Public Member Functions |
| KDB () |
| Opens the session with the Key database.
|
| KDB (Key &errorKey) |
| Opens the session with the Key database.
|
| ~KDB () throw () |
|
|
void | open (Key &errorKey) |
| Opens the session with the Key database.
|
void | close (Key &errorKey) throw () |
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int | get (KeySet &returned, std::string const &keyname) |
| Retrieve keys in an atomic and universal way.
|
int | get (KeySet &returned, Key &parentKey) |
| Retrieve keys in an atomic and universal way.
|
int | set (KeySet &returned, std::string const &keyname) |
| Set keys in an atomic and universal way.
|
int | set (KeySet &returned, Key &parentKey) |
| Set keys in an atomic and universal way.
|
Opens the session with the Key database.
Constructs a class KDB.
- Exceptions
-
KDBException | if database could not be opened |
The method will bootstrap itself the following way. The first step is to open the default backend. With it system/elektra/mountpoints will be loaded and all needed libraries and mountpoints will be determined. These libraries for backends will be loaded and with it the KDB
datastructure will be initialized.You must always call this method before retrieving or committing any keys to the database. In the end of the program, after using the key database, you must not forget to kdbClose(). You can use the atexit () handler for it.The pointer to the KDB
structure returned will be initialized like described above, and it must be passed along on any kdb*() method your application calls.Get a KDB
handle for every thread using elektra. Don't share the handle across threads, and also not the pointer accessing it:
You don't need to use the
kdbOpen() if you only want to manipulate plain in-memory
Key or
KeySet objects.
- Precondition
- errorKey must be a valid key, e.g. created with keyNew()
- Parameters
-
errorKey | the key which holds errors and warnings which were issued |
- See Also
- kdbGet(), kdbClose() to end all affairs to the Key database.
- Returns
- a KDB pointer on success
-
NULL on failure
Access to the key database.
- Invariant
- the object holds an valid connection to the key database or is empty
Opens the session with the Key database.
Constructs a class KDB.
- Exceptions
-
KDBException | if database could not be opened |
The method will bootstrap itself the following way. The first step is to open the default backend. With it system/elektra/mountpoints will be loaded and all needed libraries and mountpoints will be determined. These libraries for backends will be loaded and with it the KDB
datastructure will be initialized.You must always call this method before retrieving or committing any keys to the database. In the end of the program, after using the key database, you must not forget to kdbClose(). You can use the atexit () handler for it.The pointer to the KDB
structure returned will be initialized like described above, and it must be passed along on any kdb*() method your application calls.Get a KDB
handle for every thread using elektra. Don't share the handle across threads, and also not the pointer accessing it:
You don't need to use the
kdbOpen() if you only want to manipulate plain in-memory
Key or
KeySet objects.
- Precondition
- errorKey must be a valid key, e.g. created with keyNew()
- Parameters
-
errorKey | the key which holds errors and warnings which were issued |
- See Also
- kdbGet(), kdbClose() to end all affairs to the Key database.
- Returns
- a KDB pointer on success
-
NULL on failure
kdb::KDB::KDB |
( |
Key & |
errorKey | ) |
|
|
inline |
Opens the session with the Key database.
Constructs a class KDB.
- Parameters
-
errorKey | is useful if you want to get the warnings in the successful case, when no exception is thrown. |
- Exceptions
-
KDBException | if database could not be opened |
The method will bootstrap itself the following way. The first step is to open the default backend. With it system/elektra/mountpoints will be loaded and all needed libraries and mountpoints will be determined. These libraries for backends will be loaded and with it the KDB
datastructure will be initialized.You must always call this method before retrieving or committing any keys to the database. In the end of the program, after using the key database, you must not forget to kdbClose(). You can use the atexit () handler for it.The pointer to the KDB
structure returned will be initialized like described above, and it must be passed along on any kdb*() method your application calls.Get a KDB
handle for every thread using elektra. Don't share the handle across threads, and also not the pointer accessing it:
You don't need to use the
kdbOpen() if you only want to manipulate plain in-memory
Key or
KeySet objects.
- Precondition
- errorKey must be a valid key, e.g. created with keyNew()
- Parameters
-
errorKey | the key which holds errors and warnings which were issued |
- See Also
- kdbGet(), kdbClose() to end all affairs to the Key database.
- Returns
- a KDB pointer on success
-
NULL on failure
int kdb::KDB::get |
( |
KeySet & |
returned, |
|
|
std::string const & |
keyname |
|
) |
| |
|
inline |
Retrieve keys in an atomic and universal way.
Get all keys below keyname inside returned.
- Precondition
- kdbOpen() must be called before using this method.
-
The
returned
KeySet must be a valid KeySet, e.g. constructed with ksNew().
The returned
KeySet may already contain some keys from previous kdbGet() calls. The new retrieved keys will be appended using ksAppendKey().It will fully retrieve, at least, all keys under the parentKey
folder, with all subfolders and their children.
- Note
- kdbGet() might retrieve more keys then requested (that are not below parentKey). These keys must be passed to calls of kdbSet(), otherwise they will be lost. This stems from the fact that the user has the only copy of the whole configuration and backends only write configuration that was passed to them. For example, if you kdbGet() "system/mountpoint/interest" you will not only get all keys below system/mountpoint/interest, but also all keys below system/mountpoint (if system/mountpoint is a mountpoint as the name suggests, but system/mountpoint/interest is not a mountpoint). Make sure to not touch or remove keys outside the keys of interest, because others may need them!
- See Also
- ksCut() for further remarks on that topic.
- Example:
This example demonstrates the typical usecase within an application (without error handling).
KeySet *myConfig =
ksNew(0,KS_END);
kdbGet(handle, myConfig, pkey);
kdbGet(handle, myConfig, pkey);
- Details:
If you pass NULL on any parameter kdbGet() will fail immediately without doing anything.When a backend fails kdbGet() will return -1 with all error and warning information in the parentKey
. The parameter returned
will not be changed.
- Updates:
In the first run of kdbGet all keys are retrieved. On subsequent calls only the keys are retrieved where something was changed inside the key database. The other keys stay unchanged in the keyset, even when they were manipulated.It is your responsibility to save the original keyset if you need it afterwards.If you must get the same keyset again, e.g. in another thread you need to open a second handle to the key database using kdbOpen().
- Parameters
-
handle | contains internal information of opened key database |
parentKey | parent key holds the information which keys should be get (it is possible that more are retrieved) - an invalid name gets all keys |
ks | the (pre-initialized) KeySet returned with all keys found will not be changed on error or if no update is required |
- See Also
- ksLookup(), ksLookupByName() for powerful lookups after the KeySet was retrieved
-
kdbSet() to save the configuration afterwards and kdbClose() to finish affairs with the Key database.
- Return values
-
1 | if the keys were retrieved successfully |
0 | if there was no update - no changes are made to the keyset then |
-1 | on failure - no changes are made to the keyset then |
#include <kdb.hpp>
#include <keyio.hpp>
using namespace kdb;
int main()
{
kdb.
get(config,
"/sw/MyApp");
if (k)
{
std::cout << k <<
" is " << k.
get<
int>() << std::endl;
}
else
{
std::cerr << "No key found" << std::endl;
return 1;
}
}
- Parameters
-
returned | the keyset where the keys will be in |
keyname | the root keyname which should be used to get keys below it |
- Return values
-
0 | if no key was updated |
1 | if user or system keys were updated |
2 | if user and system keys were updated |
- Exceptions
-
KDBException | if there were problems with the database |
- See Also
- KDB::get (KeySet & returned, Key & parentKey)
int kdb::KDB::get |
( |
KeySet & |
returned, |
|
|
Key & |
parentKey |
|
) |
| |
|
inline |
Retrieve keys in an atomic and universal way.
Get all keys below parentKey inside returned.
- Precondition
- kdbOpen() must be called before using this method.
-
The
returned
KeySet must be a valid KeySet, e.g. constructed with ksNew().
The returned
KeySet may already contain some keys from previous kdbGet() calls. The new retrieved keys will be appended using ksAppendKey().It will fully retrieve, at least, all keys under the parentKey
folder, with all subfolders and their children.
- Note
- kdbGet() might retrieve more keys then requested (that are not below parentKey). These keys must be passed to calls of kdbSet(), otherwise they will be lost. This stems from the fact that the user has the only copy of the whole configuration and backends only write configuration that was passed to them. For example, if you kdbGet() "system/mountpoint/interest" you will not only get all keys below system/mountpoint/interest, but also all keys below system/mountpoint (if system/mountpoint is a mountpoint as the name suggests, but system/mountpoint/interest is not a mountpoint). Make sure to not touch or remove keys outside the keys of interest, because others may need them!
- See Also
- ksCut() for further remarks on that topic.
- Example:
This example demonstrates the typical usecase within an application (without error handling).
KeySet *myConfig =
ksNew(0,KS_END);
kdbGet(handle, myConfig, pkey);
kdbGet(handle, myConfig, pkey);
- Details:
If you pass NULL on any parameter kdbGet() will fail immediately without doing anything.When a backend fails kdbGet() will return -1 with all error and warning information in the parentKey
. The parameter returned
will not be changed.
- Updates:
In the first run of kdbGet all keys are retrieved. On subsequent calls only the keys are retrieved where something was changed inside the key database. The other keys stay unchanged in the keyset, even when they were manipulated.It is your responsibility to save the original keyset if you need it afterwards.If you must get the same keyset again, e.g. in another thread you need to open a second handle to the key database using kdbOpen().
- Parameters
-
handle | contains internal information of opened key database |
parentKey | parent key holds the information which keys should be get (it is possible that more are retrieved) - an invalid name gets all keys |
ks | the (pre-initialized) KeySet returned with all keys found will not be changed on error or if no update is required |
- See Also
- ksLookup(), ksLookupByName() for powerful lookups after the KeySet was retrieved
-
kdbSet() to save the configuration afterwards and kdbClose() to finish affairs with the Key database.
- Return values
-
1 | if the keys were retrieved successfully |
0 | if there was no update - no changes are made to the keyset then |
-1 | on failure - no changes are made to the keyset then |
- Parameters
-
returned | the keyset where the keys will be in |
parentKey | the parentKey of returned |
- Return values
-
0 | if no key was updated |
1 | if user or system keys were updated |
2 | if user and system keys were updated |
- Exceptions
-
KDBException | if there were problems with the database |
void kdb::KDB::open |
( |
Key & |
errorKey | ) |
|
|
inline |
Opens the session with the Key database.
Open the database
- Parameters
-
errorKey | is useful if you want to get the warnings in the successful case, when no exception is thrown. |
The method will bootstrap itself the following way. The first step is to open the default backend. With it system/elektra/mountpoints will be loaded and all needed libraries and mountpoints will be determined. These libraries for backends will be loaded and with it the KDB
datastructure will be initialized.You must always call this method before retrieving or committing any keys to the database. In the end of the program, after using the key database, you must not forget to kdbClose(). You can use the atexit () handler for it.The pointer to the KDB
structure returned will be initialized like described above, and it must be passed along on any kdb*() method your application calls.Get a KDB
handle for every thread using elektra. Don't share the handle across threads, and also not the pointer accessing it:
You don't need to use the
kdbOpen() if you only want to manipulate plain in-memory
Key or
KeySet objects.
- Precondition
- errorKey must be a valid key, e.g. created with keyNew()
- Parameters
-
errorKey | the key which holds errors and warnings which were issued |
- See Also
- kdbGet(), kdbClose() to end all affairs to the Key database.
- Returns
- a KDB pointer on success
-
NULL on failure
int kdb::KDB::set |
( |
KeySet & |
returned, |
|
|
std::string const & |
keyname |
|
) |
| |
|
inline |
Set keys in an atomic and universal way.
Set all keys below keyname.
If the keyname of the parentKey is invalid (e.g. empty) all keys will be set.
With parentKey
you can only store a part of the given keyset. When other keys also belong to a backend, they will be used too, even when they are above parentKey
.
- Details:
If you pass a parentKey without a name the whole keyset will be set in an atomic way.Each key is checked with keyNeedSync() before being actually committed. So only changed keys are updated. If no key of a backend needs to be synced any affairs to backends omitted and 0 is returned.
- Errors:
If some error occurs, kdbSet() will stop. In this situation the KeySet internal cursor will be set on the key that generated the error.None of the keys are actually commited.You should present the error message to the user and let the user decide what to do. Possible solutions are:
- repeat the same kdbSet (for temporary errors)
- remove the key and set it again (for validation or type errors)
- change the value and try it again (for validation errors)
- do a kdbGet and then (for conflicts ...)
- set the same keyset again (in favour of what was set by this user)
- drop the old keyset (in favour of what was set elsewhere)
- export the configuration into a file (for unresolvable errors)
- Example of how this method can be used:
int i;
KeySet *myConfig =
ksNew(0,KS_END);
kdbGet(handle, ks, parentKey);
KeySet *base =
ksDup(ks);
KeySet *ours =
ksDup(ks);
int ret=
kdbSet(handle, ks, parentKey);
while (ret == -1)
{
int userInput = showElektraErrorDialog (parentKey, problemKey);
switch (userInput)
{
case INPUT_USE_OURS:
kdbGet(handle, ks, parentKey);
ks = ours;
break;
case INPUT_DO_MERGE:
kdbGet(handle, ks, parentKey);
KeySet * res=doElektraMerge(ours, ks, base);
ks = res;
break;
case INPUT_USE_THEIRS:
kdbGet(handle, ks, parentKey);
break;
...
}
ret=
kdbSet(handle, ks, parentKey);
}
showElektraErrorDialog() and doElektraMerge() need to be implemented by the user. For doElektraMerge a 3-way merge algorithm exists in libelektra-tools.
- Precondition
- kdbGet() must be called before kdbSet():
- Parameters
-
handle | contains internal information of opened key database |
ks | a KeySet which should contain changed keys, otherwise nothing is done |
parentKey | holds the information below which key keys should be set, see above |
- Return values
-
1 | on success |
0 | if nothing had to be done |
-1 | on failure |
- See Also
- keyNeedSync()
-
ksNext(), ksCurrent() for iteration over the KeySet
-
kdbOpen() and kdbGet() that must be called first
-
kdbClose() that must be called afterwards
- Return values
-
0 | if no key was updated |
1 | if user or system keys were updated |
2 | if user and system keys were updated |
- Parameters
-
returned | the keyset where the keys will be in |
keyname | the keyname below the names should be set |
- Exceptions
-
KDBException | if there were problems with the database |
int kdb::KDB::set |
( |
KeySet & |
returned, |
|
|
Key & |
parentKey |
|
) |
| |
|
inline |
Set keys in an atomic and universal way.
Set all keys below parentKey.
If the keyname of the parentKey is invalid (e.g. empty) all keys will be set.
With parentKey
you can only store a part of the given keyset. When other keys also belong to a backend, they will be used too, even when they are above parentKey
.
- Details:
If you pass a parentKey without a name the whole keyset will be set in an atomic way.Each key is checked with keyNeedSync() before being actually committed. So only changed keys are updated. If no key of a backend needs to be synced any affairs to backends omitted and 0 is returned.
- Errors:
If some error occurs, kdbSet() will stop. In this situation the KeySet internal cursor will be set on the key that generated the error.None of the keys are actually commited.You should present the error message to the user and let the user decide what to do. Possible solutions are:
- repeat the same kdbSet (for temporary errors)
- remove the key and set it again (for validation or type errors)
- change the value and try it again (for validation errors)
- do a kdbGet and then (for conflicts ...)
- set the same keyset again (in favour of what was set by this user)
- drop the old keyset (in favour of what was set elsewhere)
- export the configuration into a file (for unresolvable errors)
- Example of how this method can be used:
int i;
KeySet *myConfig =
ksNew(0,KS_END);
kdbGet(handle, ks, parentKey);
KeySet *base =
ksDup(ks);
KeySet *ours =
ksDup(ks);
int ret=
kdbSet(handle, ks, parentKey);
while (ret == -1)
{
int userInput = showElektraErrorDialog (parentKey, problemKey);
switch (userInput)
{
case INPUT_USE_OURS:
kdbGet(handle, ks, parentKey);
ks = ours;
break;
case INPUT_DO_MERGE:
kdbGet(handle, ks, parentKey);
KeySet * res=doElektraMerge(ours, ks, base);
ks = res;
break;
case INPUT_USE_THEIRS:
kdbGet(handle, ks, parentKey);
break;
...
}
ret=
kdbSet(handle, ks, parentKey);
}
showElektraErrorDialog() and doElektraMerge() need to be implemented by the user. For doElektraMerge a 3-way merge algorithm exists in libelektra-tools.
- Precondition
- kdbGet() must be called before kdbSet():
- Parameters
-
handle | contains internal information of opened key database |
ks | a KeySet which should contain changed keys, otherwise nothing is done |
parentKey | holds the information below which key keys should be set, see above |
- Return values
-
1 | on success |
0 | if nothing had to be done |
-1 | on failure |
- See Also
- keyNeedSync()
-
ksNext(), ksCurrent() for iteration over the KeySet
-
kdbOpen() and kdbGet() that must be called first
-
kdbClose() that must be called afterwards
- Return values
-
0 | if no key was updated |
1 | if user or system keys were updated |
2 | if user and system keys were updated |
- Parameters
-
returned | the keyset where the keys are passed to the user |
parentKey | the parentKey of returned |
- Exceptions
-
KDBException | if there were problems with the database |