Attempt to make database management system for practice. You can use few tables at once, but they for now can have the only model: 2 char[20] fields, bool and int field for kind of people data storing. You can print, sort and save table, insert in it, delete or select from it. You can perform several operations in one line, make query chains(such as selection and few sorts). You can select with many operations on fields: finding equal, non-equal, containing, starting with or many other operations on rows' fields. Selection doesn't change current table. It just selects rows from it and forms new table that returns. Table methods is divided into two groups:

• That changes method's object
• That does not

Aviable methods and their usage:

Table(const char*) - just struct constructor that takes file name, but you can init table empty, just as usual struct

void print(bool) - outputs table. Takes value that defines will function print field names or not

Table select(const char*, const char*, bool comp(const char*, const char*)) - takes field name, char* value and comparison function that will be used in selection. Returns table with selected rows and doesn't alter current table

Table select(const char*, const int, bool comp(const int, const int)) - does the same, but takes int value

Table& del(const char*, const char*, bool comp(const char*, const char*)) - deletes selected rows and returns current table that you can continue work with table in one line. Takes same arguments as in select() function

Table& del(const char*, const int, bool comp(const int, const int)) - same as previous, but takes int value

Table& insert(char*, char*, bool, int) - inserts one row in current table and returns current table object that you can continue work with table in one line. Takes field values for new row. In char[n] field you can place only n-1 symbols, cause last must be null-byte terminator for struct member separating

Table& insert(Person*, const int) - insert few rows and returns table object. Takes array of row structures and their length

Table sort(const char*, const bool) - doesn't change current table, it sorts their rows and returns sorted by any field new table. You can make sort chain. Takes field name and sort order(asc/desc): asc by default(or 1), 0 for desc

void save(const char*) - saves current table. Takes file name and writes into the file/rewrites if file exists

Comparison functions:

Every single function have next syntax:
bool <comp> (<val>, <row field's val>), or, for string comparison,
bool <comp> (<substr>, <str>)
Functions:

1. eq - equality
2. ne - !eq
3. lt - less than
4. le - less or equal
5. gt - greater than
6. ge - greater or equal
7. sw - startswith
8. ew - endswith
9. in - is substring exists in string
10. ni - !in 1-6 applies for int, 1-10 applies for string(char*), 1-2 for bool(you can use 3-6 too, but this won't have any sense) There no function check, so you can try to attach sw comp function for sorting by int field and get wrong or unexpected result, but you should not do this. It's on your own.

You can not create model with other fields without code editing. Maybe, I will add this function later. For now I implemented all needed for me functionality. This isn't real DBMS, it's just for practice. Continuous developing model creating is going to be too complicated, so I stopped on this point.

Examples

Table table("table"); - Initializes table from file "table"
table.print(); - Table output with field names
table.print(0); - Table output without field names
table.select("fName", "Jo", in).print(1); - Prints table with field names and rows which fName field contains "Jo"
table.sort("fName", 0).sort("age").print(0); - Sort chain and outputting. Remember, sort doesn't change current table, only returns sorted one
table.insert("Oleg", "Benedictoxygenipropanol", 1, 99); - Insertion new row. Too long names/surnames will be cutted to 19 symbols

Multiple row insertion:
Person list[] =
{"John", "Watson", 1, 30},
{"Sherlock", "Holmes", 1, 40},
{"Qwerty", "Poiu", 0, 43}
};
table.insert(list, 3);

table.del("age", 16, gt); - Every row which age field have value more 16 will be deleted
table.del("age", 14, eq).del("male", 0, eq); - Chain deletion. You can chain any queries of aviable, but after save() you can not use any other Table methods
table.save("table"); - Save into "table" file

Files in repository and their destiny

utilities.h - contains comp functions and other utilities
models.h - contains structs such as table struct and it's method protos and table model struct
bundb.h - constains main methods such as sort, del, select and others
dbms.cpp - main DBMS file that contains main() function and performs calls to table struct and all it's methods

This program needs thourough tests. I fixed bugs I found, but no one knows, how many left unfixed