Methods to manipulate KeySets. More...

Macros
#define	KS_END ((Key *) 0)
	End of a list of keys. More...

Enumerations
enum	elektraLookupFlags { KDB_O_NONE = 0 , KDB_O_DEL = 1 , KDB_O_POP = 1 << 1 }
	Options to change the default behavior of ksLookup() functions. More...

Functions
KeySet *	ksNew (size_t alloc,...)
	Allocate, initialize and return a new KeySet object. More...

KeySet *	ksVNew (size_t alloc, va_list va)
	Allocate, initialize and return a new KeySet object. More...

KeySet *	ksDup (const KeySet *source)
	Return a duplicate of a KeySet. More...

int	ksCopy (KeySet dest, const KeySet source)
	Replace the content of a KeySet with another one. More...

int	ksDel (KeySet *ks)
	A destructor for KeySet objects. More...

int	ksNeedSync (const KeySet *ks)
	Checks if KeySet needs sync. More...

ssize_t	ksGetSize (const KeySet *ks)
	Return the number of Keys that `ks` contains. More...

ssize_t	ksAppendKey (KeySet ks, Key toAppend)
	Appends a Key to the end of `ks`. More...

ssize_t	ksAppend (KeySet ks, const KeySet toAppend)
	Append all Keys in `toAppend` to the end of the KeySet `ks`. More...

ssize_t	ksRename (KeySet ks, const Key root, const Key *newRoot)
	Moves all keys below `root` to below `newRoot`. More...

elektraCursor	ksFindHierarchy (const KeySet ks, const Key root, elektraCursor *end)
	Searches for the start and optionally end of the key hierachy rooted at `root` in `ks`. More...

KeySet *	ksCut (KeySet ks, const Key cutpoint)
	Cuts out all Keys from KeySet `ks` that are below or at `cutpoint`. More...

Key *	ksPop (KeySet *ks)
	Remove and return the last Key of `ks`. More...

int	ksRewind (KeySet *ks)
	Rewinds the KeySet internal cursor. More...

Key *	ksNext (KeySet *ks)
	Returns the next Key in a KeySet. More...

Key *	ksCurrent (const KeySet *ks)
	Return the current Key. More...

Key *	ksHead (const KeySet *ks)
	Return the first Key in the KeySet. More...

Key *	ksTail (const KeySet *ks)
	Return the last Key in the KeySet. More...

elektraCursor	ksGetCursor (const KeySet *ks)
	Get the internal cursor of the KeySet. More...

Key *	ksAtCursor (KeySet *ks, elektraCursor pos)
	Return Key at given position `pos`. More...

int	ksSetCursor (KeySet *ks, elektraCursor cursor)
	Set the KeySet internal cursor to `cursor`. More...

Key *	ksLookup (KeySet ks, Key key, elektraLookupFlags options)
	Look for a Key contained in `ks` that matches the name of the `key`. More...

Key *	ksLookupByName (KeySet ks, const char name, elektraLookupFlags options)
	Convenience method to look for a Key contained in `ks` with name `name`. More...

Detailed Description

Methods to manipulate KeySets.

A KeySet is a set of keys.

Most important properties of a KeySet:

Allows us to iterate over all keys (in any depth)
Iteration is always sorted
Fast key lookup
A Key may be shared among many KeySets.

The most important methods of KeySet:

With ksNew() you can create a new KeySet.
You can append keys with ksAppendKey() or with ksAppend() you can append a whole keyset.
Using ksLookup() you can lookup (or pop with KDB_O_POP) a key.
With ksRewind() and ksNext() you can iterate through the keyset. Be assured that you will get every key of the set in a stable order (parents before children).

Note: Because the key is not copied, also the pointer to the current metadata keyNextMeta() will be shared.

KeySets have an internal cursor . Methods should avoid to change this cursor, unless they want to communicate something with it. The internal cursor is used:

in ksLookup(): points to the found key
in kdbSet(): points to the key which caused an error

KeySet is the most important data structure in Elektra. It makes it possible to get and store many keys at once inside the database. In addition to that, the class can be used as high level datastructure in applications and it can be used in plugins to manipulate or check configuration.

With ksLookupByName() it is possible to fetch easily specific keys out of the list of keys.

You can easily create and iterate keys:

// create a new keyset with 3 keys
// with a hint that about 20 keys will be inside
KeySet * myConfig = ksNew (20, keyNew ("user:/name1", KEY_END), keyNew ("user:/name2", KEY_END), keyNew ("user:/name3", KEY_END), KS_END);
// append a key in the keyset
ksAppendKey (myConfig, keyNew ("user:/name4", KEY_END));
 
Key * current;
ksRewind (myConfig);
while ((current = ksNext (myConfig)) != 0)
{
        printf ("Key name is %s.\n", keyName (current));
}
ksDel (myConfig); // delete keyset and all keys appended

Macro Definition Documentation

◆ KS_END

#define KS_END ((Key *) 0)

End of a list of keys.

Use this macro to define the end of a variable-length list of keys.

See also: ksNew() and ksVNew()

Enumeration Type Documentation

◆ elektraLookupFlags

enum elektraLookupFlags

Options to change the default behavior of ksLookup() functions.

These options can be ORed. That is the |-Operator in C.

See also: kdbGet(), kdbSet()

Enumerator

KDB_O_NONE

No Option set.

See also: ksLookup()

KDB_O_DEL

Delete parentKey key in ksLookup().

See also: ksLookup()

KDB_O_POP

Pop Parent out of keyset key in ksLookup().

   @see ksPop().

Function Documentation

◆ ksAppend()

ssize_t ksAppend	(	KeySet *	ks,
		const KeySet *	toAppend
	)

Append all Keys in toAppend to the end of the KeySet ks.

toAppend KeySet will be left unchanged.

If a Key is both in toAppend and ks, the Key in ks will be overwritten.

Note: Because the key is not copied, also the pointer to the current metadata keyNextMeta() will be shared.

Postcondition: Sorted KeySet ks with all Keys it had before and additionally the Keys from toAppend

Parameters

ks	the KeySet that will receive the Keys
toAppend	the KeySet that provides the Keys that will be transferred

Returns: the size of the KeySet ks after transfer

Return values

-1	on NULL pointers

Since: 1.0.0

See also: ksAppendKey()

◆ ksAppendKey()

ssize_t ksAppendKey	(	KeySet *	ks,
		Key *	toAppend
	)

Appends a Key to the end of ks.

Hands the ownership of the Key toAppend to the KeySet ks. ksDel(ks) uses keyDel(k) to delete every Key unless it got its reference counter incremented by keyIncRef(), e.g. by another KeySet that contains this Key.

The reference counter of the Key will be incremented to indicate this ownership, and thus toAppend is not const.

Note: Because the key is not copied, also the pointer to the current metadata keyNextMeta() will be shared.

See also: keyGetRef().

If the Key's name already exists in the KeySet, it will be replaced with the new Key.

ksAppendKey() will also lock the Key's name from toAppend. This is necessary so that the order of the KeySet cannot be destroyed via calls to keySetName().

The KeySet internal cursor will be set to the new Key.

It is safe to directly append newly created Keys:

KeySet * ks = ksNew (1, KS_END);
ksAppendKey (ks, keyNew ("user:/my/new/key", KEY_END));
ksDel (ks);
// key deleted, too!

If you want the key to outlive the KeySet, make sure to do proper ref counting:

KeySet * ks = ksNew (1, KS_END);
Key * k = keyNew ("user:/ref/key", KEY_END);
keyIncRef (k);
ksAppendKey (ks, k);
ksDel (ks);
// now we still can work with the key k!
keyDecRef (k);
keyDel (k);

You can duplicate the Key to avoid aliasing, but then the Key in the KeySet has another identity:

KeySet * ks = ksNew (1, KS_END);
Key * k = keyNew ("user:/ref/key", KEY_END);
ksAppendKey (ks, keyDup (k, KEY_CP_ALL));
ksDel (ks);
// now we still can work with the key k!
keyDel (k);

Parameters

ks	KeySet where `toAppend` should be append
toAppend	Key that will be appended to `ks` or deleted

Returns: the size of the KeySet after appending

Return values

-1	on NULL pointers
-1	if appending failed (only on memory problems). The Key will be deleted then.

Since: 1.0.0

See also: ksAppend() for appending a KeySet to another KeySet; keyIncRef() for manually increasing a Key's reference counter

◆ ksAtCursor()

Key* ksAtCursor	(	KeySet *	ks,
		elektraCursor	pos
	)

Return Key at given position pos.

The position is a number starting from 0.

Parameters

ks	the KeySet to get the Key from
pos	the position of the Key that should be retrieved

Returns: the Key at the cursor pos on success

Return values

NULL	on NULL pointer, negative cursor position or a position that does not lie within the KeySet `ks`

Since: 1.0.0

See also: ksGetCursor() for getting the cursor at the current position; ksSetCursor() for setting the cursor to a specific position

◆ ksCopy()

int ksCopy	(	KeySet *	dest,
		const KeySet *	source
	)

Replace the content of a KeySet with another one.

Most often you may want a duplicate of a KeySet, see ksDup() or append keys, see ksAppend(). In some situations you need to copy Keys from a KeySet to another KeySet, for which this function exists.

Note: You can also use it to clear a KeySet when you pass a NULL pointer as source.

Implementation:: First all Keys in dest will be deleted. Afterwards the content of source will be added to the destination and ksCurrent() will be set properly in dest.

A flat copy is made, so Keys will not be duplicated, but their reference counter is updated, so both KeySets need to be deleted via ksDel().

Note: Because the key is not copied, also the pointer to the current metadata keyNextMeta() will be shared.

int f (KeySet *ks)
{
        KeySet *c = ksNew (20, ..., KS_END);
        // c receives keys
        ksCopy (ks, c); // pass the KeySet to the caller
 
        ksDel (c);
}       // caller needs to ksDel (ks)

Parameters

source	an initialized KeySet or NULL
dest	an initialized KeySet, where the Keys from `source` get copied to

Return values

1	on success
0	if `dest` was cleared successfully (`source` is NULL)
-1	when `dest` is a NULL pointer

Since: 1.0.0

See also: ksNew() for creating a new KeySet; ksDel() for deleting an existing KeySet; ksDup() for duplicating an existing KeySet; keyCopy() for copying Keys

◆ ksCurrent()

Key* ksCurrent ( const KeySet * ks )

Return the current Key.

The returned pointer is NULL if you reached the end or after ksRewind().

Note: You must not delete the Key or change the Key, use ksPop() if you want to delete it.

Parameters

ks	the KeySet object to get the current Key from

Returns: pointer to the Key pointed by ks's cursor

Return values

0	on NULL pointer

Since: 1.0.0

See also: ksNext() to get the next Key in the KeySet; ksRewind() for resetting the internal cursor of the KeySet

◆ ksCut()

KeySet* ksCut	(	KeySet *	ks,
		const Key *	cutpoint
	)

Cuts out all Keys from KeySet ks that are below or at cutpoint.

Searches for the cutpoint inside the KeySet ks. If found, it cuts out this Key and everything which is below (see keyIsBelow()) this Key. These Keys will be missing in the keyset ks. Instead, they will be moved to the returned KeySet. If cutpoint is not found an empty KeySet is returned and ks is not changed.

The cursor will stay at the same Key as it was before. If the cursor was inside the region of cut (moved) Keys, the cursor will be set to the Key before the cutpoint.

If you use ksCut() on a KeySet you got from kdbGet() and plan to use kdbSet() later, make sure that you keep all Keys that should not be removed permanently. You have to keep the KeySet that was returned and the KeySet ks.

Example:

You have the keyset ks:

system:/mountpoint/interest
system:/mountpoint/interest/folder
system:/mountpoint/interest/folder/key1
system:/mountpoint/interest/folder/key2
system:/mountpoint/other/key1

When you use

        Key * parentKey = keyNew ("system:/mountpoint/interest", KEY_END);
        KDB * kdb = kdbOpen (NULL, parentKey);
        KeySet * ks = ksNew (0, KS_END);
        kdbGet (kdb, ks, parentKey);
        KeySet * returned = ksCut (ks, parentKey);
        kdbSet (kdb, ks, parentKey); // all keys below cutpoint are now removed
        kdbClose (kdb, parentKey);

Then in returned are:

system:/mountpoint/interest
system:/mountpoint/interest/folder
system:/mountpoint/interest/folder/key1
system:/mountpoint/interest/folder/key2

And in ks are:

system:/mountpoint/other/key1

So kdbSet() permanently removes all keys at or below system:/mountpoint/interest.

Parameters

ks	the Keyset to cut. It will be modified by removing all Keys at or below the cutpoint.
cutpoint	the point where to cut out the Keyset

Returns: a new allocated KeySet which needs to deleted with ksDel(). The KeySet consists of all Keys (of the original KeySet ks) below the cutpoint. If the Key cutpoint exists, it will also be appended.

Return values

0	on NULL pointers, no Key name or allocation problems

Since: 1.0.0

See also: kdbGet() for an explanation on why you might get more Keys than you requested.

◆ ksDel()

int ksDel ( KeySet * ks )

A destructor for KeySet objects.

Cleans all internal dynamic attributes, decrements all reference pointers to all Keys and then calls keyDel() on all contained Keys. Afterwards elektraFree() is used to release the KeySet's object memory (that was previously allocated by ksNew()).

Parameters

ks	the KeySet that should be deleted

Return values

0	when the KeySet was successfully freed
-1	on NULL pointer

Since: 1.0.0

See also: ksNew() for creating a new KeySet

◆ ksDup()

KeySet* ksDup ( const KeySet * source )

Return a duplicate of a KeySet.

Objects created with ksDup() must be destroyed with ksDel().

Memory will be allocated as needed for dynamic properties, so you need to ksDel() the returned pointer.

A flat copy is made, so the Keys will not be duplicated, but their reference counter is updated, so both KeySets need to be deleted via ksDel().

Parameters

source has to be an initialized KeySet

Returns: a flat copy of source on success

Return values

0	on NULL pointer

Since: 1.0.0

See also: ksNew() for creating a new KeySet; ksDel() for deleting a KeySet; keyDup() for Key duplication

◆ ksFindHierarchy()

elektraCursor ksFindHierarchy	(	const KeySet *	ks,
		const Key *	root,
		elektraCursor *	end
	)

Searches for the start and optionally end of the key hierachy rooted at root in ks.

The main use-case for this function is this kind of loop:

elektraCursor end;
for (elektraCursor it = ksFindHierarchy (ks, root, &end); it < end; ++it)
{
        Key * cur = ksAtCursor (ks, it);
}

Parameters

ks	The keyset to search in
root	The root of the hierachy to find
end	If this is not NULL, it will be set to position of the first key after `root` that is not below `root`. This is useful for loops like the one above. If not keys below `root` exist in `ks`, `end` will always be set to the size of `ks`. This way a loop like the one above will still work correctly.

Return values

-1	if `ks` or `root` are NULL

Returns: the position of either root itself or the first key below root that is part of ks. If no keys below root exist in ks, the size of ks is returned. The snippet above shows why this is useful.

◆ ksGetCursor()

elektraCursor ksGetCursor ( const KeySet * ks )

Get the internal cursor of the KeySet.

Warning: Cursors are getting invalid when the Key was ksPop()ed or ksLookup() with KDB_O_POP was used.

Read ahead

With the cursors it is possible to read ahead in a KeySet:

elektraCursor jump;
ksRewind (ks);
while ((key = keyNextMeta (ks))!=0)
{
        // now mark this key
        jump = ksGetCursor(ks);
 
        //code..
        keyNextMeta (ks); // now browse on
        // use ksCurrent(ks) to check the keys
        //code..
 
        // jump back to the position marked before
        ksSetCursor(ks, jump);
}

Restoring state

It can also be used to restore the state of a KeySet in a function

int f (KeySet *ks)
{
        elektraCursor state = ksGetCursor(ks);
 
        // work with keyset
 
        // now bring the keyset to the state before
        ksSetCursor (ks, state);
}

It is of course possible to make the KeySet const and cast its const away to set the cursor. Another way to achieve the same is to ksDup() the KeySet, but it is not as efficient.

An invalid cursor will be returned directly after ksRewind(). When you set an invalid cursor ksCurrent() is 0 and ksNext() == ksHead().

Using Cursor directly

You can also use the cursor directly by initializing it to some index in the KeySet and then incrementing or decrementing it, to iterate over the KeySet.

        Key * cur;
        for (elektraCursor cursor = 0; (cur = ksAtCursor (ks, cursor)) != NULL; ++cursor)
        {
                printf ("%s\n", keyName (cur));
        }

You can also use a while loop if you need access to the last cursor position.

        elektraCursor cursor = 0;
        Key * cur;
 
        while ((cur = ksAtCursor (ks, cursor)) != 0)
        {
                printf ("%s\n", keyName (cur));
                ++cursor;
        }

Note: Only use a cursor for the same KeySet which it was made for.

Parameters

ks	the KeySet object to get the cursor from

Returns: a valid cursor on success

Return values

-1	on NULL pointer
-1	on an invalid internal cursor or after ksRewind

Since: 1.0.0

See also: ksNext() for moving the internal cursor forward; ksSetCursor() for setting the cursor to a specific position; ksAtCursor() for getting the Key at a specific position

◆ ksGetSize()

ssize_t ksGetSize ( const KeySet * ks )

Return the number of Keys that ks contains.

Parameters

ks	the KeySet object to get the size from

Returns: the number of Keys that ks contains.

Return values

-1	on NULL pointer

Since: 1.0.0

◆ ksHead()

Key* ksHead ( const KeySet * ks )

Return the first Key in the KeySet.

The KeySet's cursor will not be affected.

If ksCurrent()==ksHead() you know you are on the first Key.

Parameters

ks	the KeySet object to get the first Key from

Returns: the first Key of a KeySet

Return values

0	on NULL pointer or empty KeySet

Since: 1.0.0

See also: ksTail() for getting the last Key of the KeySet; ksRewind(), ksCurrent() and ksNext() for iterating over the KeySet

◆ ksLookup()

Key* ksLookup	(	KeySet *	ks,
		Key *	key,
		elektraLookupFlags	options
	)

Look for a Key contained in ks that matches the name of the key.

Note: Applications should only use ksLookup() with cascading Keys (Key name starting with /). Furthermore, a lookup should be done for every Key (also when iterating over Keys) so that the specifications are honored correctly. Keys of all namespaces need to be present so that ksLookup() can work correctly, so make sure to also use kdbGet() with a cascading Key.

ksLookup() is designed to let you work with a KeySet containing all Keys of the application. The idea is to fully kdbGet() the whole configuration of your application and process it all at once with many ksLookup().

This function is efficient (at least using binary search). Together with kdbGet(), which you can use to load the whole configuration, you can write very effective and short code for configuration:

Key * key = keyNew ("/sw/tests/myapp/#0/current/",  KEY_END);
KDB * handle = kdbOpen (NULL, key);
kdbGet (handle, myConfig, key);
Key * result = ksLookupByName (myConfig, "/sw/tests/myapp/#0/current/testkey1", 0);

This is the way programs should get their configuration and search for the values. It is guaranteed, that more namespaces can be added easily and that all values can be set by admin and user. Furthermore, using the kdb-tool, it is possible to introspect which values an application will get (by doing the same cascading lookup).

If found, ks internal cursor will be positioned in the matched Key (also accessible by ksCurrent()), and a pointer to the Key is returned. If not found, ks internal cursor will not move, and a NULL pointer is returned.

Cascading lookups will by default search in all namespaces (proc:/, dir:/, user:/ and system:/), but will also correctly consider the specification (=metadata) in spec:/:

override/# will make sure that another Key is considered before
namespace/# will change the number and/or order in which the namespaces are searched
fallback/# will search for other Keys when the other possibilities up to now were not successful
default to return the given value when not even fallback Keys were found.

Note: override and fallback work recursively, while default does not.

This process is very flexible, but it would be boring to manually follow all this links to find out which Key will be taken in the end. Use kdb get -v to trace the Keys.

KDB_O_POP: When KDB_O_POP is set the Key which was found will be ksPop()ed. ksCurrent() will not be changed, only iff ksCurrent() is the searched Key, then the KeySet will be ksRewind()ed.

Note: Like in ksPop() the popped Key always needs to be keyDel() afterwards, even if it is appended to another KeySet.

Warning: All cursors on the KeySet will be invalid iff you use KDB_O_POP, so don't use this if you rely on a cursor, see ksGetCursor().

The invalidation of cursors does not matter if you use multiple KeySets, e.g. by using ksDup(). E.g., to separate ksLookup() with KDB_O_POP and ksAppendKey():

void f (KeySet * iterator, KeySet * lookup)
{
        KeySet * append = ksNew (ksGetSize (lookup), KS_END);
        Key * current;
 
        ksRewind (iterator);
        while ((current = ksNext (iterator)))
        {
                Key * key = ksLookup (lookup, current, KDB_O_POP);
                // do something...
                ksAppendKey (append, key); // now append it to append, not lookup!
                keyDel (key);              // make sure to ALWAYS delete poped keys.
        }
        ksAppend (lookup, append);
        // now lookup needs to be sorted only once, append never
        ksDel (append);
}

This is also a nice example how a complete application with ksLookup() can look like.

KDB_O_DEL: Passing KDB_O_DEL will cause the deletion of the parameter key using keyDel().

Hybrid search: When Elektra is compiled with ENABLE_OPTIMIZATIONS=ON a hybrid search decides dynamically between the binary search and the OPMPHM. The hybrid search can be overruled by passing KDB_O_OPMPHM or KDB_O_BINSEARCH in the options to ksLookup().

Parameters

ks	the KeySet that should be searched
key	the Key object you are looking for
options	of type elektraLookupFlags with some `KDB_O_*` option bits - as explained above

Returns: pointer to the Key found

Return values

0	if no Key has been found
0	on NULL pointers

Since: 1.0.0

See also: ksLookupByName() to search by a name given by a string; ksCurrent(), ksRewind(), ksNext() for iterating over a KeySet

◆ ksLookupByName()

Key* ksLookupByName	(	KeySet *	ks,
		const char *	name,
		elektraLookupFlags	options
	)

Convenience method to look for a Key contained in ks with name name.

There are several options that can be used in conjunction with this function. All possible option flags can be found in elektraLookupFlags

Parameters

ks	the KeySet that should be searched
name	name of the Key you are looking for
options	some `KDB_O_*` option bits (KDB_O_POP, KDB_O_DEL): See ksLookup() or elektraLookupFlags for possible options

Returns: pointer to the Key found

Return values

0	if no Key has been found
0	on NULL pointers

Since: 1.0.0

See also: ksLookup() for explanation of the functionality and examples.; ksCurrent(), ksRewind(), ksNext() for iterating over a KeySet

◆ ksNeedSync()

int ksNeedSync ( const KeySet * ks )

Checks if KeySet needs sync.

When Keys are changed, this is reflected into keyNeedSync().

But when Keys are popped from a KeySet this can't be seen by looking at individual Keys.

ksNeedSync() allows the backends to know if a Key was popped from the KeySet, to know that this KeySet needs to be written out.

Deprecated:: Backends now work differently and do not rely on this information.

Parameters

ks	the KeySet to work with

Return values

-1	on NULL KeySet
0	if `ks` does not need sync
1	if `ks` needs sync

Since: 1.0.0

See also: keyNeedSync() for checking whether a single Key needs to be synced

◆ ksNew()

KeySet* ksNew	(	size_t	alloc,
			...
	)

Allocate, initialize and return a new KeySet object.

Objects created with ksNew() must be destroyed with ksDel().

You can use an arbitrary long list of parameters to preload the KeySet with a list of Keys. Either your first and only parameter is 0 or your last parameter must be KS_END.

So, terminate with ksNew(0, KS_END) or ksNew(20, ..., KS_END)

Warning: Never use ksNew(0, keyNew(...), KS_END). If the first parameter is 0, other arguments are ignored.

The first parameter alloc defines how many Keys can be added without reallocation. If you pass any alloc size greater than 0, but less than 16, it will default to 16.

For most uses

KeySet * keys = ksNew (1, KS_END);
// enough memory for up to 16 keys, without needing reallocation
ksDel (keys);

will be fine. The alloc size will be 16 and will double whenever size reaches alloc size, so it also performs well with large KeySets.

You can defer the allocation of the internal array that holds the Keys, by passing 0 as the alloc size. This is useful if it is unclear whether your KeySet will actually hold any Keys and you want to avoid a malloc call.

// Create KeySet without allocating memory for keys
KeySet * keys = ksNew (0, KS_END);
// The first allocation will happen in ksAppendKey
ksAppendKey(keys, keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key02", KEY_VALUE, "value02", KEY_END));
// work with the KeySet
ksDel (keys);

If the size of the KeySet is known in advance, use the alloc parameter to hint the size of the KeySet.

If your application only needs up to 15 Keys you can request a KeySet of size 15:

KeySet * keys = ksNew (15, keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key01", KEY_VALUE, "value01", KEY_END),
                       keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key02", KEY_VALUE, "value02", KEY_END),
                       keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key03", KEY_VALUE, "value03", KEY_END),
                       // ...
                       keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key15", KEY_VALUE, "value15", KEY_END), KS_END);
// work with it
ksDel (keys);

If you start having 3 Keys, and your application needs approximately 200 up to 500 Keys, you can use:

KeySet * config = ksNew (500, keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key1", KEY_VALUE, "value1", KEY_END),
                         keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key2", KEY_VALUE, "value2", KEY_END),
                         keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key3", KEY_VALUE, "value3", KEY_END),
                         KS_END); // don't forget the KS_END at the end!
// work with it
ksDel (config);

Alloc size is 500, the size of the KeySet will be 3 after ksNew. This means the KeySet will reallocate when appending more than 497 keys.

The main benefit of taking a list of variant length parameters is to be able to have one C-Statement for any possible KeySet. If you prefer, you can always create an empty KeySet and use ksAppendKey().

Postcondition: the KeySet is rewinded properly

Parameters

alloc gives a hint for how many Keys may be stored initially

Returns: a ready to use KeySet object

Return values

0	on memory error

Since: 1.0.0

See also: ksDel() to free the KeySet afterwards; ksDup() to duplicate an existing KeySet; ksAppendKey() to append individual Keys to a KeySet

◆ ksNext()

Key* ksNext ( KeySet * ks )

Returns the next Key in a KeySet.

KeySets have an internal cursor that can be reset with ksRewind(). Every time ksNext() is called, the cursor is incremented and the new current Key is returned.

You'll get a NULL pointer if the Key at the end of the KeySet has been reached. On subsequent calls of ksNext() it will still return the NULL pointer.

The ks internal cursor will be changed, so it is not const.

Note: You must not delete or change the Key, use ksPop() if you want to delete it.; That applications must do ksLookup() with an cascading Key for every single Key before using it, because specifications allow to hide or override Keys.

Parameters

ks	the KeySet object to work with

Returns: the new current Key

Return values

0	when the end of the KeySet has been reached
0	on NULL pointer

Since: 1.0.0

See also: ksRewind() for resetting the internal cursor of the KeySet; ksCurrent() for getting the Key the cursor currently points at; ksLookup() to honor specifications

◆ ksPop()

Key* ksPop ( KeySet * ks )

Remove and return the last Key of ks.

The reference counter of the Key will be decremented by one.

The KeySet's cursor will not be affected if it did not point to the popped Key.

Note: You need to keyDel() the Key afterwards, if you don't append it to another KeySet. It has the same semantics like a Key allocated with keyNew() or keyDup().

ks1=ksNew(0, KS_END);
ks2=ksNew(0, KS_END);
 
k1=keyNew("user:/name", KEY_END); // ref counter 0
ksAppendKey(ks1, k1); // ref counter 1
ksAppendKey(ks2, k1); // ref counter 2
 
k1=ksPop (ks1); // ref counter 1
k1=ksPop (ks2); // ref counter 0, like after keyNew()
 
ksAppendKey(ks1, k1); // ref counter 1
 
ksDel (ks1); // key is deleted too
ksDel (ks2);

Parameters

ks	KeySet to pop a Key from

Returns: the last Key of ks

Return values

NULL	if `ks` is empty or a NULL pointer

Since: 1.0.0

See also: ksLookup() to pop Keys by name; ksCopy() to pop all Keys; ksTail() for getting the last Key of a KeySet without removing it

◆ ksRename()

ssize_t ksRename	(	KeySet *	ks,
		const Key *	root,
		const Key *	newRoot
	)

Moves all keys below root to below newRoot.

Only keys below root will be modified. The rest of ks remains untouched.

This functions is similar to the following snippet, but there are some differences.

KeySet * toRename = ksCut (ks, root);
for (elektraCursor cursor = 0; cursor < ksGetSize (toRename); cursor++)
{
    Key * cur = keyDup (ksAtCursor (ks, cursor));
    keyReplacePrefix (cur, root, newRoot);
    ksAppendKey (ks, cur);
}
ksDel (toRename);

Firstly, the optimizations only work, if ks doesn't contain any keys below newRoot that aren't below root. If such keys exist, ksRename() will still work, but it will fall back to code similar to the for-loop above.

The second difference is that ksRename() will modify the keys in ks directly, if they aren't referenced from anywhere else (if their reference count is 1 (see keyGetRef())). Normally, this shouldn't cause problems, but if you have a direct Key * pointer to a key in ks or hold a reference to some data within a key of ks, you may need to call keyIncRef() to ensure the key isn't modified.

Parameters

ks	the keyset to manipulate
root	the old prefix that will be removed, must not be a cascading key
newRoot	the new prefix the will replace the old one, must not be a cascading key

Return values

-1	if any of `ks`, `root`, `newRoot` is NULL, or if `root` or `newRoot` are cascading keys
-2	if `ks` already contains keys below `newRoot`
0	if `ks` contains no keys below `root` (and also not `root` itself)

Returns: otherwise, the number of keys that have been renamed

◆ ksRewind()

int ksRewind ( KeySet * ks )

Rewinds the KeySet internal cursor.

Use it to set the cursor to the beginning of the KeySet. ksCurrent() will always return NULL afterwards. So you want to use ksNext() first.

ksRewind (ks);

while ((key = ksNext (ks))!=0) {}

Parameters

ks	the KeySet that should be rewound

Return values

0	on success
-1	on NULL pointer

Since: 1.0.0

See also: ksNext() for moving the cursor to the next entry in the KeySet; ksCurrent() for getting the current element in the KeySet

◆ ksSetCursor()

int ksSetCursor	(	KeySet *	ks,
		elektraCursor	cursor
	)

Set the KeySet internal cursor to cursor.

Use it to set the cursor to a stored position. ksCurrent() will then return the Key at the position of the supplied cursor.

Warning: Cursors may get invalid when the Key was ksPop()ed or ksLookup() was used together with KDB_O_POP.

elektraCursor cursor;
..
// key now in any position here
cursor = ksGetCursor (ks);
while ((key = keyNextMeta (ks))!=0) {}
ksSetCursor (ks, cursor); // reset state
ksCurrent(ks); // in same position as before

An invalid cursor will set the KeySet to its beginning like ksRewind(). When you set an invalid cursor ksCurrent() is 0 and ksNext() == ksHead().

Parameters

ks	the KeySet object where the cursor should be set
cursor	the cursor to set for `ks`

Return values

0	when the KeySet has been ksRewind()ed
1	otherwise
-1	on NULL pointer

Since: 1.0.0

See also: ksGetCursor() for getting the cursor at the current position; ksNext() for moving the internal cursor forward; ksCurrent() for getting the Key at the current position

◆ ksTail()

Key* ksTail ( const KeySet * ks )

Return the last Key in the KeySet.

The KeySet's cursor will not be affected.

If ksCurrent()==ksTail() you know you are on the last key. ksNext() will return a NULL pointer afterwards.

Parameters

ks	the KeySet object to get the last Key from

Returns: the last Key of a KeySet

Return values

0	on NULL pointer or empty KeySet

Since: 1.0.0

See also: ksHead() for getting the first Key of a KeySet; ksRewind(), ksCurrent() and ksNext() for iterating over the KeySet

◆ ksVNew()

KeySet* ksVNew	(	size_t	alloc,
		va_list	va
	)

Allocate, initialize and return a new KeySet object.

Objects created with ksNew() must be destroyed with ksDel().

You can use an arbitrary long list of parameters to preload the KeySet with a list of Keys. Either your first and only parameter is 0 or your last parameter must be KS_END.

So, terminate with ksNew(0, KS_END) or ksNew(20, ..., KS_END)

Warning: Never use ksNew(0, keyNew(...), KS_END). If the first parameter is 0, other arguments are ignored.

The first parameter alloc defines how many Keys can be added without reallocation. If you pass any alloc size greater than 0, but less than 16, it will default to 16.

For most uses

KeySet * keys = ksNew (1, KS_END);
// enough memory for up to 16 keys, without needing reallocation
ksDel (keys);

will be fine. The alloc size will be 16 and will double whenever size reaches alloc size, so it also performs well with large KeySets.

You can defer the allocation of the internal array that holds the Keys, by passing 0 as the alloc size. This is useful if it is unclear whether your KeySet will actually hold any Keys and you want to avoid a malloc call.

// Create KeySet without allocating memory for keys
KeySet * keys = ksNew (0, KS_END);
// The first allocation will happen in ksAppendKey
ksAppendKey(keys, keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key02", KEY_VALUE, "value02", KEY_END));
// work with the KeySet
ksDel (keys);

If the size of the KeySet is known in advance, use the alloc parameter to hint the size of the KeySet.

If your application only needs up to 15 Keys you can request a KeySet of size 15:

KeySet * keys = ksNew (15, keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key01", KEY_VALUE, "value01", KEY_END),
                       keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key02", KEY_VALUE, "value02", KEY_END),
                       keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key03", KEY_VALUE, "value03", KEY_END),
                       // ...
                       keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key15", KEY_VALUE, "value15", KEY_END), KS_END);
// work with it
ksDel (keys);

If you start having 3 Keys, and your application needs approximately 200 up to 500 Keys, you can use:

KeySet * config = ksNew (500, keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key1", KEY_VALUE, "value1", KEY_END),
                         keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key2", KEY_VALUE, "value2", KEY_END),
                         keyNew ("user:/sw/org/app/#0/current/fixedConfiguration/key3", KEY_VALUE, "value3", KEY_END),
                         KS_END); // don't forget the KS_END at the end!
// work with it
ksDel (config);

Alloc size is 500, the size of the KeySet will be 3 after ksNew. This means the KeySet will reallocate when appending more than 497 keys.

The main benefit of taking a list of variant length parameters is to be able to have one C-Statement for any possible KeySet. If you prefer, you can always create an empty KeySet and use ksAppendKey().

Postcondition: the KeySet is rewinded properly

Parameters

alloc gives a hint for how many Keys may be stored initially

Returns: a ready to use KeySet object

Return values

0	on memory error

Since: 1.0.0

See also: ksDel() to free the KeySet afterwards; ksDup() to duplicate an existing KeySet; ksAppendKey() to append individual Keys to a KeySet

Precondition: caller must call va_start and va_end

va the list of arguments

Parameters

alloc	the allocation size
va	the list of variable arguments

Macros

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ KS_END

Enumeration Type Documentation

◆ elektraLookupFlags

Function Documentation

◆ ksAppend()

◆ ksAppendKey()

◆ ksAtCursor()

◆ ksCopy()

◆ ksCurrent()

◆ ksCut()

◆ ksDel()

◆ ksDup()

◆ ksFindHierarchy()

◆ ksGetCursor()

Read ahead

Restoring state

Using Cursor directly

◆ ksGetSize()

◆ ksHead()

◆ ksLookup()

◆ ksLookupByName()

◆ ksNeedSync()

◆ ksNew()

◆ ksNext()

◆ ksPop()

◆ ksRename()

◆ ksRewind()

◆ ksSetCursor()

◆ ksTail()

◆ ksVNew()