JPH06103139A - Random file access method - Google Patents

Abstract

PURPOSE:To execute a forward access, as well in the order of storage by a random file which can execute a physical forward access and a direct access by designating a key. CONSTITUTION:In the case of storing records A, B and C in a random file in its order, the next record pointer 13 is added to each record, and a key of the record stored next to its record is set on its pointer 13. Also, a key (a) of the record A stored in the beginning is set in advance on the head record pointer FP on a memory. When the key (a) set on the pointer FP is designated and accessed, the record A stored in the beginning is read out, and when an access is executed by using a key (b) set on its next record pointer 13 of this read-out record A, the record B stored in the next time is read out. Moreover, when an access is executed by using a key set on its next record pointer 13, the record C stored in the end is read out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to file access control in an electronic computer, and more particularly to improvement of a randomly organized file access method.

[0002]

2. Description of the Related Art File organization in a computer is
There are various types of organization such as sequential organization, index sequential organization, and random organization, and access methods are provided for each of them.

Each file organization has its own characteristics. That is, in the sequential organization, the direct access by the key is impossible, but the sequential access in the storage order is possible, and in the index sequential organization, both the direct access by the key and the sequential access in the key order are possible. Further, the random organization can be directly accessed by a key or physically sequentially accessed.

Since each individual file organization has the unique characteristics described above, the file organization suitable for the work to be executed by the computer is actually selected and used. Therefore, when it is desired to utilize both the direct access by the key and the physical sequential access, the random organization is adopted.

[0005]

By the way, depending on the work to be executed by the computer using the random organization file, it may be convenient to be able to sequentially access the random organization file in the order of storage. That is, for example, when a record is taken in and out and processed by a so-called FIFO.

However, according to the conventional method for accessing a randomly organized file, it is not possible to sequentially access the randomly organized file in the order of storage.

Therefore, an object of the present invention is to enable sequential access in a storage order to a random organization file.

[0008]

In order to achieve the above object, the present invention provides an electronic device having a random organization file which enables physical sequential access and direct record access by designating a record key. In the random organization file access method in a computer, the key of the record stored next to the record is stored in the random organization file by storing the key of the record next to the record in the next record pointer added to the record stored in the random organization file. The records are associated in the order in which they are stored, and the key of the record stored first among the records stored in the random organization file is managed by the head record pointer on the memory.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an essential part of an electronic computer to which an embodiment of the random organization file access method of the present invention is applied. A random organization file 1, a random organization file access mechanism 2 and a random organization file 1 are shown. The program 3 to be used, and the initial setting means 7 for allowing the program 3 to access the random organization file 1 even by sequential access in the storage order, the record storing means 4, the record extracting means 5, the first record pointer FP on the memory 6. And the last record pointer EP.

A large number of records are stored in the random organization file 1, and the storage order of each record is managed by a bidirectional chain.

That is, as shown in FIG. 2, each record in the random organization file 1 includes a record body 11 and a key 1.
In addition to 2, a next record pointer 13 and a previous record pointer 14 are added, and these two pointers chain each record in both directions.

In FIG. 3, record A,
The figure shows a state in which three records are stored in the order of record B and record C, and the key b of the record B stored next to the record B is stored in the next record pointer 13 of the record A stored first. NU indicating that the key c of the record C stored next is stored in the next record pointer 13 of the next record pointer, and that the record is the last record in the next record pointer 13 of the record C stored last.
LL is set. Further, the previous record pointer 14 of the last stored record C has the key b of the record B stored immediately before it, and the previous record pointer 14 of the record B has the key a of the record A stored immediately before it.
However, the previous record pointer 14 of the first stored record A is set to NULL indicating that the record is the first record.

Also, as shown in FIG. 3, the first record A stored in the first record pointer FP on the memory 6 is
Key a is stored, and the last record pointer EP stores the key c of the last stored record C.

As described above, by chaining the records A, B, and C in the random organization file 1 in the order in which they are stored, it is possible to access them sequentially in the order in which they are stored by following the chain.

The detailed functions and overall operation of each section will be described below.

When the file of the random organization file 1 is opened by the program 3, first, the initial setting means 7 is activated.

As shown in FIG. 4, for example, the initial setting means 7 first accesses the random organization file 1 in the physical order through the random organization file access mechanism 2 and reads one record (S1). Then, when no record is stored in the random organization file 1 (YES in S2), both the first record pointer FP and the last record pointer EP on the memory 6 are set to NULL (S3), and the process ends.

On the other hand, when a record is read from the random organization file 1 (NO in S2), the processes S4 to S9 are executed to determine the following records based on the records up to the last record of the random organization file 1. Perform processing.

(1) If the previous record pointer 14 of the read record is NULL (YES in S5), that record is the first stored record, so the key value of that record is set to the first record pointer FP. Set (S7).

(2) If the next record pointer 13 of the read record is NULL (YES in S6), that record is the last stored record, so the key value of that record is set to the end record pointer EP. (S8).

Therefore, for example, when three records A, B, and C as shown in FIG. 3 are stored in the random organization file 1, the first record pointer FP is set to the record by the above-mentioned processing of the initial setting means 7. The key a of A and the key c of the record C are set at the last record pointer EP.

In order to explain how the records are sequentially stored in the random organization file 1, no records are initially stored in the random organization file 1, and therefore the initial setting means 7 does not store any records. By the process of S3, the first record pointer FP and the last record pointer EP
Is set to NULL.

Next, in this state, if the program 3 requests the random organization file 1 to store the record A having the record body and the key a, the record storage means 4 receives the request, and the record storage means 4 receives, for example, The process shown in FIG. 5 is started.

First, the areas for the next record pointer 13 and the previous record pointer 14 described in FIG. 2 are added to the record A (S11).

Next, NU is set to the next record pointer 13.
LL is set (S12).

Next, the key set in the last record pointer EP is stored in the previous record pointer 14 (S13). Therefore, in the present situation where the last record pointer EP is NULL, the previous record pointer 14 of the record A stores NULL.

Since the value of the last record pointer EP is NULL (YES in S14), the key a of the record A to be stored this time is set in the first record pointer FP (S15), and this record A is stored in the random organization file. Write to the random organization file 1 through the access mechanism 2 (S1
6). Then, the key a of the record A stored this time is set in the last record pointer EP (S20), and the process ends.

By performing the storage processing of the record A as described above, the contents of the random organization file 1 and the contents on the memory 6 become as shown in FIG.

Next, the program 3 is stored in the random organization file 1,
If it is requested to store the record B having the record body and the key b, the record storage means 4 receives the request and starts the processing shown in FIG.

First, the areas for the next record pointer 13 and the previous record pointer 14 described in FIG. 2 are added to the record B (S11), and NULL is set to the next record pointer 13 (S12).

Next, the key a set in the last record pointer EP is stored in the previous record pointer 14 (S13), and the last record pointer EP is NULL.
Since it is not (NO in S14), processing S17 to processing S20
To execute.

First, the value a of the last record pointer EP
Is designated as a key and the record A having the key a is read from the random organization file 1 through the random organization file access mechanism 2 (S17).

Next, the key b of the record B to be stored this time is stored in the next record pointer 13 of the read record A (S18).

Next, the above two records A and B are written to the random organization file 1 through the random organization file access mechanism 2 (S19).

Then, the key b of the record B stored this time is set in the last record pointer EP (S20), and the process is terminated.

By performing the storage processing of the record B as described above, the contents of the random organization file 1 and the contents on the memory 6 are changed as shown in FIGS.

Next, the program 3 is added to the random organization file 1,
If it is requested to store the record C having the record body and the key c, the record storage means 4 performs the processing shown in FIG. 5, so that the contents of the random organization file 1 and the memory 6 are shown in FIG. 7 to FIG. It will be changed to something like.

Next, the operation for extracting the record stored in the random organization file 1 by the FIFO method will be described. In the present embodiment, there are prepared two types of modes, that is, a mode of deleting the retrieved record from the random organization file 1 and a mode of not deleting it. First, the operation of fetching the records in the storage order by the FIFO method while deleting the fetched records will be described.

As shown in FIG. 3, 3 in random organization file 1
When the program 3 issues a read request in the order of storage accompanied by deletion in a state in which one record A, B, and C is stored,
The request is received by the record extracting means 5, and the record extracting means 5 executes the processing shown in FIG.

First, the random organization file access mechanism 2 using the value a of the first record pointer FP on the memory 6 as a key
Record A is read from random file 1 through
31). The read record A is notified to the program 3.

Since deletion is involved, processing S32 to processing S3
In step S3, it is determined whether the next record pointer 13 of the record A read in the process S31 is NULL. In this case, since the next record pointer 13 of the record A is the key b, the determination result is NO, and the process proceeds to step S34.

In step S34, the record B is read from the random organization file 1 through the random organization file access mechanism 2 using the value b of the next record pointer 13 of the record A read in step S31 as a key.

Next, NULL is stored in the previous record pointer 14 of this record B (S35), and the record A read in the process S31 is deleted from the random organization file 1 through the random organization file access mechanism 2 (S36).

Next, the record B subjected to the processing of the processing S35
Is written to the random organization file 1 through the random organization file access mechanism 2 (S37), and the key b of the record B is set in the head record pointer FP on the memory 6 (S3).
8), the process is completed.

By performing the record A retrieval processing as described above, the random organization file 1 and the memory 6
The above contents are changed as shown in FIGS.

Next, when the program 3 again sends a read request in the storage order accompanied by deletion, the record extracting means 5
By executing the processing shown in FIG. 8, the record B is extracted from the random organization file 1 and notified to the program 3. Then, the contents of the random organization file 1 and the memory 6 are changed as shown in FIGS.

When the program 3 further issues a read request in the storage order accompanied by deletion, the record fetching means 5 executes the processing shown in FIG. 8 to read the record C,
Notify it to program 3. At this time, record C
Since the next record pointer 13 of is NULL, processing S3
The determination result of 3 is YES, and after the record C is deleted from the random organization file 1 (S39), the first record pointer FP and the last record pointer E on the memory 6 are recorded.
Both P are set to NULL (S40).

As described above, sequential access in the storage order is possible.

Further, the record extraction without deletion is performed as follows.

As shown in FIG. 3, 3 in random organization file 1
When the program 3 issues a read request in the storage order without deletion while one record A, B, and C is stored, the record extracting means 5 starts the process shown in FIG. The record a is read from the random organization file 1 through the random organization file access mechanism 2 using the value a of the first record pointer FP of the key as a key (S31),
Notify Program 3. Then, since the deletion is not performed, the processing of FIG. 8 ends.

When the program 3 reads the record stored next to the received record A, the program 3 sends to the record fetching means 5 a read request specifying the key b set in the next record pointer 13 of the record A. , Record B is read. Further, when reading the record C stored next to the record B, the key c set in the next record pointer 13 of the record B read immediately before is used.

By doing so, the records stored in the random organization file 1 can be sequentially accessed in the storage order without being deleted.

Finally, an operation of reading a record from the random organization file 1 by designating an arbitrary key and deleting the read record from the random organization file 1 will be described.

As shown in FIG. 3, 3 in random organization file 1
When the program 3 specifies, for example, the key b and requests reading and deletion in the state where the one record A, B, and C are stored, the request is accepted by the record extracting means 5, and the record extracting means 5 For example, in FIG.
The process shown in is executed.

First, the designated key b is designated to the random organization file access mechanism 2, and the record B is read from the random organization file 1 through the mechanism 2 (S51). The read record B is notified to the program 3.

Next, since it is a request involving deletion, the processing after the processing S53 is performed in order to change the chain after the deletion of the record B.

First, it is determined whether the next record pointer 13 of the read record B is NULL (S5).
3). In the case shown in FIG. 3, since the next record pointer 13 of the record B is not NULL but the key c, the determination result is NO, and the value c of the next record pointer 13 is next.
The record C is read from the random organization file 1 through the random organization file access mechanism 2 with the key as a key (S54).
Then, the value of the previous record pointer 14 of the record B, that is, a is stored in the previous record pointer 14 of the read record C (S55).

Next, the previous record pointer 1 of the record B
It is determined whether 4 is NULL (S57). In this case N
Since it is not UL but a, the determination result is NO, and then the record A is read from the random organization file 1 using the value a as a key (S58). Then, the value of the next record pointer 13 of the record B, that is, c is stored in the next record pointer 13 of the record A (S59).

Then, the record B read this time is deleted from the random organization file 1 (S61), the records A and C are written to the random organization file 1 (S62), and the processing of FIG. 11 is terminated.

By the process of extracting the record B as described above, the contents of the random organization file 1 and the memory 6 are changed as shown in FIGS.

When the record C shown in FIG. 12 is requested to be fetched with the key c and deleted, the next record pointer 13 of the record C is NULL, so the process S56 shown in FIG. 11 is executed. The last record pointer EP is the previous record pointer 1 of the record C.
The value is changed to 4 or a. Further, when the fetching specifying the key a and the deletion thereof are requested for the record A shown in FIG. 12, since the previous record pointer 14 of the record A is NULL, the processing S60 shown in FIG. The value of the next record pointer 13 of the record A, that is, c is set in the pointer FP.

Further, in the case of the reading by the key designation without the deletion, the record extracting means 5 indicates that.
The determination is made in the processing S52 of step S52, and the chain replacement processing after the processing S53 is not performed.

[0064]

As described above, according to the random organization file access method of the present invention, the key of the record stored next to the record is stored in the next record pointer added to the record stored in the random organization file. By doing so, the records stored in the random organization file are associated in the order in which they are stored, and the key of the record stored first among the records stored in the random organization file is managed by the first record pointer on the memory. Because I did
The record stored first in the random organization file can be read by accessing the record by designating the key held in the head record pointer. Then, if the key set in the next record pointer of the read record is designated and the sequential access is performed, the random organization files can be sequentially accessed in the storage order.

[Brief description of drawings]

FIG. 1 is a configuration diagram of essential parts of an electronic computer to which an embodiment of a randomized file access method of the present invention is applied.

FIG. 2 is a diagram showing a configuration example of a record stored in a random organization file.

FIG. 3 is a diagram showing how three records A, B, and C are stored in a random organization file.

FIG. 4 is a flowchart showing a processing example of an initial setting means.

FIG. 5 is a flowchart showing a processing example of a record storage means.

FIG. 6 is a diagram showing a state in which a first record A is stored in a random organization file.

FIG. 7 is a diagram showing a state in which a second record B is stored in a random organization file.

FIG. 8 is a flowchart showing an example of a storage order access process of a record extracting unit.

9 is a diagram showing a state when the first record A is deleted from the state of FIG.

10 is a diagram showing a state when the second record B is deleted from the state of FIG.

FIG. 11 is a flowchart showing an example of a reading process by specifying a key of a record extracting unit.

FIG. 12 is a diagram showing a state when record B is deleted from the state of FIG.

[Explanation of symbols]

 1 ... Random organization file 2 ... Random organization file access mechanism 3 ... Program using random organization file 1 4 ... Record storage means 5 ... Record retrieval means 6 ... Memory 7 ... Initial setting means FP ... First record pointer EP ... last record Pointer

Claims (1)

[Claims] 1. A random organization file access method in an electronic computer having a random organization file which enables physical sequential access and direct record access by designating a record key, wherein the random organization file is stored in the random organization file. By storing the key of the record stored next to the record in the next record pointer added to the record, the records stored in the random organization file are associated with each other in the order of storage and stored in the random organization file. A randomly organized file access method characterized in that the key of the first stored record among the stored records is managed by the first record pointer on the memory.