Key is an essential class that encapsulates key name , value and metainfo . More...

Collaboration diagram for Key:

Modules
	Meta Info Manipulation Methods
	Methods to do various operations on Key metadata.

	Methods for Making Tests
	Methods to do various tests on Keys.

	Name Manipulation Methods
	Methods to do various operations on Key names.

	Value Manipulation Methods
	Methods to do various operations on Key values.

Macros
#define	KDB_PATH_SEPARATOR '/'
	`/` is used to separate key names. More...

#define	KDB_PATH_ESCAPE '\\'
	`\` is used as escape character in the key name. More...

Enumerations
enum	elektraKeyFlags { KEY_NAME = 1, KEY_VALUE = 1 << 1, KEY_FLAGS = 3, KEY_COMMENT = 1 << 3, KEY_BINARY = 1 << 4, KEY_SIZE = 1 << 11, KEY_META = 1 << 15, KEY_NULL = 1 << 16, KEY_END = 0 }
	Allows keyNew() to determine which information comes next. More...

enum	elektraCopyFlags { KEY_CP_NAME = 1 << 0, KEY_CP_STRING = 1 << 1, KEY_CP_VALUE = 1 << 2, KEY_CP_META = 1 << 3, KEY_CP_ALL = KEY_CP_NAME \| KEY_CP_VALUE \| KEY_CP_META }
	Copy options. More...

enum	elektraLockFlags { KEY_LOCK_NAME = 1 << 17, KEY_LOCK_VALUE = 1 << 18, KEY_LOCK_META = 1 << 19 }
	Lock options. More...

enum	elektraNamespace { KEY_NS_NONE = 0, KEY_NS_CASCADING = 1, KEY_NS_META = 2, KEY_NS_SPEC = 3, KEY_NS_PROC = 4, KEY_NS_DIR = 5, KEY_NS_USER = 6, KEY_NS_SYSTEM = 7, KEY_NS_DEFAULT = 8 }
	Elektra currently supported Key namespaces. More...

Functions
Key *	keyNew (const char *name,...)
	A practical way to fully create a Key object in one step. More...

Key *	keyCopy (Key dest, const Key source, elektraCopyFlags flags)
	Copy or clear a key. More...

int	keyDel (Key *key)
	A destructor for Key objects. More...

int	keyClear (Key *key)
	Key Object Cleaner. More...

ssize_t	keyIncRef (Key *key)
	Increment the viability of a key object. More...

ssize_t	keyDecRef (Key *key)
	Decrement the viability of a key object. More...

ssize_t	keyGetRef (const Key *key)
	Return how many references the key has. More...

int	keyLock (Key *key, elektraLockFlags what)
	Permanently locks a part of the key. More...

int	keyIsLocked (const Key *key, elektraLockFlags what)
	Tests if a part of a key is locked. More...

Detailed Description

Key is an essential class that encapsulates key name , value and metainfo .

To use it include:

#include <kdb.h>

Key properties are:

Key name
Key value
Key metadata , including but not limited to:

ABI: Due to ABI compatibility, the Key structure is not defined in kdb.h, only declared. So you can only declare pointers to Keys in your program, and allocate and free memory for them with keyNew() and keyDel() respectively.

Reference Counting: Every key has its reference counter (see keyGetRef() for longer explanation) that will be initialized with 0, that means a subsequent call of keyDel() will delete the key. If you append the key to a keyset the reference counter will be incremented by one (see keyIncRef()) and the key can't be deleted by a keyDel().

: As you can imagine this refcounting allows you to put the Key in your own data structures. It can be a very powerful feature, e.g. if you need your own-defined ordering or different Models of your configuration.

Macro Definition Documentation

◆ KDB_PATH_ESCAPE

#define KDB_PATH_ESCAPE '\\'

\ is used as escape character in the key name.

See also: description about key names .

◆ KDB_PATH_SEPARATOR

#define KDB_PATH_SEPARATOR '/'

/ is used to separate key names.

See also: description about key names .

Enumeration Type Documentation

◆ elektraCopyFlags

enum elektraCopyFlags

Copy options.

See also: keyCopy()

Enumerator
KEY_CP_NAME	Flag for copying the key name
KEY_CP_STRING	Flag for copying the key value, if it is a string
KEY_CP_VALUE	Flag for copying the key value
KEY_CP_META	Flag for copying the key metadata
KEY_CP_ALL	Shorthand for copying name, value and metadata

◆ elektraKeyFlags

enum elektraKeyFlags

Allows keyNew() to determine which information comes next.

See also: keyNew()

Enumerator
KEY_NAME	Flag for the key name
KEY_VALUE	Flag for the key data
KEY_FLAGS	Allows to define multiple flags at once.
KEY_COMMENT	Flag for the key comment
KEY_BINARY	Flag if the key is binary
KEY_SIZE	Flag for maximum size to limit value
KEY_META	Flag for metadata
KEY_NULL	Is not a flag, only as return value Deprecated: do not use
KEY_END	Used as a parameter terminator to keyNew()

◆ elektraLockFlags

enum elektraLockFlags

Lock options.

See also: keyLock(), keyIsLocked()

Enumerator
KEY_LOCK_NAME	lock the name of a key
KEY_LOCK_VALUE	lock the value of a key
KEY_LOCK_META	lock the meta data of a key

◆ elektraNamespace

enum elektraNamespace

Elektra currently supported Key namespaces.

See also: kdbGet(), keyGetNamespace()

Enumerator
KEY_NS_NONE	no key given as parameter to keyGetNamespace()
KEY_NS_CASCADING	cascading key, starts with /, abstract name for any of the namespaces below
KEY_NS_META	metakey, i.e. any key name not under other categories
KEY_NS_SPEC	spec contains the specification of the other namespaces
KEY_NS_PROC	proc contains process-specific configuration
KEY_NS_DIR	dir contains configuration from a specific directory
KEY_NS_USER	user key in the home directory of the current user
KEY_NS_SYSTEM	system key is shared for a computer system
KEY_NS_DEFAULT	default key used as a fallback if no other key is found

Function Documentation

◆ keyClear()

int keyClear ( Key * key )

Key Object Cleaner.

Will reset all internal data.

After this call you will receive a fresh key.

The reference counter will stay unmodified.

Note: that you might also clear() all aliases with this operation.

int f (Key *k)
{
        keyClear (k);
        // you have a fresh key k here
        keySetString (k, "value");
        // the caller will get an empty key k with an value
}

Return values

returns	0 on success
-1	on null pointer

Parameters

key	the key object to work with

◆ keyCopy()

Key* keyCopy	(	Key *	dest,
		const Key *	source,
		elektraCopyFlags	flags
	)

Copy or clear a key.

Depending on the chosen flags keyCopy() only copies certain parts of source into dest.

If KEY_CP_NAME is set, the key name will be copied from source to dest.
If KEY_CP_META is set, the meta keys will be copied from source to dest.
If KEY_CP_VALUE is set, the key value will be copied from source to dest. Additionally, if source is a binary key (keyIsBinary()), dest will also be marked as binary. This means that even if KEY_CP_META is not set, the binary meta key will be copied with KEY_CP_VALUE.
If KEY_CP_STRING is set, the key value will be copied from source to dest, but only, if source is not a binary key (keyIsBinary()). If source is binary, keyCopy() fails. If dest is binary, it will still be marked as binary after the copy. This cannot be used together with KEY_CP_VALUE. The main purpose of KEY_CP_STRING is for copying into known string keys. It ensure that you don't accidentally convert string keys into binary keys.

There is also the shorthand KEY_CP_ALL. It is equivalent to KEY_CP_NAME | KEY_CP_VALUE | KEY_CP_META, i.e. all key data supported by keyCopy() will be copied from source to dest.

Use this function when you need to copy into an existing key, e.g. because it was passed by a pointer in a function you can do so:

keyCopy (copy, orig, KEY_CP_ALL);

Most often you will want to duplicate an existing key. For this purpose the alias keyDup() exists. Calling

copy = keyDup (orig, KEY_CP_ALL);

is equivalent to

copy = keyCopy (keyNew ("/", KEY_END), orig, KEY_CP_ALL);

The reference counter will not be changed for both keys. Affiliation to keysets are also not affected.

Since metadata uses copy-on-write semantics there is only a constant memory cost to copying metadata.

When you pass a NULL-pointer as source the pieces of dest specified by flags will be cleared.

Calling keyCopy (dest, NULL, KEY_CP_ALL) is different from calling keyClear(). The key will not be fully reset, the reference counter and internal flags will remain unchanged. Additionally, keyCopy() respects keyLock() state, while keyClear() always works.

keyCopy (k, NULL, KEY_CP_ALL);
// name, value and metadata of k have now been clear
// lock flags, reference count, etc. remain unchanged

Precondition: dest must be a valid Key (created with keyNew); source must be a valid Key or NULL

Invariant: Key name stays valid until delete

Postcondition: Value from Key source is written to Key dest

Parameters

dest	the key which will be written to
source	the key which should be copied or NULL to clear the data of `dest`
flags	specifies which parts of the key should be copied

See also: keyDup()

Since: 0.9.5

Returns: dest

Return values

NULL	on memory allocation problems
NULL	when a part of `dest` that should be modified (e.g. name, value) was marked read-only, e.g. the name of `dest` will be read-only if `dest` is part of a KeySet
NULL	when `dest` is NULL
NULL	when both KEY_CP_VALUE and KEY_CP_STRING are set in `flags`
NULL	when both KEY_CP_STRING is set in `flags` and `source` is a binary key (keyIsBinary())

◆ keyDecRef()

ssize_t keyDecRef ( Key * key )

Decrement the viability of a key object.

The references will be decremented for ksPop() or successful calls of ksLookup() with the option KDB_O_POP. It will also be decremented with an following keyDel() in the case that an old key is replaced with another key with the same name.

The reference counter can't be decremented once it reached 0. In that situation nothing will happen and 0 will be returned.

Note: keyDup() will reset the references for dupped key.

Returns: the value of the new reference counter

Return values

-1	on null pointer
0	when the key is ready to be freed

Parameters

key	the key object to work with

See also: keyGetRef() for longer explanation, keyDel(), keyIncRef()

◆ keyDel()

int keyDel ( Key * key )

A destructor for Key objects.

Every key created by keyNew() must be deleted with keyDel().

It is safe to delete keys which are in a keyset, the number of references will be returned then.

It is save to delete a nullpointer, -1 will be returned then.

It is also save to delete a multiple referenced key, nothing will happen then and the reference counter will be returned.

Parameters

key	the key object to delete

See also: keyNew(), keyIncRef(), keyGetRef()

Returns: the value of the reference counter if the key is within keyset(s)

Return values

0	when the key was freed
-1	on null pointers

◆ keyGetRef()

ssize_t keyGetRef ( const Key * key )

Return how many references the key has.

The reference counting is the essential property of keys to make sure that they can be put safely into data structures. E.g. if you put a Key into a KeySet:

Key *k = keyNew("user:/proper_name", KEY_END); // ref counter = 0
KeySet *ks = ksNew (1, k, KS_END);
keyDel(k); // key will not be deleted, because its in the keyset
ksDel(ks); // now the key will be deleted

You can even add the key to more KeySets:

Key *k = keyNew("user:/proper_name", KEY_END); // ref counter 0
KeySet *ks1 = ksNew(1, k, KS_END); // ref counter of k 1
KeySet *ks2 = ksNew(1, k, KS_END); // ref counter of k 2
ksDel(ks1); // ref counter of k 1
ksDel(ks2); // k is now deleted

If you increment only by one with keyIncRef() the same as said above is valid:

Key *k = keyNew("/", KEY_END); // ref counter = 0
keyIncRef(k); // ref counter = 1
keyDel(k); // key will not be deleted
keyDecRef(k);
keyDel(k);

or use keyIncRef() more than once:

Key *k = keyNew("/", KEY_END); // ref counter 0
keyIncRef(k); // ref counter of key 1
keyDel (k);   // has no effect
keyIncRef(k); // ref counter of key 2
keyDel (k);   // has no effect
keyDecRef(k); // ref counter of key 1
keyDel (k);   // has no effect
keyDecRef(k); // ref counter is now 0
keyDel (k); // k is now deleted

The key won't be deleted by a keyDel() as long refcounter is not 0.

The references will be incremented on successful calls to ksAppendKey() or ksAppend().

Note: keyDup() will reset the references for dupped key.

For your own applications you can use keyIncRef() and keyDecRef() for reference counting, too.

Parameters

key	the key object to work with

Returns: the number of references

Return values

-1	on null pointer

See also: keyIncRef() and keyDecRef()

◆ keyIncRef()

ssize_t keyIncRef ( Key * key )

Increment the viability of a key object.

This function is intended for applications using their own reference counter for key objects. With it you can increment the reference and thus avoid destruction of the object in a subsequent keyDel().

The reference counter can't be incremented once it reached SSIZE_MAX. In that situation nothing will happen and SSIZE_MAX will be returned.

Note: keyDup() will reset the references for dupped key.

Returns: the value of the new reference counter

Return values

-1	on null pointer
SSIZE_MAX	when maximum exceeded

Parameters

key	the key object to work with

See also: keyGetRef() for longer explanation, keyDecRef(), keyDel()

◆ keyIsLocked()

int keyIsLocked	(	const Key *	key,
		elektraLockFlags	what
	)

Tests if a part of a key is locked.

See also: keyLock() for more details

Return values

>0	the bits that are locked
0	if everything is unlocked
-1	on error (nullpointer)

◆ keyLock()

int keyLock	(	Key *	key,
		elektraLockFlags	what
	)

Permanently locks a part of the key.

This can be:

KEY_LOCK_NAME to lock the name
KEY_LOCK_VALUE to lock the value
KEY_LOCK_META to lock the metadata

To unlock the key, duplicate it.

It is also possible to lock when the key is created with keyNew().

Some data structures need to lock the key (most likely its name), so that the ordering does not get confused.

Parameters

key	which name should be locked

See also: keyNew(), keyDup(), ksAppendKey()

Return values

>0	the bits that were successfully locked
0	if everything was locked before
-1	if it could not be locked (nullpointer)

◆ keyNew()

Key* keyNew	(	const char *	name,
			...
	)

A practical way to fully create a Key object in one step.

To just get a key object, simple do:

Key *k = keyNew("/", KEY_END);
// work with it
keyDel (k);

keyNew() allocates memory for a key object and keyDel() cleans everything up.

We can also give an empty key name and a KEY_END tag with the same effect as before:

Key *k =keyNew("", KEY_END); // Has the same effect as above
// work with it
keyDel (k);

But we can also give the key a proper name right from the start:

// Create and initialize a key with a name and nothing else
Key *k=keyNew("user:/some/example", KEY_END);
// work with it
keyDel (k);

If you want the key object to contain a name, value, comment and other meta info read on.

Note: When you already have a key with similar properties its easier to keyDup() the key.

You can call keyNew() in many different ways depending on the attribute tags you pass as parameters. Tags are represented as elektraKeyFlags values, and tell keyNew() which Key attribute comes next. The Key attribute tags are the following:

KEY_VALUE
Next parameter is a pointer to the value that will be used. If no KEY_BINARY was used before, a string is assumed.
// Create and initialize a key with a name and nothing else
Key *k=keyNew("user:/tmp/ex0",
KEY_VALUE, "some data", // set a string value
KEY_END); // end of args
KEY_SIZE
Define a maximum length of the value. This is only used when setting a binary key.
// Create and initialize a key with a name and nothing else
Key *k=keyNew("user:/tmp/ex1",
KEY_SIZE, 4, // has no effect on strings
KEY_VALUE, "some data", // set a string value
KEY_END); // end of args
KEY_META
Next two parameter is a metaname and a metavalue. See keySetMeta().
Key *k=keyNew("user:/tmp/ex3",
KEY_META, "comment", "a comment", // with a comment
KEY_META, "owner", "root", // and an owner
KEY_META, "special", "yes", // and any other metadata
KEY_END); // end of args
KEY_END
Must be the last parameter passed to keyNew(). It is always required, unless the keyName is 0.
KEY_FLAGS
Bitwise disjunction of flags, which don't require one or more values. recommended way to set multiple flags. overrides previously defined flags.
Key *k=keyNew("user:/tmp/ex3",
KEY_BINARY, // binary key
KEY_SIZE, 7, // assume binary length 7
KEY_VALUE, "some data", // value that will be truncated in 7 bytes
KEY_END); // end of args
KEY_BINARY
Allows one to change the key to a binary key. Make sure that you also pass KEY_SIZE before you set the value. Otherwise it will be cut off with first \0 in the string. So this flag toggle from keySetString() to keySetBinary(). If no value (nor size) is given, it will be a NULL key.
// Create and initialize a key with a name and nothing else
Key *k=keyNew("user:/tmp/ex2",
KEY_BINARY,
KEY_SIZE, 4, // now the size is important
KEY_VALUE, "some data", // sets the binary value ("some")
KEY_END); // end of args

Deprecated:

The flags below are deprecated and KEY_META should be preferred. They remain some time, however, for compatibility:

KEY_COMMENT
Next parameter is a comment. See keySetComment().
Key *k=keyNew("user:/tmp/ex4",
KEY_BINARY, // key type
KEY_SIZE, 7, // assume binary length 7
KEY_VALUE, "some data", // value that will be truncated in 7 bytes
KEY_COMMENT, "value is truncated",
KEY_END); // end of args

Parameters

name	a valid name to the key, or NULL to get a simple initialized, but really empty, object

See also: keyDel()

Returns: a pointer to a new allocated and initialized Key object.

Return values

NULL	on allocation error or if an invalid `name` was passed (see keySetName()).

Modules

Macros

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ KDB_PATH_ESCAPE

◆ KDB_PATH_SEPARATOR

Enumeration Type Documentation

◆ elektraCopyFlags

◆ elektraKeyFlags

◆ elektraLockFlags

◆ elektraNamespace

Function Documentation

◆ keyClear()

◆ keyCopy()

◆ keyDecRef()

◆ keyDel()

◆ keyGetRef()

◆ keyIncRef()

◆ keyIsLocked()

◆ keyLock()

◆ keyNew()