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Here is some more contrib-fodder, based on TIH's IP address type, for ISBN and ISSN identifiers (which I just happened to need to keep track of the things in my library).
188 lines
3.0 KiB
C
188 lines
3.0 KiB
C
/*
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* PostgreSQL type definitions for ISBNs.
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*
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* $Id: isbn.c,v 1.1 1998/08/17 03:35:04 scrappy Exp $
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*/
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#include <stdio.h>
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#include <postgres.h>
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#include <utils/palloc.h>
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/*
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* This is the internal storage format for ISBNs.
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* NB: This is an intentional type pun with builtin type `char16'.
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*/
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typedef struct isbn
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{
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char num[13];
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char pad[3];
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} isbn;
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/*
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* Various forward declarations:
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*/
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isbn *isbn_in(char *str);
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char *isbn_out(isbn * addr);
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bool isbn_lt(isbn * a1, isbn * a2);
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bool isbn_le(isbn * a1, isbn * a2);
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bool isbn_eq(isbn * a1, isbn * a2);
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bool isbn_ge(isbn * a1, isbn * a2);
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bool isbn_gt(isbn * a1, isbn * a2);
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bool isbn_ne(isbn * a1, isbn * a2);
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int4 isbn_cmp(isbn * a1, isbn * a2);
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int4 isbn_sum(char *str);
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/*
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* ISBN reader.
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*/
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isbn *
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isbn_in(char *str)
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{
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isbn *result;
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char *cp;
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int count;
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if (strlen(str) != 13) {
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elog(ERROR, "isbn_in: invalid ISBN \"%s\"", str);
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return (NULL);
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}
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if (isbn_sum(str) != 0) {
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elog(ERROR, "isbn_in: purported ISBN \"%s\" failed checksum",
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str);
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return (NULL);
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}
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result = (isbn *) palloc(sizeof(isbn));
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strncpy(result->num, str, 13);
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memset(result->pad, ' ', 3);
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return (result);
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}
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/*
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* The ISBN checksum is defined as follows:
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*
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* Number the digits from 1 to 9 (call this N).
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* Compute the sum, S, of N * D_N.
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* The check digit, C, is the value which satisfies the equation
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* S + 10*C === 0 (mod 11)
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* The value 10 for C is written as `X'.
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*
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* For our purposes, we want the complete sum including the check
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* digit; if this is zero, then the checksum passed. We also check
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* the syntactic validity if the provided string, and return 12
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* if any errors are found.
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*/
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int4
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isbn_sum(char *str)
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{
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int4 sum = 0, dashes = 0, val;
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int i;
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for (i = 0; str[i] && i < 13; i++) {
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switch(str[i]) {
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case '-':
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if (++dashes > 3)
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return 12;
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continue;
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case '0': case '1': case '2': case '3':
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case '4': case '5': case '6': case '7':
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case '8': case '9':
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val = str[i] - '0';
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break;
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case 'X': case 'x':
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val = 10;
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break;
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default:
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return 12;
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}
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sum += val * (i + 1 - dashes);
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}
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return (sum % 11);
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}
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/*
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* ISBN output function.
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*/
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char *
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isbn_out(isbn * num)
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{
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char *result;
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if (num == NULL)
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return (NULL);
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result = (char *) palloc(14);
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result[0] = '\0';
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strncat(result, num->num, 13);
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return (result);
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}
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/*
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* Boolean tests for magnitude.
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*/
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bool
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isbn_lt(isbn * a1, isbn * a2)
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{
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return (strncmp(a1->num, a2->num, 13) < 0);
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};
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bool
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isbn_le(isbn * a1, isbn * a2)
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{
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return (strncmp(a1->num, a2->num, 13) <= 0);
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};
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bool
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isbn_eq(isbn * a1, isbn * a2)
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{
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return (strncmp(a1->num, a2->num, 13) == 0);
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};
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bool
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isbn_ge(isbn * a1, isbn * a2)
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{
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return (strncmp(a1->num, a2->num, 13) >= 0);
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};
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bool
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isbn_gt(isbn * a1, isbn * a2)
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{
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return (strncmp(a1->num, a2->num, 13) > 0);
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};
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bool
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isbn_ne(isbn * a1, isbn * a2)
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{
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return (strncmp(a1->num, a2->num, 13) != 0);
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};
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/*
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* Comparison function for sorting:
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*/
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int4
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isbn_cmp(isbn * a1, isbn * a2)
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{
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return (strncmp(a1->num, a2->num, 13));
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}
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/*
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* eof
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*/
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