188 lines
3.0 KiB
C
188 lines
3.0 KiB
C
/*
|
|
* PostgreSQL type definitions for ISBNs.
|
|
*
|
|
* $Id: isbn.c,v 1.1 1998/08/17 03:35:04 scrappy Exp $
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
|
|
#include <postgres.h>
|
|
#include <utils/palloc.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;
|
|
char *cp;
|
|
int count;
|
|
|
|
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));
|
|
}
|
|
|
|
/*
|
|
* eof
|
|
*/
|