kdb

kdb is a module for storing and loading data from files.

model

the first argument to all kdb functions is of type struct kdb, which describes the database to be accessed. the first field of that struct is a pointer to a struct of type struct kdb_fmt which describes the format of the database.

kdb encodes records as a tuple of three fields: (kind, key, value). kind is a 16-bit integer, key is an integer of platform width, and value is a blob decoded according to the type of the record, which is not saved in the database itself. records are indexed by the tuple (kind, key); key may be null. kind denotes the structure of the record, and is user-defined.

to use strings as the keys for database entries, either atoms should be stored in the database or a hash function may be used. kdb contains procedures to automate the use of atoms as keys.

types

struct kdb

• struct kdb_fmt* fmt
• enum kdb_conn conn
• union { kfile* file; const kdb_store* mem; kmptr ptr; } store;

struct kdb_rec

• u16 kind
• word key
• ksraw value

enum kdb_conn

• kdb_conn_none: no database is connected; calls will fail
• kdb_conn_file: the database is stored in a file; calls to modify it will modify the file on-disk
• kdb_conn_file_static: the database is stored in a file; calls to modify it will fail. if the file is writable to the process, can be seamlessly changed to kdb_conn_file and vice-versa
• kdb_conn_mem: the database is stored in-memory, allocated by kmem and referenced by ptr. calls to modify it will re-allocate memory via the appropriate interfaces.
• kdb_conn_mem_static: the database is stored in-memory, referenced by mem; calls to modify it will fail