Elektra
0.8.8
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A Key is the essential class that encapsulates key name , value and metainfo . More...
Modules | |
Basic Methods | |
Key construction and initialization methods. | |
Meta Info Manipulation Methods | |
Methods to do various operations on Key metainfo. | |
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. |
Enumerations | |
enum | keyswitch_t { KEY_NAME = 1, KEY_VALUE = 1<<1, KEY_OWNER = 1<<2, KEY_COMMENT = 1<<3, KEY_BINARY = 1<<4, KEY_UID = 1<<5, KEY_GID = 1<<6, KEY_MODE = 1<<7, KEY_ATIME = 1<<8, KEY_MTIME = 1<<9, KEY_CTIME = 1<<10, KEY_SIZE = 1<<11, KEY_DIR = 1<<14, KEY_END = 0 } |
Functions | |
Key * | keyNew (const char *name,...) |
Key * | keyDup (const Key *source) |
int | keyCopy (Key *dest, const Key *source) |
int | keyDel (Key *key) |
int | keyClear (Key *key) |
ssize_t | keyIncRef (Key *key) |
ssize_t | keyDecRef (Key *key) |
ssize_t | keyGetRef (const Key *key) |
A Key is the essential class that encapsulates key name , value and metainfo .
enum keyswitch_t |
Switches to denote the various Key attributes in methods throughout this library.
This enum switch provide a flag for every metadata in a key.
In case of keyNew() they give Information what Parameter comes next.
KEY_NAME |
Flag for the key name |
KEY_VALUE |
Flag for the key data |
KEY_OWNER |
Flag for the key user domain |
KEY_COMMENT |
Flag for the key comment |
KEY_BINARY |
Flag if the key is binary |
KEY_UID |
Flag for the key UID |
KEY_GID |
Flag for the key GID |
KEY_MODE |
Flag for the key permissions |
KEY_ATIME |
Flag for the key access time |
KEY_MTIME |
Flag for the key change time |
KEY_CTIME |
Flag for the key status change time |
KEY_SIZE |
Flag for maximum size to limit value |
KEY_DIR |
Flag for the key directories |
KEY_END |
Used as a parameter terminator to keyNew() |
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.
key | the key object to work with |
int keyCopy | ( | Key * | dest, |
const Key * | source | ||
) |
Copy or Clear a key.
Most often you may prefer keyDup() which allocates a new key and returns a duplication of another key.
But 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:
The reference counter will not be changed for both keys. Affiliation to keysets are also not affected.
When you pass a NULL-pointer as source the data of dest will be cleaned completely (except reference counter, see keyClear()) and you get a fresh dest key.
The meta data will be duplicated for the destination key. So it will not take much additional space, even with lots of metadata.
If you want to copy all metadata, but keep the old value you can use keyCopy() too.
dest | the key which will be written to |
source | the key which should be copied or NULL to clean the destination key |
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.
key | the key object to work with |
int keyDel | ( | Key * | key | ) |
A destructor for Key objects.
Every key created by keyNew() must be deleted with keyDel().
It is save 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.
key | the key object to delete |
Key* keyDup | ( | const Key * | source | ) |
Return a duplicate of a key.
Memory will be allocated as needed for dynamic properties.
The new key will not be member of any KeySet and will start with a new reference counter at 0. A subsequent keyDel() will delete the key.
Like for a new key after keyNew() a subsequent ksAppend() makes a KeySet to take care of the lifecycle of the key.
Duplication of keys should be preferred to keyNew(), because data like owner can be filled with a copy of the key instead of asking the environment. It can also be optimized in the checks, because the keyname is known to be valid.
source | has to be an initialized source Key |
ssize_t keyGetRef | ( | const Key * | key | ) |
Return how many references the key has.
The references will be incremented on successful calls to ksAppendKey() or ksAppend().
For your own applications you can use keyIncRef() and keyDecRef() for reference counting. Keys with zero references will be deleted when using keyDel().
key | the key object to work with |
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.
key | the key object to work with |
Key* keyNew | ( | const char * | name, |
... | |||
) |
A practical way to fully create a Key object in one step.
This function tries to mimic the C++ way for constructors.
To just get a key object, simple do:
If you want the key object to contain a name, value, comment and other meta info read on.
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. See http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html#AEN135
You can call it in many different ways depending on the attribute tags you pass as parameters. Tags are represented as the keyswitch_t values, and tell keyNew() which Key attribute comes next.
The simplest and minimum way to use it is with no tags, only a key name:
keyNew() allocates memory for a key object and cleans everything up. After that, it processes the given argument list.
The Key attribute tags are the following:
keyswitch_t::KEY_GID
keyName
is 0.The reference counter (see keyGetRef()) 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 keyInc()) and the key can't be be deleted by a keyDel().
If you increment only by one with keyInc() the same as said above is valid:
If you add the key to more keySets:
or use keyInc() more than once:
they key won't be deleted by a keyDel() as long refcounter is not 0.
The key's sync bit will always be set for any call, except:
name | a valid name to the key, or NULL to get a simple initialized, but really empty, object |
NULL | on malloc error or if an invalid name was passed (see keySetName()). |