Arrays In User Data Types

[Consolemu]

Hello everyone,

I'm not sure if this question has been asked before and if so my apologies.  I tried searching online for the topic but those solutions weren't necessarily applicable to what I'm looking for.  I'm working on a program for practice where I take a text file, read and parse the data into an array, then save the array to my own custom binary file.  This task is tricky in most languages but a breeze in C as far as creating a struct that contains an array that can be written to or read from a binary file.  But with QB when I try this code for example I get an error:

Type MyPalette
HeaderTag as String
    Colors(20) As integer

End Type

For as long as I've been coding off and on in Basic and QB especially I didn't know you couldn't simply create a fixed array in a custom data.  With binary files I'll typically create a data type with a header and variables where each variable in succession including large chunks of data can be organized into a contained array so I can write the entire custom data type to a binary file with one line of code.  Is this even possible with QB or is there any type of workaround?  I did glance at the new _MEM command but not too familiar with that either.

Thanks for reading and your input.

[justsomeguy]

Sorry to say, to my knowledge QB64 does not directly support that. However I have had a similar issue and have a couple of work arounds.

Two methods I have are to use STRINGS or to use _MEM's. They both have their pro and cons.

String method is the simpliest.

Code: (Select All)

' String Array Test

' Arrays must start at index 1



TYPE tUDT

  longArray AS STRING * 1028 ' arraysize * 4 + 4

END TYPE



DIM udt AS tUDT

DIM iter AS LONG



FOR iter = 1 TO 256

  SetArrayLong udt.longArray, iter, iter * 2000000

  PRINT iter; ": "; getArrayLong(udt.longArray, iter)

NEXT



FUNCTION getArrayLong& (s AS STRING, p AS LONG)

  IF p > 0 AND p * 4 + 4 <= LEN(s) THEN getArrayLong = CVL(MID$(s, p * 4, 4))

END FUNCTION



SUB SetArrayLong (s AS STRING, p AS LONG, v AS LONG)

  IF p > 0 AND p * 4 + 4 <= LEN(s) THEN MID$(s, p * 4) = MKL$(v)

END SUB



FUNCTION getArraySingle! (s AS STRING, p AS LONG)

  IF p > 0 AND p * 4 + 4 <= LEN(s) THEN getArraySingle = CVS(MID$(s, p * 4, 4))

END FUNCTION



SUB SetArraySingle (s AS STRING, p AS LONG, v AS SINGLE)

  IF p > 0 AND p * 4 + 4 <= LEN(s) THEN MID$(s, p * 4) = MKS$(v)

END SUB



FUNCTION getArrayInteger% (s AS STRING, p AS LONG)

  IF p > 0 AND p * 2 + 2 <= LEN(s) THEN getArrayInteger = CVI(MID$(s, p * 2, 2))

END FUNCTION



SUB SetArrayInteger (s AS STRING, p AS LONG, v AS INTEGER)

  IF p > 0 AND p * 2 + 2 <= LEN(s) THEN MID$(s, p * 2) = MKI$(v)

END SUB



FUNCTION getArrayDouble# (s AS STRING, p AS LONG)

  IF p > 0 AND p * 8 + 8 <= LEN(s) THEN getArrayDouble = CVL(MID$(s, p * 8, 8))

END FUNCTION



SUB SetArrayDouble (s AS STRING, p AS LONG, v AS DOUBLE)

  IF p > 0 AND p * 8 + 8 <= LEN(s) THEN MID$(s, p * 8) = MKD$(v)

END SUB

The demo above uses longs which is 4 bytes. Integers in QB64 are 2 bytes.

The _MEM method is a bit more complicated.

Code: (Select All)

' Program to create an arrays in a UDT

SCREEN 12: _FONT 8

_TITLE "UDT_ARRAYS.bas"

DIM AS LONG i

DIM AS DOUBLE v

CONST cMAXELEMENTS = 10



' set byte counts for the data types

CONST cDT_BYTE = 1

CONST cDT_INTEGER = 2

CONST cDT_LONG = 4

CONST cDT_SINGLE = 4

CONST cDT_DOUBLE = 8

CONST cDT_INTEGER64 = 8

CONST cDT_FLOAT = 32



TYPE tARRAYS

  UDT_Array0 AS _MEM ' Array of Doubles

  UDT_Array1 AS _MEM ' Array of Singles

  UDT_Array2 AS _MEM ' Array of Integers

END TYPE



DIM AS tARRAYS UDT



' initialize the array

createUDTArray UDT.UDT_Array0, cDT_DOUBLE, cMAXELEMENTS

createUDTArray UDT.UDT_Array1, cDT_SINGLE, cMAXELEMENTS

createUDTArray UDT.UDT_Array2, cDT_INTEGER, cMAXELEMENTS

PRINT "ARRAY Doubles      ARRAY Singles        ARRAY Integers"

' set the array to random values

PRINT "Create initial Values, Store them, and retrieve"

FOR i = 0 TO cMAXELEMENTS

  v = INT(RND * 5 * 100) / 100

  setElementDBL UDT.UDT_Array0, i, v

  PRINT USING "index: ##-> #.##    "; i; getElementDBL(UDT.UDT_Array0, i);

  v = INT(RND * 5 * 100) / 100

  setElementSIGL UDT.UDT_Array1, i, v

  PRINT USING "index: ##-> #.##    "; i; getElementSIGL(UDT.UDT_Array1, i);

  v = INT(RND * 5)

  setElementINT UDT.UDT_Array2, i, v

  PRINT USING "index: ##-> #.##"; i; getElementINT(UDT.UDT_Array2, i)

NEXT



'resize array

resizeUDTArray UDT.UDT_Array0, cDT_DOUBLE, cMAXELEMENTS * 2

resizeUDTArray UDT.UDT_Array1, cDT_SINGLE, cMAXELEMENTS * 2

resizeUDTArray UDT.UDT_Array2, cDT_INTEGER, cMAXELEMENTS * 2



' retrieve values from array

PRINT "Double the size of the array"

FOR i = 0 TO cMAXELEMENTS * 2

  PRINT USING "index: ##-> #.##    "; i; getElementDBL(UDT.UDT_Array0, i);

  PRINT USING "index: ##-> #.##    "; i; getElementSIGL(UDT.UDT_Array1, i);

  PRINT USING "index: ##-> #.##"; i; getElementINT(UDT.UDT_Array2, i)

NEXT



'resize array

resizeUDTArray UDT.UDT_Array0, cDT_DOUBLE, cMAXELEMENTS / 2

resizeUDTArray UDT.UDT_Array1, cDT_SINGLE, cMAXELEMENTS / 2

resizeUDTArray UDT.UDT_Array2, cDT_INTEGER, cMAXELEMENTS / 2



' retrieve values from array

PRINT "Half the size of the array"

FOR i = 0 TO cMAXELEMENTS / 2

  PRINT USING "index: ##-> #.##    "; i; getElementDBL(UDT.UDT_Array0, i);

  PRINT USING "index: ##-> #.##    "; i; getElementSIGL(UDT.UDT_Array1, i);

  PRINT USING "index: ##-> #.##"; i; getElementINT(UDT.UDT_Array2, i)

NEXT





SUB createUDTArray (o AS _MEM, dt AS LONG, size AS LONG)

  ' make array one larger than number of elements

  o = _MEMNEW((size + 1) * dt) ' 'dt' is the number of bytes in the datatype

END SUB



SUB resizeUDTArray (o AS _MEM, dt AS LONG, size AS LONG)

  DIM AS _MEM old

  DIM AS LONG iter

  ' Copy old _MEM to a temp _MEM

  old = o

  ' Create new array of the new size

  createUDTArray o, dt, size

  'clear new array

  iter = 0: DO WHILE iter < o.SIZE

    _MEMPUT o, o.OFFSET + iter, 0 AS _BYTE

  iter = iter + 1: LOOP

  ' Copy data from old array to new array

  iter = 0: DO WHILE iter < o.SIZE AND iter < old.SIZE

    _MEMPUT o, o.OFFSET + iter, _MEMGET(old, old.OFFSET + iter, _BYTE) AS _BYTE

  iter = iter + 1: LOOP

  ' free old array

  _MEMFREE old

END SUB



FUNCTION getElementBYTE%% (o AS _MEM, element AS LONG)

  getElementBYTE = _MEMGET(o, o.OFFSET + (element * cDT_BYTE), _BYTE)

END FUNCTION



SUB setElementBYTE (o AS _MEM, element AS LONG, v AS _BYTE)

  _MEMPUT o, o.OFFSET + (element * cDT_BYTE), v AS _BYTE

END SUB



FUNCTION getElementINT% (o AS _MEM, element AS LONG)

  getElementINT = _MEMGET(o, o.OFFSET + (element * cDT_INTEGER), INTEGER)

END FUNCTION



SUB setElementINT (o AS _MEM, element AS LONG, v AS INTEGER)

  _MEMPUT o, o.OFFSET + (element * cDT_INTEGER), v AS INTEGER

END SUB



FUNCTION getElementLNG& (o AS _MEM, element AS LONG)

  getElementLNG = _MEMGET(o, o.OFFSET + (element * cDT_LONG), LONG)

END FUNCTION



SUB setElementLNG (o AS _MEM, element AS LONG, v AS LONG)

  _MEMPUT o, o.OFFSET + (element * cDT_LONG), v AS LONG

END SUB



FUNCTION getElementSIGL! (o AS _MEM, element AS LONG)

  getElementSIGL = _MEMGET(o, o.OFFSET + (element * cDT_SINGLE), SINGLE)

END FUNCTION



SUB setElementSIGL (o AS _MEM, element AS LONG, v AS SINGLE)

  _MEMPUT o, o.OFFSET + (element * cDT_SINGLE), v AS SINGLE

END SUB



FUNCTION getElementDBL# (o AS _MEM, element AS LONG)

  getElementDBL = _MEMGET(o, o.OFFSET + (element * cDT_DOUBLE), DOUBLE)

END FUNCTION



SUB setElementDBL (o AS _MEM, element AS LONG, v AS DOUBLE)

  _MEMPUT o, o.OFFSET + (element * cDT_DOUBLE), v AS DOUBLE

END SUB



FUNCTION getElementINT64&& (o AS _MEM, element AS LONG)

  getElementINT64 = _MEMGET(o, o.OFFSET + (element * cDT_INTEGER64), _INTEGER64)

END FUNCTION



SUB setElementINT64 (o AS _MEM, element AS LONG, v AS _INTEGER64)

  _MEMPUT o, o.OFFSET + (element * cDT_INTEGER64), v AS _INTEGER64

END SUB



FUNCTION getElementFLT## (o AS _MEM, element AS LONG)

  getElementFLT = _MEMGET(o, o.OFFSET + (element * cDT_FLOAT), _FLOAT)

END FUNCTION



SUB setElementFLT (o AS _MEM, element AS LONG, v AS _FLOAT)

  _MEMPUT o, o.OFFSET + (element * cDT_FLOAT), v AS _FLOAT

END SUB

_MEM have to be initialized before use, but they can be resized.

[bplus]

To add to what justsomeguy said here is a demo for using a variable length string to hold an array of Long Values:

Code: (Select All)

Option _Explicit
' I modified this for LONG type only do one one for floats DOUBLE 2021-01-31  stored in handy
DefLng A-Z
ReDim i
Type t
    s As String
End Type
Dim v As t

For i = 10 To 0 Step -1
    setLong v.s, i, i ^ 2
Next i

For i = 0 To 10
    Print getLong&(v.s, i)
Next i

' just for kicks lets jump to 100
setLong v.s, 100, 100 ^ 2

' now check the index 90 to 100
For i = 90 To 100
    Print getLong&(v.s, i)
Next


Sub setLong (array$, index, value&) ' Luke's Method except option explicit requires mod, no variables needed for one type
    If Len(array$) < 4 * (index + 1) Then
        array$ = array$ + String$(4 * (index + 1) - Len(array$), Chr$(0))
    End If
    Mid$(array$, index * 4 + 1) = _MK$(Long, value&)
End Sub

Function getLong& (array$, index)
    getLong& = _CV(Long, Mid$(array$, index * 4 + 1, 4))
End Function

I also want to add the way to do variable length string arrays is to put a demilter like a comma if text that does not use commas between each item then I use:

You build the string anyway that you need just putting delimiter between each items and pull items out by item number ( this is also base 1 stuff ie the first item has index 1).

Code: (Select All)

'Description: Use Item$() Function to treat strings like arrays without having to use an array structure.
' This function does not throw a fit if you ask for an item number (index) it does not have, it just returns an empty string.
' In QB64, Functions can't return arrays through the function name, but they can return strings that the Item$() function can
' translate like an an array index.  nItem numbers are the same as Counting numbers positive integers starting at 1.
'  eg Item7$ = Item$(CommaDelimitedString$, 7, ",") 'get 7th Item in string
Function Item$ (s$, nItem As Long, delimiter$)
    Dim c As Long, d As Long, lastd As Long
    If Len(s$) = 0 Then Item$ = "": Exit Function
    lastd = 1: d = InStr(lastd, s$, delimiter$)
    While d > 0
        c = c + 1
        If c = nItem Then
            Item$ = Mid$(s$, lastd, d - lastd): Exit Function
        Else
            lastd = d + 1: d = InStr(lastd, s$, delimiter$)
        End If
    Wend
    c = c + 1
    If c <> nItem Then Item$ = "" Else Item$ = Mid$(s$, lastd, Len(s$))
End Function