I'm trying to add 00 for each byte array element that is missing, to explain it better, if lenght of an array is 20 and the string fills only 9 spaces (reversed), I need the rest 11 spaces to be 00. An example will explain it better.
This is my code so far:
var
dateAndTimeOfIssue, taxPayerId: Tarray<Byte>;
dateOfIssueMS, DOIReversed: int64;
begin
dateOfIssueMS := StrToInt64(MilliSecondsBetween(f.InvoiceRequest.dateAndTimeOfIssue,
UnixDateDelta).ToString);
ReverseBytes(@(dateofIssueMS), @(DOIReversed), SizeOf(dateofIssueMS));
setLength(dateAndTimeOfIssue, 8);
Move(DOIReversed, dateAndTimeOfIssue[0], SizeOf(DOIReversed));
// result of this byte array casted into hex string is
'0000313B23048B31' // which is correct
setlength(taxPayerId, 20);
taxPayerId := TEncoding.UTF8.GetBytes(F.MyCompany.taxpayerId);
// result of this byte array casted into hex string is
'303231313331363832' // and I need it to be
'0000000000000000000000303231313331363832'
What I am actually trying to achieve is add multiple byte arrays into one final array that will be sent to SmartCard, these are just the 2 arrays here for example (I'm using hexadecimal strings only to represent what the bytes look like because I have a full example of how it should be). APDU Commands are weird, thanks in advance.
The actual tax payer Id seems to be 9 characters: '021131682'. For a total length of 20 bytes you need 11 null bytes first in the ArrTaxPayerId array. So, with BufferSize=20, StrTaxPayerId='021131682' you can set the initial length of ArrTaxPayerId:
SetLength(ArrTaxPayerId, BufferSize - Length(StrTaxPayerId);
That will now hold 11 null bytes. Then you concatenate it with the bytes of the actual tax payer ID:
ArrTaxPayerId := ArrTaxPayerId + TEncoding.UTF8.GetBytes(StrTaxPayerId);
Then the final step is to convert the 20 byte ArrTaxPayerId to hex representation using BinToHex() which you already have the code for.
When I tried the above I got a result of 0000000000000000000000303231313331363832