Registers – Records – Conductive
Reexamination Certificate
1998-11-12
2001-05-01
Tremblay, Mark (Department: 2876)
Registers
Records
Conductive
C235S380000
Reexamination Certificate
active
06223991
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to the management of the memory resources in a microcircuit card, more commonly referred to as a smart card. It relates more particularly to an improvement for re-allocating storage spaces by giving the card operating system the task of reclaiming the allocated memory, irrespective of whether this is a read-write memory (usually a “RAM”-type volatile memory) or a reprogrammable read-only memory (usually an “E
2
PROM”-type or “FLASH”-type alterable non-volatile memory).
2. Description of Related Art
Although the memory resources in microcircuit cards are gradually increasing as a result of more efficient new components, they are relatively limited. It is nevertheless becoming possible and advantageous to carry out dynamic storage allocations. However, it is preferable not to leave the de-allocation of the storage spaces already allocated to the initiative of the programmer as a result of possible programming errors and errors in the additional code then required. The latter would then reside in the applications and not in the card operating system. It might consume the reprogrammable read-only memory, a rare and precious resource in the card.
SUMMARY OF THE INVENTION
In order to prevent these disadvantages, the invention proposes giving the card operating system the task of managing the allocated memory in order to reclaim the storage units which were previously allocated at the request of the means for running the program, but which have become irrelevant to the continued progress thereof.
The invention therefore relates more precisely to a process for managing the memory resources in a microcircuit card comprising, inter alia, alterable volatile and/or non-volatile memories and means for running a program, characterized in that storage spaces are allocated as requests are made, each space comprising a header and a number of storage units corresponding to the request of the said running means, in that updating of a number of references representative of a plurality of references of this kind, requesting at a given moment the data of the corresponding storage space, is organized in each header and in that chaining of the said headers is organized and can be scanned and in that an existing storage space is re-allocated if its number of references has been reduced to zero, if a new storage space is requested and if the number of storage units of the said new storage space is less than or equal to the number of storage units of the said existing storage space.
A reference may be a pointer (direct or indirect) designating a particular storage space in the program or in a sub-program. One feature of the invention therefore consists in storing in each header the number of references requiring the corresponding storage space and in updating this number. When the storage space is defined, this means that the program or a sub-program has requested the formation thereof. Its number of references is therefore equal to one. Other program or sub-program parts may then require the same storage space, as a result of which the number of references may increase. On the other hand, if, for example, a sub-program arrives at its end, all of the storage spaces it requires have their number of references decreased by one unit. Consequently, the number of references of a storage space can be reduced to zero. In this case, the invention allows under certain circumstances for re-allocation in the event of a new allocation request.
Re-allocation can only be effected (except at the end of chaining) if the storage space is larger than or preferably equal to the new request. In order to preserve the continuity of the chaining, a new header must be created in the event of re-allocation, allowing for access to the part of the storage space not re-allocated.
Other features of the invention allow for optimum management of the development of these storage spaces. E.g. it is necessary to prevent as far as possible the creation of storage spaces which, although they have become available, have too small a number of storage units to have a chance of being re-allocated. This can be achieved by means of the type of re-allocation procedure used, as will be seen hereinafter. The process of the invention moreover provides for the merging of storage spaces when they are adjacent in the said chaining and when their numbers of references have all been reduced to zero. A new unique header is therefore assigned to the new storage space resulting from merging of this kind. This merging process (also referred to as defragmentation) means that it is possible to limit the persistence of storage spaces which are too small. Several procedures allowing for the merging of adjacent storage spaces capable of being re-allocated will be described hereinafter.
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Chamley Olivier
Soussana Isaac-Jacques
De la rue Cartes et Systemes
Oliff & Berridg,e PLC
Tremblay Mark
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