193 lines
2.7 KiB
C
193 lines
2.7 KiB
C
/*
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* PostgreSQL type definitions for ISSNs.
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*
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* $Id: issn.c,v 1.2 1999/05/25 16:05:42 momjian 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 ISSNs.
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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 issn
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{
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char num[9];
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char pad[7];
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} issn;
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/*
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* Various forward declarations:
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*/
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issn *issn_in(char *str);
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char *issn_out(issn * addr);
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bool issn_lt(issn * a1, issn * a2);
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bool issn_le(issn * a1, issn * a2);
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bool issn_eq(issn * a1, issn * a2);
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bool issn_ge(issn * a1, issn * a2);
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bool issn_gt(issn * a1, issn * a2);
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bool issn_ne(issn * a1, issn * a2);
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int4 issn_cmp(issn * a1, issn * a2);
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int4 issn_sum(char *str);
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/*
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* ISSN reader.
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*/
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issn *
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issn_in(char *str)
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{
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issn *result;
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char *cp;
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int count;
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if (strlen(str) != 9)
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{
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elog(ERROR, "issn_in: invalid ISSN \"%s\"", str);
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return (NULL);
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}
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if (issn_sum(str) != 0)
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{
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elog(ERROR, "issn_in: purported ISSN \"%s\" failed checksum",
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str);
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return (NULL);
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}
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result = (issn *) palloc(sizeof(issn));
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strncpy(result->num, str, 9);
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memset(result->pad, ' ', 7);
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return (result);
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}
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/*
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* The ISSN checksum works just like the ISBN sum, only different
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* (of course!).
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* Here, the weights start at 8 and decrease.
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*/
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int4
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issn_sum(char *str)
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{
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int4 sum = 0,
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dashes = 0,
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val;
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int i;
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for (i = 0; str[i] && i < 9; i++)
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{
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switch (str[i])
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{
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case '-':
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if (++dashes > 1)
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return 12;
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continue;
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case '0':
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case '1':
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case '2':
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case '3':
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case '4':
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case '5':
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case '6':
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case '7':
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case '8':
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case '9':
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val = str[i] - '0';
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break;
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case 'X':
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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 * (8 - (i - dashes));
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}
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return (sum % 11);
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}
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/*
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* ISSN output function.
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*/
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char *
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issn_out(issn * 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, 9);
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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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issn_lt(issn * a1, issn * a2)
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{
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return (strncmp(a1->num, a2->num, 9) < 0);
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};
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bool
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issn_le(issn * a1, issn * a2)
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{
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return (strncmp(a1->num, a2->num, 9) <= 0);
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};
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bool
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issn_eq(issn * a1, issn * a2)
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{
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return (strncmp(a1->num, a2->num, 9) == 0);
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};
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bool
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issn_ge(issn * a1, issn * a2)
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{
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return (strncmp(a1->num, a2->num, 9) >= 0);
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};
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bool
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issn_gt(issn * a1, issn * a2)
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{
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return (strncmp(a1->num, a2->num, 9) > 0);
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};
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bool
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issn_ne(issn * a1, issn * a2)
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{
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return (strncmp(a1->num, a2->num, 9) != 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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issn_cmp(issn * a1, issn * a2)
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{
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return (strncmp(a1->num, a2->num, 9));
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}
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/*
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* eof
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*/
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