OpenEuphoria

Converting/Verifying ISBN numbers

• Posted by begin Jul 03, 2018
• 1045 views

hi,

i needed to verify and convert ISBN numbers. maybe someone can use the routines.

richard

-- Calculate an ISBN13-13 checkdigit from the first 12 digits in an ISBN13-13 string 
-- param: isbn - the first 12 digits of an ISBN13-13. 
-- return: checkdigit (last digit) for an ISBN13-13 
function genchksum13(string isbn) 
  integer oddNumbs = 0 
  integer evenNumbs = 0 
  integer checksum1 = 0 
  for i = 1 to 12 by 2 do 
    oddNumbs += (isbn[i]-48) 
  end for 
  for j = 2 to 12 by 2 do 
    evenNumbs += (isbn[j]-48) 
  end for 
  checksum1 = mod((oddNumbs + (evenNumbs * 3)), 10) 
  if checksum1 != 0 then 
    checksum1 = 10 - checksum1 
  end if 
  return to_string(checksum1) 
end function 
         
-- Calculate an ISBN13-10 checkdigit from the first 9 digits in an ISBN13-10 string 
-- param: isbn - the first 9 digits of an ISBN13-10. 
-- return: checkdigit (last digit) for an ISBN13-10 
function genchksum10(string isbn) 
   integer checkDigit = 0 
   for i = 1 to 9 do 
     checkDigit += ((10 - i + 1) *  (isbn[i]-48)) 
   end for 
   checkDigit = 11 - mod(checkDigit, 11) 
   string checksum1 = to_string(checkDigit) 
   if checkDigit = 10 then 
     checksum1 = "X" 
   else 
     if checkDigit = 11 then 
       checksum1 = "0" 
     end if 
   end if 
   return checksum1 
end function 
 
--Validate an ISBN13-10 using the checkdigit (last digit) 
--param: isbn - ISBN13-10 
function validISBN10(string isbn) 
  if upper(genchksum10(isbn[1..9])) = upper(isbn[10]&"") then 
    return true 
  else 
    return false 
  end if 
end function 
     
--Validate an ISBN13-13 using the checkdigit (last digit) 
--param: isbn - ISBN13-13 
function validISBN13(string isbn) 
  string checksum1 = genchksum13(isbn[1..12]) 
  if checksum1 = isbn[13]&"" then 
    return true 
  else 
    return false 
  end if 
end function 
 
-- Convert an ISBN13-10 to ISBN13-13 or ISBN13-13 to ISBN13-10. 
-- Note: Only ISBN13-13 that start with 978 can be converted to ISBN13-10, as ISBN13-13 begining with other 
-- digits will not result in a unique ISBN13-10 (i.e. they are not backward convertible) 
-- param: ISBN13-10 or ISBN13-13 
-- return: a string containing the ISBN13-10, ISBN13-13 or an error message 
function convertISBN(string isbn) 
    if length(isbn) = 13 then 
      if isbn[1..3] = "978" then 
        if validISBN13(isbn) = true then 
          return isbn[4..$-1] & genchksum10(isbn[4..$]) 
        else 
          return "Not a valid ISBN13" 
        end if 
      else 
        return "ISBN13-13 must begin with 978" 
      end if 
    elsif length(isbn) = 10 then 
      if isbn[1] = 'B' then 
        return isbn 
      end if 
      if validISBN10(isbn) then 
        return "978" & isbn[1..9] & genchksum13("978" & isbn[1..9]) 
      else 
        return "Not a valid ISBN10" 
      end if 
    else 
      return "" 
    end if 
end function 
 
--?validISBN13("9783442151479") 
--?validISBN10("3442151473") 
--?convertISBN("9783442151479") 
--?convertISBN("3442151473")