is done
* purely to assist debugging. The kernel itself only ever references a timer by
* its handle, and never by its name.
*
* @param xTimerPeriod The timer period. The time is defined in tick periods so
* the constant portTICK_RATE_MS can be used to convert a time that has been
* specified in milliseconds. For example, if the timer must expire after 100
* ticks, then xTimerPeriod should be set to 100. Alternatively, if the timer
* must expire after 500ms, then xPeriod can be set to ( 500 / portTICK_RATE_MS )
* provided configTICK_RATE_HZ is set to less than or equal to 1000.
*
* @param uxAutoReload If uxAutoReload is set to pdTRUE then the timer will
* expire repeatedly with a frequency set by the xTimerPeriod parameter. If
* uxAutoReload is set to pdFALSE then the timer will be a one-shot timer and
* will expire once only xTimerPeriod ticks from the time it is started.
*
* @param pvTimerID An identifier to assign to the timer being created.
* Typically this would be used to identify the timer that expired within the
* timers callback function when multiple timers are assigned the same callback
* function.
*
* @param pxCallbackFunction The function to call when the timer expires.
*
* @return If the timer is successfully create then a handle to the newly
* created timer is returned. If the timer cannot be created (because either
* there is insufficient FreeRTOS heap remaining to allocate the timer
* structures, or the timer period was set to 0) then 0 is returned.
*
* Example usage:
*
*
* #define NUM_TIMERS 5
*
* // An array to hold handles to the created timers.
* xTimerHandle xTimers[ NUM_TIMERS ];
*
* // An array to hold a count of the number of times each timer expires.
* long lExpireCounters[ NUM_TIMERS ] = { 0 };
*
* // Define a callback function that will be used by multiple timer instances.
* // The callback function does nothing but count the number of times the
* // associated timer expires, and stop the timer once the timer has expired
* // 10 times.
* void vTimerCallback( xTIMER *pxTimer )
* {
* long lArrayIndex;
* const long xMaxExpiryCountBeforeStopping = 10;
*
* // Optionally do something if the pxTimer parameter is NULL.
* configASSERT( pxTimer );
*
* // Which timer expired?
* lArrayIndex = ( long ) pvTimerGetTimerID( pxTimer );
*
* // Increment the number of times that pxTimer has expired.
* lExpireCounters[ lArrayIndex ] += 1;
*
* // If the timer has expired 10 times then stop it from running.
* if( lExpireCounters[ lArrayIndex ] == xMaxExpiryCountBeforeStopping )
* {
* // Do not use a block time if calling a timer API function from a
* // timer callback function, as doing so could cause a deadlock!
* xTimerStop( pxTimer, 0 );
* }
* }
*
* void main( void )
* {
* long x;
*
* // Create then start some timers. Starting the timers before the scheduler
* // has been started means the timers will start running immediately that
* // the scheduler starts.
* for( x = 0; x < NUM_TIMERS; x++ )
* {
* xTimers[ x ] = xTimerCreate( "Timer", // Just a text name, not used by the kernel.
* ( 100 * x ), // The timer period in ticks.
* pdTRUE, // The timers will auto-reload themselves when they expire.
* ( void * ) x, // Assign each timer a unique id equal to its array index.
* vTimerCallback // Each timer calls the same callback when it expires.
* );
*
* if( xTimers[ x ] == NULL )
* {
* // The timer was not created.
* }
* else
* {
* // Start the timer. No block time is specified, and even if one was
* // it would be ignored because the scheduler has not yet been
* // started.
* if( xTimerStart( xTimers[ x ], 0 ) != pdPASS )
* {
* // The timer could not be set into the Active state.
* }
* }
* }
*
* // ...
* // Create tasks here.
* // ...
*
* // Starting the scheduler will start the timers running as they have already
* // been set into the active state.
* xTaskStartScheduler();
*
* // Should not reach here.
* for( ;; );
* }
*/
xTimerHandle xTimerCreate( const signed char *pcTimerName, portTickType xTimerPeriod, unsigned portBASE_TYPE uxAutoReload, void * pvTimerID, tmrTIMER_CALLBACK pxCallbackFunction ) PRIVILEGED_FUNCTION;
/**
* void *pvTimerGetTimerID( xTimerHandle xTimer );
*
* Returns the ID assigned to the xTimer parameter.
*
* IDs are assigned to timers using the pvTimerID parameter of the call to
* xTimerCreated() used to create the timer.
*
* If the same callback function is assigned to multiple tasks then the timer
* ID can be used within the callback function to identify which timer actually
* expired.
*
* @param xTimer The timer being queried.
*
* @return The ID assigned to the timer being queried.
*
* Example usage:
*
* See the xTimerCreate() API function example usage scenario.
*/
void *pvTimerGetTimerID( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
portBASE_TYPE xTimerGenericCommand( xTimerHandle xTimer, portBASE_TYPE xCommandID, portTickType xOptionalValue, portBASE_TYPE *pxHigherPriorityTaskWoken, portTickType xBlockTime ) PRIVILEGED_FUNCTION;
/**
* portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer );
*
* Queries a timer to see if it is active or dormant.
*
* A timer will be ormant if:
* 1) It has been created but not started, or
* 2) It is an expired on-shot timer that has not been restarted.
*
* Timers can be started using the xTimerStart(), xTimerReset(),
* xTimerStartFromISR(), xTimerResetFromISR(), xTimerChangePeriod() and
* xTimerChangePeriodFromISR() API functions.
*
* @param xTimer The timer being queried.
*
* @return pdFALSE will be returned if the timer is dormant. A value other than
* pdFALSE will be returned if the timer is active.
*
* Example usage:
*
* // This function assumes xTimer has already been created.
* void vAFunction( xTimerHandle xTimer )
* {
* if( xTimerIsTimerActive( xTimer ) != pdFALSE ) // or more simply and equivalently "if( xTimerIsTimerActive( xTimer )" )
* {
* // xTimer is active, do something.
* }
* else
* {
* // xTimer is not active, do something else.
* }
* }
*/
portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer ) PRIVILEGED_FUNCTION;
/**
* portBASE_TYPE xTimerStart( xTimerHandle xTimer, portTickType xBlockTime );
*
* Timer functionality is provided by a timer service/daemon task. Many of the
* public FreeRTOS timer API functions send commands to the timer service task
* though a queue called the timer command queue. The timer command queue is
* private to the kernel itself and is not directly accessible to application
* code. The length of the timer command queue is set by the
* configTIMER_QUEUE_LENGTH configuration constant.
*
* xTimerStart() starts a timer that was previously created using the
* xTimerCreate() API function. If the timer had already been started and was
* already in the active state, then xTimerStart() has equaivalent functionality
* to the xTimerReset() API function.
*
* Starting a timer ensures the timer is in the active state. If the timer
* is not stopped, deleted, or reset in the mean time, the callback function
* associated with the timer will get called 'n 'ticks after xTimerStart() was
* called, where 'n' is the timers defined period.
*
* It is valid to call xTimerStart() before the scheduler has been started, but
* when this is done the timer will not actually start until the scheduler is
* started, and the timers expiry time will be relative to when the scheduler is
* started, not relative to when xTimerStart() was called.
*
* The configUSE_TIMERS configuration constant must be set to 1 for xTimerStart()
* to be available.
*
* @param xTimer The handle of the timer being started/restarted.
*
* @param xBlockTime Specifies the time, in ticks, that the calling task should
* be held in the Blocked state to wait for the start command to be successfully
* sent to the timer command queue, should the queue already be full when
* xTimerStart() was called. xBlockTime is ignored if xTimerStart() is called
* before the scheduler is started.
*
* @return pdFAIL will be returned if the start command could not be sent to
* the timer command queue even after xBlockTime ticks had passed. pdPASS will
* be returned if the command was successfully send to the timer command queue.
* When the command is actually processed will depend on the priority of the
* timer service/daemon task relative to other tasks in the system, although the
* timers expiry time is relative to when xTimerStart() is actually called. The
* timer service/daemon task priority is set by the configTIMER_TASK_PRIORITY
* configuration constant.
*
* Example usage:
*
* See the xTimerCreate() API function example usage scenario.
*
*/
#define xTimerStart( xTimer, xBlockTime ) xTimerGenericCommand( xTimer, tmrCOMMAND_START, xTaskGetTickCount(), NULL, xBlockTime )
/**
* portBASE_TYPE xTimerStop( xTimerHandle xTimer, portTickType xBlockTime );
*
* Timer functionality is provided by a timer service/daemon task. Many of the
* public FreeRTOS timer API functions send commands to the timer service task
* though a queue called the timer command queue. The timer command queue is
* private to the kernel itself and is not directly accessible to application
* code. The length of the timer command queue is set by the
* configTIMER_QUEUE_LENGTH configuration constant.
*
* xTimerStop() stops a timer that was previously started using either of the
* The xTimerStart(), xTimerReset(), xTimerStartFromISR(), xTimerResetFromISR(),
* xTimerChangePeriod() or xTimerChangePeriodFromISR() API functions.
*
* Stopping a timer ensures the timer is not in the active state.
*
* The configUSE_TIMERS configuration constant must be set to 1 for xTimerStop()
* to be available.
*
* @param xTimer The handle of the timer being stopped.
*
* @param xBlockTime Specifies the time, in ticks, that the calling task should
* be held in the Blocked state to wait for the stop command to be successfully
* sent to the timer command queue, should the queue already be full when
* xTimerStop() was called. xBlockTime is ignored if xTimerStop() is called
* before the scheduler is started.
*
* @return pdFAIL will be returned if the stop command could not be sent to
* the timer command queue even after xBlockTime ticks had passed. pdPASS will
* be returned if the command was successfully send to the timer command queue.
* When the command is actually processed will depend on the priority of the
* timer service/daemon task relative to other tasks in the system. The timer
* service/daemon task priority is set by the configTIMER_TASK_PRIORITY
* configuration constant.
*
* Example usage:
*
* See the xTimerCreate() API function example usage scenario.
*
*/
#define xTimerStop( xTimer, xBlockTime ) xTimerGenericCommand( xTimer, tmrCOMMAND_STOP, 0, NULL, xBlockTime )
#define xTimerChangePeriod( xTimer, xNewPeriod, xBlockTime ) xTimerGenericCommand( xTimer, tmrCOMMAND_CHANGE_PERIOD, xNewPeriod, NULL, xBlockTime )
/**
* portBASE_TYPE xTimerChangePeriod( xTimerHandle xTimer,
* portTickType xNewPeriod,
* portTickType xBlockTime );
*
* Timer functionality is provided by a timer service/daemon task. Many of the
* public FreeRTOS timer API functions send commands to the timer service task
* though a queue called the timer command queue. The timer command queue is
* private to the kernel itself and is not directly accessible to application
* code. The length of the timer command queue is set by the
* configTIMER_QUEUE_LENGTH configuration constant.
*
* xTimerChangePeriod() changes the period of a timer that was previously
* created using the xTimerCreate() API function.
*
* xTimerChangePeriod() can be called to change the period of an active or
* dormant state timer.
*
* The configUSE_TIMERS configuration constant must be set to 1 for
* xTimerChangePeriod() to be available.
*
* @param xTimer The handle of the timer being stopped.
*
* @param xNewPeriod The new period for xTimer. Timer periods are specified in
* tick periods, so the constant portTICK_RATE_MS can be used to convert a time
* that has been specified in milliseconds. For example, if the timer must
* expire after 100 ticks, then xNewPeriod should be set to 100. Alternatively,
* if the timer must expire after 500ms, then xNewPeriod can be set to
* ( 500 / portTICK_RATE_MS ) provided configTICK_RATE_HZ is set to less than
* or equal to 1000.
*
* @param xBlockTime Specifies the time, in ticks, that the calling task should
* be held in the Blocked state to wait for the change period command to be
* successfully sent to the timer command queue, should the queue already be
* full when xTimerChangePeriod() was called. xBlockTime is ignored if
* xTimerChangePeriod() is called before the scheduler is started.
*
* @return pdFAIL will be returned if the change period command could not be
* sent to the timer command queue even after xBlockTime ticks had passed.
* pdPASS will be returned if the command was successfully send to the timer
* command queue. When the command is actually processed will depend on the
* priority of the timer service/daemon task relative to other tasks in the
* system. The timer service/daemon task priority is set by the
* configTIMER_TASK_PRIORITY configuration constant.
*
* Example usage:
*
* // This function assumes xTimer has already been created. If the timer
* // referenced by xTimer is already active when it is called, then the timer
* // is deleted. If the timer referenced by xTimer is not active when it is
* // called, then the period of the timer is set to 500ms and the timer is
* // started.
* void vAFunction( xTimerHandle xTimer )
* {
* if( xTimerIsTimerActive( xTimer ) != pdFALSE ) // or more simply and equivalently "if( xTimerIsTimerActive( xTimer )" )
* {
* // xTimer is already active - delete it.
* xTimerDelete( xTimer );
* }
* else
* {
* // xTimer is not active, change its period to 500ms. This will also
* // cause the timer to start. Block for a maximum of 100 ticks if the
* // change period command cannot immediately be sent to the timer
* // command queue.
* if( xTimerChangePeriod( xTimer, 500 / portTICK_RATE_MS, 100 ) == pdPASS )
* {
* // The command was successfully sent.
* }
* else
* {
* // The command could not be sent, even after waiting for 100 ticks
* // to pass. Take appropriate action here.
* {
* }
* }
*/
#define xTimerChangePeriod( xTimer, xNewPeriod, xBlockTime ) xTimerGenericCommand( xTimer, tmrCOMMAND_CHANGE_PERIOD, xNewPeriod, NULL, xBlockTime )
/**
* portBASE_TYPE xTimerDelete( xTimerHandle xTimer, portTickType xBlockTime );
*
* Timer functionality is provided by a timer service/daemon task. Many of the
* public FreeRTOS timer API functions send commands to the timer service task
* though a queue called the timer command queue. The timer command queue is
* private to the kernel itself and is not directly accessible to application
* code. The length of the timer command queue is set by the
* configTIMER_QUEUE_LENGTH configuration constant.
*
* xTimerDelete() deletes a timer that was previously created using the
* xTimerCreate() API function.
*
* The configUSE_TIMERS configuration constant must be set to 1 for
* xTimerDelete() to be available.
*
* @param xTimer The handle of the timer being stopped.
*
* @param xBlockTime Specifies the time, in ticks, that the calling task should
* be held in the Blocked state to wait for the delete command to be
* successfully sent to the timer command queue, should the queue already be
* full when xTimerDelete() was called. xBlockTime is ignored if xTimerDelete()
* is called before the scheduler is started.
*
* @return pdFAIL will be returned if the delete command could not be sent to
* the timer command queue even after xBlockTime ticks had passed. pdPASS will
* be returned if the command was successfully send to the timer command queue.
* When the command is actually processed will depend on the priority of the
* timer service/daemon task relative to other tasks in the system. The timer
* service/daemon task priority is set by the configTIMER_TASK_PRIORITY
* configuration constant.
*
* Example usage:
*
* See the xTimerChangePeriod() API function example usage scenario.
*/
#define xTimerDelete( xTimer, xBlockTime ) xTimerGenericCommand( xTimer, tmrCOMMAND_DELETE, 0, NULL, xBlockTime )
/**
* portBASE_TYPE xTimerReset( xTimerHandle xTimer, portTickType xBlockTime );
*
* Timer functionality is provided by a timer service/daemon task. Many of the
* public FreeRTOS timer API functions send commands to the timer service task
* though a queue called the timer command queue. The timer command queue is
* private to the kernel itself and is not directly accessible to application
* code. The length of the timer command queue is set by the
* configTIMER_QUEUE_LENGTH configuration constant.
*
* xTimerReset() re-starts a timer that was previously created using the
* xTimerCreate() API function. If the timer had already been started and was
* already in the active state, then xTimerReset() will cause the timer to
* re-evaluate its expiry time so that it is relative to when xTimerReset() was
* called. If the timer was in the dormant state then xTimerReset() has
* equaivalent functionality to the xTimerStart() API function.
*
* Resetting a timer ensures the timer is in the active state. If the timer
* is not stopped, deleted, or reset in the mean time, the callback function
* associated with the timer will get called 'n 'ticks after xTimerReset() was
* called, where 'n' is the timers defined period.
*
* It is valid to call xTimerReset() before the scheduler has been started, but
* when this is done the timer will not actually start until the scheduler is
* started, and the timers expiry time will be relative to when the scheduler is
* started, not relative to when xTimerReset() was called.
*
* The configUSE_TIMERS configuration constant must be set to 1 for xTimerReset()
* to be available.
*
* @param xTimer The handle of the timer being started/restarted.
*
* @param xBlockTime Specifies the time, in ticks, that the calling task should
* be held in the Blocked state to wait for the reset command to be successfully
* sent to the timer command queue, should the queue already be full when
* xTimerReset() was called. xBlockTime is ignored if xTimerReset() is called
* before the scheduler is started.
*
* @return pdFAIL will be returned if the reset command could not be sent to
* the timer command queue even after xBlockTime ticks had passed. pdPASS will
* be returned if the command was successfully send to the timer command queue.
* When the command is actually processed will depend on the priority of the
* timer service/daemon task relative to other tasks in the system, although the
* timers expiry time is relative to when xTimerStart() is actually called. The
* timer service/daemon task priority is set by the configTIMER_TASK_PRIORITY
* configuration constant.
*
* Example usage:
*
* // This scenario assumes xTimer has already been created. When a key is
* // pressed, an LCD backlight is switched on. If 5 seconds pass without a key
* // being pressed, then the LCD backlight is switched off. In this case, the
* // timer is a one-shot timer.
*
* xTimerHandle xBacklightTimer = NULL;
*
* // The callback function assigned to the one-shot timer. In this case the
* // parameter is not used.
* void vBacklightTimerCallback( xTIMER *pxTimer )
* {
* // The timer expired, therefore 5 seconds must have passed since a key
* // was pressed. Switch off the LCD backlight.
* vSetBacklightState( BACKLIGHT_OFF );
* }
*
* // The key press event handler.
* void vKeyPressEventHandler( char cKey )
* {
* // Ensure the LCD backlight is on, then reset the timer that is
* // responsible for turning the backlight off after 5 seconds of
* // key inactivity. Wait 10 ticks for the command to be successfully sent
* // if it cannot be sent immediately.
* vSetBacklightState( BACKLIGHT_ON );
* if( vTimerReset( xBacklightTimer, 100 ) != pdPASS )
* {
* // The reset command was not executed successfully. Take appropriate
* // action here.
* }
*
* // Perform the rest of the key processing here.
* }
*
* void main( void )
* {
* long x;
*
* // Create then start the one-shot timer that is responsible for turning
* // the backlight off if no keys are pressed within a 5 second period.
* xBacklightTimer = xTimerCreate( "BacklightTimer", // Just a text name, not used by the kernel.
* ( 5000 / portTICK_RATE_MS), // The timer period in ticks.
* pdFALSE, // The timer is a one-shot timer.
* 0, // The id is not used by the callback so can take any value.
* vBacklightTimerCallback // The callback function that switches the LCD backlight off.
* );
*
* if( xBacklightTimer == NULL )
* {
* // The timer was not created.
* }
* else
* {
* // Start the timer. No block time is specified, and even if one was
* // it would be ignored because the scheduler has not yet been
* // started.
* if( xTimerStart( xBacklightTimer, 0 ) != pdPASS )
* {
* // The timer could not be set into the Active state.
* }
* }
*
* // ...
* // Create tasks here.
* // ...
*
* // Starting the scheduler will start the timer running as it has already
* // been set into the active state.
* xTaskStartScheduler();
*
* // Should not reach here.
* for( ;; );
* }
*/
#define xTimerReset( xTimer, xBlockTime ) xTimerGenericCommand( xTimer, tmrCOMMAND_START, xTaskGetTickCount(), NULL, xBlockTime )
/**
* portBASE_TYPE xTimerStartFromISR( xTimerHandle xTimer,
* portBASE_TYPE *pxHigherPriorityTaskWoken );
*
* Description goes here ####
*
* @param xTimer
*
* @return
*
* Example usage:
*/
#define xTimerStartFromISR( xTimer, pxHigherPriorityTaskWoken ) xTimerGenericCommand( xTimer, tmrCOMMAND_START, xTaskGetTickCountFromISR(), pxHigherPriorityTaskWoken, 0 )
/**
* portBASE_TYPE xTimerStopFromISR( xTimerHandle xTimer,
* portBASE_TYPE *pxHigherPriorityTaskWoken );
*
* Description goes here ####
*
* @param xTimer
*
* @return
*
* Example usage:
*/
#define xTimerStopFromISR( xTimer, pxHigherPriorityTaskWoken ) xTimerGenericCommand( xTimer, tmrCOMMAND_STOP, 0, pxHigherPriorityTaskWoken, 0 )
/**
* portBASE_TYPE xTimerChangePeriodFromISR( xTimerHandle xTimer,
* portTickType xNewPeriod,
* portBASE_TYPE *pxHigherPriorityTaskWoken );
*
* Description goes here ####
*
* @param xTimer
*
* @return
*
* Example usage:
*/
#define xTimerChangePeriodFromISR( xTimer, xNewPeriod, pxHigherPriorityTaskWoken ) xTimerGenericCommand( xTimer, tmrCOMMAND_CHANGE_PERIOD, xNewPeriod, pxHigherPriorityTaskWoken, 0 )
/**
* portBASE_TYPE xTimerResetFromISR( xTimerHandle xTimer,
* portBASE_TYPE *pxHigherPriorityTaskWoken );
*
* Description goes here ####
*
* @param xTimer
*
* @return
*
* Example usage:
*/
#define xTimerResetFromISR( xTimer, pxHigherPriorityTaskWoken ) xTimerGenericCommand( xTimer, tmrCOMMAND_START, xTaskGetTickCountFromISR(), pxHigherPriorityTaskWoken, 0 )
/*
* Functions beyond this part are not part of the public API and are intended
* for use by the kernel only.
*/
portBASE_TYPE xTimerCreateTimerTask( void ) PRIVILEGED_FUNCTION;
portBASE_TYPE xTimerGenericCommand( xTimerHandle xTimer, portBASE_TYPE xCommandID, portTickType xOptionalValue, portBASE_TYPE *pxHigherPriorityTaskWoken, portTickType xBlockTime ) PRIVILEGED_FUNCTION;
#ifdef __cplusplus
}
#endif

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