JPH0553734A - Access system for write-once storage medium - Google Patents

Abstract

PURPOSE:To enable an operator to quickly correct and update the date stored in a write-once storage medium and also to easily control the corrected and updated data on the storage medium. CONSTITUTION:A memory 15 consists of a RAM, for example, and a storage 18 consists of an optical disk OD, for example, and its driving device, etc. A CPU 11 reads the data written into the OD and searches an unwritten area following a written area by a 2-split searching method to successively write the updated data into the unwritten area. Furthermore the CPU 11 searches the area where the latest updated data written in the data area of the OD are written and reeds out the latest updated data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a write-once type storage medium access system in which storage data cannot be physically modified or updated and is additionally written in a storage area.

[0002]

2. Description of the Related Art Generally, a storage medium such as a hard disk (HD) or a floppy disk (FD) has a property of accessing storage data at the same storage position as shown in FIG. It is easy to physically correct and update. On the other hand, storage media such as optical discs (OD)
The so-called destructive writing method is adopted, and by its nature, data cannot be physically corrected or updated at the same storage location. If correction or update is attempted in this way, a write error will occur.

Therefore, in the conventional write-once type storage medium access method, when the storage data is modified or updated, the update data is updated.
When the updated data is read by writing the management table in another unwritten area and additionally writing the management table, the operator reads the management table on the display screen of the CRT, for example. It is configured to select update data.

[0004]

However, in the above-mentioned conventional write-once type storage medium access method, the update data is not updated.
When reading the data, the operator reads the management table on the display screen of the CRT and selects the latest update data, so that the operator can correct and update the stored data. In addition, there is a problem that it is difficult to manage modification data and update data.

The present invention has been made in view of the above-mentioned conventional problems, and allows an operator to quickly correct and update the storage data of the write-once type storage medium, and also the write-once type storage medium. It is an object of the present invention to provide an access method of a write-once type storage medium which can easily manage the correction data and update data of the above.

[0006]

In order to achieve the above-mentioned object, the access system of the write-once type storage medium of the present invention has the data written at the end of the data storage area of the write-once type storage medium. The unwritten area next to the written area is searched by the binary search method, and the writing means for writing the updated data to the searched unwritten area, and the data is written at the end of the data storage area. And a reading means for searching the written area and reading the data from the searched written area.

[0007]

According to the present invention, the writing means searches for the unwritten area next to the last written area in the data storage area of the write-once type storage medium.
The update data is sequentially written to the unwritten area found. Here, since the unwritten area next to the written area is searched by the binary search method, such a search can be performed quickly. The binary search method here means that the data storage area to be searched is divided into two parts, one of them is discarded, and an unwritten area in which a similar division process is searched for in the remaining one is found. A type of iterative search method.
Further, after the data is written in this way, the reading means searches for the last written area in the data storage area in which the data has been written, and reads the data from the found written area. Therefore, data is stored in the data storage area.
When reading data, the latest update data can be read. Therefore, the operator can quickly correct and update the storage data of the write-once storage medium.
The update data of the write-once type storage medium can be easily managed.

From the following examples of the present invention, such an effect of the present invention will be further clarified, and further another effect of the present invention will be clarified.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of an access device for a write-once storage medium according to the present invention, FIG. 2 is an explanatory diagram showing a storage area of an optical disc of the storage apparatus of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing block positions, and FIG. 4 is a flowchart for explaining the operation of the access device for the write-once type storage medium of FIG.

In FIG. 1, a CPU (Central Processing Unit) 11
Processes the data and commands input via the keyboard 12, and controls the display of the CRT 13 and the writing and reading of the memory 15 via the control circuit 14. The CPU 11 also processes data read by the scanner 17 via the I / F (interface) circuit 16, controls writing and reading of the write-once type storage device 18, and controls the printer 19. Control printing. The memory 15 is, for example, a RAM
(Random access memory), storage device
The numeral 18 is composed of, for example, an optical disk (OD) and its drive device.

The storage area of each file F on the optical disk of the storage device 18 is composed of, for example, the minimum unit block B1 of 512 bytes or 1024 bytes, and one area of one file B is stored in one block B1. -Data is stored. The capacities of the blocks B1 to B1 are different for each storage medium.

First, the CPU 11 responds to the data and commands input via the keyboard 12 by each data file F.
The position and size of the area for storing are fixed and allocated. In this case, when there are a plurality of files F to be handled, allocation is performed for that, and the size is determined in consideration of the expected number of updates.

When storing the data on the optical disk, the data is stored from the first block B1 of the area of the file F, and when updating the stored data, the CPU 11
First, the stored data is read from the optical disk to the memory 15 and displayed on the screen of the CRT 13, and is corrected on the memory 15 according to the data and commands input via the keyboard 12.
Then, when registering this update data in the optical disc,
As shown in FIG. 2, the data is transferred from the memory 15 to the optical disk and is finally written in the data storage area (data allocation area) which constitutes the file F out of all the data storage areas 101 of the optical disk. Register the block Bn + 1 next to the block Bn. In this way, when the data is updated on the file F, the written area F1 becomes large and the unwritten area F2 becomes small.

Next, the detailed operations of the update process and the update data read process will be described with reference to FIGS.

As shown in FIG. 3, in the file F, the data area Fs for writing data is from the block position A to the block position B (B> A).

Now, let s, u, x be variables indicating block positions for executing the binary search method, and write states of block positions indicated by variables s, u, x are (s), (u),
(X). In the case of the update processing, first, the block position A is set to the variable s and the block position B is set to the variable u (step a1 in FIG. 4). Then step a2
Then, the write state (u) corresponding to the variable u, that is, the data
It is determined whether the writing state at the last position of the data area Fs is unwritten. If it is not written in step a2 (NO), the process branches to step a9, and it is determined that all the data is written in the data area Fs to be searched, that is, there is no empty area.

If it is not written in step a2 (YES), the process branches to step a3, and the write state (s) corresponding to the variable s, that is, the write state at the first position of the data area Fs is not yet written. It is determined whether it is writing. In step a3, if not written (YE
S), the process branches to step a10, the variable s is set to the variable u, and the position indicated by the variable u becomes the desired position (step a11). That is, no data is written in the data area Fs, and the first position of the unwritten area is the first position of the data area Fs to be searched. In step a11, it is preferable to check the size of the data area Fs.

If it is not written in step a3 (NO), the process branches to step a4, and it is determined whether u = s + 1. If u = s + 1 (YES), the process branches to step a11, and the position indicated by the variable u becomes the position to be obtained.

In step a4, if u = s + 1 is not satisfied (NO), the process branches to step a5 and INT {(s + u) /
2} is set to the variable x, and in step a6, whether the write state (x) corresponding to the variable x, that is, the state of the block position in the middle of the positions indicated by these variables s and u is unwritten. Determine whether or not. If it is not written in step a6 (NO), the process branches to step a7 and x is set to s, that is, the position indicated by the variable x at this time is set as the first position of the next search target region, and step a4
Return to and continue the 2-minute search method. If it is not written in step a6 (YES), the process branches to step a8 to set x to u, that is, the position indicated by the variable x at this time is set as the last position of the next search target area, and the process proceeds to step a4. Return 2
Continue the min search method.

The processing in steps a4 to a8 is continued until u = s + 1 in step a4. That is, the search target area is checked by the dichotomizing search method as the middle or the middle, and the search area is narrowed to finally determine the last block position (variable s
The position corresponding to 2) and the position of the first block in the unwritten state (the position corresponding to the variable u) can be narrowed down to the range of two blocks.

When the first position of the unwritten area found as described above is obtained, the updated data is stored in the data area Fs from this position. At this time, it is preferable to check the storage data in consideration of the write error.

When reading the updated data written in this way, the last block of the written area is searched by the binary search method to find the latest updated data, as in the case of the above-mentioned writing. read out. It should be noted that the data is sequentially read from the block position A to search the unwritten area next to the latest updated data, and whether the data in the written area before this unwritten area is valid or not. It is also possible to read out the latest update data of the written area by judging.

As described above, according to the present embodiment, the unwritten area can be searched much faster than the method of searching for the unwritten block in order from the first block shown below as a reference example. It is advantageous.

FIG. 5 and FIG. 6 show the operations of the update process and the update data read process in such a comparative example. In the comparative example, the writing state of data is checked in order from the head of the data storage area without using the binary search method in the configuration of the present embodiment shown in FIGS. It searches for an unwritten area. In FIG. 5, T is the start address of the file F, Y is the end address of the written area F1 of the file F, and X is the start address of the unwritten area F2 of the file F.

In the case of the updating process, first, the address T indicating the position of the first block B1 of the file F is set to the read address n (step S1 in FIG. 6), and the data of the read address n is read from the optical disk. Store in memory 15 (step S2). Next, it is determined whether or not the area of the read address n is in the unwritten state (area F2) (step S3), and if it is not in the written state, the read address n is incremented (step S4) and step S2.
Then, the area F2 in the unwritten state is searched.

When the unwritten area F2 is obtained, the process branches from step S3 to step S5, the read address n is set to the write address X of the update data, and then the read address n is the first of the above-mentioned storage data. Address T
It is determined whether or not it is larger (step S6). When n> T, the read address n is decremented by 1 (step S7), the read address n is set to the last address Y of the stored data (step S8), and then the start address X of the unwritten area F2. The update data is stored in the area of.

In step S6, if n≤T, the optical disc is in a completely unwritten state, so step S9
Then, the last address Y of the stored data is set to the address "0" and the data is stored in the area of the write address X.

As described above, this comparative example is effective when the data storage area is small as a whole, but for a large capacity storage medium such as an optical disk, it takes a long time to search and it is quick. Can not be expected to be processed. On the other hand, according to the above-described embodiment, the binary search method makes it possible to quickly search for an unwritten area following the written area.
It is extremely advantageous. As a result, the operator can quickly correct and update the storage data of the write-once type storage medium, and can easily manage the correction data and update data of the optical disk. In this case also, the history of update data can be managed, which is convenient. In addition,
Similarly, the binary search method can be used for searching for the written area in reading data, and more rapid data update processing is possible.

In the above embodiment, a non-rewritable storage medium such as an optical disc has been described as an example. However, when the present invention is applied to a rewritable storage medium such as a hard disc, the stored data is erased. Since the update data can be sequentially added without performing the operation, the history of the update data can be managed according to the property of the data, and the stored data can be stored.
The safety of the computer can be secured. In this case, if the flag indicating the unwritten state is set in a predetermined area of each block of the storage medium, the unwritten area is supported.
It is possible to simplify the processing for switching.

[0030]

As described above in detail, since the writing means searches the unwritten area next to the written area in which the data is finally written by the binary search method, such a search is performed. Can be done quickly. Further, after the data is written in this way, the reading means searches for the last written area in the data storage area in which the data has been written, and reads the data from the found written area. Therefore, when reading the data from the data storage area, the latest updated data can be read. Therefore, the operator can quickly correct and update the storage data of the write-once storage medium, and can easily manage the update data of the write-once storage medium.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an access device for a write-once storage medium according to the present invention.

FIG. 2 is an explanatory diagram showing a storage area of an optical disc of the storage device of FIG.

FIG. 3 is an explanatory diagram showing block positions of a storage area.

FIG. 4 is a flowchart for explaining the operation of the access device for the write-once type storage medium of FIG.

FIG. 5 is an explanatory diagram showing addresses of storage areas in a comparative example.

FIG. 6 is a flowchart for explaining the operation of the write-once type storage medium access device in a comparative example.

FIG. 7 is an explanatory diagram showing update processing of a storage medium capable of physically modifying and changing storage data.

[Explanation of symbols]

 11 CPU (central processing unit) 18 Storage device (optical disk)

Claims (2)

[Claims] 1. An unwritten area next to the last written area in which data is written in the data storage area of the write-once type storage medium is searched for by the binary search method, and the searched unwritten area is set to the searched unwritten area. A writing means for writing the update data and a reading means for searching the written area where the data is written last in the data storage area and reading the data from the searched written area. A write-once type storage medium access method characterized by the above. 2. The access system of the write-once type storage medium according to claim 1, wherein the reading means searches for a written area in which the last data is written by a binary search method.