JP2000020280A - Data reference method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce character code converting processing at the time of referring to data at any arbitrary position of a file with a character code different from a recorded character code by storing the data length of each recording unit after character code conversion and the position of each recording unit on a recording medium in a table. SOLUTION: File data are converted into different character codes for every recording unit of data and the data length of each recording unit after the character code conversion and the position of each recording unit on the recording medium are stored in the table. In such a conversion table 110, data for one block are stored in continuous areas on the recording medium. The conversion table 110 stores a file ID 100 for identifying an object file, character code classes 101-103 and data lengths 105-107 after various kinds of character code conversion corresponding to a recording position 104 of each block on the recording medium. Besides, the number 108 of all the blocks belonging to the object file is recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a computer system, and more particularly to a file data referencing method with character code conversion of a computer file system.

[0002]

2. Description of the Related Art One method of recording character data in a computer system includes a one-byte code representing an alphabet or a kana character using a one-byte code and a character system having a character type such as a kanji character of more than 256 characters. There is a two-byte code to represent.

As a method of recording text data in which alphabets, kana characters, and kanji are mixed, there are a method of mixing 1-byte codes and 2-byte codes by using a switching code, and a method of expressing all characters by 2-byte codes. .

Since the length of data differs depending on the character code used even in the same text, if input / output of a text file is performed using a character code different from the recorded character code, the text file is positioned at an arbitrary data position in the file. Needed to perform character code conversion of the entire file data.

[0005]

As described above, in order to refer to data at an arbitrary position in a file with another character code, there has been a problem that the character code of the entire file data must be converted.

An object of the present invention is to provide a method for reducing a character code conversion process when data at an arbitrary position in a file is referred to by a character code different from a recorded character code.

[0007]

In order to achieve the above object, according to the data reference method of the present invention, file data is converted into another character code for each recording unit of data, and the character code of each recording unit is converted. And storing the data length of each recording unit and the position on the recording medium of each recording unit in a table.

Further, in the data reference method of the present invention, the data length after the character code conversion recorded in the table is added, the position of each recording unit from the file head is obtained, and the data to be input / output is included. Calculating a relative position of the recording unit on the recording medium and the input / output target data within the recording unit.

According to the data reference method of the present invention, when referencing data at an arbitrary position after character code conversion of a file in which a table is created, the file is positioned as input / output target data without performing character code conversion of the entire file data. be able to.

[0010]

Embodiments of the present invention will be described below.

FIG. 1 shows a conversion table for storing the data length of each block after character code conversion for each character code type. A block is a recording unit on a recording medium of data that can be read and written by one input / output request, and one block of data is stored in a continuous area on the recording medium. The conversion table 110 includes a file ID 100 for identifying the target file, and character code types 101, 102, and 10.
3, and data lengths 105 and 10 after various character code conversions corresponding to the recording position 104 on the recording medium of each block.
6,107 are stored. Also, the number 108 of all blocks belonging to the target file is recorded.

FIG. 2 is a diagram showing an opportunity for executing a procedure for creating a conversion table and a procedure for positioning a file according to the data reference method of the present invention. When the user issues a request 10 to a file, a request interpretation process 11 is executed, and one of a file OPEN process 12, a READ process 13, a WRITE process 14, and a file CLOSE process 15 is executed according to the user's request.

If the user's request is to open a file, a file OPEN process 12 is executed. If the character code type is specified at the time of the request, the conversion table creation processing 16 is called, and the conversion table 110 is created. The contents of the conversion table 110 are recorded in the system as a special file.

FIG. 3 shows an example of a file open user program. The character code type CODE1 (40
1) to specify the file “userfile01” (4
02), the conversion table is created if the conversion table has not been created, and the character code type 101 and the designated code 4
The information is stored in the data length 105 for each block after conversion to 01. READ (403) indicates that the file is opened for reading only.

In the file control information of the designated file 402, a file name of a special file storing the corresponding conversion table or an address of a file control block of the special file is recorded. Thereafter, if the same character code is specified and opened, the already created conversion table 110 is used.

When a different character code is specified and opened for the second time, the character code type 102 and the data length 106 after each block is converted are added to the created conversion table 110. Similarly, after the third time, the character code type and the data length of each block after the character code conversion are added to the conversion table 110.

If the user request 10 is a data input from a file, a READ process 13 is executed, and if the user request 10 is a data output to a file, a WRITE process 14
Is executed. READ processing 13 and WRITE processing 14
Then, the file positioning process 17 is called to position the input / output target data, and then input / output data.

FIG. 4 shows a procedure for creating a conversion table in the data reference method of the present invention. First, the number of blocks is initialized to 0 (201). Next, one block of data is input (20
2) Determine whether the end of the file has been reached (2)
03). If it is not the end of the file, the input data is subjected to character code conversion (204), and the recording position of the input data and the converted data length are recorded in the conversion table (20).
5) Add 1 to the number of blocks (206). Returning to the process of inputting the next block (202), the process is repeated until the end of the file is reached. Finally, the number of blocks and the character code type are recorded in the conversion table (207).

FIG. 5 shows a positioning procedure of the data reference method of the present invention. Given the input / output position in the file after the character code conversion, the position SA on the recording medium of the block including the data at the position and the relative position OF of the data within the block are obtained.

FIG. 6 shows a file on a recording medium. 50
1 is the head of the recording medium, 502 is the head of the input / output target block, and 503 is the head of the next block. SA is the position of the head 502 of the input / output target block starting from the head 501 of the recording medium, and OF is the input / output target data 50 starting from the head 502 of the input / output target block.
4 position.

In the positioning procedure of FIG. 5, first, the total RA of the converted data length is initialized to 0 (301). Next, it is determined whether all blocks of the file have been processed (302).
If the data length has not been processed yet, the converted data length of the current block is added to RA (303). The RA is compared with the input / output position (304), and if the RA is smaller, the process returns to 302 and the next block is processed. When RA reaches the input / output position, the current position of the block is subtracted from the input / output position to obtain a relative position in the block (30).
5). Further, the position of the block on the recording medium is obtained from the conversion table (305). If the total data length RA of all blocks does not reach the input / output position, an error is returned (3
06).

[0022]

According to the present invention, once a conversion table is created, when text data is input / output with subsequent character code conversion, only the character code conversion of the data in the recording unit of the input / output portion is required. Therefore, there is an effect that the character code conversion process at the time of file input / output and the time required for the process can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conversion table according to an embodiment of the present invention.

FIG. 2 is a diagram showing an opportunity to execute a conversion table creation process and a file positioning process according to the present invention.

FIG. 3 is a diagram showing an example of a file open program specifying a character code type;

FIG. 4 is a flowchart of a conversion table creation procedure.

FIG. 5 is a flowchart of a file positioning procedure.

FIG. 6 is a diagram showing the position of input / output target data on a recording medium.

[Explanation of symbols]

100: File ID, 101, 102, 103: Character code type storage area, 104: Recording position storage area on the recording medium, 105, 106, 107: Converted data length storage area, 108: File block number storage area
110: conversion table, 10: request from user, 11
... Request interpretation processing, 12 ... File open processing, 13 ...
File input processing, 14 File output processing, 15 File close processing, 16 Conversion table creation processing, 17 File positioning processing, 501 Head position of recording medium, 502 Head position of input / output target block, 503 Input The start position of the next block to be output,
504: Input / output target data.

Claims (2)

[Claims] In a method of referring to data of a text file, a step of performing a character code conversion of data for each physically continuous recording unit on a recording medium, a position of the data of each recording unit on the recording medium, and each recording unit Creating a table in which the length of the unit data after the character code conversion is recorded in order from the beginning of the file. 2. A step of adding a length of data after the character code conversion recorded in the table according to claim 1 to obtain a position from a head of a file of each recording unit, and an input / output object from the position. A recording unit that contains the data that
Obtaining a relative position of the data to be input / output in the recording unit.