Converting long hexadecimal string to decimal string
lazarus / 21-General

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arneolav · 2025-01-07 23:10

I had to convert this long hex string: 2809E6CD040000F4 to decimal;
Result of Rapidtables: 2885090804517306612:

I found the following example in Stackoverflow:
  https://stackoverflow.com/questions/74417788/delphi-converting-long-
hexadecimal-string-to-decimal-string


// Usage:  DecStr := ConvertToDecimal(s, '16' );
// It even works not only for hexadecimal (base 16) input but also for
others.

I tested on some more long hex strings, and all correspond with
Rapidtables

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  type
TArrayString= Array of String; procedure MinLen( var s: String; iLen:
Integer );begin while Length( s )< iLen do s:= '0'+ s;end;   //
Addition of multiple long numbersfunction Summe( aSummand:
TArrayString ): String;var iLenMax, iA, iPos, iSum, iAdvance:
Integer; c: Char;begin result:= '0'; case Length( aSummand ) of   0:
exit;  // Nothing to add at all   1: begin     result:= aSummand[Low(
aSummand )];  // Sum equals the only summand     exit;   end; end;  //
Find the longest text, then make all texts as long as the longest, //
so we can simply access an existing character at that
position. iLenMax:= 0; for iA:= Low( aSummand ) to High( aSummand ) do
begin   if Length( aSummand[iA] )> iLenMax then iLenMax:= Length(
aSummand[iA] ); end; for iA:= Low( aSummand ) to High( aSummand ) do
MinLen( aSummand[iA], iLenMax ); MinLen( result, iLenMax );  // All
have the same length: process from the least significant digit //
(right) to the most significant digit (left). for iPos:= iLenMax
downto 1 do begin   // Manual addition: write all numbers in one row,
then add single   // digits per row. Nobody will ever give this
function so many   // summands that the sum of single digits will come
near the Integer   // capacity.   iSum:= 0;   for iA:= Low( aSummand )
to High( aSummand ) do begin     Inc( iSum, Ord( aSummand[iA][iPos] )-
$30 );  // Add digit from each number   end;   Inc( iSum, Ord(
result[iPos] )- $30 );  // Also add result's digit from potential
previous carry    // Turn that Integer sum into text again, digit by
digit   iAdvance:= 0;  // Exceeding the current position if we need to
carry   while iSum> 0 do begin     c:= Chr( (iSum mod 10)+ $30 );  //
Only the rightmost digit     if iPos- iAdvance< 1 then begin  //
Outside the String?       result:= c+ result;  // Prepend     end else
begin       result[iPos- iAdvance]:= c;  // Set new digit in overall
sum     end;      iSum:= iSum div 10;  // This digit has been process,
go to next one     Inc( iAdvance );  // Not in the current position
anymore, but processing potential carries   end; end;end;     //
Multiplication of two long numbersfunction Produkt( s1, s2: String ):
String;var  iPos, iStep, iA, iNine: Integer;  aSummand, aStep:
TArrayString;begin  // For each digit of one factor we will make a
separate multiplication  SetLength( aSummand, Length( s1 ) );   //
This time it doesn't matter how long both numbers are: just again go 
// from least significant digit (right) to most significant digit
(left).  for iPos:= Length( s1 ) downto 1 do begin    iA:= Length( s1
)- iPos;  // Array index per digit    // As per our position the sum
must be shifted by 10: first (rightmost)    // digit needs no shift
(0), second needs one (10), third needs two (100)...    MinLen(
aSummand[iA], iA );     // Current digit    iStep:= Ord( s1[iPos] )-
$30;    case iStep of      0: ;  // Multiplication by 0 always results
in 0, an empty summand equals one of "0"      1: aSummand[iA]:= s2+
aSummand[iA];  // No multiplication needed, just prepend with factor 
 else      // Cheap multiplication: use addition with 2 to 9 times the
same summand      SetLength( aStep, iStep );      for iNine:= 0 to
iStep- 1 do aStep[iNine]:= s2;      aSummand[iA]:= Summe( aStep )+
aSummand[iA];  // Prepend sum, zeroes must be trailing    end;  end;  
// Now just add all sums that we got per digit  result:= Summe(
aSummand );end; // Convert base 2..36 long number into base 10 long
numberfunction ConvertToDecimal( sFrom: String; sBase: String= '16' ):
String;var sStep, sPos: String; cFrom: Char;// a: TArrayString; a:
TArrayString;begin SetLength( a, 2 ); a[0]:= '0';  // Overall sum =
result sPos:= '1';  // Current digit's power while Length( sFrom )> 0
do begin  // Process least significant digit (right)   cFrom:=
sFrom[Length( sFrom )];   case cFrom of  // For now at max base 36 is
supported, which includes hexadecimal     '0'.. '9': sStep:= cFrom;
 // Same as text     'A'.. 'Z': sStep:= IntToStr( Ord( cFrom )- $41+
10 );  // Turn "B" into "11"   end;   a[1]:= Produkt( sPos, sStep );
 // Multiply current digit's value by current position's power 
 a[0]:= Summe( a );  // Add both product and current overall result  
 sPos:= Produkt( sPos, sBase );  // Increase power to next digit
position   Delete( sFrom, Length( sFrom ), 1 );  // Remove rightmost
digit end; result:= a[0];end;  Good idea to test valid Hex in
front:function HexIsValid(s: string): Boolean;var  i: integer;begin 
Result := True;  for i := 1 to length(s) do    if not (s[i] in
['0'..'9','A'..'F','a'..'f']) then    begin      Result := False;    
exit;    end;end;

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jollytall · 2025-01-08 16:35

There is a good Wiki article with many options. Many support
conversion to different bases:
https://wiki.freepascal.org/BigInteger

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jamie · 2025-01-09 00:21

Interesting.

wouldn't using something that already exists in the libs be simpler or
did I miss something?

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.Button1Click(Sender: TObject);begin  Caption
:=Hex2Dec64('2809E6CD040000F4').ToString;end;                        
                             
Thet produces your number. include the "strUtils" unit.

jamie

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jamie · 2025-01-09 00:28

btw
 you don't need to use the "StrUtils" unit, I just find it has lots of
goodies in it.


You can use StrToInt64('$'+'your hex number')