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=head1 Database backends |
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Ermyth has a powerful modular database facility. The core merely provides an |
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interface, backend modules do the rest. Everything database-related lives |
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under the C<database> namespace. |
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=head2 Writing a new database backend |
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First, you will want to include the headers defining data structures for all |
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data you want to load/store. |
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#include <boost/foreach.hpp> // provides the foreach macro |
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|
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#include "atheme.h" |
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#include <ermyth/database.h> |
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#include <account/chanacs.h> |
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#include <account/kline.h> |
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#include <account/metadata.h> |
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#include <account/mychan.h> |
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#include <account/mymemo.h> |
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#include <account/mynick.h> |
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#include <account/myuser.h> |
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#include <account/svsignore.h> |
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|
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Every translation unit requires an rcsid: |
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|
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static char const rcsid[] = "$Id: database.pod,v 1.1 2007-08-28 17:14:42 pippijn Exp $"; |
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Define the handler class: |
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|
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namespace database |
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{ |
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struct mybackend : handler |
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{ |
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mybackend () |
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{ |
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backend_loaded = true; |
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} |
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// backends won't be unloaded at runtime, |
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// so we need no destructor |
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|
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virtual void save (); |
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virtual void load (); |
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}; |
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|
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void |
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mybackend::save () |
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{ |
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/** |
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* Maybe open a file, a database connection, a http |
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* connection or anything else where you want to store |
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* the data. The following is an example of a fictive |
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* storage facility. This is not part of ermyth. |
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*/ |
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dbconnection conn ("http://localhost/ermythdata", 8000); |
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|
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/** |
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* The following is an example of what you can do with |
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* the structures. Internal structures are described in |
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* the Datastructures developer document. |
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*/ |
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foreach (myuser_t *mu, myuser_t::map) |
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{ |
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printf ("Storing myuser %s\n", mu->name); |
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printf ("his/her password is %s\n", mu->pass); |
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printf ("and the email address is %s\n", mu->email); |
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conn.store ("myuser", mu->name, mu->pass, mu->email); |
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} |
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// Here you can do the same with other data. Storing |
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// data should not change it. |
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} |
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|
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void |
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mybackend::load () |
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{ |
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// Open storage like you did in mybackend::save () |
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dbconnection conn ("http://localhost/ermythdata", 8000); |
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|
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/** |
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* Depending on what kind of storage you used, you will |
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* have to do specific things with the connection. Here is |
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* a more or less pseudo-code example: |
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*/ |
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while (conn.has_more ("myuser")) |
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{ |
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char *muname = conn.load<char *> ("myuser", "name"); |
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char *mupass = conn.load<char *> ("myuser", "pass"); |
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char *mumail = conn.load<char *> ("myuser", "email"); |
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long muregistered = conn.load<long> ("myuser", "registered"); |
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myuser_t *mu = myuser::create (muname, mupass, mumail, muregistered); |
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} |
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} |
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} // namespace database |
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The last thing we need to do is register our database backend with the |
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database factory: |
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#define FACREG_TYPE database::mybackend |
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#define FACREG_TYPE_NAME "mybackend" |
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#define FACREG_INTERFACE_TYPE database::handler |
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#include <ermyth/factory_reg.h> |
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=head2 Using the new backend |
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Now, after compiling the module, the backend is available to the services and |
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can be loaded using the C<backend> configuration directive: |
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backend "mybackend"; |
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Usage of the database backend within ermyth is simple. Saving the current |
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state is done by invoking C<< backend->save () >> and loading is |
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C<< backend->load () >>. |
