Data file writing method and system, and data file reading method and system

A non-transitory computer readable medium having instructions stored thereon that, when executed by at least one processor, cause the at least one processor to perform following operations:

• obtaining one or more piece of to-be-written data;
• setting a first character string;
• taking each piece of to-be-written data as a unit and adding the first character string in each unit, and locating the first character string at the front end of each unit for identifying each unit;
• writing each unit to the data file;
• searching the data file for the first character string, wherein if one or more first character string is found, it indicates that a unit where the one or more first character string is located is found;
• and
• reading to-be-read data in the unit according to a predetermined rule.