Provided by: libopendbx1-dev_1.4.6-9build1_amd64 
NAME
OpenDBX::Conn - Encapsulates a connection to a database.
SYNOPSIS
Public Member Functions
void bind (const char *database, const char *who='', const char *cred='', odbxbind
method=ODBX_BIND_SIMPLE) throw ( std::exception )
Authenticates the user and selects the database using C style string parameters.
void bind (const string &database, const string &who='', const string &cred='', odbxbind
method=ODBX_BIND_SIMPLE) throw ( std::exception )
Authenticates the user and selects the database using C++ style string parameters.
Conn () throw ()
The default constructor for newly created connection objects without parameters.
Conn (const char *backend, const char *host='', const char *port='') throw (
std::exception )
Creates a connection object using C style string parameters.
Conn (const string &backend, const string &host='', const string &port='') throw (
std::exception )
Creates a connection object using C++ style string parameters.
Conn (const Conn &ref) throw ()
Copy constructor.
Stmt create (const char *sql, unsigned long size=0, Stmt::Type type=Stmt::Simple) throw (
std::exception )
Creates a statement object from a SQL text string using a C style buffer.
Stmt create (const string &sql, Stmt::Type type=Stmt::Simple) throw ( std::exception )
Creates a statement object from a SQL text string using a C++ string.
string & escape (const char *from, unsigned long fromlen, string &to) throw (
std::exception )
Escapes potentially dangerous characters in user input using a C style buffer.
string & escape (const string &from, string &to) throw ( std::exception )
Escapes potentially dangerous characters in user input using a C++ style string
parameter.
void finish () throw ( std::exception )
Cleans up the connection object.
bool getCapability (odbxcap cap) throw ( std::exception )
Tests if the database driver module does understand certain extensions.
void getOption (odbxopt option, void *value) throw ( std::exception )
Gets the value of a certain option provided by the database driver module.
Conn & operator= (const Conn &ref) throw ()
Assigns a connection instance to another one.
void setOption (odbxopt option, void *value) throw ( std::exception )
Sets a certain option provided by the database driver module.
void unbind () throw ( std::exception )
Releases the connection to the database and resets the authentication status.
~Conn () throw ()
Destroys the connection instance if no other references exist.
Detailed Description
Encapsulates a connection to a database.
Author:
Norbert Sendetzky norbert@linuxnetworks.de
Version:
1.0
Constructor & Destructor Documentation
OpenDBX::Conn::Conn ()
The default constructor for newly created connection objects without parameters. This is
method is provided to enable programmers to use connection objects as member variables of
other classes. They are initialized at construction time of the encapsulating object when
no values for backend, host and port are available yet.
It's necessary to replace the created object later on by a connection instance where the
necessary parameters have been given via one of the other constructors. Calling one of the
member functions of an instance created by the default constructor isn't possible and will
throw an exception.
Returns:
Empty connection instance
See also:
Conn( const char*, const char*, const char* )
Conn( const string&, const string&, const string& )
OpenDBX::Conn::Conn (const char * backend, const char * host = '', const char * port =
'')std::exception
Creates a connection object using C style string parameters. Initializes a new connection
using the parameters backend, host and port, but doesn't open the connection to the
database yet. This method allows C style strings as values for all parameters. Another
constructor for C++ style strings is also available. It returns a new connection instance,
which can be used to query options implemented by the driver or to create a statement. In
case of an error, it throws an OpenDBX exception with error message, code and severity.
The parameter backend is the name of the driver the OpenDBX library should use to connect
to a database. The name must be one of the implemented and available drivers on the system
and is case sensitive. All driver names are in lower case, e.g. 'mysql'.
Depending on the database driver, host can have different meanings. Normally, it's the
name or IP address of the server hosting the database server application. In case of
serverless database implementations like SQLite it's the directory path where the database
file is located. The path must contain the platform specific path separators like slash
('/') on Unix-like systems and backslash ('\') on Windows systems. Also the path must end
with the path separator like '/path/to/file/'.
Furthermore port can be the number or name the database server application is listening
to. If a name instead of the number is allowed depends on the database client library but
the number as string does always work. If an empty string is given, the default port of
the database server application is used by the database client library.
Parameters:
backend Name of the backend module to use
host Name or IP address of the database server
port Name or number of the port used by the database server
Returns:
Connection instance
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
See also:
Conn( const string&, const string&, const string& )
OpenDBX::Conn::Conn (const string & backend, const string & host = '', const string & port =
'')std::exception
Creates a connection object using C++ style string parameters. Initializes a new
connection using the parameters backend, host and port, but doesn't open the connection to
the database yet. This method allows C++ style strings as values for all parameters.
Another construtor for C style strings is also available. It returns a new connection
instance, which can be used to query options implemented by the driver or to create a
statement. In case of an error, it throws an OpenDBX exception with error message, code
and severity.
The parameter backend is the name of the driver the OpenDBX library should use to connect
to a database. The name must be one of the implemented and available drivers on the system
and is case sensitive. All driver names are in lower case, e.g. 'mysql'.
Depending on the database driver, host can have different mearings. Normally, it's the
name or IP address of the server hosting the database server application. In case of
serverless database implementations like SQLite it's the directory path where the database
file is located. The path must contain the platform specific path separators like slash
('/') on Unix-like systems and backslash ('\') on Windows systems. Also the path must end
with the path separator like '/path/to/file/'.
Furthermore port can be the number or name the database server application is listening
to. If a name instead of the number is allowed depends on the database client library but
the number as string does always work. If an empty string is given, the default port of
the database server application is used by the database client library.
Parameters:
backend Name of the backend module to use
host Name or IP address of the database server
port Name or number of the port used by the database server
Returns:
Connection instance
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
See also:
Conn( const char*, const char*, const char* )
OpenDBX::Conn::~Conn ()
Destroys the connection instance if no other references exist. Each connection object uses
a reference counter to remember if the connection is shared with other objects. If this
isn't the case or if this object is the last one referencing the connection, the
connection is closed and the allocated memory is freed.
OpenDBX::Conn::Conn (const Conn & ref)
Copy constructor. Enables the transfer of the internal state of an object ref of the same
type to this object. Both objects share the same database connection and the reference
counter afterwards. The reference counter is incremented each time an object is copied and
will be decremented if it is destroyed.
Parameters:
ref Original connection object instance
Member Function Documentation
void OpenDBX::Conn::bind (const char * database, const char * who = '', const char * cred =
'', odbxbind method = ODBX_BIND_SIMPLE)std::exception
Authenticates the user and selects the database using C style string parameters. After
initializing the object instance with one of the constructors taking a backend, host and
port string as parameter, it's necessary to authenticate the user and select a database.
Depending on the database client library, it also establishes the connection to the
database server. This method accepts C style strings for the database name, the user name
and the password.
The first parameter, the name of the database will be used to select the database all
further commands are operating on. The database is the container for the tables, views,
etc., which store the records and provide access to them.
Authentication is done in most cases by a combination of a user name and a password. If
the user name is known by the database server and the supplied password matches with the
stored one, the database server will allow the user to operate on the selected database
and its tables provided the user has permissions to read and/or modify the content.
The method parameter can be used to select different methods of authentication. At the
moment, only simple authentication (ODBX_BIND_SIMPLE) with user name and password is
available.
Parameters:
database Name of the database managed by the database server
who Name of the user account known by the database server
cred Necessary credential which belongs to the user account
method Method used for authentication
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
void OpenDBX::Conn::bind (const string & database, const string & who = '', const string &
cred = '', odbxbind method = ODBX_BIND_SIMPLE)std::exception
Authenticates the user and selects the database using C++ style string parameters. After
initializing the object instance with one of the constructors taking a backend, host and
port string as parameter, it's necessary to authenticate the user and select a database.
Depending on the database client library, it also establishes the connection to the
database server. This method accepts C++ style strings for the database name, the user
name and the password.
The first parameter, the name of the database will be used to select the database all
further commands are operating on. The database is the container for the tables, views,
etc., which store the records and provide access to them.
Authentication is done in most cases by a combination of a user name and a password. If
the user name is known by the database server and the supplied password matches with the
stored one, the database server will allow the user to operate on the selected database
and its tables provided the user has permissions to read and/or modify the content.
The method parameter can be used to select different methods of authentication. At the
moment, only simple authentication (ODBX_BIND_SIMPLE) with user name and password is
available.
Parameters:
database Name of the database managed by the database server
who Name of the user account known by the database server
cred Necessary credential which belongs to the user account
method Method used for authentication
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
Stmt OpenDBX::Conn::create (const char * sql, unsigned long size = 0, Stmt::Type type =
Stmt::Simple)std::exception
Creates a statement object from a SQL text string using a C style buffer. This method
returns an instance of the Stmt class that contains the statement sent to the database
server later on. Currently, only simple statements are supported, which are sent to the
database server for parsing and returning the result after calling Stmt::execute(). Later
on also prepared statements will be possible which are parsed by the database server when
creating the object and only the parameters will be sent to the database server on
execution. This can speed up processing especially if the statement is executed multiple
times with different content for the parameters.
The parameter named sql must contain the SQL text string that should be sent to the
database server for execution. It have to be a C style buffer in this case. For a
reference of valid SQL statements, please have a look at the documentation of your
database server.
The length of the statement excluding the trailing '0' byte should be given via the second
parameter size. If the length of the statement is unknown, you can also supply zero (0) as
size value which is also the default value if you hand over only one parameter. In this
case, the length of the string is calculated internally by this function before the
statement is given to the native database library.
Via the last parameter it can be selected how the statement should be treated internally
by the OpenDBX and the native database library. Currently, only simple processing is
available which sends complete SQL statements including its parameters as string to the
database server for parsing and execution. Later on, also prepared statement handling will
be available which parses the statements first and sends only the parameters to the server
before execution. This parameter is also optional.
The returned object is representing the given statement, which can be executed later on.
The statement is only valid for the current connection and as soon as the connection gets
invalid or is closed, working with this object will throw an error.
Parameters:
sql SQL text string containing a valid statement understood by the database server
size Size of the SQL text string in bytes
type Type of statement object that should be created
Returns:
Statement instance bound to this connection
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
See also:
Stmt
Stmt OpenDBX::Conn::create (const string & sql, Stmt::Type type = Stmt::Simple)std::exception
Creates a statement object from a SQL text string using a C++ string. This method returns
an instance of the Stmt class that contains the statement sent to the database server
later on. Currently, only simple statements are supported, which are sent to the database
server for parsing and returning the result after calling Stmt::execute(). Later on also
prepared statements will be possible which are parsed by the database server when creating
the object and only the parameters will be sent to the database server on execution. This
can speed up processing especially if the statement is executed multiple times with
different content for the parameters.
The parameter named sql must contain the SQL text string that should be sent to the
database server for execution. It have to be a C++ style string in this case. For a
reference of valid SQL statements, please have a look at the documentation of your
database server.
Via the last parameter type it can be selected how the statement should be treated
internally by the OpenDBX and the native database library. Currently, only simple
processing is available which sends complete SQL statements including its parameters as
string to the database server for parsing and execution. Later on, also prepared statement
handling will be available which parses the statements first and sends only the parameters
to the server before execution. This parameter is also optional.
The returned object is representing the given statement, which can be executed later on.
The statement is only valid for the current connection and as soon as the connection gets
invalid or is closed, working with this object will throw an error.
Parameters:
sql SQL text string containing a valid statement understood by the database server
type Type of statement object that should be created
Returns:
Statement instance bound to this connection
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
See also:
Stmt
string& OpenDBX::Conn::escape (const char * from, unsigned long fromlen, string &
to)std::exception
Escapes potentially dangerous characters in user input using a C style buffer. For
preventing SQL injection attacks which can have desasterous effects, all text input that
will be part of an SQL statement must be escaped. This does also apply to user content
that is already stored in the database and should be copied to another record or stored
again as the escaping is removed before the database server writes the content to disk.
The first parameter must contain the character sequence that should be escaped as C style
string. This string itself won't be modified by this method.
The escaped string will be written to the third parameter named to, which have to be also
an C++ style string. After transforming the input to an escaped string, the result may be
more then twice the size of the original input. The additional escape sequences aren't
stored in the database column so only the original string will be written to the disk.
A C++ reference of the third parameter containing the escaped string afterwards is also
returned by this method to providing the possibility to write more elegant code.
Parameters:
from Input string with which may contain dangerous characters
fromlen Size of the input string to escape in bytes
to String instance where the escaped characters should be written to
Returns:
Reference to the second parameter containing the escaped characters
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
string& OpenDBX::Conn::escape (const string & from, string & to)std::exception
Escapes potentially dangerous characters in user input using a C++ style string parameter.
For preventing SQL injection attacks which can have desasterous effects, all text input
that will be part of an SQL statement must be escaped. This does also apply to user
content that is already stored in the database and should be copied to another record or
stored again as the escaping is removed before the database server writes the content to
disk.
The first parameter must contain the character sequence that should be escaped as C++
style string. This string itself won't be modified by this method.
The escaped string will be written to the third parameter named to, which have to be also
an C++ style string. After transforming the input to an escaped string, the result may be
more then twice the size of the original input. The additional escape sequences aren't
stored in the database column so only the original string will be written to the disk.
A C++ reference of the second parameter containing the escaped string afterwards is also
returned by this method too, providing the possibility to write more elegant code.
Parameters:
from Input string with which may contain dangerous characters
to String instance where the escaped characters should be written to
Returns:
Reference to the second parameter containing the escaped characters
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
void OpenDBX::Conn::finish ()std::exception
Cleans up the connection object.
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
bool OpenDBX::Conn::getCapability (odbxcap cap)std::exception
Tests if the database driver module does understand certain extensions. The OpenDBX
library consists of a basic set of functions that must be implemented by all drivers and
optional sets for additional functionality. This method allows an application to ask the
driver selected by the first parameter of the constructor of this object if it supports
one or more optional sets. The available sets and its constants are:
• ODBX_CAP_BASIC
The core function set which have to be implemented by all backends. It consists of all
functions necessary to connect to, send textual queries to and process simple results
returned from the database server as well as error handling functions.
• ODBX_CAP_LO
The function set for handling large objects whose content isn't accessible by the basic
function. Currently, Firebird/Interbase and Oracle requires using the LOB functions.
The basic set makes sure that all drivers can handle connections to the databases, send
statements and retrieve results. It's supported by all drivers and usually don't have to
be checked.
Some databases client libraries provide the content of large objects not via the basic
functions. Instead, the Result::fieldValue() method returns only a handle to the large
object and reading or modifying the content of this data object requires calling
additional methods.
Parameters:
cap Constant of the capability
Returns:
True if supported, false if not
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
void OpenDBX::Conn::getOption (odbxopt option, void * value)std::exception
Gets the value of a certain option provided by the database driver module. It asks the
backend module for implemented options and their current values. This function can be used
at every stage and its primary use is to find out supported features of the backend
module. This features can be enable with setOption() before the connection to the database
server is established by calling bind().
There are several option values defined as named constants in the opendbx/api.h header
file. A few of them are for informational purpose only while most of the options can also
be set to different values by setOption() to change the behavior of the backend module.
These options are:
• ODBX_OPT_API_VERSION
The API version implemented by the backend. It returns a five digit number representing
the API version of the backend module in the form XYYZZ where X is the major number, YY
the revision and ZZ the minor number of the API.
• ODBX_OPT_THREAD_SAFE
If it is safe to use this backend and especially the native database client library in
an application which uses threads where more than one thread opens database connections
via the OpenDBX library.
• ODBX_OPT_TLS
The database client library may support transmitting all data securely by encrypting
the network traffic via SSL or TLS.
• ODBX_OPT_MULTI_STATEMENTS
The database server may be able to support multiple SQL statements in one string sent
to the database.
• ODBX_OPT_PAGED_RESULTS
All database servers and client libraries are able to transfer the records row by row.
Some of them can also transfer multiple rows or even all at once to minimize server
load, network traffic and latency. The downside of this is an increased memory
consumption.
• ODBX_OPT_COMPRESS
Support of compressed network traffic between database client and server. This can lead
to higher throughput if the network is the bottleneck.
• ODBX_OPT_MODE
Some database servers support different modes of operation, e.g. modes for compliance
to other SQL implementations or completely different query languages.
The parameter value must be a pointer to an integer variable where the backend module will
store the result for the supplied option. If it's not stated otherwise, the value assigned
to the this parameter will be of boolean nature and therefore is ODBX_ENABLE for a
supported option or ODBX_DISABLE for an option which isn't supported.
Parameters:
option Constant of the option
value Pointer to memory where the result is stored
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
Conn& OpenDBX::Conn::operator= (const Conn & ref)
Assigns a connection instance to another one. Assigns the internal state of an object ref
of the same type to this object. Both objects share the same database connection and the
reference counter afterwards. The reference counter is incremented each time an object is
copied and will be decremented if it is destroyed.
Parameters:
ref Connection instance
Returns:
Connection reference of this instance
void OpenDBX::Conn::setOption (odbxopt option, void * value)std::exception
Sets a certain option provided by the database driver module. Changes the value of the
specified option in the backend module or the native database library. Before trying to
set an option, it should be tested with getOption() first to ensure that it is supported
by the backend. Almost all options need to be set before connecting to the database server
using bind() to take any effect.
There are several option values defined as named constants in the opendbx/api.h header
file. The possible options are:
• ODBX_OPT_TLS
Use encryption to transmit all data securely over the network via SSL or TLS. This
option can be set to ODBX_TLS_NEVER (the default value) to prevent encrpytion,
ODBX_TLS_ALWAYS to enforce encryption and to fail if it can't be used between the client
library and the server or ODBX_TLS_TRY to use encryption if possible with the option to
fall back to a connection which isn't encrypted.
• ODBX_OPT_MULTI_STATEMENTS
Enables the database server to accept multiple statements in one string to the database
if the value of value is set to ODBX_ENABLE. Although, it might be possible to disable
it by setting it to ODBX_DISABLE.
• ODBX_OPT_PAGED_RESULTS
All database servers and client libraries are able to transfer the records row by row.
Some of them can also transfer multiple rows or even all at once to minimize server
load, network traffic and latency. The downside of this is an increased memory
consumption. If paged results are supported by the backend, passing positive values will
fetch the specified number of records at once from the database server. The value of
zero ('0') is special in this case because it asks the backend module to retrieve all
records at once.
• ODBX_OPT_COMPRESS
Enable compressed network traffic between database client and server. This can maximize
the throughput if the network is the bottleneck. Pass an integer variable with
ODBX_ENABLE to enable compression or with ODBX_DISABLE to disable it for this
connection.
• ODBX_OPT_MODE
Some database servers support different modes of operation, e.g. modes for compliance
to other SQL implementations or completely different query languages. The value for this
option must point to a zero terminated string.
If not stated otherwise, the type of the variable passed to the second parameter named
value must be an integer pointer. Its values must be in the range specified by the option
being changed.
Parameters:
option Constant of the option
value Pointer to memory which contains the new value
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
void OpenDBX::Conn::unbind ()std::exception
Releases the connection to the database and resets the authentication status.
Exceptions:
std::invalid_argument If the object was only initialized by the default constructor
OpenDBX::Exception If the underlying database library returns an error
Author
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