haiku/docs/user/support/List.dox

// 
// Copyright 2007, Haiku Inc. All Rights Reserved.
//
// Distributed under the terms of the MIT License.
//
//
// Documentation by: 
//   Niels Sascha Reedijk <niels.reedijk@gmail.com
// Corresponds to:
//   /trunk/headers/os/support/List.h  rev 19972
//   /trunk/src/kits/support/List.cpp  rev 18649
//

/*!
  \file List.h
  \brief Defines the BList class.
*/

/*!
  \class BList
  \ingroup support
  \ingroup libbe
  \brief An ordered container that is designed to hold generic \c void * 
    objects.

  This class is designed to be used for a variety of tasks. Unlike similar
  implementations in other libraries, this class is not based on templates,
  and as such is inherently not typed. So it will be the job of the coder to
  make sure proper data will be entered, since the compiler cannot check this.

  BList contains a list of items that will grow and shrink depending on
  how much items are in it. So you will not have to do any of the
  memory management. Furthermore, it's ordered. Those properties make it
  useful in a whole range of situations, for example in the interface kit in 
  the BListView class.

  A note on ownership of the objects might come in handy. BList at no time
  assumes ownership of the objects, so removing items from the list will
  only remove those items from the list, it will not delete the item. In the
  same spirit you should also make sure that before you might delete an
  object that's in a list, you will remove it from the list first. 

  \warning This class is not thread-safe.

  The class implements methods to add and remove items, reorder items,
  retrieve items, querying for items and some advanced methods which let
  you perform a certain tasks to all the items of the list.
*/

/*!
  \fn BList::BList(int32 count = 20)
  \brief Create a new list with a number of empty slots.

  The memory management of this class allocates new memory per block. The
  \c count parameter can be tweaked to determine the size of those blocks.
  In general, if you know your list is only going to contain a fixed maximum
  number of items, pass that value. If you expect your list to have very few 
  items, it's probably safe to choose a low number. This is as to prevent the 
  list from taking up unneccesary memory. If you expect the list to contain a 
  large number of items, choose a higher value, since every time the memory is 
  full, all the items have to be copied into a new piece of allocated memory 
  which is an expensive operation.

  If you are unsure, you don't have to break your head over this. As long as 
  you don't use a lot of lists or as long as the list isn't used in one of the
  performance critical parts of the code, you are safe to go with the default
  value.

  \param count The size of the blocks of memory allocated.
*/

/*!
  \fn BList::BList(const BList& anotherList)
  \brief Copy constructor. Copy a complete list into this one.
*/

/*!
  \fn BList::~BList()
  \brief Destroy the list.

  Please note that as BList does not assume ownership of the objects,
  only the list will be freed, not the objects that are held in it.
*/

/*!
  \fn BList& BList::operator=(const BList &list)
  \brief Copy another list into this object.
*/

/*!
  \name Adding and removing items
*/

//! @{

/*!
  \fn bool BList::AddItem(void *item, int32 index)
  \brief Add an item at a certain position.

  \param item The item to add.
  \param index The place in the list.
  \retval true The item was added.
  \retval false Item was not added. Either the index was  negative or invalid,
    or resizing the list failed.
  \see AddItem(void *item)
*/

/*!
  \fn bool BList::AddItem(void *item)
  \brief Append an item to the list.

  \param item The item to add.
  \retval true The item was appended.
  \retval false Item was not appended, since resizing the list failed.
  \see AddItem(void *item, int32 index)
*/

/*!
  \fn bool BList::AddList(const BList *list, int32 index)
  \brief Add items from another list to this list at a certain position.

  Note that the \a list parameter is \c const, so the original list will not be
  altered.

  \param list The list to be added.
  \param index The position in the current list where the new item(s) should be
    put.
  \retval true The list was added. 
  \retval false Failed to insert the list, due to the fact that resizing our
    list failed. 
  \see AddList(const BList *list)
*/

/*!
  \fn bool BList::AddList(const BList *list)
  \brief Append a list to this list.

  Note that the \a list parameter is \c const, so the original list will not
  be altered.

  \param list The list to be appended.
  \retval true The list was appended. 
  \retval false Failed to append the list, due to the fact that resizing our
    list failed. 
  \see AddList(const BList *list, int32 index)
*/

/*!
  \fn bool BList::RemoveItem(void *item)
  \brief Remove an item from the list.

  \param item The item that should be removed.
  \retval true The item was found and removed.
  \retval false The item was not in this list and thus not removed.
  \see RemoveItem(int32 index)
*/

/*!
  \fn void * BList::RemoveItem(int32 index)
  \brief Remove the item at \a index from the list.

  \param index The item that should be removed.
  \return The pointer to the item that was removed, or \c NULL in case the
    index was invalid.
  \see RemoveItem(void *item)
*/

/*!
  \fn bool BList::RemoveItems(int32 index, int32 count)
  \brief Remove a number of items starting at a certain position.

  If the count parameter is larger than the number of items in the list,
  all the items from the offset to the end will be removed.

  \param index The offset in the list where removal should start.
  \param count The number of items to remove.
  \retval true Removal succeeded.
  \retval false Failed to remove the items because the index was invalid.
*/

/*!
  \fn bool BList::ReplaceItem(int32 index, void *newItem)
  \brief Replace a item with another one.

  \param index The offset in the list where to put the item.
  \param newItem The new item to put in the list.
  \retval true Item replaced.
  \retval false The index was invalid.
*/

/*!
  \fn void BList::MakeEmpty()
  \brief Clear all the items from the list.

  Please note that this does not free the items. 
*/

//! @}

/*!
  \name Reordering items
*/

//! @{

/*!
  \fn void BList::SortItems(int (*compareFunc)(const void *, const void *))
  \brief Sort the items with the use of a supplied comparison function.

  The function should take two \c const pointers as arguments and should return
  an integer.

  For an example, see the Compare(const BString *, const BString *) function. 
*/

/*!
  \fn bool BList::SwapItems(int32 indexA, int32 indexB)
  \brief Swap two items.

  \param indexA The first item.
  \param indexB The second item.
  \retval true Swap succeeded.
  \retval false Swap failed because one of the indexes were invalid.
*/

/*! 
  \fn bool BList::MoveItem(int32 fromIndex, int32 toIndex)
  \brief Move an item to a new place

  This moves a list item from posititon a to position b, moving the appropriate 
  block of list elements to make up for the move.  For example, in the array:
  \verbatim
A B C D E F G H I J
  \endverbatim

  Moveing 1(B)->6(G) would result in this:
  \verbatim
A C D E F G B H I J
  \endverbatim

  \param fromIndex The original location.
  \param toIndex The new location.
  \retval true Move succeeded.
  \retval false Move failed since the indexes were invalid.
*/

//! @}

/*!
  \name Retrieving items
*/

//! @{

/*!
  \fn void *BList::ItemAt(int32 index) const
  \brief Get an item.

  \param index The item to retrieve.
  \return A pointer to the item in that position, or \c NULL if the index is
    out of bounds.
  \see ItemAtFast(int32 index) const
*/

/*!
  \fn void *BList::FirstItem() const
  \brief Get the first item.
  
  \return A pointer to the first item, or \c NULL if the list is empty.
*/

/*!
  \fn void *BList::ItemAtFast(int32 index) const
  \brief Get an item.

  This method does not performs any boundary checks when it retrieves an item.
  Use this method in a performance critical area of your program where you are
  sure you won't get an invalid item.

  \return A pointer to the item.
*/

/*!
  \fn void *BList::LastItem() const
  \brief Get the last item.
  \return A pointer to the last item, or \c NULL if the list is empty.
*/

/*!
  \fn void *BList::Items() const
  \brief Return the internal list of objects.

  This method will return a pointer to the internal pointer list. This means
  you should be careful   what you are doing, since you are directly working
  with the internals of the class.

  It is definately not a good idea to make any changes to the list, since it
  will mess up the internal consistency. 

  \warning If there is anything you want for which you need the list of
    objects, please realize that that probably means that what you want to do
    is a bad idea to begin with. Avoid this method. The list of objects doesn't
    belong to you. Check if DoForEach() can help you.
  \return The internal list of pointers.
*/

//! @}

/*!
  \name Querying for items
*/

//! @{

/*!
  \fn bool BList::HasItem(void *item) const
  \brief Check if an item is in the list.
*/

/*!
  \fn int32 BList::IndexOf(void *item) const
  \brief Get the index of an item.

  \return The index of the item, or -1 when the item is not in the list.
*/

/*!
  \fn int32 BList::CountItems() const
  \brief Get the number of items in the list.
*/

/*!
  \fn bool BList::IsEmpty() const
  \brief Check if there are items in the list.
*/

//! @}

/*!
  \name Iterating over the list
*/

//! @{

/*!
  \fn void BList::DoForEach(bool (*func)(void* item))
  \brief Perform an action on every item in the list.

  If one of the actions on the items fails, meaning that the \a func function
  returned \c false, then the processing of the list will be stopped.

  \param func A function that takes a \c void * argument and returns a boolean.
*/

/*!
  \fn void BList::DoForEach(bool (*func)(void* item, void* arg2), void *arg2)
  \brief Perform an action on every item in the list with an argument.

  If one of the actions on the items fails, meaning that the \a func function
  returned \c false, then the processing of the list will be stopped.

  \param func A function with the first \c void * argument being the item,
    and the second \c void * being the argument that you supply. It should
    return a boolean value on whether it succeeded or not.
  \param arg2 An argument to supply to \a func.
*/

//! @}