postgresql/contrib/isbn_issn/isbn_issn.c
2001-11-05 17:46:40 +00:00

377 lines
5.6 KiB
C

/*
* PostgreSQL type definitions for ISBNs.
*
* $Id: isbn_issn.c,v 1.4 2001/11/05 17:46:23 momjian Exp $
*/
#include "postgres.h"
/*
* This is the internal storage format for ISBNs.
* NB: This is an intentional type pun with builtin type `char16'.
*/
typedef struct isbn
{
char num[13];
char pad[3];
} isbn;
/*
* Various forward declarations:
*/
isbn *isbn_in(char *str);
char *isbn_out(isbn * addr);
bool isbn_lt(isbn * a1, isbn * a2);
bool isbn_le(isbn * a1, isbn * a2);
bool isbn_eq(isbn * a1, isbn * a2);
bool isbn_ge(isbn * a1, isbn * a2);
bool isbn_gt(isbn * a1, isbn * a2);
bool isbn_ne(isbn * a1, isbn * a2);
int4 isbn_cmp(isbn * a1, isbn * a2);
int4 isbn_sum(char *str);
/*
* ISBN reader.
*/
isbn *
isbn_in(char *str)
{
isbn *result;
if (strlen(str) != 13)
{
elog(ERROR, "isbn_in: invalid ISBN \"%s\"", str);
return (NULL);
}
if (isbn_sum(str) != 0)
{
elog(ERROR, "isbn_in: purported ISBN \"%s\" failed checksum",
str);
return (NULL);
}
result = (isbn *) palloc(sizeof(isbn));
strncpy(result->num, str, 13);
memset(result->pad, ' ', 3);
return (result);
}
/*
* The ISBN checksum is defined as follows:
*
* Number the digits from 1 to 9 (call this N).
* Compute the sum, S, of N * D_N.
* The check digit, C, is the value which satisfies the equation
* S + 10*C === 0 (mod 11)
* The value 10 for C is written as `X'.
*
* For our purposes, we want the complete sum including the check
* digit; if this is zero, then the checksum passed. We also check
* the syntactic validity if the provided string, and return 12
* if any errors are found.
*/
int4
isbn_sum(char *str)
{
int4 sum = 0,
dashes = 0,
val;
int i;
for (i = 0; str[i] && i < 13; i++)
{
switch (str[i])
{
case '-':
if (++dashes > 3)
return 12;
continue;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
val = str[i] - '0';
break;
case 'X':
case 'x':
val = 10;
break;
default:
return 12;
}
sum += val * (i + 1 - dashes);
}
return (sum % 11);
}
/*
* ISBN output function.
*/
char *
isbn_out(isbn * num)
{
char *result;
if (num == NULL)
return (NULL);
result = (char *) palloc(14);
result[0] = '\0';
strncat(result, num->num, 13);
return (result);
}
/*
* Boolean tests for magnitude.
*/
bool
isbn_lt(isbn * a1, isbn * a2)
{
return (strncmp(a1->num, a2->num, 13) < 0);
};
bool
isbn_le(isbn * a1, isbn * a2)
{
return (strncmp(a1->num, a2->num, 13) <= 0);
};
bool
isbn_eq(isbn * a1, isbn * a2)
{
return (strncmp(a1->num, a2->num, 13) == 0);
};
bool
isbn_ge(isbn * a1, isbn * a2)
{
return (strncmp(a1->num, a2->num, 13) >= 0);
};
bool
isbn_gt(isbn * a1, isbn * a2)
{
return (strncmp(a1->num, a2->num, 13) > 0);
};
bool
isbn_ne(isbn * a1, isbn * a2)
{
return (strncmp(a1->num, a2->num, 13) != 0);
};
/*
* Comparison function for sorting:
*/
int4
isbn_cmp(isbn * a1, isbn * a2)
{
return (strncmp(a1->num, a2->num, 13));
}
/* ----------------------------- ISSN --------------------------- */
/*
* This is the internal storage format for ISSNs.
* NB: This is an intentional type pun with builtin type `char16'.
*/
typedef struct issn
{
char num[9];
char pad[7];
} issn;
/*
* Various forward declarations:
*/
issn *issn_in(char *str);
char *issn_out(issn * addr);
bool issn_lt(issn * a1, issn * a2);
bool issn_le(issn * a1, issn * a2);
bool issn_eq(issn * a1, issn * a2);
bool issn_ge(issn * a1, issn * a2);
bool issn_gt(issn * a1, issn * a2);
bool issn_ne(issn * a1, issn * a2);
int4 issn_cmp(issn * a1, issn * a2);
int4 issn_sum(char *str);
/*
* ISSN reader.
*/
issn *
issn_in(char *str)
{
issn *result;
if (strlen(str) != 9)
{
elog(ERROR, "issn_in: invalid ISSN \"%s\"", str);
return (NULL);
}
if (issn_sum(str) != 0)
{
elog(ERROR, "issn_in: purported ISSN \"%s\" failed checksum",
str);
return (NULL);
}
result = (issn *) palloc(sizeof(issn));
strncpy(result->num, str, 9);
memset(result->pad, ' ', 7);
return (result);
}
/*
* The ISSN checksum works just like the ISBN sum, only different
* (of course!).
* Here, the weights start at 8 and decrease.
*/
int4
issn_sum(char *str)
{
int4 sum = 0,
dashes = 0,
val;
int i;
for (i = 0; str[i] && i < 9; i++)
{
switch (str[i])
{
case '-':
if (++dashes > 1)
return 12;
continue;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
val = str[i] - '0';
break;
case 'X':
case 'x':
val = 10;
break;
default:
return 12;
}
sum += val * (8 - (i - dashes));
}
return (sum % 11);
}
/*
* ISSN output function.
*/
char *
issn_out(issn * num)
{
char *result;
if (num == NULL)
return (NULL);
result = (char *) palloc(14);
result[0] = '\0';
strncat(result, num->num, 9);
return (result);
}
/*
* Boolean tests for magnitude.
*/
bool
issn_lt(issn * a1, issn * a2)
{
return (strncmp(a1->num, a2->num, 9) < 0);
};
bool
issn_le(issn * a1, issn * a2)
{
return (strncmp(a1->num, a2->num, 9) <= 0);
};
bool
issn_eq(issn * a1, issn * a2)
{
return (strncmp(a1->num, a2->num, 9) == 0);
};
bool
issn_ge(issn * a1, issn * a2)
{
return (strncmp(a1->num, a2->num, 9) >= 0);
};
bool
issn_gt(issn * a1, issn * a2)
{
return (strncmp(a1->num, a2->num, 9) > 0);
};
bool
issn_ne(issn * a1, issn * a2)
{
return (strncmp(a1->num, a2->num, 9) != 0);
};
/*
* Comparison function for sorting:
*/
int4
issn_cmp(issn * a1, issn * a2)
{
return (strncmp(a1->num, a2->num, 9));
}
/*
* eof
*/