NAME¶

kdb::KeySet - A keyset holds together a set of keys.

SYNOPSIS¶

#include <keyset.hpp>

Public Member Functions¶

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.

Detailed Description¶

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: 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.0, keyName (current));
}
ksDel (myConfig); // delete keyset and all keys appended

Invariant: Note:

Constructor & Destructor Documentation¶

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 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: Parameters: Returns:

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: See also:

kdb::KeySet::KeySet (const KeySet &other) [inline]¶

Duplicate a keyset. This keyset will be a duplicate of the other afterwards. Note: See also:

kdb::KeySet::KeySet (size_talloc, va_listap) [inline], [explicit]¶

Create a new keyset. Parameters: 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: Parameters: Returns: Precondition: va the list of arguments

kdb::KeySet::KeySet (size_talloc, ...) [inline], [explicit]¶

Create a new keyset. Parameters: 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: Parameters: Returns: Precondition: va the list of arguments

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 free()s the release the KeySet object memory (that was previously allocated by ksNew()). Parameters: Returns: See also:

Member Function Documentation¶

ssize_t kdb::KeySet::append (const Key &toAppend) [inline]¶

append a key Parameters: Returns: 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: 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: Parameters: See also:

ssize_t kdb::KeySet::append (const KeySet &toAppend) [inline]¶

append a keyset Parameters: Returns: 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: Postcondition: Returns: Parameters: See also:

Key kdb::KeySet::at (cursor_tpos) const [inline]¶

Lookup a key by index. Parameters: Returns:

void kdb::KeySet::clear () [inline]¶

Clear the keyset. Keyset will have no keys afterwards.

void kdb::KeySet::copy (const KeySet &other) [inline]¶

Copy a keyset. Parameters: 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:

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: Returns: See also:

Key kdb::KeySet::current () const [inline]¶

Return the current Key. The pointer is NULL if you reached the end or after ksRewind(). Note: Parameters: Returns: See also:

KeySet kdb::KeySet::cut ( Keyk) [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. 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: Return values: Parameters:

ckdb::KeySet * kdb::KeySet::dup () const [inline]¶

Duplicate a keyset. Returns: 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: Returns: See also:

cursor_t kdb::KeySet::getCursor () const [inline]¶

Get the KeySet internal cursor. Use it to get the cursor of the actual position. Warning:

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(). Note: Parameters: Returns: See also:

ckdb::KeySet * kdb::KeySet::getKeySet () const [inline]¶

Passes out the raw keyset pointer. Returns: See also:

Key kdb::KeySet::head () const [inline]¶

Returns: 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: Returns: See also:

Key kdb::KeySet::lookup (const Key &key, const option_toptions = KDB_O_NONE) const [inline]¶

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

Introduction¶

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.

Usage¶

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.

KDB_O_NOALL¶

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.

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: Warning: 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: Returns: See also: Note:

Key kdb::KeySet::lookup (std::string const &name, const option_toptions = KDB_O_NONE) const [inline]¶

Lookup a key by name. Parameters: Returns: See also: Note:

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: Parameters: Returns: See also:

KeySet & kdb::KeySet::operator= ( KeySet const &other) [inline]¶

Duplicate a keyset. This keyset will be a duplicate of the other afterwards. Note:

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 effected if it did not point to the popped key. Note:

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: Parameters: See also:

ckdb::KeySet * kdb::KeySet::release () [inline]¶

If you don't want destruction of keyset at the end you can release the pointer.

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: Returns: See also:

void kdb::KeySet::setCursor (cursor_tcursor) const [inline]¶

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:

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: Returns: See also:

void kdb::KeySet::setKeySet (ckdb::KeySet *k) [inline]¶

Take ownership of passed keyset. Parameters: See also:

ssize_t kdb::KeySet::size () const [inline]¶

The size of the keyset. Returns:

Key kdb::KeySet::tail () const [inline]¶

Returns: 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: Returns: See also:

Author¶

Generated automatically by Doxygen for Elektra from the source code.