Difference between revisions of "OpenDBX/C API/odbx init"

Latest revision as of 09:46, 24 September 2012

Allocate per connection data structures

#include <opendbx/api.h>

int odbx_init(
    odbx_t** handle,
    const char* backend,
    const char* host,
    const char* port )

Description

odbx_init() allocates and initializes an opaque object required for all further operations within the OpenDBX library which is used to identify the connection and to maintain per connection information. Depending on the backend it can open a connection to the database server but often this is done not until performing authentication through odbx_bind().

The pointer of the newly allocated connection object is stored in handle if odbx_init() completes successfully. Otherwise, the value of the handle variable will be undefined and must not be used as input for other functions of the library. The returned connection object must be freed by odbx_finish() to avoid memory leaks if it will be no longer used by the application.

The OpenDBX library provides access to several different database implementations through a single interface and therefore has to know which one of the available backend modules it should use for the operations. The backend parameter will be used to perform the lookup of the requested module. It has to be a zero-terminated ASCII string with all characters in in lower case. Currently, these backend modules are available:

• firebird (Firebird/Interbase)
• mssql (MS SQL Server via FreeTDS)
• mysql (MySQL)
• oracle (Oracle 8i/9i/10g)
• pgsql (PostgreSQL)
• sqlite (SQLite v2)
• sqlite3 (SQLite v3)
• sybase (Sybase ASE)

Connecting to a database server requires at least an identifier to know where the database is located. There are several kinds of identifiers like host names, IP addresses, named pipes, etc. which could be used. One of them can be provided via the host parameter and it is up to the native database library what it will accept. Most native libraries accept at least host names and IP addresses and also use the provided port in this case. The available methods for host are:

host name string 

supported by Firebird/Interbase, MySQL, Oracle and PostgreSQL backends

IP address string 

supported by Firebird/Interbase, MySQL, Oracle and PostgreSQL backends

absolute path to Unix domain socket 

currently supported by the PostgreSQL and MySQL backends only

(relative) directory path with trailing slash/backslash 

required by SQLite and SQLite3 backends

section name in configuration file 

required by MS SQL Server and Sybase ASE backends

Depending on the native database library, it's also possible to use database specific default values for the host and port parameters by supplying empty, zero-terminated strings or a NULL value.

Return value

odbx_init() returns ODBX_ERR_SUCCESS, or an error code whose value is less than zero if one of the operations couldn't be completed successfully. Possible error codes are listed in the error section and they can be feed to odbx_error() and odbx_error_type() to get further details.

Errors

-ODBX_ERR_BACKEND 

The backend module returned an error because it couldn't setup the necessary structures

-ODBX_ERR_PARAM 

handle is NULL and the allocated connection object can't be stored

-ODBX_ERR_NOMEM 

Allocating new memory for the connection object failed

-ODBX_ERR_SIZE 

The length of a string exceeded the available buffer size

-ODBX_ERR_NOTEXIST 

A backend module with this name wasn't found. Either the module isn't installed, the given name was wrong or not in the correct character case

-ODBX_ERR_NOOP 

The backend module doesn't provide the required function

See also

• odbx_bind()
• odbx_capabilities()
• odbx_error()
• odbx_finish()
• odbx_get_option()
• odbx_set_option()