You can also use it to produce custom projections for your own set of. Scott Jones first demonstrated this at CppCon earlier this year. You can watch our whole CppCon talk here:
ODB is highly flexible and customizable. It can either completely hide the relational nature of the underlying database or expose some of the details as required.
ODB is not a framework. It does not dictate how you should write your application. Rather, it is designed to fit into your style and architecture by only handling object persistence and not interfering with any other functionality. There is no Codesynthesis base type that all Codesynthesis classes should derive from nor are there any restrictions on the data member types in persistent classes.
Existing classes can be made persistent with a few or no modifications. ODB has been designed for high performance and low memory overhead. Prepared statements are used to send and receive object state in binary Codesynthesis instead of text which reduces the load on the Codesynthesis and the database server.
Extensive caching of connections, prepared statements, and buffers saves time and resources on connection establishment, statement parsing, and memory allocations.
Finally, persistent classes have zero memory overhead. There are no hidden "database" members that each class must have nor are there per-object data structures allocated by ODB.
In this chapter we present a high-level overview of ODB. The next chapter takes a more hands-on approach and shows the concrete steps necessary to implement object persistence in a simple "Hello World" application.
For instance, if Codesynthesis application is going to use the MySQL database for object persistence, then the three ODB components that this application will use are the ODB compiler, libodb and libodb-mysql. The ODB compiler generates the database support code for persistent classes in your application.
The ODB compiler can also generate a database schema file that creates tables necessary to store the persistent classes.
The common runtime library defines database system-independent interfaces that your application can use to manipulate persistent objects.
The database-specific runtime library provides implementations of these interfaces for a concrete database as well as other database-specific utilities that are used by the generated code. Normally, the application does not use the database-specific runtime library directly but rather works with it via the common interfaces from libodb.
The following diagram shows the object persistence architecture of an application that uses MySQL as the underlying database system: The ODB system also defines two special-purpose languages: The ODB Query Language is an object-oriented database query language that can be used to search for objects matching certain criteria.
The use of the ODB compiler to generate database support code adds an additional step to your application build sequence. The following diagram outlines the typical build workflow of an application that uses ODB: Writing this code manually has the following drawbacks: Difficult and time consuming.
Writing database conversion code for any non-trivial application requires extensive knowledge of the specific database system and its APIs. It can also take a considerable amount of time to write and maintain. Supporting multi-threaded applications can complicate this task even further.
Optimal conversion often requires writing large amounts of extra code, such as parameter binding for prepared statements and caching of connections, statements, and buffers. Writing code like this in an ad-hoc manner is often too difficult and time consuming.
The conversion code is written for a specific database which makes it hard to switch to another database vendor. Lack of type safety. It is easy to misspell column names or pass incompatible values in SQL queries.
Such errors will only be detected at runtime. The database conversion code often ends up interspersed throughout the application making it hard to debug, change, and maintain.
With ODB hiding the details of the underlying database, the application logic is written using the natural object vocabulary instead of tables, columns and SQL. The resulting code is simpler and thus easier to read and understand. All the available optimization techniques, such as prepared statements and extensive connection, statement, and buffer caching, are used to provide the most efficient implementation for each database operation.
Because the database conversion code is automatically generated, it is easy to switch from one database vendor to another. In fact, it is possible to test your application on several database systems before making a choice. All this helps catch programming errors at compile-time rather than at runtime.
Automatic code generation minimizes the effort needed to adapt the application to changes in persistent classes.Free C or C++ XML Parser Libraries.
Last Update: This page tries to give a comparison of existing free C or C++ XML parser libraries. C++/WinRT shipped inside the Windows SDK () for the first time at the beginning of November.
The SDK included the C++/WinRT headers, so you don’t have to first get them from GitHub. Instead, you can simply include the appropriate headers from within any C++ project and start writing modern C++ code using the Windows API. Hdl Chip Design: A Practical Guide for Designing, Synthesizing & Simulating Asics & Fpgas Using Vhdl or Verilog [Douglas J.
Smith] on . Eventually we will have C++/WinRT fully integrated into Visual Studio, but until then you must do a little bit of work to get it all integrated smoothly. This is a list of free and open-source software packages, computer software licensed under free software licenses and open-source timberdesignmag.comre that fits the Free Software Definition may be more appropriately called free software; the GNU project in particular objects to their works being referred to as open-source.
For more information about the philosophical background for open-source.
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