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/*
* PostgreSQL type definitions for ISSNs.
*
* $Id: issn.c,v 1.3 2000/05/29 05:44:26 tgl Exp $
*/
#include <stdio.h>
#include <postgres.h>
#include <utils/palloc.h>
/*
* 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
*/
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