Mega Code Archive
Converting Integers to Base n
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Title: Converting Integers to Base n
Question: How do I convert integers from Decimal to Base n and vice versa.
Answer:
unit BaseFunctions;
{Unit for conversion functions Dec_To_Base and Base_To_Dec.}
{These functions are designed to convert integers from Decimal to Base n}
{They can be used to create serial numbers for Compaq, etc.}
{See below for usage.}
{Written by Dave Murray, Nov 2000.}
interface
uses
SysUtils;
function Dec_To_Base(nBase, nDec_Value, Lead_Zeros:integer; cOmit:string):string;
function Base_To_Dec(nBase:integer;cBase_Value, cOmit:string):integer;
implementation
function Dec_To_Base(nBase, nDec_Value, Lead_Zeros:integer; cOmit:string):string;
{Function : converts decimal integer to base n, max = Base36
Parameters : nBase = base number, ie. Hex is base 16
nDec_Value = decimal to be converted
Lead_Zeros = min number of digits if leading zeros required
cOmit = chars to omit from base (eg. I,O,U,etc)
Returns : number in base n as string}
var
Base_PChar : PChar;
Base_String : string;
To_Del, Modulus, DivNo : integer;
temp_string : string;
i, nLen, Len_Base : integer;
begin
{initialise..}
Base_String := '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'; {max = Base36}
To_Del := 0;
Modulus := 0;
DivNo := nDec_Value;
result := '';
if (nBase 36) then nBase := 36; {max = Base36}
cOmit := UpperCase(cOmit);
{build string to fit specified base}
if not(cOmit = '') then begin
{iterate thru' ommited letters}
nLen := Length(cOmit);
for i := 1 to nLen do begin
To_Del := Pos(cOmit[i], Base_String); {find position of letter}
if (To_Del 0) then begin
{remove letter from base string}
Len_Base := Length(Base_String);
temp_string := Copy(Base_String, 0, To_Del - 1);
temp_string := temp_string + Copy(Base_String,To_Del + 1,Len_Base - To_Del);
Base_String := temp_string;
end; {if To_Del0..}
end; {for i..}
end; {if not cOmit=''..}
{ensure string is required length for base}
SetLength(Base_String, nBase);
Base_PChar := PChar(Base_String);
{divide decimal by base & iterate until zero to convert it}
while DivNo 0 do begin
Modulus := DivNo mod nBase; {remainder is next digit}
result := Base_PChar[Modulus] + result;
DivNo := DivNo div nBase;
end; {while..}
{fix zero value}
if (Length(result) = 0) then result := '0';
{add required leading zeros}
if (Length(result) for i := 1 to (Lead_Zeros - Length(result)) do result := '0' + result;
end; {function Dec_To_Base}
function Base_To_Dec(nBase:integer;cBase_Value, cOmit:string):integer;
{Function : converts base n integer to decimal, max = Base36
Parameters : nBase = base number, ie. Hex is base 16
cBase_Value = base n integer (as string) to be converted
cOmit = chars to omit from base (eg. I,O,U,etc)
Returns : number in decimal as string}
var
Base_PChar : PChar;
Base_String : string;
To_Del, Unit_Counter : integer;
temp_string : string;
i, nLen, Len_Base : integer;
begin
{initialise..}
Base_String := '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'; {max = Base36}
To_Del := 0;
Unit_Counter := nBase;
result := 0;
if (nBase 36) then nBase := 36; {max = Base36}
cOmit := UpperCase(cOmit);
cBase_Value := UpperCase(cBase_Value); {ensure uppercase letters}
{build string to fit specified base}
if not(cOmit = '') then begin
{iterate thru' ommited letters}
nLen := Length(cOmit);
for i := 1 to nLen do begin
To_Del := Pos(cOmit[i], Base_String); {find position of letter}
if (To_Del 0) then begin
{remove letter from base string}
Len_Base := Length(Base_String);
temp_string := Copy(Base_String, 0, To_Del - 1);
temp_string := temp_string + Copy(Base_String,To_Del + 1,Len_Base - To_Del);
Base_String := temp_string;
end; {if To_Del0..}
end; {for i..}
end; {if not cOmit=''..}
{ensure string is required length for base}
SetLength(Base_String, nBase);
Base_PChar := PChar(Base_String);
{iterate thru digits of base n value, each digit is a multiple of base n}
nLen := Length(cBase_Value);
if (nLen = 0) then result := 0 {fix zero value}
else begin
for i := 1 to nLen do begin
if (i = 1) then unit_counter := 1 {1st digit = units}
else if (i 1) then unit_counter := unit_counter * nBase; {multiples of base}
result := result
+ ((Pos(Copy(cBase_Value, (Length(cBase_Value)+1)-i, 1), Base_PChar) - 1)
* unit_counter);
end; {for i:=1..}
end; {else begin..}
end; {function Base_To_Dec}
end. {unit BaseFunctions}
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