JPH0895835A - Method for reserving file space - Google Patents

Abstract

PURPOSE: To reserve spaces by files as many as required without spoiling the convenience of an OS which does not have a procedure for reserving the file spaces by previously writing dummy data in an external storage device. CONSTITUTION: When a file space reservation type file allocation request 31 is inputted, a function 'create' 43 of an OS(operating system) 2 for generating a file and a function 'write' 44 of the OS 2 for outputting management information and dummy data are passed from a file reservation processing part 41 to the OS 2 by a reservation routine 4, and the OS 2 generates a file 10 having a space as large as the number of the output bytes of the management information and dummy data on a magnetic disk device 1. When a data output request 32 for actual data is inputted to the reservation routine 4 for the file 10, a data output processing part 42 passes a function 'write' 45 of the OS 2 to the OS 2 and overwrites the actual data to the dummy data in the file 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reserving a file space when a file is created in an external storage device such as a magnetic disk.

[0002]

2. Description of the Related Art Management of files created in an external storage device in a computer system is one of the important functions of an operating system. However, when a file is created in an external storage device from an application program, necessary files are created. Was reserved from the application program.

However, there is a problem that the operation for that purpose is troublesome and the operation is difficult when the size of the file space cannot be determined in advance.

Therefore, like the OS (operating system) such as UNIX (operating system for TSS developed by AT & T Bell Laboratories in the United States), the file space reservation procedure is abolished and the file space can be expanded freely. Things are being developed.

[0005]

However, although the operation of the file has become simpler, on the other hand, one file may exhaust the medium of the external storage device. There is a problem that overflow of one file leads to overflow of the entire external storage medium.

[0006] An object of the present invention is to provide a file space reservation method capable of reserving a space for each file without impairing the convenience of an OS having no file space reservation procedure.

[0007]

In order to achieve the above object, the present invention provides a file space required by an application program that performs data processing via an operating system when the application program uses the external storage device. It is characterized in that a considerable amount of dummy data is written in advance in the external storage device via the operating system, and the actual data output by the application program is overwritten on the dummy data.

[0008]

According to the present invention, the dummy data corresponding to the required file space is written in the external storage device in advance via the operating system, whereby the file space required by the application program is secured. The actual data is overwritten (overwritten) on the dummy data.

The dummy data refers to data whose value has no meaning, and is usually "zero" or "blank". However, data other than "zero" or "blank" can be used as long as it is distinguishable from the actual data.

Therefore, the space for each file can be reserved without impairing the convenience of the OS having no file space reservation procedure.

[0011]

EXAMPLES The present invention will now be described in detail based on examples.

FIG. 1 is a functional block diagram showing an embodiment of a file space reservation mechanism of a computer system to which the present invention is applied. A request from an application program 3 by an OS 2 is issued to a magnetic disk device 1 which is an external storage device. File is created. A capacity reservation type file 10 and a capacity non-reservation type file 11 can be created in the magnetic disk device 1.

Next, when the actual data from the application program 3 is output, the actual data is overwritten on the dummy data of the file 10.

As shown in the example of FIG. 4B, if the 1000-byte actual data 102 is output, the actual data is overwritten on the dummy data of 1000 bytes from the output position indicated by the output position.

After this overwriting, the value of the output position 100 is updated to the management information length + 1000.

The OS 2 is an OS such as UNIX which has no file space reservation procedure.

In this embodiment, a reservation routine 4 is provided between the application program 3 and the OS 2 in order to reserve the file space.

The reservation routine 4 is composed of a file reservation processing section 41 for reserving a file space and a data output processing section 42. When a file space reservation type file allocation request 31 is input from the application program 3. , OS from file reservation processor 41
2, the function "cre" of OS2 that creates a file
"ate" 43 and a function "write" 44 of OS2 for outputting management information and dummy data are passed, and the file 10 having a space for the number of output bytes of the management information and dummy data is stored in the magnetic disk device 1 by the OS2. Created.

When a data output request 32 for real data is input to the reservation routine 4 from the application program 3 for the file 10, the data output processing unit 42 of the reservation routine 4 outputs a function of the OS 2 for outputting the real data. The “write” 45 is passed to the OS 2, and the actual data is overwritten on the dummy data of the file 10.

On the other hand, when creating the capacity unreserved file 11, the application program 3 uses the file 1
A function "create" 33 of OS2 for generating 1.
OS2 function "write" 34 for outputting actual data
Is input to OS2. OS2 is the function "create"
File 11 is created based on 33, and this file 11
The actual data is sequentially written to.

FIG. 2 is a flow chart showing the processing procedure of the file reservation processing section 41.

When a file space reservation type file allocation request 31 is input from the application program 3, a function "create" of the OS2 for generating a file is generated.
e ”43 is issued to the OS 2 (step 21
0). Next, the management information length is set to the output position 100, and the reserved capacity value requested by the application program 3 is set to the reserved capacity value 101 (step 220), and the function "write" 44 of OS2 for writing data is set to OS2.
To write the management information (step 230). Next, the OS that generates dummy data for the reserved capacity value (step 240) and writes the data
Issue the second function "write" 44 to the OS2 to write dummy data (step 250).
finish.

FIG. 3 is a flow chart showing the processing procedure of the data output processing unit 42.

When the actual data output request 32 for the file 10 is input from the application program 3, the data output processing unit 42 causes the data output processing unit 42 to write data length passed from the application program 3 to the output position recorded in the output position 100. It is determined whether or not the value obtained by adding is within the reserved capacity value recorded in the reserved capacity value 110 (step 310), and if it is exceeded, an error notification is returned to the application program 3 (step 35).
0). If it is within the reserved capacity value, the function "write" of the OS2 that writes data with the actual data write position as the output position recorded in the output position 100
44 is issued to OS2 to write actual data (step 320). Next, the output position recorded in the output position 100 in the management information is updated. Specifically, the data length of the actual data just written is added to the output position (step 330). Then, the function "write" 44 of the OS2 for writing is issued to the OS2 to write the management information (step 340).
finish. If necessary, the updated output position may be passed to the application program 3.

When there is a data input request for the file 10 from the application program 3, it is judged whether the "read position + read length" is within the "output position" recorded in the output position 100, and the output is made. If it is within the position, a read request is issued to the OS2. If it exceeds the “output position”, an error notification is returned to the application program 3.

Further, in the present embodiment, the process of reading the management information from the file 10 in order to confirm the validity of the data input / output request of the application program 3 is omitted.

FIG. 4A is an explanatory diagram showing an example immediately after the capacity reservation type file 10 is created.

The capacity reservation type file 10 has management information consisting of an output position 100 and a reservation capacity value 101 which are not present in the capacity non-reservation type file 11. The management information is used to confirm the validity of the input / output request from the application program 3.

After the management information, dummy data is written by the capacity requested by the application program 3.

At the output position 100 which constitutes the management information,
The output position indicating the write position of the added actual data is recorded. Immediately after creating file 10, output position 10
The management information length is recorded in 0. Further, the reserved capacity value 101 constituting the management information records a reserved capacity value which is a capacity value requested by the application program 3. FIG. 4 shows an example in which a capacity of 10000 bytes is reserved, so the reserved capacity 101 is "100.
00 ”is recorded, and after this, 10000 bytes of dummy data are written, and as a result, a space having a capacity of 10000 bytes is secured.

[0031]

As described above, according to the present invention, when an application program that performs data processing via the operating system uses an external storage device, dummy data corresponding to the file space required by the application program is generated. Since the file space required by the application program is secured by prewriting in the external storage device via the operating system, the actual data output by the application program is used by being overwritten on the dummy data. A situation in which the space for each file can be reserved as much as necessary without impairing the convenience of an OS that does not have a file space reservation procedure, and overflow of one file leads to overflow of the entire external storage medium. Can avoid Can.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a file space reservation mechanism of a computer system to which the present invention is applied.

FIG. 2 is a flowchart showing a processing procedure of a file reservation processing unit.

FIG. 3 is a flowchart showing a processing procedure of a data output processing unit.

FIG. 4 is an explanatory diagram showing an example of creating a capacity reservation type file.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk device, 2 ... OS, 3 ... Application program, 4 ... Reservation routine, 10 ... Capacity reservation type file, 11 ... Capacity non-reservation type file, 41 ... File reservation processing part, 42 ... Data output processing part, 100 ... output position, 101 ... reserved capacity value.

Claims (1)

[Claims] 1. In a computer system using an operating system that secures a file space in an external storage device without going through a file space reservation procedure, an application program that performs data processing via the operating system stores the external storage device. When using, dummy data corresponding to a file space required by the application program is written in advance in an external storage device via the operating system, and actual data output by the application program is overwritten on the dummy data. How to reserve a file space.