C Language Development Kit/Snippets/Database

From OptiWiki

The database functions that will be described in this section can be used to create and use databases with the following properties.

Record size	Fixed (All records must have same length)
Support of sorted and unsorted databases	Both
Availability of search functions	Yes
Availability of sort functions	Yes
Possibility to add an index file to the database	Yes

Contents 1 Sources of all database functions 2 Creating, opening and closing a database 3 Database properties 4 Read, write and delete records of a database 5 Searching records in a database 6 Sorting records of a database 7 Creating and using index files

Sources of all database functions

To be able to use the database functions, include the following header file and source file in your project.

Header file	database.h (source)
Source file	database.c (source)

Creating, opening and closing a database

The following functions can be used to create, open and close a database.

• CreateDatabase() Creates a new database file and opens it
• OpenDatabase() Opens a database file.
• CloseDatabase() Closes a database file that was opened or created.

Database properties

The following functions return general properties and information of the current state of the database.

• GetCurrentRecord() Gets the current record number.
• GetTotalRecords() Gets the total number of records that are stored in the database.

Read, write and delete records of a database

The following functions make it possible to read, write, delete and jump to every desired record of the database.

• GotoRecord() Jumps to a specific record in the database. (Sets the current record number.)
• ReadCurrentRecord() Reads the record where GetCurrentRecord() points to.
• ReadFirstRecord() Reads the first record in the database.
• ReadLastRecord() Reads the last record in the database.
• ReadPreviousRecord() Reads the record before the current.
• ReadNextRecord() Reads one record after current.
• DeleteRecord() Deletes a specific record in the database.
• WriteRecord() Appends or overwrites a record to the database.

Searching records in a database

The following functions can be used to search records in a database. Use BinarySearch() for sorted databases and use LineairSearch() for unsorted databases.

• BinarySearch() Searches in database for a searchkey. Works only on sorted databases.
• LineairSearch() Searches database for a searchkey. Works on sorted and not sorted databases, but is slow.

Sorting records of a database

Depending on whether the database is already almost sorted or not and the amount of resources that may be used, the following sorting functions are available.

• InsertionSort() Sorts database with insertion sort algorithm. Fast for almost sorted databases.
• HeapSort() Sorts database with heapsort algorithm. Good performance on not sorted databases.
• QuickSort() Sorts database with quicksort algorithm. Very good performance on not sorted databases.

Creating and using index files

Sorted index files can be added to a database to be able to quickly search in unsorted databases that may not be sorted. It is also possible to add multiple sorted index to a single database to quickly search for different aspects of a record.

• CreateIndexFile() Creates an index file on a not sorted database.
• OpenIndexFile() Opens an index file
• SearchIndexFile() Searches for a searchkey in an indexed file.
• AddNewSearchkeyToIndex() Adds a new searchkey to an index file.