JPH03282841A - Direct input/output processing system for variable length record - Google Patents

Abstract

PURPOSE:To take a variable length record as the object to directly input and output it by inputting a record information table and providing a record information adding means which adds record information to a file. CONSTITUTION:A file location processing means 1 changes the position of the file to the record position corresponding to an input/output record number 8 in a record information table 3. A record information table changing means 2 changes the record information table 3 based on the input/output record number 8 and the record length of an outputted logical record. A record information table generating means 4 generates the record information table 3 from record information added to the file, and a record information adding means 5 takes the record information table 3 as the input and adds record information to the file. Thus, the variable length record is taken as the object and is directly inputted and outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a file input/output processing method, and particularly to a direct input/output processing method for variable length records.

[Conventional technology]

Conventionally, files that allow direct input/output have had a constant record length or maximum record length within the file. Furthermore, it was necessary to specify the record length or the longest record length when creating a file, and then when opening the file.

[Problem to be solved by the invention]

The conventional method described above has the disadvantage that variable-length records cannot be handled in files to which direct input/output is intended.

Another disadvantage is that the maximum record length of 1fcrC must be specified at the time of file creation or file download, and the maximum value of the logical record must be calculated in advance and set to 2.

Additionally, all records in the file are created with the specified record length or maximum record length, so
If a logical record shorter than the record length is output, there is a drawback that an unused area is created and a file area is wasted.

[Means to solve the problem]

The direct input/output processing method for variable-length records of the present invention requires that, for each logical record, the record number, the record position indicating the start of the logical record within the file, the record length of the logical record, and the maximum record length of the logical record are determined. , an input/output record number indicating the record number of the logical record to be input/output, and a file for changing the file position to the record position corresponding to the input/output record number in the record information table. The positioning is performed by a processing means, a record information table changing means for changing the record information table based on the input/output record number and the record length of the logical record to be output, and a record information table changing means for changing the record information table from the record information added to the file. inputting a record information table creation means to be created and the record information table;
and record information adding means for adding record information to the file.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a variable-length record direct input/output processing method according to the present invention.

In the figure, solid lines indicate the flow of data, and dashed lines indicate the flow of control.

When opening the file IO, the record information table creation means 4 is called. The record information table creation means 4 inputs the record position information added to the file IO, and includes a record number, a record position indicating the start position of the logical record corresponding to the record number, and the maximum record length of the logical record. A record information table 3 made up of record information is created.

When executing the input statement directly on file 10,
The program 11 stores the record number of the logical record to be input into the input/output record number 8 and directly calls the input processing means 6't-. Direct input processing means 6 calls processing means 1 for file positioning. For file positioning, the processing means 1 obtains the record position corresponding to input/output record number 8 from the record information table 3, changes the file position of the file IO to the position indicated by the record position, and directly controls the input processing means 6. Return. When the file positioning control is returned from the processing means 1, the direct input processing means 6 inputs only the record length corresponding to the input/output record number 8 in the record information table from the file 10 as one logical record.

When executing the output statement directly on file 10,
The program 11 stores the record number of the logical record to be output in the input/output record number 8, stores the record length in the output record length 9, and directly calls the output processing means 7. The record information table changing means 2 is directly called to the output processing means 7. Record information table changing means 2
After performing the record information table change process described later,
File location calls processing means l. For file positioning, the processing means 1a acquires the record position corresponding to input/output record number 8 from the record information table 3, changes the file position of the file IO to the position indicated by the record position, and changes the record information table. Control is returned to means 2. When the file positioning control is returned from the processing means 1, the record information table changing means 2 directly returns control to the output processing means 7. When control is returned from the record information table changing means 2, the direct output processing means 7 outputs one logical record to the file 10.

When closing the file IO, the record information adding means 5 is called. The record information adding means 5 adds the record number, record position, record length, and large record length stored in the record information table to the file 10.

FIG. 2 is an explanatory diagram showing the record information table 3.

In the figure, record information (i) is the first record information in the D record information table 3, and N(i)rt
L/co)' number, P(i)d is the record position of the logical record of record number N(i), and L(i
) is the record length of the logical record with record number N(i), and M(i) is the maximum record length of the logical record with record number N(i).

In the record information table changing process, first, the record information table 3 is searched for record information having the same record number as the input/output record number 8.

If there is record information with the same record number, please use the following (
Perform the process in 1), and if there is none, perform the process in (2) below.

(1) Record information with the same record number as input/output record number 8 exists. The retrieved record information is referred to as record information [i). And the output record length 9 is M
(i) If it is less than or equal to, the record information table change process is ended.

If the output record length 9 is greater than M(i), the following process (a) is performed.

(a) If record information (i) is the last record information in record information table 3, process (b) is performed.

Also, if N (i+1) is not 0 and N(i+
Even if 1) is 0, if M(i+x) is 0, process (
Perform b).

In cases other than the above, the output record length is 9 and M(i) + M
Compare (i+1). If the output record lengths 9 are smaller or equal, then M(i) has M(i)+M(i
+1), 0 is stored in M(i+1), and the record information table changing process ends.

If the output record length 9 is larger than M(i)+M(i+1), i is read as i+1 and process (a) is repeated. However, the comparison with the output record length 9 is M(i)+
Each time M (i+1) +M (i+2) +--- is repeated, the maximum record length of the record information is added.

(b) If record information (i) is the first record information in record information table 3, process [C] is performed.

Also, if N(i-1) is not 0 and N(i-1)
Even if is 0, if M(i-t) is 0, process (C)
I do.

In cases other than the above, if processing (a) is repeated until record information (j), the output record length is 9 and M(i-1)
+M(i)+M(i+1)+----+Msu),
If the output record length 9 is smaller or equal, then M(
i) to M(i-1) +M(i)+M(i+1)+--
−+M(j), M(1-1), M(i+t),
---, stores 0 in M(j), and ends the record information table change process.

If the output record length 9 is larger, i is read as i-1 and the process (b) is repeated.

However, for comparison with the output record length 9, the maximum record length of the record information is added each time it is repeated, as in process (a).

(c) Store 0 in N(i). If processing (b) is repeated using record information (h) 1, the following processing (2) is performed by excluding the record information (j) 4 from record information (h).

(2) There is no record information with the same record number as input/output record number 8. N(i) in record information table 3
Search for record information (i) where is O and M(i) is not 0. If record information (i) is found, N
Considering (i)=input/output record number 8, process (1) is performed.

If the above record information (i) is not found, new record information (n+t) is added to the record information table 3, input/output record number 8 is stored in N(n+1), and P (n-)- 1) stores the end position of the file at that time, stores the output record length 9 in L(n+1) and M(n+1), and ends the record information table changing process.

〔Effect of the invention〕

As explained above, according to the present invention, there is an effect that direct input/output can be performed for variable length records. Also,
Since there is no need to specify the record length or maximum record length when creating or opening a file, there is an advantage that there is no need to calculate the maximum length of a logical record in advance.

Furthermore, when outputting a logical record, it is sufficient to have a file area equal to the length of the record to be output, so there is an effect that no wasted file area is required.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a record information table. 1...File positioning is a processing means, 2...
...Record information table changing means, 3...Record information table, 4...Record information table creation means, 5...Record information adding means,
8...Input/output record number.

Claims (1)

[Claims] A record information table containing, for each logical record, the record number, the record position indicating the start of the logical record in the file, the record length of the logical record, and the maximum record length of the logical record, and the logical record to be input/output. an input/output record number indicating a record number of a record; a file positioning means for changing the position of the file to a record position corresponding to the input/output record number in the record information table; and logic for outputting the input/output record number. A record information table changing means for changing a record information table based on the record length of a record, a record information table creating means for creating the record information table from record information added to a file, and a record information table creating means for inputting the record information table. 1. A direct input/output processing method for variable length records, comprising: a record information adding means for adding record information to a file.