Subject: [Boost-commit] svn:boost r72792 - sandbox/SOC/2011/checks/boost/checks
From: pierre.talbot.6114_at_[hidden]
Date: 2011-06-29 08:53:49
Author: trademark
Date: 2011-06-29 08:53:48 EDT (Wed, 29 Jun 2011)
New Revision: 72792
URL: http://svn.boost.org/trac/boost/changeset/72792
Log:
Add a function to compute the check digit with the luhn algorithm
Minor corrections of the check_luhn function
Text files modified:
sandbox/SOC/2011/checks/boost/checks/modulus.hpp | 98 ++++++++++++++++++++++++++++++++++++---
1 files changed, 90 insertions(+), 8 deletions(-)
Modified: sandbox/SOC/2011/checks/boost/checks/modulus.hpp
==============================================================================
--- sandbox/SOC/2011/checks/boost/checks/modulus.hpp (original)
+++ sandbox/SOC/2011/checks/boost/checks/modulus.hpp 2011-06-29 08:53:48 EDT (Wed, 29 Jun 2011)
@@ -24,7 +24,7 @@
template <typename In>
inline bool check_luhn(In &begin, const In &end, unsigned int nbr_digits)
{
- // If the number of digits isn't given (equal to 0), we compute it.
+ // If the number of digits isn't given (equal to 0), we count these.
if(!nbr_digits)
{
In iter = begin;
@@ -34,7 +34,7 @@
++nbr_digits;
++iter;
}
- // Return false if there is no digits in the expression given.
+ // Return false if there is no digit in the expression given.
if(!nbr_digits)
{
begin = end;
@@ -42,6 +42,10 @@
}
}
int sum = 0,v;
+ /* We start with the leftmost digit and we multiply by two
+ * if the total number of digit is even. We alternate the multiplication
+ * for all the digits. We subtract 9 from the digit greater than 9
+ * after the multiplication. */
while(nbr_digits > 0 && begin != end)
{
if(*begin >= '0' && *begin <= '9')
@@ -49,9 +53,86 @@
++begin;
}
// Return true if the number of digit is equal to the number specified and the sum is valid.
- return !nbr_digits && sum % 10 ;
+ return !nbr_digits && !(sum % 10) ;
}
+/** Calculate the check digit of the number provided with the Luhn algorithm.
+ * \tparam Iterator which represents the beginning or the ending of a sequence of character.
+ * \tparam unsigned int which represents a size.
+ * \param [in] begin Represents the beginning of the sequence to check.
+ * \param [in] end Represents one off the limit of the sequence to check.
+ * \param [unsigned int] nbr_digits Represents the number of digits on which the Luhn algorithm will operate. If the size is < 1, the luhn algorithm will calculate the check digit with all the digit encountered.
+ * \pre begin and end are valid initialized iterators. They represent a sequence of character encoded in big-endian mode in a format compatible with the 7 bits ASCII.
+ * \post begin is equal to the position of the check digit plus one if the expression provided is correct, otherwise is equal to end.
+ * \result 0 is returned if the expression given have not nbr_digits (or 0 digit if nbr_digits is equal to 0). Otherwise the ASCII character of check digit is returned.
+ */
+template <typename Out, typename In>
+inline Out compute_luhn(In &begin, const In &end, unsigned int nbr_digits)
+{
+ // If the number of digits isn't given (equal to 0), we count these.
+ if(!nbr_digits)
+ {
+ In iter = begin;
+ while(iter != end)
+ {
+ if(*iter >= '0' && *iter <= '9')
+ ++nbr_digits;
+ ++iter;
+ }
+ // Return 0 if there is no digit in the expression given.
+ if(!nbr_digits)
+ {
+ begin = end;
+ return 0;
+ }
+ }
+ int sum = 0,v;
+ /* We start with the leftmost digit and we multiply by two
+ * if the total number of digit is even. We alternate the multiplication
+ * for all the digits. We subtract 9 from the digit greater than 9
+ * after the multiplication. */
+ while(nbr_digits > 0 && begin != end)
+ {
+ if(*begin >= '0' && *begin <= '9')
+ sum += (v= (*begin & 15) << (nbr_digits--&1)) - 9 * (v>9);
+ ++begin;
+ }
+ return (10 - sum % 10) % 10 + '0';
+}
+
+template <typename In>
+inline char compute_luhn(In &begin, const In &end, unsigned int nbr_digits)
+{
+ // If the number of digits isn't given (equal to 0), we count these.
+ if(!nbr_digits)
+ {
+ In iter = begin;
+ while(iter != end)
+ {
+ if(*iter >= '0' && *iter <= '9')
+ ++nbr_digits;
+ ++iter;
+ }
+ // Return 0 if there is no digit in the expression given.
+ if(!nbr_digits)
+ {
+ begin = end;
+ return 0;
+ }
+ }
+ int sum = 0,v;
+ /* We start with the leftmost digit and we multiply by two
+ * if the total number of digit is odd. We alternate the multiplication
+ * for all the digits. We subtract 9 from the digit greater than 9
+ * after the multiplication. */
+ while(nbr_digits > 0 && begin != end)
+ {
+ if(*begin >= '0' && *begin <= '9')
+ sum += (v= (*begin & 15) << (nbr_digits--&1)) - 9 * (v>9);
+ ++begin;
+ }
+ return (10 - sum % 10) % 10 + '0';
+}
/** Validate the check digit of the number provided with the modulus 11 algorithm.
* \tparam Iterator which represents the beginning or the ending of a sequence of character.
* \tparam unsigned int which represents a size.
@@ -65,7 +146,7 @@
template <typename In>
inline bool check_mod11(In &begin, const In end, unsigned int nbr_digits)
{
- // If the number of digits isn't given (equal to 0), we compute it.
+ // If the number of digits isn't given (equal to 0), we count these.
if(!nbr_digits)
{
In iter = begin;
@@ -75,7 +156,7 @@
++nbr_digits;
++iter;
}
- // Return false if there is no digits in the expression given.
+ // Return false if there is no digit in the expression given.
if(!nbr_digits)
{
begin = end;
@@ -83,14 +164,15 @@
}
}
int sum = 0;
- // Sum the n-1 first digit with a weigth of n
+ // Sum the n-1 first digit with a weigth of n. (The weigth is the contribution
+ // of a digit to the final sum).
while(nbr_digits > 1 && iter != end)
{
if(*begin >= '0' && *begin <= '9')
sum += *begin & 15 * nbr_digits--;
++begin;
}
- // Add the check digit to the sum (add 10 if the check digit equals 'x' or 'X')
+ // Add the check digit to the sum (add 10 if the check digit equals 'x' or 'X').
while(begin != end)
{
if(*begin >= '0' && *begin <= '9')
@@ -109,7 +191,7 @@
++iter;
}
// Return true if the number of digit is equal to the number specified and the sum is valid.
- return !nbr_digits && sum % 11;
+ return !nbr_digits && !(sum % 11);
}
template <class In>