Abstract:
A file system converting method converts a first file system to a second file system. The first file system manages a storages apparatus via a file allocation table (FAT). The file system converting method includes formatting the FAT to divide the storage apparatus into a plurality of storage units, and establishing a storage unit index table to record information of the plurality of storage units.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATIONS 
     This patent application claims priority from Taiwan Patent Application No. 098117964, filed in the Taiwan Patent Office on Jun. 1, 2009, entitled “File System and File System Converting Method”, and incorporates the Taiwan patent application in its entirety by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a file system converting method and a file system for managing a storage apparatus, and more particularly, to a method for converting a file allocation table (FAT) system to a data bulk system. 
     BACKGROUND OF THE PRESENT DISCLOSURE 
     In the prior art, an FAT system applied to a storage apparatus serves as a tool for managing storage space and memory data of the storage apparatus. However, when data is accessed via an FAT system, a next available cluster is first searched for with the aid of an FAT index table, which also needs to be updated. Under such a situation, a search time is different according to distribution (or a disk fragmentation) of used and available storage spaces of the storage apparatus. Generally speaking, the more dispersed the storage space is distributed, the longer the search time it takes. Moreover, the FAT index table is searched from a header every time the FAT index table is updated. Therefore, the time-consuming flow cannot meet read/write requirements of an apparatus (e.g., a personal video recorder (PVR)) which needs a fast data read/write speed. 
     In addition, certain environments supporting the FAT file system provide only one read or write authority to a same file at a time. Therefore, when a write operation is desired on a file which has just been read, the file needs to be first closed and then reopened to perform the write operation, and vice versa. However, the above approach inevitably reduces read/write efficiency of a storage apparatus using the FAT system. 
     SUMMARY OF THE PRESENT DISCLOSURE 
     Therefore, one object of the present disclosure is to provide a file system and a file system converting method for generating the file system to overcome disadvantages of having a low search speed and being unable to simultaneously read and write as associated with conventional solutions. 
     According to an embodiment of the present disclosure, a file system converting method is for converting a first file system to a second file system. The first file system manages a storage apparatus via an FAT. The file system converting method comprises formatting the FAT to divide the storage apparatus into a plurality of storage units, and establishing a storage unit index table for recording information of the plurality of storage units. 
     According to another embodiment of the present disclosure, a file system for managing file data stored in a storage apparatus comprises an FAT, formatted to a plurality of virtual files to divide the storage apparatus into a plurality storage units for storing data, wherein each of the virtual files corresponds to one of the plurality of storage units; and a storage unit index table, for recording information of the plurality of storage units. 
     From the above embodiments, a data access speed of a conventional file system is accelerated, and a disadvantage of being unable to simultaneously read and write according to the conventional file system is overcome. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial schematic diagram of formatting in advance a FAT index table to numerous data bulks by implementing a file system converting method in accordance with the present disclosure. 
         FIG. 2  is a schematic diagram of data bulk files and data bulks in accordance with an embodiment of the present disclosure. 
         FIG. 3  is a schematic diagram of a data bulk index table in accordance with another embodiment of the present disclosure. 
         FIG. 4  is a flow chart of a file system converting method in accordance with yet another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the known art, file allocation table (FAT) system applies an FAT index table (file allocation table) to manage a storage apparatus. Data may be dispersedly stored into a storage apparatus using the conventional FAT system, and the addresses at which the data are stored are recorded in the FAT index table, which will be looked up when accessing a desired data. 
     In an embodiment of the present disclosure, under the structure of FAT system, file allocation table (FAT index table) is formatted in advance so that storage space of a storage apparatus is divided into a plurality of data bulks in a way that the data bulks can be regarded as different storage units. And a data bulk index table is generated to build a data bulk system for managing the storage apparatus. In other words, the bulk index table is a storage unit index table of the data bulk system of the embodiment in the present disclosure. 
     In particular, in a file system converting method provided by the present disclosure, appropriate values are filled in advance into a FAT index table to establish a plurality of data bulks, each of which is regarded as a file in a FAT system. That is, in the file system converting method provided by the present disclosure, a plurality of files are established in advance in the FAT index table, and each of the files (each of the data bulks) is allocated to a predetermined storage space of the storage apparatus. Therefore, each of the data bulks is regarded as a storage unit. In an embodiment, the data bulks are consecutively distributed in the storage apparatus, and each of the data bulks has a same size, that is, each of the data bulks occupies a storage space of the same size. Although the plurality of files are established in the FAT index table, at the beginning, each of the files in fact does not have any corresponding data in the storage apparatus, i.e., the plurality of files are regarded as virtual files. For example,  FIG. 1  shows partial schematic diagram of the data bulks in the FAT index table of the present disclosure. This is achieved by formatting in advance the FAT index table to form a plurality of data bulks by implementing a file system converting method according to the present disclosure. A FAT index table  101 , formatted to form a plurality of 64 Mb-sized data bulks, is for managing file data of a storage apparatus  103 . After formatting the FAT index table, according to file system converting method of the present disclosure, the next step is generating a data bulk index table to record utilization conditions of the data bulks. The data bulks, the data bulk files and the data bulk index table are described below in detail. 
       FIG. 2  shows a schematic diagram of data files and data bulks in accordance with an embodiment of the present disclosure. At least one part of a storage space  200  in a storage apparatus is divided into a plurality of storage units, e.g., data bulks  201  to  217 ; storage space  218  is an unoccupied storage space. The data bulks  201  to  217  are provided in different sizes according to different requirements. Data files  219 ,  221 ,  223 ,  225  and  227  are stored in the data bulks  201  to  217 . More specifically, the data file  219  is stored in two consecutive data bulks  201  and  203 , the data files  221 ,  223  and  225  are respectively stored in the data bulks  207  to  211 , and the data file  227  is stored in two consecutive data bulks  215  and  217 . Accordingly, when a data file needs to be stored in more than two data bulks, the data file is successively stored in two consecutive data bulks instead of being stored dispersedly in a conventional FAT system. Moreover, in the present disclosure, address associated information of the data file is stored in a data bulk index table (storage unit index table), when the file system of the present disclosure is about to access certain data file, it only needs to look up the address information in the data bulk index table instead of searching data files again and again located in dispersed blocks (in other words, searching for different addresses in the system) as what is done in the conventional FAT system. Therefore, the data file system of the present disclosure provides an increase read/write speed of the storage apparatus. In an embodiment, each of the data bulk stores a single data file, i.e., if a data bulk already stores a data file, the data bulk will not be used to store other data files even if this data bulk still has storage space available. When the size of a data file is greater than a capacity of one data bulk, the data file is stored into a plurality of consecutive data bulks. 
       FIG. 3  shows a schematic diagram of a data bulk index table  300  in accordance with an embodiment of the present disclosure. The data bulk table  300  comprises header information  301 , start information  303 , an allocation table  305 , and a plurality of data bulk entry information  307  to  317 . In this embodiment, each part of the data bulk index table  300  (storage unit index table) is allocated to have a 4K space, and thus the whole data bulk index table  300  has a space of (3+N)*4K, where number 3 refers number of data bulks that header information  301 , start information  303 , and allocation table  305  occupy, and, N is number of data bulk entries each recording information of a data file stored in a data bulk. The header information  301  of data bulks is regarded as system information comprising various types of information of a data bulk system, e.g., a total number of data bulks of the data bulk system, a capacity of storage apparatus used by the data bulk system, number of data bulks already stored with data files, etc. The start information  303  records physical information of data bulks (storage units) in the storage apparatus, i.e., corresponding physical sector allocations of the storage apparatus of the data bulks (storage units) divided according to the embodiment of the present disclosure. For example, the start information  303  records the physical addresses of the start points of each of the data bulks in the storage apparatus; or, at which physical sector the data bulk starts. 
     The file allocation table  305 , having associated information of the storage units and the data files, records correlations between the storage units (e.g., the data bulks) and the data files. For example, the file allocation table  305  records a data bulk or data bulks in which each of the data files is stored. Each of the data bulk entry information  307  to  317  records detailed information of the data file stored in that data bulk. For example, the data bulk entry information  307  to  317  respectively records identification code, file name, file length, operation mode, and the like, of the stored data file. 
     When a data file is accessed, the data bulk system supports at least two access parameters (e.g., a read pointer and a write pointer) to record an access position of the data file. For example, the read pointer and the write pointer are dynamically stored in the data bulk system, and the access parameters are updated according to a data amount of the data files to be accessed. In particular, before writing the data file, an absolute address (a physical address in the storage apparatus) of the data file is determined by a file search function and the access address of the data file, so as to write the data file into the storage apparatus. Such step is in brief described as Formula 1.
 
accessing sector(s)=data start sector+(data bit length/bits per sector)  Formula 1
 
     “Sector” means the physical sectors in the storage apparatus. In short, Formula 1 represents that the data to be accessed can be located in the accessing sectors when the data start point and the length of data is provided. From the foregoing step, read and write sectors are calculated by Formula 2 and Formula 3.
 
read sector=read data start sector+(read data bit length/bits per sector)  Formula 2
 
write sector=write data start sector+(write data bit length/bits per sector)  Formula 3
 
     According to the foregoing access operations, data file is directly accessed at an absolute position (physical address) instead of having to first search an FAT index to find a next available cluster as in a conventional FAT system, so that the access speed is accelerated. Further, the embodiments of the present disclosure are different from conventional FAT systems where only one read or write authority is provided to a same file at a time, and accordingly it is not necessary to continuously open or close the file, so that a time for accessing the file is reduced. 
       FIG. 4  shows a flow chart of a file system converting method in accordance with an embodiment of the present disclosure. In this embodiment, the file system converting method according to the present disclosure, for converting an FAT system to a data bulk system, comprises steps below. 
     The method includes Step  401 , formatting a file allocation table (FAT) of the FAT system to divide a storage apparatus into a plurality of data bulks, each of which being regarded as a storage unit. In this step, a plurality of virtual files is established in the FAT, with each of the virtual files corresponding to one of the storage units. 
     The method further includes Step  402 , establishing a data bulk index table (storage unit index table) to record information of the plurality of storage units. The data bulk index table comprises header information, start information, an allocation table, and a plurality of data bulk entry information. 
     Detail characteristics of the file system applied in the file system converting method according to the present disclosure are disclosed in the foregoing embodiments, and detailed description thereof shall not be described for brevity. In an embodiment, the foregoing steps are realized from executing predetermined firmware or software by a control circuit (e.g., a processor); however, other circuits can also be implemented to realize the foregoing steps. 
     According to a file system converting method of the present disclosure, an FAT system is converted to a data bulk system, and a data bulk system of the present disclosure can accelerate a data access speed as well as solving a problem that a file cannot be simultaneously read or written in a conventional FAT system. 
     While the present disclosure has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the present disclosure needs not to be limited to the above embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.