JPH04242424A - Data compression controller and data restoration controller - Google Patents

Abstract

PURPOSE:To offer a data compression controller which increases compression efficiency by automatically judging the data compression effect and performing data compression selectively and a compressed data-recording and -reproducing device which records and controls data compression ON/OFF information. CONSTITUTION:Input data from an input/output part 1 are fetched in a buffer memory 3, whose output is compressed by a data compression part 4 and fetched in a buffer memory 5. The data lengths of the buffer memories 3 and 5 are counted by counters 15 and 16 respectively and their output values are compared by a comparison part 17 to find the compressibility, which is sent to a data compression ON/OFF switching part 18 to control the data compression part 4 so that only data which has compression effect. A tape control information control part 19 sends attribute information indicating whether or not the data are compressed to a buffer memory 14, whose output is recorded and reproduced by a recording and reproduction part 6. The reproduced data are restored according to the attribute information.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data recording/reproducing apparatus for backup or data exchange, and a data compression/reconstruction control apparatus connected to or included therein.

0002

[Prior Art] Currently, tape drive devices for recording and reproducing data from a host computer are commercially available.
It is used for computer data backup and data exchange. In recent years, as the capacity of hard disks on host computers has increased, there has been a desire for larger capacity external storage devices. Therefore, a helical scan rotary head type tape drive using a digital audio tape recorder (DAT) or the like has been proposed as a large capacity storage device, but at present there is no end to the demand for increased capacity.

On the other hand, data compression technology is attracting attention as a technology that can increase the apparent capacity. Several algorithms have been proposed as data compression algorithms, including the method of Lempel and Ziv. Some algorithms perform data compression on the host computer side, while others have a data compression function on the external storage device side. is proposed. Data compression on the host computer side has conventionally been performed on a file-by-file basis by a human who issues instructions as necessary. When compressing data on the external storage device side, the only choice is whether to always turn on the data compression function or always turn it off, and it cannot be selected on a file-by-file basis. Therefore, information on whether data compression is on or off is not recorded on tape.

0004

[Problem to be Solved by the Invention] However, the data sent from the host side includes compressed data and uncompressed data.
If data that has already been compressed on the host side is further compressed on the external storage device side, the data compression will be applied twice, and as a result, the amount of output data will usually increase instead. . In addition, simply providing a data compression function on the host side and the external storage device side has the problem that it is impossible to tell which side performed the compression, making it difficult to accurately restore the data to its original state. .

[0005] In view of the above problems, the present invention is a data compression method that selectively compresses data to improve the compression effect even if the file data sent from the host includes compressed data and non-compressed data. It is an object of the present invention to provide a control device and a data restoration control device that automatically selects data restoration on/off from recorded data compression on/off information.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the data compression control device of the present invention includes an input means for receiving data from the outside, and a first input means for temporarily storing data inputted to the input means. buffer memory means, and said first buffer memory means;
data compression means for compressing or passing the data stored in the buffer memory means of the buffer memory means; and data compression function on/off switching means for controlling the data compression means and selecting whether to compress the data or pass it as is; a second buffer memory means for storing the compressed data; a first counter means for measuring the length of the uncompressed data stored in the first buffer memory means; A second counter means for measuring the length of the stored compressed data is compared with the results of the first and second counter means, and the data compression function on/off switching means is controlled based on the comparison result. Compression rate determining means.

The data compression control device of the present invention also includes file attribute information generation means for generating data compression function on/off information for each series of input data and registering it as part of file management information. It is.

The data compression control device of the present invention also includes file data dividing means for dividing data input into the input means into blocks of a predetermined length and outputting the blocks to the first buffer memory. be.

The data compression control device of the present invention also includes an input means for receiving data from the outside, and a file data division means for dividing the data inputted into the input means into blocks of a predetermined length. , first buffer memory means for temporarily storing the divided data blocks;
data compression means for compressing or passing through the data block stored in the first buffer memory means; and data compression function on/off for controlling the data compression means to select whether to compress the data or pass it through as is. a switching means; a second buffer memory means for storing the compressed data; a first counter means for measuring the length of the uncompressed data block stored in the first buffer memory means; a second counter means for measuring the length of the compressed data block stored in the buffer memory means; and a second counter means for measuring the length of the compressed data block stored in the buffer memory means; a compression rate determining means for comparing the results and controlling the data compression function on/off switching means based on the comparison result; generating data compression function on/off information for each data block divided by the file data dividing means; The block attribute information generation means is registered as part of block management information.

Further, the data restoration control device of the present invention includes a data restoration means for restoring input data as compressed data or for passing the data as is, and a data restoration means for controlling the data restoration means to restore the data or for passing the data as is. A data restoration function on/off switching means for selecting, and a data compression function on/off for pre-loaded file management information.
The apparatus further includes a file attribute information determining means for controlling the data restoration function on/off switching means based on off information.

Further, the data restoration control device of the present invention includes a data restoration means for restoring input data as compressed data or for passing the input data as is, and a data restoration means for controlling the data restoration means to restore the data or for passing the data as is. A data restoration function on/off switching means for selecting the
The apparatus further includes block attribute information determining means for controlling the data restoration function on/off switching means for each block based on off information.

0012

[Operation] With the above configuration, the data compression control device of the present invention determines based on the compression ratio whether the file data sent from the host has already been compressed, that is, whether there is an effect of further data compression. , only compresses file data that can be compressed. It also divides the recorded file and automatically selects data compression on/off for each block. Furthermore, file attribute information or block attribute information is generated so that information on whether or not the compression function of recorded data can be recorded in the management section on the recording medium.

Furthermore, the data restoration control device of the present invention has the above-described configuration and switches the data restoration function on/off based on the read file attribute information or block attribute information.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the data compression control device and data restoration control device of the present invention are applied to a rotary head type magnetic recording/reproducing device will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a data recording/reproducing device including a data compression control device and a data restoration control device in a first embodiment of the present invention.

First, some terms used here will be defined. A "file" is a series of related data groups, and is a unit transferred from a host computer during backup or the like. A "block" refers to a unit into which a file is divided. A "block header" is data that is added to the beginning of block data and indicates information regarding that block. When recording data on a tape, a "record" is the minimum unit for data transfer with the recording/reproducing section and data management on the tape. There are two types of records: fixed-length records, which have a fixed length, and variable-length records, which have an undefined length.

In FIG. 1, an input/output unit 1 receives data from a host computer (not shown) and also sends data reproduced from a tape to the host computer. The file data dividing section 2 receives file data from the input/output section 1 and divides it into blocks of a predetermined length. The buffer memory 3 temporarily stores the data received from the file data dividing section 2. The data compression unit 4 receives data from the buffer memory 3 and compresses the data. The buffer memory 5 temporarily stores data output from the data compression section 4, as well as tape management information and block header information. A recording/reproducing section 6 receives data from the buffer memory 5, records it on a tape, and reproduces data from the tape. The recording and reproducing section 6 is composed of a mechanism section 7 and a recording and reproducing control section 8. The mechanism section 7 is a mechanism section that drives the tape 9, rotates the cylinder 10, forms diagonal tracks on the tape with the head 11 attached to the cylinder 10, and records and reproduces data. The recording/reproducing control section 8 performs signal processing on the data received from the buffer memory 5. During recording, the head 11 adds error correction codes and forms tracks on the tape.
A recording current is supplied to the mechanism section 7, and an operation instruction is given to the mechanism section 7. During reproduction, the signals reproduced from the head 11 are subjected to signal processing opposite to that during recording, and data is read out. The buffer memory 12 temporarily stores data read from the tape, tape management information, and header information. The data restoration unit 13 receives compressed data from the buffer memory 12,
Perform data restoration. The buffer memory 14 temporarily stores the data output from the data restoration section 13 and outputs the data to the input/output section 1. The counter 15 measures the data length of the uncompressed data stored in the buffer memory 3. Similarly, the counter 16 measures the data length of the compressed data stored in the buffer memory 5. A comparison section (compression ratio determining means) 17 compares the outputs of the counter 15 and the counter 16. The data compression on/off switching section 18 is the comparison section 1
The data compression unit 4 receives an instruction based on the comparison result of 7.
Controls on/off of functions. A tape management information management unit (file attribute information generation/judgment means) 19 forms data for recording tape management information about a group of files recorded on the tape on the tape, and also generates data from the tape. The attributes of each file are determined by looking at the tape management information read into the buffer memory 12. The data restoration on/off switching unit 20 controls on/off of the function of the data restoration unit 13 based on the determination result of the tape management information management unit 19. The control unit 21 inputs and outputs control information to and from the host computer, controls the data compression control device, the data restoration control device, and the entire data recording and reproducing device. Normally, a dictionary buffer memory is required when compressing and restoring data, but here, to simplify the explanation, the dictionary buffer memory for compression and restoration is included in the data compression section 4 and the data restoration section 13. Not shown. Further, although the buffer memories 3, 5, 12, and 14 are shown as separate blocks, they may be configured as one block, and a portion thereof may be shared.

The operations of the data compression control device and data restoration control device configured as described above will now be described.

First, the operation at the stage of recording data when file data is not divided into blocks will be explained with reference to the flowchart shown in FIG. File data transferred from the host computer is received by the input/output section 1 and sent to the file data division section 2 (step 401).
). If the file data is not divided into blocks, the file data dividing section 2 does not perform any processing. The data received by the file data dividing section 2 is sent as is to the buffer memory 3. File data is first stored in the buffer memory 3, and at the same time the counter 15 measures how many bytes the data length is (step 402). The capacity of the buffer memory 3 is here assumed to be 32 kilobytes. When all of the file data is stored in the buffer memory 3, or if the file data is larger than the capacity of the buffer memory 3, the file data stored in the buffer memory 3 is transferred to all of the buffer memory 3. The data is sent to the data compression unit 4 and subjected to data compression processing. The compressed data is stored in the buffer memory 5, and at the same time the data length is stored in the counter 1.
6 (step 403). When the compressed data length stored in the buffer memory 5 reaches 32 kilobytes, no more data is added to the buffer memory 5. The capacity of the buffer memory 5 is 48 kilobytes, including 16 kilobytes for tape management information, which will be described later. Various compression algorithms have been proposed, including the Lempel and Ziv method. For example, if the same data continues, how to replace it with a code indicating the data and length,
There are methods such as assigning a short bit length to data or data groups that appear frequently and converting the code, and replacing repeatedly appearing data groups with pointer information to the previous data group and a code of the data length. In either case, input data (bit string) is subjected to code conversion using a compression algorithm, and compressed data (bit string) is output. A detailed explanation of the compression algorithm itself will be omitted here. Furthermore, it does not matter which compression algorithm is used. When all of the file data stored in the buffer memory 3 has been compressed by the data compression unit 4, the comparator 17 calculates the uncompressed data length and the compressed data length measured by the counters 15 and 16. are compared (step 404). If the uncompressed data length measured by the counter 15 is larger, it means that there is a compression effect, so the comparison unit 17 outputs an instruction to turn on data compression to the data compression on/off switching unit 18 (step 405). On the other hand, if the compressed data length measured by the counter 16 is larger or equal, it means that there is no compression effect, so the comparing unit 17 instructs the data compression on/off switching unit 18 to turn off data compression. is output (step 409). Data compression on/off switching section 18
controls on/off of the data compression function of the data compression section 4 in accordance with instructions from the comparison section 17. At the same time, the comparator 17 also outputs an instruction to turn data compression on or off to the tape management information management section 19, informing it whether or not the file is to be recorded with data compression. The tape management information management unit 19 sets the compression attribute information of the file in the directory information to "1" meaning compressed or "0" meaning not compressed (step 406
, 410). Note that details regarding the directory information will be described later. In the case of an instruction to turn on data compression, the compressed data stored in the buffer memory 5 is sent to the recording/reproducing section 6 and recorded on the tape (step 407). Furthermore, when the continuation of the file data is transferred from the host computer, the file data is taken into the buffer memory 3, compressed by the data compression unit 4, sent to the buffer memory 5, and then transferred to the recording/reproducing unit 6. The data is sent and recorded on tape (step 408). In the case of an instruction to turn off data compression, the compressed data stored in the buffer memory 5 is discarded, and the uncompressed data stored in the buffer memory 3 is sent to the recording/reproducing unit 6 via the data compression unit 4 and buffer memory 5. and recorded on tape (step 411). Since data compression has been instructed to be turned off, even if the data passes through the data compression unit 4, no compression processing is performed and the original file data is sent to the recording/reproducing unit 6. Furthermore, when the continuation of the file data is transferred from the host computer, when the file data is taken into the buffer memory 3, it passes through the data compression section 4 and the buffer memory 5 to the recording/reproducing section 6.
The original file data is recorded on the tape (step 412).

Next, the operation at the stage of updating the directory on the tape will be explained with reference to the flowchart shown in FIG. When the control section 21 receives a file mark recording command from the host computer after the transfer of file data is completed, the control section 21 outputs a file mark recording instruction to the recording/playback control section 8 , and the recording/playback control section 8 writes a file mark on the tape 9 . Form a record (steps 501, 502, 5)
03). Further, in this embodiment, a directory section indicating the attributes of each file is provided at the beginning of the tape 9, and this directory section is updated when a file is additionally recorded on the tape. FIG. 2 shows one pattern of the structure on the tape recorded by the data recording/reproducing apparatus in this embodiment. As shown in FIG. 2, from the beginning of the tape 9, there is a tape header section 201 that includes ID information (tape format information, etc.) for recognizing the tape, and a directory section 20 that indicates the attributes of each file recorded on the tape.
2. Data recording unit 203 that records file data, EOI (End Of In) indicating the end of recorded data.
(formation) section 204. Furthermore, a gap portion 205 is provided between each portion, and a file mark 206 is recorded in the data recording portion 203 at each division of file data. An example of the contents of the directory section 202 is shown in FIG. 3(a). The contents of the directory section 202 are configured as a table with a length of 8 bytes for each file, and the information for one file includes a file mark number 301 (3 bytes), file size information 302 (4 bytes), and file attribute information. 30
It consists of 3 (1 byte). File size information 302 is a value representing the length of the file in bytes. When the file attribute information 303 is "1", it indicates that the file data is data compressed, and when it is "0", it indicates that the file data is compressed.
Indicates that the data is not compressed. The previous directory information is stored in the directory section 20 of tape 9 in advance.
2 and stored in the buffer memory 12, and when recording file data, the directory information in the buffer memory 12 is updated by adding information about the current file as described above. After the recording of the file data is completed, new directory information is set in the buffer memory 5, recorded on the tape 9, and the directory section 202 on the tape is also updated.

[0021] Now, if file number 3 is to be additionally recorded after file number 2, the new directory information will be as shown in Figure 3.
The data will be as shown in (a). Here, the file attribute information is set to "1", and an example is shown in which file data is compressed. If compression is not performed, the file attribute information is set to "0". The updated directory information in the buffer memory 12 is converted into the data to be recorded on the tape and set in the buffer memory 5 (step 504). The directory information set in the buffer memory 5 is sent to the recording/reproducing section 6, and the recording/reproducing controller 8 rewinds the tape 9 and records new directory information in the directory section 202 according to instructions from the control section 21 (step 505). This means that recording of file data has ended.

Next, the operation when reproducing file data will be explained with reference to the flowchart shown in FIG. When the control section 21 receives a file data read command from the host computer, it outputs an instruction to read the information in the directory section 202 to the recording/reproduction control section 8 . In response, the recording/reproduction control section 8 drives the mechanism section 7 to read directory information from the directory section 202 of the tape 9 and send it to the buffer memory 12. Buffer memory 1
2, the data shown in FIG. 3(a) is read out (step 601). Now from the host computer 3
If there is an instruction to read the 3rd file, the tape management information management unit 19 advances the tape to the file mark position of the previous (i.e. 2nd) file data, and reads the data from there to the 3rd file mark position. An instruction to output the data is output to the recording/reproducing controller 8, and the recording/reproducing controller 8 sends the read data to the buffer memory 12 (step 602). Also, tape management information management section 19
The file attribute information 303 of the third file is “1”.
”, it is known that this file has been subjected to data compression processing, and an instruction to turn on data restoration is output to the data restoration on/off switching unit 20 (step 604). The data restoration on/off switching unit 20 controls on/off of the data restoration function of the data restoration unit 13 according to instructions from the tape management information management unit 19 . In this example, the data restoration function is turned on, and the compressed data read into the buffer memory 12 passes through the data restoration unit 13, undergoes data restoration processing, and is sent to the buffer memory 14 (
Step 605). The processing of the data restoration section 13 is the reverse processing of the data compression section 4, and a detailed explanation of the data restoration algorithm will be omitted here. The data stored in the buffer memory 14 is sent to the host computer via the input/output section 1. Note that if the file attribute information 303 is "0", this file has not been data compressed, so the tape management information management unit 1
9 outputs an instruction to turn off data restoration to the data restoration on/off switching unit 20 (step 606). The data restoration on/off switching unit 20 turns off the data restoration function of the data restoration unit 13, so even if the data passes through the data restoration unit 13, the data restoration unit does not process it, and the data remains as it is in the buffer memory 14. It is sent to the host computer via the output section 1. (Step 607).

[0023] In this way, the user does not have to judge whether data compression processing should be performed sequentially, and only files that have a data compression effect are automatically compressed.
Data can be communicated or recorded efficiently.

Next, the case of dividing file data into blocks will be explained using FIG. 1 in the same manner as above. First, the operation at the stage of recording data will be explained with reference to the flowchart shown in FIG.

File data transferred from the host computer is received by the input/output unit 1, and sent to the buffer memory 3 via the file data dividing unit 2 (step 70).
1). The file data dividing section 2 has a counter means for measuring the data length, measures the data length at the same time as sending the file data to the buffer memory 3, and outputs a block separation signal when data of a predetermined length has passed. The data is output to the comparison section 17 and tape management information management section 19 (steps 702 and 703). Similarly to the above, when file data is stored in the buffer memory 3, the counter 15 measures how many bytes the data length is. At the same time, the file data stored in the buffer memory 3 is sent to the data compression section 4 and subjected to data compression processing. The compressed data is stored in the buffer memory 5, and at the same time its data length is measured by the counter 16 (step 704).
). In this embodiment, the block length is set as 16 kilobytes, so the file data division section 2 outputs a block delimiter signal when it receives 16 kilobytes of data from the host computer. The comparison unit 17 that receives the block delimiter signal compares the uncompressed data length and the compressed data length measured by the counters 15 and 16 (
Step 705). If the uncompressed data length measured by the counter 15 is larger, it means that there is a compression effect.
8 to output an instruction to turn on data compression (step 706
). On the other hand, if the compressed data length measured by the counter 16 is larger or equal, it means that there is no compression effect, so the comparing unit 17 instructs the data compression on/off switching unit 18 to turn off data compression. is output (step 709). The data compression on/off switching section 18 controls on/off of the data compression function of the data compression section 4 according to instructions from the comparison section 17 . At the same time, the comparator 17 also outputs an instruction to turn data compression on or off to the tape management information management section 19, informing it whether or not the file is to be recorded with data compression. The tape management information management unit 19 sets the compression attribute information of the first block of the file in the directory information to "1" meaning compressed or "0" meaning not compressed (step 707, 710). Here, the structure of directory information when dividing file data into blocks is shown in Figure 3.
Shown in (b). Directory information is 12 per block
It is configured as a table with a byte length, and the information of one block is the file mark number 304 (3
bytes), block number 305 (4 bytes), block size information 306 (4 bytes), block attribute information 30
It consists of 7 (1 byte). Block attribute information 3
07 indicates that the block data is compressed when it is "1", and indicates that the data is not compressed when it is "0". In the case of an instruction to turn on data compression, the compressed data stored in the buffer memory 5 is sent to the recording/reproducing section 6 and recorded on the tape (step 708). If the continuation of the file data is further transferred from the host computer, the process from step 701 is repeated (step 712). In the case of an instruction to turn off data compression, the compressed data stored in the buffer memory 5 is discarded, and the uncompressed data stored in the buffer memory 3 is sent to the recording/reproducing unit 6 via the data compression unit 4 and buffer memory 5. and recorded on tape (step 711). Since data compression is instructed to be turned off, no compression processing is performed even if the file data passes through the data compression unit 4, and the original file data remains as it is in the recording/reproduction unit 6.
sent to. If the continuation of the file data is further transferred from the host computer, the process from step 701 is repeated as described above (step 712).

Regarding the operation at the stage of updating the directory on the tape, the directory section 202 is updated according to the flowchart shown in FIG. 5, as in the case where the tape is not divided into blocks.

FIG. 8 shows a flowchart regarding the operation when reproducing file data. Since the same processing as in the case of not dividing into blocks in FIG. 6 is performed, detailed explanation will be omitted. The difference from FIG. 6 described above is that reading of data and determining whether the data is compressed data are performed block by block (steps 802, 803), and this is repeated until the file data ends (step 808). ).

[0028] By compressing data by dividing it into blocks in this way, it becomes possible to judge the compression effect more accurately than when judging the compression effect only based on the beginning of the file data, and more efficiently compress the data. communication or data recording.

Next, a second embodiment of the present invention will be described. Note that since the purpose is the same as that of the first embodiment, the explanation will focus on the configuration and operation that are different from the first embodiment.

FIG. 9 is a block diagram showing the configuration of a data recording/reproducing device including a data compression control device and a data restoration control device in a second embodiment of the present invention. The difference between the first embodiment and FIG. 1 is that the tape management information management section 1
9 is replaced by a block header management section 22. A block header management unit (block attribute information generation/judgment unit) 22 forms management information for each block as a block header, records it on a tape together with the block data, and also records it on a tape from the tape to a buffer memory 12.
The attributes of each file are determined by looking at the tape management information read in. In this embodiment, the same effects as in the first embodiment can be achieved even if the tape is not provided with the directory section 202 for managing directory information.

In the data recording and reproducing apparatus including the data compression control device and data restoration control device configured as described above, the operation will be described below when file data is divided into blocks and data compression determination is made. Even when determining data compression on a file-by-file basis, similar processing is possible by replacing the block header with the file header, so only the case of dividing into blocks will be described here. The operation at the stage of recording data will be explained with reference to the flowchart shown in FIG. An operation similar to that shown in FIG. 7 in the case of dividing file data into blocks in the first embodiment is performed. Step 1001 to Step 1
The operations up to step 004 are similar to steps 701 to 704, in which file data is received from the host computer, divided into blocks, compressed, and the length of each data is measured. Similarly, the comparator 17 that receives the block delimiter signal compares the uncompressed data length and the compressed data length measured by the counters 15 and 16 to determine the compression effect (step 1005), and determines whether data compression is on or not. An instruction to turn data compression on or off is output to the off switching unit 18 (steps 1006, 1009). At the same time, the comparison unit 17 also outputs an instruction to turn data compression on or off to the block header management unit 22, and informs it whether or not the file is to be recorded with data compression. The block header management unit 22 sets in the buffer memory 5 a block header in which "1" meaning compressed or "0" meaning not compressed is set as block compression attribute information (steps 1007, 1010).
. Here, the structure of the block header in this embodiment is shown in FIG. The block header consists of 12 bytes, including block header recognition data 1201 (2 bytes), block number 1202 (4 bytes), block size 1203 (4 bytes), and block attribute information 1204 (4 bytes).
1 byte) and a spare 1205 (1 byte). When the block attribute information 1204 is "1", it indicates that the block data is data compressed, and "
0" indicates that the data is not compressed. In the case of an instruction to turn on data compression, the block header set in the buffer memory 5 and the compressed data stored in the buffer memory 5 are sent to the recording/reproducing section 6 and recorded on the tape (step 1008). If the continuation of the file data is further transferred from the host computer, the process from step 1001 is repeated (step 1012).
). In the case of an instruction to turn off data compression, the compressed data stored in the buffer memory 5 is discarded, and following the block header set in the buffer memory 5, the uncompressed data stored in the buffer memory 3 is compressed. Part 4,
The data is sent to the recording/reproducing section 6 via the buffer memory 5 and recorded on a tape (step 1011). Since data compression off is instructed, no compression processing is performed even if the data passes through the data compression unit 4, and the original file data is stored in the recording/playback unit 6.
sent to. If the continuation of the file data is further transferred from the host computer, the process from step 1001 is repeated as described above (step 1012).

FIG. 11 shows a flowchart regarding the operation when reproducing file data. Since the same processing as shown in FIG. 8 in the case of dividing file data into blocks in the first embodiment is performed, detailed explanation will be omitted. The difference from the above-mentioned FIG. 8 is that there is no process of first reading the directory information, and that the block attribute information 1204 of the block header is used to determine whether the data is compressed data (steps 1102 and 110).
3).

In this way, by providing a block header for each block and having data compression information, it is possible to accurately judge the compression effect, as in the first embodiment, and to efficiently communicate or record data. can. Furthermore, since there is no need to manage directory information, it can be applied to a wide range of applications including simple systems.

[0034] Here, an example has been shown in which the data compression control device and the data restoration control device are included in the data recording/reproducing device, but it is also possible to adopt a configuration in which they are provided in the host computer. Also, a file data dividing section 2, a recording/playback control section 8, counters 15, 16, a comparison section 17, a data compression on/off switching section 18, a tape management information management section 1
9. The data restoration on/off switching unit 20, the control unit 21, and the block header management unit 22 may be integrated into a microcomputer.

[0035] Furthermore, it is possible to connect to a communication line instead of the data recording/reproducing device, and the amount of data to be communicated can be reduced.

[0036]

As described above, the data compression control device of the present invention includes a data compression function on/off switching means, a first counter means for measuring the length of uncompressed data, and a data compression function measuring means for measuring the length of uncompressed data. and compression ratio determining means for comparing the results of the first and second counter means, or dividing data input from the outside into blocks of a predetermined length. A file data dividing means, a data compression means for compressing data for each block, a first counter means for measuring the length of uncompressed data for each block, and a first counter means for measuring the data length after compression for each corresponding block. By providing a second counter means that performs compression, and a compression rate determination means that compares the results of the first and second counter means, only the file data sent from the host can be compressed. Since compression is performed, data can be communicated or recorded efficiently. Furthermore, when compressing data by dividing it into blocks, it is possible to judge the compression effect more accurately than when judging the compression effect only based on the beginning of the file data, and it is possible to more efficiently communicate or compress data. Can record.

[0037] Furthermore, the data restoration control device of the present invention can
File attribute information determination means that controls the data restoration function on/off switching means, or block attribute information determination means that controls the data restoration function on/off switching means for each block based on the data compression function on/off information of the block management information. By providing this, the data restoration function can be turned on or off based on the compression function on/off information recorded on the tape, and regardless of whether compression is performed on the host side or the external storage device side, It is possible to accurately restore the data to its original state.

[0038] In this way, simply by sending file data from the host to the storage device, data compression is performed automatically and efficiently and selectively. Since there is no need to judge whether or not to perform data compression processing, the burden on the user and host is lightened, and a storage device that is extremely easy to use can be provided, which has great effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a data recording and reproducing device including a data compression control device and a data restoration control device in a first embodiment of the present invention.

FIG. 2 is a pattern diagram showing an example of a configuration on a tape recorded by the data recording/reproducing apparatus in the first embodiment.

FIG. 3 is an explanatory diagram showing an example of the contents of a directory section on a tape.

FIG. 4 is a flowchart illustrating a data recording operation when file data is not divided into blocks in the first embodiment.

FIG. 5 is a flowchart illustrating a directory update operation in the first embodiment.

FIG. 6 is a flowchart illustrating a data reproduction operation when file data is not divided into blocks in the first embodiment.

FIG. 7 is a flowchart illustrating a data recording operation when file data is divided into blocks in the first embodiment.

FIG. 8 is a flowchart illustrating a data reproduction operation when file data is divided into blocks in the first embodiment.

FIG. 9 is a block diagram showing the configuration of a data recording/reproducing device including a data compression control device and a data restoration control device in a second embodiment of the present invention.

FIG. 10 is a flowchart illustrating a data recording operation in the second embodiment.

FIG. 11 is a flowchart illustrating data reproduction operation in the second embodiment.

FIG. 12 is a schematic diagram showing an example of the configuration of a block header.

[Explanation of symbols]

1 Input/output section 2 File data division section 3, 5, 12, 14 Buffer memory 4 Data compression section 6 Recording/playback section 7 Mechanism section 8 Recording/playback control section 9 Tape 10 Cylinder 11 Head 13 Data restoration section 15, 16 Counter 17 Comparison section (compression rate determination means) 18 Data compression on/off switching section 19 Tape management information management section 20 Data restoration on/off switching section 21 Control section 22 Block header management section

Claims (6)

[Claims] 1. Input means for receiving data from the outside, first buffer memory means for temporarily storing data input to the input means, and compressing the data stored in the first buffer memory means. a data compression function switching means for controlling the data compression means to select whether to compress the data or to pass the data as is; and a second data compression function for storing the compressed data. buffer memory means;
a first counter means for measuring the length of the uncompressed data stored in the buffer memory means; and a second counter means for measuring the length of the compressed data stored in the second buffer memory means. and compression ratio determining means for comparing the results of the first and second counter means and controlling the data compression function on/off switching means based on the comparison result. 2. The data compression control device according to claim 1, further comprising file attribute information generation means for generating data compression function on/off information for each series of input data and registering the information as part of the file management information. . 3. The method according to claim 1, further comprising file data dividing means for dividing data input into the input means into blocks of a predetermined length and outputting the blocks to the first buffer memory.
Or the data compression control device according to 2. 4. Input means for receiving data from the outside; file data division means for dividing the data input into the input means into blocks of a predetermined length; a first buffer memory means for temporarily storing the data; a data compression means for compressing the data block stored in the first buffer memory means or passing it through as is; and a data compression means for controlling the data compression means to compress the data or pass it through as is. a data compression function on/off switching means for selecting whether to use the compressed data; a second buffer memory means for storing the compressed data; and a length of the uncompressed data block stored in the first buffer memory means. a first counter means for
a second counter means for measuring the length of the compressed data block stored in the buffer memory means; and a second counter means for measuring the length of the compressed data block stored in the buffer memory means; a compression rate determining means for comparing the results and controlling the data compression function on/off switching means based on the comparison result; generating data compression function on/off information for each data block divided by the file data dividing means; A data compression control device comprising block attribute information generation means that is registered as part of block management information. 5. Data restoration means for restoring input data as compressed data or passing it through as is; and a data restoration function on/off for controlling the data restoration means and selecting whether to restore the data or pass it through as is. A data restoration control device comprising: an off switching means; and a file attribute information determining means for controlling the data restoration function on/off switching means based on data compression function on/off information of file management information read in advance. 6. Data restoration means for restoring input data as compressed data or passing it through as is; and a data restoration function on/off for controlling the data restoration means and selecting whether to restore the data or pass it through as is. A data restoration control device comprising: an off switching means; and a block attribute information determination means for controlling the data restoration function on/off switching means for each block based on data compression function on/off information of block management information read in advance. .