CN107239526A - File system implementation method, scrap cleaning method, operating position localization method - Google Patents
File system implementation method, scrap cleaning method, operating position localization method Download PDFInfo
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F16/00—Information retrieval; Database structures therefor; File system structures therefor
- G06F16/10—File systems; File servers
- G06F16/13—File access structures, e.g. distributed indices
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F16/00—Information retrieval; Database structures therefor; File system structures therefor
- G06F16/10—File systems; File servers
- G06F16/11—File system administration, e.g. details of archiving or snapshots
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F16/00—Information retrieval; Database structures therefor; File system structures therefor
- G06F16/10—File systems; File servers
- G06F16/17—Details of further file system functions
- G06F16/1724—Details of de-fragmentation performed by the file system
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Abstract
The present invention provides a kind of file system implementation method, and distribution is stored in block Zhong FST areas, FDT areas, FAT area and aggregate of data area in memory block；FST areas represent file system information area；FDT areas represent file description information area；FAT area represents file allocation information area, aggregate of data area storage file content；FST areas store the initial address in FDT areas and the initial address of FAT area simultaneously；FDT areas set FDT tables；FAT area sets FAT table；FDT areas and FAT area are indexed by the initial address in FST areas, while passing through FDT table index file starting clusters, by the linking relationship of each cluster of FAT table index file, the whole file content stored by the annexation index data cluster area of each cluster.Block position where the FDT areas of the present invention, FAT area can update rotation with file, the corresponding area's initial address updated in FST is added while FDT areas, FAT area transfer, it is achieved thereby that FDT areas, FAT area, aggregate of data area are in the balanced rotation of whole memory space and erasable balance.
Description
Technical field
The present invention relates to embedded file system field, and in particular to a kind of realization side of file system suitable for IC-card
Method, the scope of application of the invention includes but is not limited to IC-card, is equally applicable to the file system of other memories similar with IC-card
The realization of system.
Background technology
As electronic technology, computer technology are developed rapidly, either PC systems or embedded system, storage and
The application demand for managing mass data is further extensive.IC cards are the flash cards designed exclusively for massive store, with cost
Low, compatible good the advantages of.In some sector applications, in order to which IC cards can be with PC systems, embedded system according to spy
Fixed form easily carries out data exchange, it is necessary to design document system, to shield the ins and outs of physical storage, being managed
The information of reason is organized into document form, so as to increase the portable and maintainability of application, is easy to user effectively to manage largely
Data, meanwhile, some special industries have certain confidentiality and privately owned customized demand to file content and form, thus build one
The dedicated file system planted suitable for IC cards has certain practical significance.
Current many ripe file system existing on a general-purpose computer, such as FAT, NTFS file system and Unix,
Linux file system, but above-mentioned file system be not suitable for IC cards directly use, subject matter has：First, IC cards are applied to
Operated during PC systems by read write line, application environment is more severe, there is unstable supply voltage, burst power-off, frequently plug etc.
Problem, universal document system considers not enough for the design of reliability；Secondly, when IC cards are applied to embedded device read-write, lead to
With file system disc driver based on resourceful PC platforms and at a slow speed, it is necessary to expend ample resources, and it is embedded
System often resource-constrained；Again, the Flash memory chip build-in attributes of IC cards determine that universal document system is uncomfortable
With it is generally constituted by some pieces, and block is made up of some page/sectors, and page then includes the memory cell of certain amount byte.
The read operation of Flash memories is consistent with disk, but write operation is different from disk, and universal document system is not corresponding to this
Special design.Memory space base unit shared by Flash memory files is block, and data write operation must be in clear area
Carried out after block or erasing in block, erasing requires to carry out in units of block Block（OxFF is write to memory to be erased
Block), write operation is carried out by page/sector Page modes（It once must be written into a Page）, and the erasing of Flash memories
Number of times is limited, and Flash memories these inherent characteristics are must take into consideration when file system is set up on Flash memories, certain
A little block over-erasures can cause the service life for substantially reducing flash storage.In view of general FAT file system is in IC-card
The disadvantages mentioned above of upper application, needs a kind of file system implementation method suitable for IC-card of proposition badly.
The content of the invention
The present invention provides a kind of implementation method of file system, to solve the problem of prior art is present.
The present invention uses following technical scheme：
Distribution is stored in block Zhong FST areas, FDT areas, FAT area and aggregate of data area in file system implementation method, memory block；
The FST areas represent file system information area, for storage file system essential information；FDT areas represent file description letter
Area is ceased, the essential information for storing description file, the essential information of the file at least includes file name, starting cluster, big
Small, creation time；FAT area represents file allocation information area, for the distribution information of storage file, in aggregate of data area storage file
Hold；
FST areas store the initial address in FDT areas and the initial address of FAT area simultaneously；
FDT areas set the file description information of storage file in FDT tables, FDT tables；When the operation to file causes file description letter
When breath changes, FDT areas generate new FDT tables and stored；
FAT area sets cluster distribution condition and cluster annexation of the storage file in aggregate of data area in FAT table, FAT table；When to file
Operation cause when changing of file allocation information, FAT area generates new FAT table and simultaneously stored；
When the operation to file causes file description information and/or file allocation information to change, FDT areas generate new
FDT tables are simultaneously stored, and FAT area generates new FAT table and stored；
FDT areas and FAT area are indexed by the initial address in FST areas, while by FDT table index file starting clusters, passing through FAT
The linking relationship of each cluster of table index file, the whole file content stored by the annexation index data cluster area of each cluster.
FST areas fixed storage is stored in different masses in block i, FDT areas and FAT area, and aggregate of data area is stored in remaining block；
Wherein 0≤i≤N-1, N represent the number of block in memory block, and i represents i-th piece of memory block；
The FDT divides into FDT tables area and FDT table index areas, and FDT tables are stored in FDT tables area, can by FDT table index areas
Index FDT tables；
FAT area is divided into FAT table area and FAT table index area, and FAT table is stored in FAT table area, can be indexed by FAT table index area
To FAT table；
When the operation to file causes file description information to be changed with file allocation information, FDT areas and FAT area are carried out
Operate below：
FDT areas：New FDT tables are regenerated, and are incrementally appended to next position of a FDT table, while in FDT table ropes
Draw and be incremented by new effective call number in area, effective call number can index new FDT tables；When FDT table index areas are write completely, then
The new Kuai Gei FDT areas of distribution, and the block where current FDT areas is wiped, while the initial address in Xin FDT areas is updated into FST
Qu Zhong；
FAT area：New FAT table is regenerated, and is incrementally appended to next position of a FAT table, while in FAT table rope
Draw and be incremented by new effective call number in area, effective call number can index new FAT table；When FAT table index area is write completely, then
The new block of distribution wipes the block where current FAT area to FAT area, while the initial address of new FAT area is updated into FST
Qu Zhong；
The initial address in FDT areas and the initial address of FAT area of FST areas storage are with block where block where FDT areas and FAT area
Transfer is updated, and the update mode is the incremental additional mode write；After the block i that FST areas are stored adds full, whole block is triggered
I erasing and rewriting.
The file system essential information of the FST areas storage includes system sector, cluster, block message, and the memory block is IC
The flash storage of card.
The FDT tables, FAT table set mapping copy in internal memory, when the operation to file causes file description information
With file allocation information when changing, the FDT tables and FAT table in internal memory are regenerated first, after the completion of generation,
FDT tables and FAT table in internal memory is respectively written into memory block Zhong FDT areas and FAT area, by the FDT in FDT areas and FAT area
Table and FAT table are updated to currently valid FDT tables and FAT table；
The FDT tables, the mapping copy of FAT table set dirty mark, the dirty FDT tables being marked in internal memory, FAT table hair respectively
During changing, setting should be labeled as true, after FDT tables, FAT table are written back into memory block, and the dirty mark is eliminated；
When FDT tables in internal memory are synchronously written into the FDT areas of memory block：If the dirty mark of FDT tables has been removed and current memory
In FDT tables it is consistent with the currently active FDT tables content in the FDT areas of memory block, then without being synchronously written；When any one is discontented
When sufficient, the FDT tables in internal memory are synchronously written to the FDT tables in FDT areas, as the currently active FDT tables of memory block, simultaneously will
The dirty mark of FDT tables in internal memory is removed；
When FAT table in internal memory is synchronously written into the FAT area of memory block：If the dirty mark of FAT table has been removed and current memory
In FAT table it is consistent with the currently active FAT table content in the FAT area of memory block, then without being synchronously written；When any one is discontented
When sufficient, the FAT table in internal memory is synchronously written to the FAT table in FAT area, as the currently active FAT table of memory block, simultaneously will
The dirty mark of FAT table in internal memory is removed.
When specifying file write data in the area to aggregate of data, Write post area is set up in internal memory first, works as Write post
After area is write completely, the tail cluster of currently assigned file is retrieved from FAT table first, while the residue for calculating cluster where the tail cluster is empty
Between, if remaining space is not less than the size in Write post area, write-in length is the data of Write post area size；Otherwise tail is write
The data of cluster remaining space size, while the new cluster write-in remaining data of continuation application.
The FAT table is made up of the tufted state of multiple 2 bytes, the tufted state include it is unallocated, distributed, it is dirty, terminate
4 kinds of states.
Scrap cleaning method：
Memory block is scanned in units of block, the ratio shared by the dirty cluster in each block is calculated, when the ratio is beyond setting
Arrangement threshold value when, to file system carry out defragmentation；The dirty cluster is：Deletion action to file makes cluster shared by this document
As dirty cluster；
When carrying out defragmentation to file system, FAT table is first checked for, effective cluster in block to be arranged is retrieved, finds effective cluster
Afterwards, free cluster is applied now, by effective cluster copy content into the free cluster newly applied；If effective cluster is end-of-file cluster,
Only effective length in copy cluster, otherwise copies whole cluster content；
While copying cluster content, new FAT table is generated, while writing new cluster chain in new FAT table；Current cluster has been shifted
Put dirty into rear whole cluster；
Operated more than repeating, until being dirty cluster entirely in whole block, wipe monoblock, and discharge correspondence FAT table, complete a fragment whole
Reason.
Operating position localization method：
Fast Lookup Table is created in internal memory, one section of successive clusters is referred to as a cluster piece by multiple clusters for storing identical file
Section, all cluster fragments are concentrated and are mapped in Fast Lookup Table, corresponding successive clusters sequence number is calculated by file operation position, are led to
Cross Fast Lookup Table and obtain correspondence cluster number；
The step of realizing quickly searched is：
Travel through FAT table；Defining operation position successive clusters number=reading location/cluster size；All cluster fragments of Fast Lookup Table are traveled through,
Successive clusters number subtracts the continuous number of clusters in current clip every time, until successive clusters number is less than the successive clusters in current clip
Number, return the starting cluster number of this fragment and residue successive clusters number and the as corresponding cluster number of operating position.
Beneficial effects of the present invention：The present invention distributes four class regions, respectively file system in the memory block of memory
Information data cluster area（FST）Area, file description information（FDT）Area, file allocation information（FAT）Area, aggregate of data area.FST areas consolidate
Surely it is stored in some block, block position where FDT areas, FAT area can update rotation with file, FDT areas, FAT area are shifted
While the additional corresponding area's initial address updated in FST, it is achieved thereby that FDT areas, FAT area, aggregate of data area are in whole storage sky
Between balanced rotation and erasable balance.
Brief description of the drawings
Fig. 1 is IC-card file system management subregion schematic diagram.
Internal memory write-back schematic diagram of the Tu2Shi FDT areas when FDT tables change.
Fig. 3 is IC-card file system initialization schematic diagram.
Fig. 4 is the quick positioning schematic diagram of cluster where file operation position.
Embodiment
Below in conjunction with the accompanying drawings 1 ~ 4 and embodiment the present invention is described in further detail.
The present invention provides a kind of implementation method of file system, is especially adapted for use in IC-card and its storage similar with IC-card
The file system implementation method of device, this method is accomplished by the following way.
Distribution is stored in block Zhong FST areas, FDT areas, FAT area and aggregate of data area first in the memory block of memory；Its
Middle FST areas represent file system information area, and the area is used for storage file system essential information, the information such as sector, block, cluster；
FDT areas represent file description information area, and the area is used for the essential information for storing description file, and the essential information of file at least includes
File name, starting cluster, size, creation time, state of file etc.；FAT area represents file allocation information area, for storing text
The distribution information of part, aggregate of data area storage file content.FST areas fixed storage is stored in difference in block i, FDT areas and FAT area
Block, aggregate of data area is stored in remaining block；Wherein 0≤i≤N-1, N represent the number of block in memory block, and i represents the i-th of memory block
Block；Block position where FDT areas, FAT area update rotation with file.
FST areas store the initial address in FDT areas and the initial address of FAT area simultaneously, and these addresses with FDT areas and
The transfer of block is updated where FAT areas, and its address updates can be using WriteMode be incrementally added, so that existing in FST areas many
Group FDT areas and the initial address in FAT areas, but only one group of latest update is currently valid, and then whenever all to ensure
Neng Cong FST index FDT areas and FAT areas in area.
FDT areas and FAT area are indexed by the initial address in FST areas, while by FDT table index file starting clusters, passing through
The linking relationship of each cluster of FAT table index files, the whole file of index data cluster area storage is capable of by the annexation of each cluster
Content.
FDT areas set the file description information of storage file in FDT tables, FDT tables；When the operation to file causes file to retouch
When stating information and changing, FDT areas generate new FDT tables and simultaneously stored.
It is of the invention preferential using the renewal that WriteMode carries out FDT tables is incrementally added, now, FDT divide into FDT tables area and
FDT table index areas, FDT tables are stored in FDT tables area, and FDT tables can be indexed by FDT table index areas；The storage of FDT tables area is more
Individual FDT tables, and it is effective that any time, which only has a FDT table, the effective table is usually the table of latest update.It is used as one kind
The description information of most 256 files can be stored in embodiment, FDT tables, the description information includes the state of file, risen
The information such as beginning cluster, title, size, creation time.The operation such as read-write, additions and deletions, renaming of file would generally cause above- mentioned information
Change, so as to need the FDT tables that upgrade in time.
, it is necessary to regenerate new FDT tables first when updating FDT tables, and incrementally it is appended to a upper FDT in FDT tables area
Next position of table, while being incremented by new effective call number in FDT table index areas, effective call number can be indexed newly
FDT tables；When FDT table index areas write full, the block where representing FDT areas has write full, now distributes new Kuai Gei FDT areas, and
The block where current FDT areas is wiped, while the initial address in Xin FDT areas is updated in FST areas.
FAT area sets cluster distribution condition and cluster annexation of the storage file in aggregate of data area in FAT table, FAT table；When right
The operation of file causes when changing of file allocation information, and FAT area generates new FAT table and stored.
When using the renewal for incrementally adding WriteMode progress FAT table, FAT area is divided into FAT table area and FAT table index area,
FAT table is stored in FAT table area, and FAT table can be indexed by FAT table index area.FAT table area stores multiple FAT tables, and arbitrarily
It is effective that moment, which only has a FAT table, and the effective table is usually the table of latest update.FAT table is used for characterizing All Files
Cluster distribution condition and cluster linking relation in whole aggregate of data area, it is made up of the tufted state of multiple 2 bytes, and tufted state includes
It is unallocated, distributed, it is dirty, terminate 4 kinds of states, done state represents that current cluster is end of file cluster.Read-write, the additions and deletions of file
And the operation such as defragmentation would generally cause the new distribution of document cluster, the state change such as dirty be put, so as to need the FAT that upgrades in time
Table.
When updating FAT table, new FAT table is regenerated first, and be incrementally appended to a upper FAT table in FAT table area
Next position, while being incremented by new effective call number in FAT table index area, effective call number can index new
FAT table；When FAT table index area writes full, the block where representing FAT area has write full, then distributes new block to FAT area, and wipe
Block where current FAT area, while the initial address of new FAT area is updated in FST areas.
In above process, the initial address in FDT areas and the initial address of FAT area of FST areas storage are with where FDT areas
The transfer of block is updated where block and FAT area, and also address incrementally adds the mode write, the storage of Ji FST areas to the update mode
The initial address in a upper FDT area and next position of initial address of a upper FAT area increase new initial address, should
Initial address can index currently valid FDT areas and FAT area；After the block i that FST areas are stored adds full, because FST areas are solid
Surely it is stored in a certain piece, therefore, no longer carries out position fast where rotation updates, but directly trigger whole block i erasing
And the rewriting in block i.Based on foregoing, realize FDT areas, FAT areas, aggregate of data area whole memory space equilibrium rotation
With erasable balance.
Because each operation to file is required to update FAT table and/or FDT tables, therefore in order to avoid in memory block
The frequent rewriting of FDT tables and FAT table, causes some pieces in memory block of reading-writing life-span to shorten.The present invention is by the FDT in memory block
Table, FAT table set the identical mapping copy of form in internal memory, when the operation to file cause file description information with
When changing of file allocation information, regenerates to the FDT tables and FAT table in internal memory first, after the completion of generation, will
FDT tables and FAT table in internal memory are respectively written into memory block Zhong FDT areas and FAT area, by the FDT tables in FDT areas and FAT area
Currently valid FDT tables and FAT table are updated to FAT table.
Need to set dirty mark respectively in FDT tables, the mapping copy of FAT table, dirty FDT tables, the FAT being marked in internal memory
When table changes, setting should be labeled as true, after FDT tables, FAT table are written back into memory block, and the dirty mark is eliminated.
When FDT tables in internal memory are synchronously written into the FDT areas of memory block：If the dirty mark of FDT tables has been removed and currently
FDT tables in internal memory are consistent with the currently active FDT tables content in the FDT areas of memory block, then without being synchronously written；When above-mentioned
FDT tables in internal memory when being unsatisfactory for, are synchronously written the FDT tables in FDT areas, are used as the currently active FDT of memory block by one
Table, while the dirty mark of the FDT tables in internal memory is removed.
When FAT table in internal memory is synchronously written into the FAT area of memory block：If the dirty mark of FAT table has been removed and currently
FAT table in internal memory is consistent with the currently active FAT table content in the FAT area of memory block, then without being synchronously written；Work as any one
When being unsatisfactory for, the FAT table in internal memory is synchronously written to the FAT table in FAT area, as the currently active FAT table of memory block, together
When the dirty mark of the FAT table in internal memory is removed.
When specifying file write data into file system data cluster area, in order to avoid too frequent writes, it is limited to simultaneously
The minimum writing unit of current flash storage, this invention takes the mode for being previously written buffering area.Built first in internal memory
Vertical Write post area, after Write post area is write completely, retrieves the tail cluster of currently assigned file from FAT table first, should while calculating
The remaining space of cluster where tail cluster, if remaining space is not less than the size in Write post area, write-in length is that Write post area is big
Small data；Otherwise the data of tail cluster remaining space size are write, while the new cluster write-in remaining data of continuation application.
When reading specified file from file system, it is necessary first to the first cluster content of file, Ran Hougen are found in FDT areas
Cluster where reading original position along the cluster chain search in FAT table according to incoming reading skew, then reads this cluster inclined out of cluster
Move on to the data of cluster tail, if compare reading length it is still inadequate when, continue other clusters on across cluster readings cluster chain data until reading
Length needed for enough.
Cluster shared by this document is caused to turn into dirty cluster due to carrying out deletion action to file, therefore file system needs to provide broken
Piece arrangement function, to rearrange file, is stored in continuous cluster block, while discharging dirty cluster space by file as far as possible.
When carrying out defragmentation, memory block is scanned in units of block first, calculated shared by the dirty cluster in each block
Ratio, when the ratio beyond setting arrangement threshold value when, carry out defragmentation.During arrangement, FAT table is first checked for, retrieval is treated
Effective cluster in block is arranged, finds after effective cluster, applies for free cluster in non-block to be arranged immediately, by effective cluster copy content
Into the free cluster newly applied；If effective cluster is end-of-file cluster, the effective length in effective cluster is only copied, is otherwise copied whole
Cluster content；While copying cluster content, new FAT table is generated, while writing new cluster chain in new FAT table；Current cluster turns
Whole cluster puts dirty after the completion of shifting；Operated more than repeating, until being dirty cluster entirely in whole block, wipe monoblock, and discharge correspondence FAT table,
Complete a defragmentation.Block to be arranged refers to block of the ratio shared by dirty cluster beyond the arrangement threshold value of setting.
As shown in figure 4, the chain type of file disperses to need to travel through cluster chain when storage causes the positioning of file operation position, and very
When many, some clusters of identical file are adjacent, and one section of successive clusters is referred to as into a cluster fragment, one is now set in internal memory
Individual Fast Lookup Table, all cluster fragments of identical file are concentrated and are mapped in a Fast Lookup Table, by file operation position
Corresponding successive clusters sequence number is calculated, correspondence cluster number can be obtained by Fast Lookup Table.Quick finding step：FAT is traveled through, is created
Fast Lookup Table；Operating position successive clusters number=reading location/cluster size；Travel through all fragments of Fast Lookup Table, successive clusters number
The continuous number of clusters in current clip is subtracted every time, until successive clusters number is less than the continuous number of clusters in current clip, returns to this
The starting cluster number of fragment and remaining successive clusters number and the as corresponding cluster number of operating position.
It is, as FST fixed memory block, file system to be used to the IC-card using Flash using block 0 as shown in Fig. 1 ~ 3
The method of system.
Used in the Flash memories of IC-card before file system, it is necessary to carry out newly-built i.e. form to file system
Change.The formatting of file system includes two steps of hard format and soft formatization, is to carry out hard format to IC chip first,
So that all bytes set to 0 xFF, then need to carry out soft format according to File system design form.
The soft format of file system includes：
As shown in Figure 1,3, corresponding document system Global Information is filled according to flash storage block, cluster, sector auxiliary information, is assigned to FST
The corresponding informance in area, then, the address of block 1 is assigned to the FDT areas initial address message (IAM) in FST areas, the address of block 2 is assigned into FST
The FAT area initial address message (IAM) in area, Bing Jiang FST areas write-in block 0.So far, the initialization in FST areas is completed.
According to Zhong FDT areas of FST areas initial address message (IAM), FDT tables are indexed, its table content is all set to 0 into xFF and by rope
Draw byte and be set to 0x55550000, so far, complete FDT initialization.
Mentioned above, system FST takes block 0, and FDT takes block 1, meanwhile, design FAT takes block 2.So, FAT table
Preceding 3 pieces of FAT bytes are set to particular value 0xFFF1,0xFFF2,0xFFF3 respectively, are taken with characterizing it by special, remaining FAT table
Byte put full 0, to characterize it as still unappropriated cluster.Then, index byte is set to 0xAAAA0000, so far, completes FAT
Initialization.
Need to carry out carry before file system operation., it is necessary to by currently valid FDT during the carry of file system
Table, FAT tables are moved into internal memory from Flash to adapt to possible frequent modification, meanwhile, to ensure in internal memory and Flash
The uniformity of appearance, designing FDT in the dirty mark of respective table, internal memory, the change of FAT table can cause the dirty mark to be, and to Flash
Write-back can remove dirty mark.
File write operations can cause the change of file size, change of cluster chain etc., generally require to update FDT tables, FAT
Table.Because FDT tables, FAT table all have mapping copy in internal memory, then corresponding renewal operation is directly depositing into row, internal memory inside
After FDT tables, the change of FAT tables, Flash is written back into synchronize by two kinds of mechanism, a kind of is fixed, critical
Running node, such as write-back FAT will be forced to prevent that FAT is asynchronous after data write-in failure by writing before data, and another is certain
A little operations, such as file close operation.
The synchronous write FDT tables into Flash：Check that dirty mark has been removed, and compare internal memory FDT tables content and reading
Whether the currently active FDT tables contents of Flash are consistent, and write-in need not be synchronized if meet simultaneously.Otherwise, having FDT areas
Effect table index number Jia 1, sequentially writes newest call number in index area, performed simultaneously, sequentially renewal table area is write in location, by current memory
Newest index of the FDT table copy contents into Flash points to position, and clear dirty mark.When incrementally writing call number, if currently
Index area has write full, then block where characterizing current FDT areas has been write full, it is necessary to move, that is, distributes new Kuai Gei FDT areas, simultaneously
Initial address message (IAM) of the FDT areas in FST is updated, and because new block distributes the FAT table caused change, then by original piece
Erasing.
The synchronous write FAT table into Flash：Check that dirty mark has been removed, and compare internal memory FAT table content and reading
Whether the currently active FAT table contents of Flash are consistent, and write-in need not be synchronized if meet simultaneously.Otherwise, by FAT directorial areas
Effective table index number Jia 1, sequentially write newest call number in index area, performed simultaneously, sequentially renewal table area is write in location, will be current
Newest index of the internal memory FAT table copy content into Flash points to position, and clear dirty mark.When incrementally writing call number, if
Current index area has write full, then block where characterizing current FAT directorial areas has been write full, it is necessary to move, that is, distributes new block and managed to FAT
Area is managed, while to update initial address message (IAM) of the FAT directorial areas in FST, and is become because new block distributes the FAT table caused
Change, then by original piece of erasing.
Above-described is only the preferred embodiment of the present invention, it is noted that for those skilled in the art,
Under the premise of general idea of the present invention is not departed from, some changes and improvements can also be made, these should also be considered as the present invention's
Protection domain.
Claims (8)
1. file system implementation method, it is characterised in that：In memory block distribution be stored in block Zhong FST areas, FDT areas, FAT area and
Aggregate of data area；
The FST areas represent file system information area, for storage file system essential information；FDT areas represent file description letter
Area is ceased, the essential information for storing description file, the essential information of the file at least includes file name, starting cluster, big
Small, creation time；FAT area represents file allocation information area, for the distribution information of storage file, in aggregate of data area storage file
Hold；
FST areas store the initial address in FDT areas and the initial address of FAT area simultaneously；
FDT areas set the file description information of storage file in FDT tables, FDT tables；When the operation to file causes file description letter
When breath changes, FDT areas generate new FDT tables and stored；
FAT area sets cluster distribution condition and cluster annexation of the storage file in aggregate of data area in FAT table, FAT table；When to file
Operation cause when changing of file allocation information, FAT area generates new FAT table and simultaneously stored；
When the operation to file causes file description information and/or file allocation information to change, FDT areas generate new
FDT tables are simultaneously stored, and FAT area generates new FAT table and stored；
FDT areas and FAT area are indexed by the initial address in FST areas, while by FDT table index file starting clusters, passing through FAT
The linking relationship of each cluster of table index file, the whole file content stored by the annexation index data cluster area of each cluster.
2. file system implementation method according to claim 1, it is characterised in that：
FST areas fixed storage is stored in different masses in block i, FDT areas and FAT area, and aggregate of data area is stored in remaining block；Wherein
0≤i≤N-1, N represent the number of block in memory block, and i represents i-th piece of memory block；
The FDT divides into FDT tables area and FDT table index areas, and FDT tables are stored in FDT tables area, can by FDT table index areas
Index FDT tables；
FAT area is divided into FAT table area and FAT table index area, and FAT table is stored in FAT table area, can be indexed by FAT table index area
To FAT table；
When the operation to file causes file description information to be changed with file allocation information, FDT areas and FAT area are carried out
Operate below：
FDT areas：New FDT tables are regenerated, and are incrementally appended to next position of a FDT table, while in FDT table ropes
Draw and be incremented by new effective call number in area, effective call number can index new FDT tables；When FDT table index areas are write completely, then
The new Kuai Gei FDT areas of distribution, and the block where current FDT areas is wiped, while the initial address in Xin FDT areas is updated into FST
Qu Zhong；
FAT area：New FAT table is regenerated, and is incrementally appended to next position of a FAT table, while in FAT table rope
Draw and be incremented by new effective call number in area, effective call number can index new FAT table；When FAT table index area is write completely, then
The new block of distribution wipes the block where current FAT area to FAT area, while the initial address of new FAT area is updated into FST
Qu Zhong；
The initial address in FDT areas and the initial address of FAT area of FST areas storage are with block where block where FDT areas and FAT area
Transfer is updated, and the update mode is the incremental additional mode write；After the block i that FST areas are stored adds full, whole block is triggered
I erasing and rewriting.
3. file system implementation method according to claim 1, it is characterised in that：The file system of the FST areas storage
Essential information includes system sector, cluster, block message, and the memory block is the flash storage of IC-card.
4. file system implementation method according to claim 1, it is characterised in that：The FDT tables, FAT table are in internal memory
It is middle that mapping copy is set, when the operation to file causes file description information and when changing of file allocation information, first
FDT tables and FAT table in internal memory is regenerated, after the completion of generation, the FDT tables and FAT table in internal memory are respectively written into
To memory block Zhong FDT areas and FAT area, the FDT tables and FAT table in FDT areas and FAT area are updated to currently valid FDT tables
And FAT table；
The FDT tables, the mapping copy of FAT table set dirty mark, the dirty FDT tables being marked in internal memory, FAT table hair respectively
During changing, setting should be labeled as true, after FDT tables, FAT table are written back into memory block, and the dirty mark is eliminated；
File system implementation method according to claim 4, it is characterised in that：
When FDT tables in internal memory are synchronously written into the FDT areas of memory block：If the dirty mark of FDT tables has been removed and current memory
In FDT tables it is consistent with the currently active FDT tables content in the FDT areas of memory block, then without being synchronously written；When any one is discontented
When sufficient, the FDT tables in internal memory are synchronously written to the FDT tables in FDT areas, as the currently active FDT tables of memory block, simultaneously will
The dirty mark of FDT tables in internal memory is removed；
When FAT table in internal memory is synchronously written into the FAT area of memory block：If the dirty mark of FAT table has been removed and current memory
In FAT table it is consistent with the currently active FAT table content in the FAT area of memory block, then without being synchronously written；When any one is discontented
When sufficient, the FAT table in internal memory is synchronously written to the FAT table in FAT area, as the currently active FAT table of memory block, simultaneously will
The dirty mark of FAT table in internal memory is removed.
5. file system implementation method according to claim 1, it is characterised in that：
When specifying file write data in the area to aggregate of data, Write post area is set up in internal memory first, when Write post area is write
After full, the tail cluster of currently assigned file is retrieved from FAT table first, while calculating the remaining space of cluster where the tail cluster, such as
Fruit remaining space is not less than the size in Write post area, then writes the data that length is Write post area size；Otherwise write-in tail cluster is remained
The data of complementary space size, while the new cluster write-in remaining data of continuation application.
6. file system implementation method according to claim 1, it is characterised in that：
The FAT table is made up of the tufted state of multiple 2 bytes, the tufted state include it is unallocated, distributed, it is dirty, terminate 4 kinds
State.
7. the scrap cleaning method based on the file system described in claim 1, it is characterised in that：
Memory block is scanned in units of block, the ratio shared by the dirty cluster in each block is calculated, when the ratio is beyond setting
Arrangement threshold value when, to file system carry out defragmentation；The dirty cluster is：Deletion action to file makes cluster shared by this document
As dirty cluster；
When carrying out defragmentation to file system, FAT table is first checked for, effective cluster in block to be arranged is retrieved, finds effective cluster
Afterwards, free cluster is applied now, by effective cluster copy content into the free cluster newly applied；If effective cluster is end-of-file cluster,
Only effective length in copy cluster, otherwise copies whole cluster content；
While copying cluster content, new FAT table is generated, while writing new cluster chain in new FAT table；Current cluster has been shifted
Put dirty into rear whole cluster；
Operated more than repeating, until being dirty cluster entirely in whole block, wipe monoblock, and discharge correspondence FAT table, complete a fragment whole
Reason.
8. the operating position localization method based on the file system described in claim 1, it is characterised in that：
Fast Lookup Table is created in internal memory, one section of successive clusters is referred to as a cluster piece by multiple clusters for storing identical file
Section, all cluster fragments are concentrated and are mapped in Fast Lookup Table, corresponding successive clusters sequence number is calculated by file operation position, are led to
Cross Fast Lookup Table and obtain correspondence cluster number；
The step of realizing quickly searched is：
Travel through FAT table；Defining operation position successive clusters number=reading location/cluster size；All cluster fragments of Fast Lookup Table are traveled through,
Successive clusters number subtracts the continuous number of clusters in current clip every time, until successive clusters number is less than the successive clusters in current clip
Number, return the starting cluster number of this fragment and residue successive clusters number and the as corresponding cluster number of operating position.
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