Abstract: A terminal configured to receive data from a broadcast station that may simultaneously participate in a wireless network via transmissions to a wireless base station. The terminal determines time periods when data of interest to the terminal will be broadcast and schedules transmissions to the base station to avoid these time periods, thereby avoiding the transmissions preventing reception of the data of interest. The time periods may be determined amongst other means from scheduling information transmitted by the broadcast station.

Abstract: A method for controlling an interactive application comprises receiving a data stream comprising an interactive application and monitoring the data stream to identify a change in the stream. In response to the change, the method further comprises preventing the interactive application from accessing files, identifying those files present in the data stream, and enabling the interactive application to access only those files present in the data stream.

Abstract: A terminal (60) in a digital broadcasting system supports a virtual machine (150), such as a Java™ virtual machine, which processes applications in a first code format, such as Java™ byte code. A plug-in (110) is provided which converts applications that are received in a second code format into the first code format. The plug-in (110) can compile (120) the application into the first code format. The application can be compiled (120) upon receipt, or it may be stored (69) and compiled at a later time, such as overnight or when the virtual machine (150) has spare processing capacity (114). Applications can be converted based on monitored usage statistics (112).

Abstract: A data playback apparatus (14) and method for the operation of the same, for the handling of a recorded data stream and associated linear application, are provided. The apparatus includes a data stream playback stage (19) operable to perform linear real-time and non-linear playback of a stored data stream from storage (18). An application processing stage (16) runs a linear application from a given start point on commencement of linear real-time playback of the data stream. To avoid problems where the application is unsuited to the non-linearity, the application processing stage (16) stops running of said application and, on recommencing of linear real-time playback, recommences running of the application from the given start point.

Abstract: A data playback apparatus and method for handling of a recorded data stream and associated linear application include a data stream playback stage operable to perform linear real-time and non-linear playback of a stored data stream from storage. An application processing stage runs a linear application from a given start point on commencement of linear real-time playback of the data stream. To avoid problems where the application is unsuited to the non-linearity, the application processing stage stops running of said application and, on recommencing of linear real-time playback, recommences running of the application from the given start point.

Abstract: A method of reclaiming memory space allocated to a data structure comprising data objects (910-960) linked by identifying pointers, in which the memory allocated to data objects is reclaimed using two systems: a first system (980), by which a selected part of the data structure is traversed by following the pointers, one of at least two identifiers being allocated to the data objects, a first identifier which indicates that the data object has been traversed so that the data objects referenced by the pointers of that data object have been identified, and a second identifier which indicates that the data object is referenced by a pointer, but the data object has not yet been traversed; and a second system (990), by which an individual data object is selected for deletion to enable the associated memory space to be reclaimed.

Abstract: A data processing apparatus for handling multi-thread programs comprises a data processor coupled with a random-access memory containing a plurality of data objects. Each data object is accessed via respective pointers carried by memory stacks associated with respective threads. Periodically, a garbage collection procedure is applied to the random-access memory with those data objects having no extant pointers thereto from any source being identified and deleted. Subject to a locking constraint applied to some of the data objects, the remainder are compacted to free space in the memory. To enable localising of the garbage collection procedure, reference stacks are provided for each thread stack frame such as to identify, preferably via a per-thread reference table, data objects referenced from only a single frame, which objects are deleted on conclusion of that frame.

Abstract: A method for controlling an interactive application comprises receiving a data stream comprising an interactive application and monitoring the data stream to identify a change in the stream. In response to the change, the method further comprises preventing the interactive application from accessing files, identifying those files present in the data stream, and enabling the interactive application to access only those files present in the data stream.

Abstract: A method of scheduling instructions to be executed concurrently by a processor, the processor being capable of executing a predetermined number of instructions concurrently. Instructions from a first process and a second process are interleaved according to a predetermined rule to give a third process. Instructions from the third process are then scheduled for execution at a first time point by the processor. Instructions of the first process generate data structures comprising data objects linked by identifying pointers in a memory heap. The second process comprises a garbage collection process for traversing the memory heap and reclaiming memory allocated to data structures unused by the first process.

Abstract: A method of reclaiming memory space allocated to a data structure comprising data objects (910-960) linked by identifying pointers, in which the memory allocated to data objects is reclaimed using two systems: a first system (980), by which a selected part of the data structure is traversed by following the pointers, one of at least two identifiers being allocated to the data objects, a first identifier which indicates that the data object has been traversed so that the data objects referenced by the pointers of that data object have been identified, and a second identifier which indicates that the data object is referenced by a pointer, but the data object has not yet been traversed; and a second system (990), by which an individual data object is selected for deletion to enable the associated memory space to be reclaimed.

Abstract: A method and apparatus for reclaiming memory space allocated to data structures comprising data objects linked by identifying pointers. The memory allocated to data objects is reclaimed using two systems. In the first system (240), the data structures are traversed to identify those objects to which no references are made by the pointers of other objects, and the memory allocated to those objects to which no references are made is reclaimed. In the second system (210), objects which are not descendants of root objects are determined and the memory allocated to those objects is reclaimed. Cycles of the first system are interleaved with cycles of the second system.

Abstract: A method of reclaiming memory space allocated to a data structure comprising data objects (910-960) linked by identifying pointers, in which the memory allocated to data objects is reclaimed using two systems: a first system (980), by which a selected part of the data structure is traversed by following the pointers, one of at least two identifiers being allocated to the data objects, a first identifier which indicates that the data object has been traversed so that the data objects referenced by the pointers of that data object have been identified, and a second identifier which indicates that the data object is referenced by a pointer, but the data object has not yet been traversed; and a second system (990), by which an individual data object is selected for deletion to enable the associated memory space to be reclaimed.

Abstract: A transmission system, comprising a transmitter (10) and at least one receiver (14) is configured to receive signals (12) transmitted therefrom. Broadcast data in the transmitted stream is accompanied by one or more applications defined in one or more data carousels formed of data file and directory objects sent in cycles with predetermined groups of file and directory objects being formed into respective modules at the transmitter and with each module being transmitted as a whole. For each object carousel defining the root hierarchy of the data objects there is transmitted in the stream a list of identifiers for the component data carousels respectively defining all or a part of the data objects associated with an application. The receiver (14) is arranged, on identification of a particular application to be recorded, to use the list of identifiers to identify and subsequently store the received file data and directory objects for that application.

Abstract: A data processing method and apparatus are described for mark-sweep garbage collection through stored data structures defined by data objects in a multi threading environment supporting the handling of finalizers. The sweeping stage consists of a linear sweep across the heap in which any objects with a mark-state of Deletable are deleted, while objects with finalizers and mark-state of pending are placed on a finalizers queue and marked. The number of objects with finalizers is tracked and compared with the known total allocated to the heap. If not all finalizable objects are found, a further marking operation is required to identify all objects reachable by finalizers. However, if all finalizable objects are found by the first marking operation, as indicated by a match between the found and stored totals, the marked unreachable objects may all be deleted in a single pass.

Abstract: A data processing apparatus includes a heap memory (HM) containing a plurality of data objects (DO) each accessed by respective pointers originating from programme thread memory stacks (SF). In one embodiment, a garbage collection utility (100) periodically sweeps the heap (HM) and identifies redundant data objects to a free-list (FL) to enable their memory space to be re-used. System requests for memory (AREQ), if they cannot be met by the free list (FL), are stored (ALLIST) to be handled subsequently. As further data objects are marked redundant during sweeping, the space they occupy is first offered to the stored system requests (ALLIST) before being made generally available through the free-list (FL).

Abstract: A data playback apparatus (14) and method for the operation of the same, for the handling of a recorded data stream and associated linear application, are provided. The apparatus includes a data stream playback stage (19) operable to perform linear real-time and non-linear playback of a stored data stream from storage (18). An application processing stage (16) runs a linear application from a given start point on commencement of linear real-time playback of the data stream. To avoid problems where the application is unsuited to the non-linearity, the application processing stage (16) stops running of said application and, on recommencing of linear real-time playback, recommences running of the application from the given start point.

Abstract: A method of garbage collection and data processing apparatus embodying the same. Within a heap memory, data objects are accessed via respective pointers carried by memory stacks; the memory is periodically swept to mark, for each object, a count of the number of extant pointers thereto from any source and, on detection that an object's count has reached zero, deleting that object. To permit concurrency of mark and sweep operations, a pair of reference count fields are maintained for each object: one holds an ongoing pointer count for the present mark operation and the other holds the value for the preceding one. At the conclusion of each mark operation, the mapping of counts into fields is reversed. An objects count is taken as zero, and the object deleted, when both counts are zero.

Abstract: A data processing method and apparatus are described for mark-sweep garbage collection through stored data structures defined by data objects in a multi threading environment supporting the handling of finalisers. Pipelining of the marking (MA) and sweeping (GC) states is enabled by increasing the number of mark states M to four, namely Marked, Unmarked, Pending or Deletable. The sweeping stage GC consists of a linear sweep across the heap in which any objects with M=Deletable (detected non-reachables) are deleted at point D1, whilst objects with finalisers and M=Pending are placed on a finaliser queue and marked. The finalising stage executes finalisers for objects on the finaliser queue (D2). The method includes a synchronisation point (SP) where the results of the mark phase are passed onto the sweeping phase.

Abstract: A data processing apparatus for handling multi-thread programs comprises a data processor coupled with a random-access memory containing a plurality of data objects. Each data object is accessed via respective pointers carried by memory stacks associated with respective threads. Periodically, a garbage collection procedure is applied to the random-access memory with those data objects having no extant pointers thereto from any source being identified and deleted. Subject to a locking constraint applied to some of the data objects, the remainder are compacted to free space in the memory. To enable localising of the garbage collection procedure, reference stacks are provided for each thread stack frame such as to identify, preferably via a per-thread reference table, data objects referenced from only a single frame, which objects are deleted on conclusion of that frame.

Abstract: A data processing method and apparatus are described for tracing paths through stored data structures defined by data objects coupled by identifying pointers and within a contiguous area of memory. A fixed sized marking stack or queue builds up a list of located objects as the structure or structures are traversed. The contiguous memory is divided into discrete pages with the linked data objects within each being considered in turn: any link to an object in another page causes an identifier for that page to be entered in a page list if one does not already exist, and a page table for each page identifies the location of the first and last identified objects within a page to set a range for subsequent scanning.