Utility Library

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Utility Library

Utility library is the home for all the OS functions which don't fit in the other libraries. Among the calls in utility library are calls to manage tags and tag lists, callback hooks, and some generic 32-bit math functions, all discussed below.

Data Structures

Splay Trees

Splay trees are a form of binary tree which organizes itself in response to insertions and searches. Whenever a search finds a specific tree node, that node is "pulled up" into the tree root, and the tree is subsequently reorganized. This reorganization is called "splaying" and has the effect of making the tree flatter, shortening the distances between the root and leaf nodes. Also, more frequently-used nodes will move more closely to the root of the tree during each splay operation. The more splay operations are performed, the more closely the tree will represent the frequency of the node accesses, and will eventually place the most frequently-used nodes close to the root of the tree. This self-organization makes splay trees well-suited for use in caches or dictionaries. Because search operations will modify the splay tree, you should always use an arbitration mechanism such as a Mutex if you share the same splay tree with several Tasks or Processes.

See Wikipedia for more generic information about splay trees.

CreateSplayTree()	Allocate a splay tree data structure.
DeleteSplayTree()	Free a splay tree and all its nodes.
FindSplayNode()	Search for a key in a splay tree.
InsertSplayNode()	Insert a new key into a splay tree.
RemoveSplayNode()	Remove a node from a splay tree.

Skip Lists

Skip lists combine linked lists with a look-ahead data structure which makes search and insertion operations efficient. You can add data in any particular order to the skip list, and the list will always take care of keeping that data stored in a specific order. The effort spent to maintain this order is small and grows slowly the more list items are added. Traversing the list is very fast and will always return the list items in sorted order. Retrieving specific list items is very efficient, too. Skip lists are useful if you need to be able to retrieve list items in a sorted order at any time while you are building the list. The drawback of skip lists is that the amount of memory required to maintain the list grows faster than the number of list items added.

See Wikipedia for more generic information about skip lists.

CreateSkipList()	Allocate a skip list data structure.
DeleteSkipList()	Free a skip list and all its nodes.
FindSkipNode()	Search for a key in a skip list.
GetFirstSkipNode()	Get a pointer to the first node of a skip list.
GetNextSkipNode()	Get a pointer to the following node in a skip list.
InsertSkipNode()	Insert a new key into a skip list.
RemoveSkipNode()	Remove a node from a skip list.

Function Reference

The tables which follow contain breif descriptions of the functions inside the utility library. See the SDK for details on each function call.

Tag Function Reference

The following are brief descriptions of the utility library functions which pertain to tags and tag lusts.

Function	Description
AllocSysObjectTags(ASOT_TAGLIST)	Allocate a TagItem array (or chain).
FreeSysObject(ASOT_TAGLIST)	Frees allocated TagItem lists.
CloneTagItems()	Copies a TagItem list.
RefreshTagItemClone()	Rejuvenates a clone from the original.
FindTagItem()	Scans TagItem list for a tag.
GetTagData()	Obtain data corresponding to tag.
NextTagItem()	Iterate TagItem lists.
TagInArray()	Check if a tag value appears in a Tag array.
FilterTagChanges()	Eliminate TagItems which specify no change.
FilterTagItems()	Remove selected items from a TagItem list.
MapTags()	Convert ti_Tag values in a list via map pairing.
PackBoolTags()	Builds a "Flag" word from a TagItem list.

Callback Hook Function Reference

The following are brief descriptions of the utility library functions which pertain to callback hooks.

Function	Description
CallHookPkt()	Call a standard callback Hook function.

International String Function Reference

The following are brief descriptions of the utility library functions which pertain to string operations using the international ASCII character set.

Function	Description
Stricmp()	Compare strings, case-insensitive.
Strnicmp()	Compare strings, case-insensitive, with specified length.
ToLower()	Convert a character to lower case.
ToUpper()	Convert a character to upper case.

Date Function Reference

The following are brief descriptions of the utility library functions which pertain to date conversion.

Function	Description
CheckDate()	Check the legality of a date.
Amiga2Date()	Calculate the date from a specified timestamp.
Date2Amiga()	Calculate the timestamp from a specified date.