User-defined typed lists

[ReneMiner]

Today I have some small example to store any list of UDT to some enumerated List-Index without the need of creating arrays for those list-elements because it uses local virtual variables mostly and hides your data in the endless depth of heap.
It uses one small global array to organize this. The array-size depends on count of lists * 16 bytes - so the array uses only 16 Bytes for one complete list, no matter how many elements it has.
Size of a list is limited by your memory and the count of elements per list which must not exceed 2^31-1 (&H7FFFFFFF)

UserLists-Unit comes with 9 Functions, short description:

First of all you'll have to create some list, therefore call

List_CreateNew(yourListIndex, sizeOf(yourType))
- will return value <> 0 if succeeds
(value is the associated index of Userlists-array)
thereafter you can add new elements to your list using:

List_AddElement(yourListIndex)
which will return a pointer to the new created element or 0 if fails

List_Exists(yourListIndex)
will return a value <> 0 if a list with yourListIndex exists
the number represents the index of Userlists-array which is assigned to yourListIndex

List_CurrentElement(yourListIndex)
will return a pointer to the current element of your list or 0 if fails

List_FirstElement(yourListIndex)
will return a pointer to the first element of your list and make this the current element of yourListIndex or 0 if fails

List_LastElement(yourListIndex)
will return a pointer to the last element of your list and make this the current element of yourListIndex or 0 if fails
List_NextElement(yourListIndex)
will return a pointer to the next element of your list and make this the current element of yourListIndex or 0 if fails
List_PreviousElement(yourListIndex)
will return a pointer to the previous element of your list and make this the current element of yourListIndex or 0 if fails

List_Reset(yourListIndex)
will set the current element of yourListIndex to 0 - so you are before the first element and can go through the list using for example
While List_NextElement(yourListIndex)
' do something with current element
Wend

' this is demonstration how to use
Uses "Console"

#INCLUDE "UserLists.tBasicU"

Type t_myType
  A As Long
  B As Byte
  C As String
End Type     

%myList1  = 333  ' can be any from 1 To &H7FFFFFFF
  
Function TBMain()

If List_CreateNew(%myList1, SizeOf(t_myType)) Then
  
  Local lType As t_myType At List_AddElement(%myList1)
  
  lType.A = 123
  lType.B = 1
  lType.C = "Hello"
  
  SetAt( lType, List_AddElement(%myList1) )
  
  lType.A = 345
  lType.B = 2
  lType.C = "World"

  SetAt( lType, List_AddElement(%myList1) )

  lType.A = 567
  lType.B = 3
  lType.C = "Nice weather today..."
  
  ' go through list without use of additional variables:
  
  List_Reset(%myList1)      ' set current element-index before first listed element
 
  While List_NextElement(%myList1)
    SetAt( lType, List_CurrentElement(%myList1) ) 
    PrintL lType.C
  Wend 
  PrintL
  
  ' now backward, needs a storage-var:
  DWord pElement = List_LastElement(%myList1)
  
  While pElement
    SetAt( lType, pElement)
    PrintL Str$(lType.A)
    pElement = List_PreviousElement(%myList1)
  Wend
  
  PrintL
  
  ' now total list- (create array of pointers):
  
  Long lListNumber = List_Exists(%myList1)
  Long i
  Local dElement(HEAP_Size(Userlists(lListNumber).Elements)/SizeOf(DWord)) As DWord At Userlists(lListNumber).Elements
  
  If UBound(dElement) Then
    For i = 1 To UBound(dElement)
      SetAt( lType, dElement(i) )
      PrintL Str$(lType.B)
    Next
  EndIf
EndIf


WaitKey   


End Function

and this is the Userlists.tBasicU, save next to the "main-file"

Type t_UserList
  UserID   As Long
  lSize    As Long
  Current  As Long 
  Elements As DWord
End Type

Dim Userlists() As t_UserList : ReDim Userlists(1)

' --------------------------------------------------------------------------
Function List_CreateNew(ByVal lID As Long, ByVal lSize As Long) As Long
  
  If lID < 1 Or lSize < 1 Then Return 0
  
  Local lList   As Long
  Local sID     As String = MKL$(lID)
  
  lList = Array Scan Userlists, Byte(UDT_ElementByte(Userlists(1).UserID),SizeOf(Long)), = sID
  If lList Then Return 0
 
  sID = MKL$(0)
 
  lList = Array Scan Userlists, Byte(UDT_ElementByte(Userlists(1).UserID),SizeOf(Long)), = sID
  If lList = 0 Then 
    ReDim Preserve Userlists(UBound(Userlists) + 1)
    lList = UBound(Userlists)
  EndIf
  
  With Userlists(lList)
    .UserID  = lID
    .lSize   = lSize
  End With
  
  Function = lList
  
End Function  
 
' --------------------------------------------------------------------------

Function List_Exists(ByVal lID As Long) As Long 
  
  Static sID As String 
  
  sID = MKL$(lID)
  Function = Array Scan Userlists, Byte(UDT_ElementByte(Userlists(1).UserID),SizeOf(Long)), = sID

End Function

' --------------------------------------------------------------------------

Function List_AddElement(ByVal lID As Long) As DWord
  
  Local lList As Long = List_Exists(lID)
  If Not lList Then Return 0
  
  Local sBuffer As String = String$(Userlists(lList).lSize, MKBYT$(0))
  Local pResult As DWord  = HEAP_AllocByStr(sBuffer)
  
  If Userlists(lList).Elements Then
    sBuffer = Peek$(Userlists(lList).Elements, HEAP_Size(Userlists(lList).Elements)) + MKDWD$(pResult)
    Userlists(lList).Elements = HEAP_Realloc(Userlists(lList).Elements, StrPtrLen(StrPtr(sBuffer)) )
    Poke$(Userlists(lList).Elements, sBuffer)
  Else
    Userlists(lList).Elements = HEAP_AllocByStr(MKDWD$(pResult))
  EndIf                      
  Userlists(lList).Current = HEAP_Size(Userlists(lList).Elements)/SizeOf(DWord)
  
  Function = pResult

End Function

' --------------------------------------------------------------------------

Function List_FirstElement(ByVal lID As Long) As DWord
  
  Local lList As Long = List_Exists(lID)
  If Not lList Then Return 0
  
  If Userlists(lList).Elements Then
    Userlists(lList).Current = 1
    Function = Peek(DWord, Userlists(lList).Elements) 
  EndIf
  
End Function

' --------------------------------------------------------------------------

Function List_NextElement(ByVal lID As Long) As DWord
  
  Local lList As Long = List_Exists(lID)
  If Not lList Then Return 0
  
  If Userlists(lList).Elements Then
    If HEAP_Size(Userlists(lList).Elements)/SizeOf(DWord) > Userlists(lList).Current Then
      Function = Peek(DWord, Userlists(lList).Elements + Userlists(lList).Current * SizeOf(DWord) )
      Userlists(lList).Current += 1
    EndIf
  EndIf
  
End Function
' --------------------------------------------------------------------------

Function List_LastElement(ByVal lID As Long) As DWord
  
  Local lList As Long = List_Exists(lID)
  If Not lList Then Return 0
  
  If Userlists(lList).Elements Then
    Userlists(lList).Current = HEAP_Size( Userlists(lList).Elements) / SizeOf(DWord)
    Function = Peek(DWord, Userlists(lList).Elements + HEAP_Size(Userlists(lList).Elements) - SizeOf(DWord) ) 
  EndIf
  
End Function
' --------------------------------------------------------------------------

Function List_PreviousElement(ByVal lID As Long) As DWord
  
  Local lList As Long = List_Exists(lID)
  If Not lList Then Return 0
  
  If Userlists(lList).Elements Then
    If Userlists(lList).Current > 1 Then
      Userlists(lList).Current -= 1
      Function = Peek(DWord, Userlists(lList).Elements + (Userlists(lList).Current - 1) * SizeOf(DWord) ) 
    EndIf 
  EndIf
  
End Function
' --------------------------------------------------------------------------

Function List_CurrentElement(ByVal lID As Long) As DWord
  
  Local lList As Long = List_Exists(lID)
  If Not lList Then Return 0
  
  If Userlists(lList).Elements Then 
    If Userlists(lList).Current Then
      If HEAP_Size(Userlists(lList).Elements)/SizeOf(DWord) >= Userlists(lList).Current Then
        Function = Peek(DWord, Userlists(lList).Elements + (Userlists(lList).Current - 1) * SizeOf(DWord) )
      EndIf
    EndIf
  EndIf
  
End Function

' --------------------------------------------------------------------------

Function List_Reset(ByVal lID As Long) As Boolean
  
  Local lList As Long = List_Exists(lID)
  If Not lList Then Return FALSE
  Userlists(lList).Current = 0
  Function = TRUE
  
End Function
' --------------------------------------------------------------------------

'Function List_GetElementCount(ByVal lID as Long) as Long
  
' Local lList As Long = List_Exists(lID)
'  If Not lList Then Return 0

' Function = HEAP_Size(Userlists(lList).Elements)/SizeOf(DWord)

'End Function

have fun!