A keyset holds together a set of keys. More...

#include <keyset.hpp>

Public Member Functions
	KeySet ()
	Creates a new empty keyset with no keys. More...

	KeySet (ckdb::KeySet *k)
	Takes ownership of keyset! More...

	KeySet (const KeySet &other)
	Duplicate a keyset. More...

	KeySet (size_t alloc,...) ELEKTRA_SENTINEL
	Create a new keyset. More...

	KeySet (VaAlloc alloc, va_list ap)
	Create a new keyset. More...

	~KeySet ()
	Deconstruct a keyset. More...

ckdb::KeySet *	release ()
	If you don't want destruction of keyset at the end you can release the pointer.

ckdb::KeySet *	getKeySet () const
	Passes out the raw keyset pointer. More...

void	setKeySet (ckdb::KeySet *k)
	Take ownership of passed keyset. More...

KeySet &	operator= (KeySet const &other)
	Duplicate a keyset. More...

ssize_t	size () const
	The size of the keyset. More...

ckdb::KeySet *	dup () const
	Duplicate a keyset. More...

void	copy (const KeySet &other)
	Copy a keyset. More...

void	clear ()
	Clear the keyset. More...

ssize_t	append (const Key &toAppend)
	append a key More...

ssize_t	append (const KeySet &toAppend)
	append a keyset More...

Key	head () const
	Return the first key in the KeySet. More...

Key	tail () const
	Return the last key in the KeySet. More...

void	rewind () const
	Rewinds the KeySet internal cursor. More...

Key	next () const
	Returns the next Key in a KeySet. More...

Key	current () const
	Return the current Key. More...

void	setCursor (cursor_t cursor) const
	Set the KeySet internal cursor. More...

cursor_t	getCursor () const
	Get the KeySet internal cursor. More...

Key	pop ()
	Remove and return the last key of `ks`. More...

Key	at (cursor_t pos) const
	Lookup a key by index. More...

KeySet	cut (Key k)
	Cuts out a keyset at the cutpoint. More...

Key	lookup (const Key &k, const option_t options=KDB_O_NONE) const
	Look for a Key contained in `ks` that matches the name of the `key`. More...

Key	lookup (std::string const &name, const option_t options=KDB_O_NONE) const
	Lookup a key by name. More...

template<typename T >
T	get (std::string const &name, const option_t options=KDB_O_NONE) const
	Generic lookup+get for keysets. More...

Detailed Description

A keyset holds together a set of keys.

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", 0), keyNew ("user/name2", 0), keyNew ("user/name3", 0), KS_END);
// append a key in the keyset
ksAppendKey (myConfig, keyNew ("user/name4", 0));
 
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

Invariant: always holds an underlying elektra keyset.

Note: that the cursor is mutable, so it might be changed even in const functions as described.

Constructor & Destructor Documentation

◆ KeySet() [1/5]

kdb::KeySet::KeySet ( )

inline

Creates a new empty keyset with no keys.

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", 0));
// work with the KeySet
ksDel (keys);

But if you have any clue how large your keyset may be, you should read the next statements.

If you want a keyset with length 15 (because you know of your application that you only need up to 15 keys), use:

KeySet * keys = ksNew (15, keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key01", KEY_VALUE, "value01", 0),
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key02", KEY_VALUE, "value02", 0),
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key03", KEY_VALUE, "value03", 0),
                       // ...
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key15", KEY_VALUE, "value15", 0), 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", 0),
                         keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key2", KEY_VALUE, "value2", 0),
                         keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key3", KEY_VALUE, "value3", 0),
                         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

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

Parameters

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

Returns: a ready to use KeySet object

Return values

0	on memory error

◆ KeySet() [2/5]

kdb::KeySet::KeySet ( ckdb::KeySet * k )

inline

Takes ownership of keyset!

Keyset will be destroyed at destructor you cant continue to use keyset afterwards!

Use KeySet::release() to avoid destruction.

Parameters

k	the keyset to take the ownership from

See also: release(); setKeySet()

◆ KeySet() [3/5]

kdb::KeySet::KeySet ( const KeySet & other )

inline

Duplicate a keyset.

This keyset will be a duplicate of the other afterwards.

Note: that they still reference to the same Keys, so if you change key values also the keys in the original keyset will be changed.

So it is shallow copy, to create a deep copy you have to dup() every key (it still won't copy metadata, but they are COW):

kdb::KeySet ksDeepCopy (kdb::KeySet orig)
{
        kdb::KeySet deepCopy;
        orig.rewind ();
        while (orig.next ())
        {
                deepCopy.append (orig.current ().dup ());
        }
        return deepCopy;
}

See also: dup

◆ KeySet() [4/5]

kdb::KeySet::KeySet	(	size_t	alloc,
			...
	)

inlineexplicit

Create a new keyset.

Parameters

alloc	minimum number of keys to allocate
...	variable argument list

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", 0));
// work with the KeySet
ksDel (keys);

But if you have any clue how large your keyset may be, you should read the next statements.

If you want a keyset with length 15 (because you know of your application that you only need up to 15 keys), use:

KeySet * keys = ksNew (15, keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key01", KEY_VALUE, "value01", 0),
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key02", KEY_VALUE, "value02", 0),
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key03", KEY_VALUE, "value03", 0),
                       // ...
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key15", KEY_VALUE, "value15", 0), 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", 0),
                         keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key2", KEY_VALUE, "value2", 0),
                         keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key3", KEY_VALUE, "value3", 0),
                         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

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

Parameters

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

Returns: a ready to use KeySet object

Return values

0	on memory error

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

◆ KeySet() [5/5]

kdb::KeySet::KeySet	(	VaAlloc	alloc,
		va_list	av
	)

inlineexplicit

Create a new keyset.

Parameters

alloc	minimum number of keys to allocate
ap	variable arguments list

Use va as first argument to use this constructor, e.g.:

KeySet ks(va, 23, ...);

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", 0));
// work with the KeySet
ksDel (keys);

But if you have any clue how large your keyset may be, you should read the next statements.

If you want a keyset with length 15 (because you know of your application that you only need up to 15 keys), use:

KeySet * keys = ksNew (15, keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key01", KEY_VALUE, "value01", 0),
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key02", KEY_VALUE, "value02", 0),
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key03", KEY_VALUE, "value03", 0),
                       // ...
                       keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key15", KEY_VALUE, "value15", 0), 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", 0),
                         keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key2", KEY_VALUE, "value2", 0),
                         keyNew ("user/sw/org/app/#0/current/fixedConfiguration/key3", KEY_VALUE, "value3", 0),
                         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

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

Parameters

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

Returns: a ready to use KeySet object

Return values

0	on memory error

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

◆ ~KeySet()

kdb::KeySet::~KeySet ( )

inline

Deconstruct a keyset.

A destructor for KeySet objects. Cleans all internal dynamic attributes, decrement all reference pointers to all keys and then keyDel() all contained Keys, and elektraFree ()s the release the KeySet object memory (that was previously allocated by ksNew()).

Parameters

ks	the keyset object to work with

Return values

0	when the keyset was freed
-1	on null pointer

See also: ksNew()

Member Function Documentation

◆ append() [1/2]

ssize_t kdb::KeySet::append ( const Key & toAppend )

inline

append a key

Parameters

toAppend key to append

Returns: number of keys in the keyset

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 refcount incremented by keyIncRef(), e.g. by another keyset that contains this key.

The reference counter of the key will be incremented to show 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 keyname already existed 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);

Or if you want to avoid aliasing at all, you can duplicate the key. But then 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));
ksDel (ks);
// now we still can work with the key k!
keyDel (k);

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.

Parameters

ks	KeySet that will receive the key
toAppend	Key that will be appended to ks or deleted

See also: ksAppend(), keyNew(), ksDel(); keyIncRef()

◆ append() [2/2]

ssize_t kdb::KeySet::append ( const KeySet & toAppend )

inline

append a keyset

Parameters

toAppend keyset to append

Returns: number of keys in the keyset

Append all toAppend contained keys to the end of the ks. toAppend KeySet will be left unchanged.

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

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

Returns: the size of the KeySet after transfer

Return values

-1	on NULL pointers

Parameters

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

See also: ksAppendKey()

◆ at()

Key kdb::KeySet::at ( cursor_t pos ) const

inline

Lookup a key by index.

Parameters

pos	cursor position

Returns: the found key

◆ clear()

void kdb::KeySet::clear ( )

inline

Clear the keyset.

Keyset will have no keys afterwards.

◆ copy()

void kdb::KeySet::copy ( const KeySet & other )

inline

Copy a keyset.

Parameters

other other keyset to copy

This is only a shallow copy. For a deep copy you need to dup every key.

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(). But in some situations you need to copy a keyset to an existing 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 the source will be added to the destination and the ksCurrent() is set properly in dest.

A flat copy is made, so the keys will not be duplicated, but there reference counter is updated, so both keysets need to be 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	has to be an initialized source KeySet or NULL
dest	has to be an initialized KeySet where to write the keys

Return values

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

See also: ksNew(), ksDel(), ksDup(); keyCopy() for copying keys

◆ current()

Key kdb::KeySet::current ( ) const

inline

Return the current Key.

The 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 work with

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

Return values

0	on NULL pointer

See also: ksNext(), ksRewind()

◆ cut()

KeySet kdb::KeySet::cut ( Key k )

inline

Cuts out a keyset at the cutpoint.

Searches for the cutpoint inside the KeySet ks. If found it cuts out 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 make a 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 (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 below system/mountpoint/interest.

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

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

Parameters

ks	the keyset to cut. It will be modified by removing all keys below the cutpoint. The cutpoint itself will also be removed.
cutpoint	the point where to cut out the keyset

◆ dup()

ckdb::KeySet * kdb::KeySet::dup ( ) const

inline

Duplicate a keyset.

Returns: a copy of the keys

This is only a shallow copy. For a deep copy you need to dup every key.

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 ksDel().

Parameters

source has to be an initialized source KeySet

Returns: a flat copy of source on success

Return values

0	on NULL pointer

See also: ksNew(), ksDel(); keyDup() for Key duplication

◆ get()

template<typename T >

T kdb::KeySet::get	(	std::string const &	name,
		const option_t	options = `KDB_O_NONE`
	)		const

inline

Generic lookup+get for keysets.

Parameters

name	the key name to get
options	the options to be passed to lookup()

Exceptions

KeyNotFoundException if no key found

Note: To specialize more complex types (which are generic themselves) you can also specialize KeySetTypeWrapper<T>.

Use

#include <keysetget.hpp>

to include specializations for std types.

Returns: the requested type

◆ getCursor()

cursor_t kdb::KeySet::getCursor ( ) const

inline

Get the KeySet internal cursor.

Use it to get the cursor of the actual position.

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:

cursor_t 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)
{
        cursor_t 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 (cursor_t 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.

        cursor_t 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 work with

Returns: a valid cursor on success; an invalid cursor on NULL pointer or after ksRewind()

See also: ksNext(), ksSetCursor()

◆ getKeySet()

ckdb::KeySet * kdb::KeySet::getKeySet ( ) const

inline

Passes out the raw keyset pointer.

Returns: pointer to internal ckdb KeySet

See also: release(); setKeySet()

◆ head()

Key kdb::KeySet::head ( ) const

inline

Return the first key in the KeySet.

Returns: alphabetical first key

The KeySets cursor will not be affected.

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

Parameters

ks	the keyset object to work with

Returns: the first Key of a keyset

Return values

0	on NULL pointer or empty keyset

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

◆ lookup() [1/2]

Key kdb::KeySet::lookup	(	const Key &	key,
		const option_t	options = `KDB_O_NONE`
	)		const

inline

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 can you load the whole configuration you can write very effective but short code for configuration:

Key * key = keyNew ("/sw/tests/myapp/#0/current/",  KEY_END);
KDB * handle = kdbOpen (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 after 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	where to look for
key	the key object you are looking for
options	of type option_t with some `KDB_O_*` option bits as explained above

Returns: pointer to the Key found, 0 otherwise

Return values

0	on NULL pointers

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

Note: That the internal key cursor will point to the found key

◆ lookup() [2/2]

Key kdb::KeySet::lookup	(	std::string const &	name,
		const option_t	options = `KDB_O_NONE`
	)		const

inline

Lookup a key by name.

Parameters

name	the name to look for
options	some options to pass

Returns: the found key

See also: lookup (const Key &Key, const option_t options)

Note: That the internal key cursor will point to the found key

◆ next()

Key kdb::KeySet::next ( ) const

inline

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 after the end of the KeySet was 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 is reached
0	on NULL pointer

See also: ksRewind(), ksCurrent(); ksLookup() to honor specifications

◆ operator=()

KeySet & kdb::KeySet::operator= ( KeySet const & other )

inline

Duplicate a keyset.

This keyset will be a duplicate of the other afterwards.

Note: that they still reference to the same Keys, so if you change key values also the keys in the original keyset will be changed.

◆ pop()

Key kdb::KeySet::pop ( )

inline

Remove and return the last key of ks.

The reference counter will be decremented by one.

The KeySets 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);

Returns: the last key of ks

Return values

NULL	if `ks` is empty or on NULL pointer

Parameters

ks	KeySet to work with

See also: ksLookup() to pop keys by name; ksCopy() to pop all keys; commandList() for an example

◆ rewind()

void kdb::KeySet::rewind ( ) const

inline

Rewinds the KeySet internal cursor.

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

ksRewind (ks);

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

Parameters

ks	the keyset object to work with

Return values

0	on success
-1	on NULL pointer

See also: ksNext(), ksCurrent()

◆ setCursor()

void kdb::KeySet::setCursor ( cursor_t cursor ) const

inline

Set the KeySet internal 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.

cursor_t 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

cursor	the cursor to use
ks	the keyset object to work with

Return values

0	when the keyset is ksRewind()ed
1	otherwise
-1	on NULL pointer

See also: ksNext(), ksGetCursor()

◆ setKeySet()

void kdb::KeySet::setKeySet ( ckdb::KeySet * k )

inline

Take ownership of passed keyset.

Parameters

k	the keyset to take ownership from

See also: release(); getKeySet()

◆ size()

ssize_t kdb::KeySet::size ( ) const

inline

The size of the keyset.

Returns: the number of keys in the keyset

◆ tail()

Key kdb::KeySet::tail ( ) const

inline

Return the last key in the KeySet.

Returns: alphabetical last key

The KeySets 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 work with

Returns: the last Key of a keyset

Return values

0	on NULL pointer or empty keyset

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

The documentation for this class was generated from the following file:

keyset.hpp

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ KeySet() [1/5]

◆ KeySet() [2/5]

◆ KeySet() [3/5]

◆ KeySet() [4/5]

◆ KeySet() [5/5]

◆ ~KeySet()

Member Function Documentation

◆ append() [1/2]

◆ append() [2/2]

◆ at()

◆ clear()

◆ copy()

◆ current()

◆ cut()

◆ dup()

◆ get()

◆ getCursor()

Read ahead

Restoring state

Using Cursor directly

◆ getKeySet()

◆ head()

◆ lookup() [1/2]

◆ lookup() [2/2]

◆ next()

◆ operator=()

◆ pop()

◆ rewind()

◆ setCursor()

◆ setKeySet()

◆ size()

◆ tail()