![\"Sqlite](\"https:\/\/www.acquireforensics.com\/blog\/wp-content\/uploads\/2015\/09\/database1.png\")
<\/a><\/p>\nThe above figure describes the block diagram showing the Sqlite database components and their relationship.<\/p>\n
Let us grab an idea of each components from the below segment.<\/p>\n
Interface<\/u><\/p>\n
The library of Sqlite is implemented using the functions; main.c<\/strong>, legacy.c<\/strong>, and vdbeapi.c. <\/strong>In-order to avoid the collision with other application, Sqlite library starts with Sqlite3<\/strong>.<\/p>\n Tokenizer<\/u><\/p>\n Tokenizer breaks downs the strings and separates the token then, passes the tokens to the parser.<\/p>\n Parser<\/u><\/p>\n The parser is generated with the Lemon LALR(1) parser generator. Parse assigns meaning to the token.<\/p>\n Code Generator<\/u><\/p>\n Code generator generates virtual machine codes for the SQL statements thus, enables to satisfy the request made by the user. There are many files in the generator, which helps to generate the codes such as, build.c<\/strong>, delete.c<\/strong>, attach.c<\/strong>, expr.c<\/strong>, insert.c<\/strong>, pragma.c<\/strong>, select.c<\/strong>, auth.c<\/strong>, etc.<\/p>\n Virtual Machine<\/u><\/p>\n The virtual machine under Sqlite database structure runs the code generated by the code generator. It has its own header file called; vdbe.h <\/strong>and the entire machine is stored in single vdbe.c <\/strong>file.<\/p>\n B-Tree<\/u><\/p>\n The database follows B-tree structure and different B-trees are meant for index as well as the tables. All these trees are stored under one disk.<\/p>\n Page Cache<\/u><\/p>\n Information is seen in fixed chunks and the B-trees module request this data or information. The page cache helps to attain the reading, writing, etc. of the chunks.<\/p>\n OS Interface<\/u><\/p>\n To get interfaced with the OS, Sqlite uses abstraction layer and it is defined in os.h<\/strong>. The implementation may vary according to the Operating Systems.<\/p>\n Utilities<\/u><\/p>\n The util.c <\/strong>contains the memory allocations and the routines of the string.<\/p>\n All the reads and writes of Sqlite database structure are done to an ordinary disk and since all the transactions follow ACID property, failure or power loss does not affect the transaction processing. Sqlite is a self-contained, serverless database system engine, has a cross-platform file format. The detail of its file format is discussed in the coming up sessions. And that will give you an idea on the file format of Sqlite.<\/p>\n The database is carried in a single file called \u201cmain database file\u201d and there is a second file for storing the additional information that may be added during the transaction process called as, \u2018rollback journals\u2019 or write-ahead log file. Suppose, suddenly the system crashed then, rollback journal or write-ahead log file that contains critical state information is used to restore the main database file. In such situations, rollback journal are called as, \u201chot journals or \u201chot WAL file\u201d; contains necessary information for bringing back the database.<\/p>\n Pages<\/u><\/strong><\/p>\n The database file consists of more than one page and the size of a page depends on the power of two between 512 and 65536. The page numbering starts from 1 and the maximum number is (231<\/sup>\u00a0– 2). All the pages in the main database have a single use either;<\/p>\n Remember, before modifying the database page, the unmodified contents will be written to WAL file. The first two pages are only described here. For more details about Sqlite file format, you can refer sqlite.org.<\/p>\nSqlite File Format<\/h2>\n
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