A keyset holds together a set of keys.
#include <keyset.hpp>
KeySet ()
KeySet (ckdb::KeySet *k)
KeySet (const KeySet &other)
KeySet (size_t alloc, va_list ap)
Create a new keyset. KeySet (size_t alloc,...)
Create a new keyset. ~KeySet ()
Deconstruct a keyset. ckdb::KeySet * release ()
ckdb::KeySet * getKeySet () const
Passes out the raw keyset pointer. void setKeySet (ckdb::KeySet *k)
Take ownership of passed keyset. KeySet & operator= (KeySet const &other)
ssize_t size () const
The size of the keyset. ckdb::KeySet * dup () const
Duplicate a keyset. void copy (const KeySet &other)
Copy a keyset. void clear ()
Clear the keyset. ssize_t append (const Key &toAppend)
append a key ssize_t append (const KeySet &toAppend)
append a keyset Key head () const
Key tail () const
void rewind () const
Key next () const
Key current () const
void setCursor (cursor_t cursor) const
cursor_t getCursor () const
Key pop ()
KeySet cut (Key k)
Key lookup (const Key &k, const option_t options=KDB_O_NONE) const
Key lookup (std::string const &name, const option_t options=KDB_O_NONE) const
Lookup a key by name. Key at (cursor_t pos) const
Lookup a key by index.
A keyset holds together a set of keys.
Methods to manipulate KeySets. A KeySet is a sorted set of keys. So the correct name actually would be KeyMap.
With ksNew() you can create a new KeySet.
You can add keys with ksAppendKey() in the keyset. Using ksAppend() you can append a whole keyset.
Note:
Because the key is not copied, also the pointer to the current metadata keyNextMeta() will be shared.
ksGetSize() tells you the current size of the keyset.
With ksRewind() and ksNext() you can navigate through the keyset. Don't expect any particular order, but it is assured that you will get every key of the set.
KeySets have an internal cursor . This is used for ksLookup() and kdbSet().
KeySet has a fundamental meaning inside 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. With ksLookupByName() it is possible to fetch easily specific keys out of the list of keys.
You can easily create and iterate keys:
#include <kdb.h>
// 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.
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 a various 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 KEY_END.
So, terminate with ksNew(0) or ksNew(20, ..., KS_END)
For most uses
KeySet *keys = ksNew(0); // work with it ksDel (keys);
goes ok, the alloc size will be 16, defined in kdbprivate.h. The alloc size will be doubled whenever size reaches alloc size, so it also performs out large keysets.
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 normally need about 12 up to 15 keys), use:
KeySet * keys = ksNew (15,
keyNew ("user/sw/app/fixedConfiguration/key01", KEY_SWITCH_VALUE, "value01", 0),
keyNew ("user/sw/app/fixedConfiguration/key02", KEY_SWITCH_VALUE, "value02", 0),
keyNew ("user/sw/app/fixedConfiguration/key03", KEY_SWITCH_VALUE, "value03", 0),
// ...
keyNew ("user/sw/app/fixedConfiguration/key15", KEY_SWITCH_VALUE, "value15", 0),
KS_END);
// work with it
ksDel (keys);
If you start having 3 keys, and your application needs approximately 200-500 keys, you can use:
KeySet * config = ksNew (500,
keyNew ("user/sw/app/fixedConfiguration/key1", KEY_SWITCH_VALUE, "value1", 0),
keyNew ("user/sw/app/fixedConfiguration/key2", KEY_SWITCH_VALUE, "value2", 0),
keyNew ("user/sw/app/fixedConfiguration/key3", KEY_SWITCH_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.
Due to ABI compatibility, the KeySet structure is only declared in kdb.h, and not defined. So you can only declare pointers to KeySets in your program. See http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html#AEN135
See also:
ksDel() to free the KeySet afterwards
ksDup() to duplicate an existing KeySet
Parameters:
alloc gives a hint for the size how many Keys may be stored initially
Returns:
a ready to use KeySet object
0 on memory error
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()
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.
See also:
dup
Create a new keyset.
Parameters:
alloc minimum number of keys to allocate
ap variable arguments list
Allocate, initialize and return a new KeySet object.
Objects created with ksNew() must be destroyed with ksDel().
You can use a various 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 KEY_END.
So, terminate with ksNew(0) or ksNew(20, ..., KS_END)
For most uses
KeySet *keys = ksNew(0); // work with it ksDel (keys);
goes ok, the alloc size will be 16, defined in kdbprivate.h. The alloc size will be doubled whenever size reaches alloc size, so it also performs out large keysets.
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 normally need about 12 up to 15 keys), use:
KeySet * keys = ksNew (15,
keyNew ("user/sw/app/fixedConfiguration/key01", KEY_SWITCH_VALUE, "value01", 0),
keyNew ("user/sw/app/fixedConfiguration/key02", KEY_SWITCH_VALUE, "value02", 0),
keyNew ("user/sw/app/fixedConfiguration/key03", KEY_SWITCH_VALUE, "value03", 0),
// ...
keyNew ("user/sw/app/fixedConfiguration/key15", KEY_SWITCH_VALUE, "value15", 0),
KS_END);
// work with it
ksDel (keys);
If you start having 3 keys, and your application needs approximately 200-500 keys, you can use:
KeySet * config = ksNew (500,
keyNew ("user/sw/app/fixedConfiguration/key1", KEY_SWITCH_VALUE, "value1", 0),
keyNew ("user/sw/app/fixedConfiguration/key2", KEY_SWITCH_VALUE, "value2", 0),
keyNew ("user/sw/app/fixedConfiguration/key3", KEY_SWITCH_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.
Due to ABI compatibility, the KeySet structure is only declared in kdb.h, and not defined. So you can only declare pointers to KeySets in your program. See http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html#AEN135
See also:
ksDel() to free the KeySet afterwards
ksDup() to duplicate an existing KeySet
Parameters:
alloc gives a hint for the size how many Keys may be stored initially
Returns:
a ready to use KeySet object
0 on memory error
Precondition:
caller must call va_start and va_end
va the list of arguments
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 a various 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 KEY_END.
So, terminate with ksNew(0) or ksNew(20, ..., KS_END)
For most uses
KeySet *keys = ksNew(0); // work with it ksDel (keys);
goes ok, the alloc size will be 16, defined in kdbprivate.h. The alloc size will be doubled whenever size reaches alloc size, so it also performs out large keysets.
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 normally need about 12 up to 15 keys), use:
KeySet * keys = ksNew (15,
keyNew ("user/sw/app/fixedConfiguration/key01", KEY_SWITCH_VALUE, "value01", 0),
keyNew ("user/sw/app/fixedConfiguration/key02", KEY_SWITCH_VALUE, "value02", 0),
keyNew ("user/sw/app/fixedConfiguration/key03", KEY_SWITCH_VALUE, "value03", 0),
// ...
keyNew ("user/sw/app/fixedConfiguration/key15", KEY_SWITCH_VALUE, "value15", 0),
KS_END);
// work with it
ksDel (keys);
If you start having 3 keys, and your application needs approximately 200-500 keys, you can use:
KeySet * config = ksNew (500,
keyNew ("user/sw/app/fixedConfiguration/key1", KEY_SWITCH_VALUE, "value1", 0),
keyNew ("user/sw/app/fixedConfiguration/key2", KEY_SWITCH_VALUE, "value2", 0),
keyNew ("user/sw/app/fixedConfiguration/key3", KEY_SWITCH_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.
Due to ABI compatibility, the KeySet structure is only declared in kdb.h, and not defined. So you can only declare pointers to KeySets in your program. See http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html#AEN135
See also:
ksDel() to free the KeySet afterwards
ksDup() to duplicate an existing KeySet
Parameters:
alloc gives a hint for the size how many Keys may be stored initially
Returns:
a ready to use KeySet object
0 on memory error
Precondition:
caller must call va_start and va_end
va the list of arguments
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 free()s the release the KeySet object memory (that was previously allocated by ksNew()).
Parameters:
ks the keyset object to work with
Returns:
0 when the keyset was freed
-1 on null pointer
See also:
ksNew()
append a key
Parameters:
toAppend key to append
Returns:
number of keys in the keyset
Appends a Key to the end of ks.
A pointer to the key will be stored, and not a private copy. So a future ksDel() on ks may keyDel() the toAppend object, see keyGetRef().
The reference counter of the key will be incremented, and thus toAppend is not const.
Note:
Because the key is not copied, also the pointer to the current metadata keyNextMeta() will be shared.
If the keyname already existed, it will be replaced with the new key.
The KeySet internal cursor will be set to the new key.
It is save to use ksAppendKey(ks, keyNew(..)).
Returns:
the size of the KeySet after insertion
-1 on NULL pointers
-1 if insertion failed, 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 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
-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()
Lookup a key by index.
Parameters:
pos cursor position
Returns:
the found key
Clear the keyset. Keyset will have no keys afterwards.
Copy a keyset.
Parameters:
other other keyset to copy
Copy a keyset.
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 a existing keyset, for that this function exists.
You can also use it to clear a keyset when you pass a NULL pointer as source.
Note that 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
Returns:
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
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
0 on NULL pointer
See also:
ksNext(), ksRewind()
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. If not found an empty keyset is returned.
The cursor will stay at the same key as it was before. If the cursor was inside the region of cutted (moved) keys, the cursor will be set to the key before the cutpoint.
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
Duplicate a keyset.
Returns:
a copy of the keys
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 there reference counter is updated, so both keysets need ksDel().
Parameters:
source has to be an initializised source KeySet
Returns:
a flat copy of source on success
0 on NULL pointer
See also:
ksNew(), ksDel()
keyDup() for Key duplication
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.
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);
}
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().
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()
Passes out the raw keyset pointer.
Returns:
pointer to internal ckdb KeySet
See also:
release()
setKeySet()
Returns:
alphabetical first key
Return the first key in the KeySet.
The KeySets cursor will not be effected.
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
0 on NULL pointer or empty keyset
See also:
ksTail() for the last Key
ksRewind(), ksCurrent() and ksNext() for iterating over the KeySet
Look for a Key contained in ks that matches the name of the key.
ksLookup() is designed to let you work with entirely pre-loaded KeySets, so instead of kdbGetKey(), key by key, the idea is to fully kdbGet() for your application root key and process it all at once with ksLookup().
This function is very efficient by using binary search. Together with kdbGet() which can you load the whole configuration with only some communication to backends you can write very effective but short code for configuration.
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 is done if the first character is a /. This leads to ignoring the prefix like system/ and user/.
if (kdbGet(handle, "user/myapp", myConfig, 0 ) == -1)
errorHandler ("Could not get Keys");
if (kdbGet(handle, "system/myapp", myConfig, 0 ) == -1)
errorHandler ("Could not get Keys");
if ((myKey = ksLookup(myConfig, key, 0)) == NULL)
errorHandler ("Could not Lookup Key");
This is the way multi user Programs should get there 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.
When KDB_O_NOALL is set the keyset will be only searched from ksCurrent() to ksTail(). You need to ksRewind() the keyset yourself. ksCurrent() is always set properly after searching a key, so you can go on searching another key after the found key.
When KDB_O_NOALL is not set the cursor will stay untouched and all keys are considered. A much more efficient binary search will be used then.
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().
You can solve this problem by using KDB_O_NOALL, risking you have to iterate n^2 instead of n.
The more elegant way is to separate the keyset you use for ksLookup() and ksAppendKey():
int f(KeySet *iterator, KeySet *lookup)
{
KeySet *append = ksNew (ksGetSize(lookup), KS_END);
Key *key;
Key *current;
ksRewind(iterator);
while (current=ksNext(iterator))
{
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);
}
Parameters:
ks where to look for
key the key object you are looking for
options some KDB_O_* option bits:
KDB_O_NOCASE
Lookup ignoring case.
KDB_O_WITHOWNER
Also consider correct owner.
KDB_O_NOALL
Only search from ksCurrent() to end of keyset, see above text.
KDB_O_POP
Pop the key which was found.
KDB_O_DEL
Delete the passed key.
Returns:
pointer to the Key found, 0 otherwise
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 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
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.
Parameters:
ks the keyset object to work with
Returns:
the new current Key
0 when the end is reached
0 on NULL pointer
See also:
ksRewind(), ksCurrent()
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.
Remove and return the last key of ks.
The reference counter will be decremented by one.
The KeySets cursor will not be effected 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);
ks2=ksNew(0);
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
NULL if ks is empty or on NULL pointer
Parameters:
ks KeySet to work with
See also:
ksAppendKey(), ksAppend()
commandList() for an example
If you don't want destruction of keyset at the end you can release the pointer.
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
Returns:
0 on success
-1 on NULL pointer
See also:
ksNext(), ksCurrent()
Set the KeySet internal cursor.
Use it to set the cursor to a stored position. ksCurrent() will then be the position which you got with.
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
Returns:
0 when the keyset is ksRewind()ed
1 otherwise
-1 on NULL pointer
See also:
ksNext(), ksGetCursor()
Take ownership of passed keyset.
Parameters:
k the keyset to take ownership from
See also:
release()
getKeySet()
The size of the keyset.
Returns:
the number of keys in the keyset
Returns:
alphabetical last key
Return the last key in the KeySet.
The KeySets cursor will not be effected.
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
0 on NULL pointer or empty keyset
See also:
ksHead() for the first Key
ksRewind(), ksCurrent() and ksNext() for iterating over the KeySet
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