From: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>

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).

contrib/README

@@ -35,6 +35,10 @@ ip_and_mac -
 	PostgreSQL type extensions for IP and MAC addresses
 	by Tom Ivar Helbekkmo <tih@Hamartun.Priv.NO>
 
+isbn_issn -
+	PostgreSQL type extensions for ISBN (books) and ISSN (serials)
+	by Garrett A. Wollman <wollman@khavrinen.lcs.mit.edu>
+
 linux -
 	Start postgres back end system
 	by Thomas Lockhart <lockhart@alumni.caltech.edu>
@@ -80,3 +84,5 @@ userlock -
 	User locks
 	by Massimo Dal Zotto <dz@cs.unitn.it>
 
+
+

contrib/isbn_issn/Makefile

+#
+#	PostgreSQL types for ISBN and ISSN identifiers.
+#
+#	$Id: Makefile,v 1.1 1998/08/17 03:35:04 scrappy Exp $
+
+all: isbn.so issn.so
+
+isbn.so: isbn.o
+	ld -Bshareable -o isbn.so isbn.o
+
+isbn.o: isbn.c
+	cc -g -O -fPIC -I/usr/local/pgsql/include -c isbn.c
+
+issn.so: issn.o
+	ld -Bshareable -o issn.so issn.o
+
+issn.o: issn.c
+	cc -g -O -fPIC -I/usr/local/pgsql/include -c issn.c
+
+install: isbn.so issn.so
+	install -c isbn.so issn.so /usr/local/pgsql/modules
+
+#
+#	eof
+#

contrib/isbn_issn/README

+This directory contains definitions for a couple of PostgreSQL
+external types, for a couple of international-standard namespaces:
+ISBN (books) and ISSN (serials).  Rather than just using a char()
+member of the appropriate length, I wanted my database to include
+the validity-checking that both these numbering systems were designed
+to encompass.  A little bit of research revealed the formulae
+for computing the check digits, and I also included some validity
+constraints on the number of hyphens.
+
+The internal representation of these types is intended to be
+compatible with `char16', in the (perhaps vain) hope that
+this will make it possible to create indices of these types
+using char16_ops.
+
+These are based on Tom Ivar Helbekkmo's IP address type definition,
+from which I have copied the entire form of the implementation.
+
+Garrett A. Wollman, August 1998

contrib/isbn_issn/isbn.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
+ */

contrib/isbn_issn/isbn.sql

+--
+--	PostgreSQL code for ISBNs.
+--
+--	$Id: isbn.sql,v 1.1 1998/08/17 03:35:05 scrappy Exp $
+--
+
+load '/usr/local/pgsql/modules/isbn.so';
+
+--
+--	Input and output functions and the type itself:
+--
+
+create function isbn_in(opaque)
+	returns opaque
+	as '/usr/local/pgsql/modules/isbn.so'
+	language 'c';
+
+create function isbn_out(opaque)
+	returns opaque
+	as '/usr/local/pgsql/modules/isbn.so'
+	language 'c';
+
+create type isbn (
+	internallength = 16,
+	externallength = 13,
+	input = isbn_in,
+	output = isbn_out
+);
+
+--
+--	The various boolean tests:
+--
+
+create function isbn_lt(isbn, isbn)
+	returns bool
+	as '/usr/local/pgsql/modules/isbn.so'
+	language 'c';
+
+create function isbn_le(isbn, isbn)
+	returns bool
+	as '/usr/local/pgsql/modules/isbn.so'
+	language 'c';
+
+create function isbn_eq(isbn, isbn)
+	returns bool
+	as '/usr/local/pgsql/modules/isbn.so'
+	language 'c';
+
+create function isbn_ge(isbn, isbn)
+	returns bool
+	as '/usr/local/pgsql/modules/isbn.so'
+	language 'c';
+
+create function isbn_gt(isbn, isbn)
+	returns bool
+	as '/usr/local/pgsql/modules/isbn.so'
+	language 'c';
+
+create function isbn_ne(isbn, isbn)
+	returns bool
+	as '/usr/local/pgsql/modules/isbn.so'
+	language 'c';
+
+--
+--	Now the operators.  Note how some of the parameters to some
+--	of the 'create operator' commands are commented out.  This
+--	is because they reference as yet undefined operators, and
+--	will be implicitly defined when those are, further down.
+--
+
+create operator < (
+	leftarg = isbn,
+	rightarg = isbn,
+--	negator = >=,
+	procedure = isbn_lt
+);
+
+create operator <= (
+	leftarg = isbn,
+	rightarg = isbn,
+--	negator = >,
+	procedure = isbn_le
+);
+
+create operator = (
+	leftarg = isbn,
+	rightarg = isbn,
+	commutator = =,
+--	negator = <>,
+	procedure = isbn_eq
+);
+
+create operator >= (
+	leftarg = isbn,
+	rightarg = isbn,
+	negator = <,
+	procedure = isbn_ge
+);
+
+create operator > (
+	leftarg = isbn,
+	rightarg = isbn,
+	negator = <=,
+	procedure = isbn_gt
+);
+
+create operator <> (
+	leftarg = isbn,
+	rightarg = isbn,
+	negator = =,
+	procedure = isbn_ne
+);
+
+--
+--	eof
+--

contrib/isbn_issn/issn.c

+/*
+ *	PostgreSQL type definitions for ISSNs.
+ *
+ *	$Id: issn.c,v 1.1 1998/08/17 03:35:05 scrappy 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;
+	char	   *cp;
+	int			count;
+
+	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
+ */

contrib/isbn_issn/issn.sql

+--
+--	PostgreSQL code for ISSNs.
+--
+--	$Id: issn.sql,v 1.1 1998/08/17 03:35:05 scrappy Exp $
+--
+
+load '/usr/local/pgsql/modules/issn.so';
+
+--
+--	Input and output functions and the type itself:
+--
+
+create function issn_in(opaque)
+	returns opaque
+	as '/usr/local/pgsql/modules/issn.so'
+	language 'c';
+
+create function issn_out(opaque)
+	returns opaque
+	as '/usr/local/pgsql/modules/issn.so'
+	language 'c';
+
+create type issn (
+	internallength = 16,
+	externallength = 9,
+	input = issn_in,
+	output = issn_out
+);
+
+--
+--	The various boolean tests:
+--
+
+create function issn_lt(issn, issn)
+	returns bool
+	as '/usr/local/pgsql/modules/issn.so'
+	language 'c';
+
+create function issn_le(issn, issn)
+	returns bool
+	as '/usr/local/pgsql/modules/issn.so'
+	language 'c';
+
+create function issn_eq(issn, issn)
+	returns bool
+	as '/usr/local/pgsql/modules/issn.so'
+	language 'c';
+
+create function issn_ge(issn, issn)
+	returns bool
+	as '/usr/local/pgsql/modules/issn.so'
+	language 'c';
+
+create function issn_gt(issn, issn)
+	returns bool
+	as '/usr/local/pgsql/modules/issn.so'
+	language 'c';
+
+create function issn_ne(issn, issn)
+	returns bool
+	as '/usr/local/pgsql/modules/issn.so'
+	language 'c';
+
+--
+--	Now the operators.  Note how some of the parameters to some
+--	of the 'create operator' commands are commented out.  This
+--	is because they reference as yet undefined operators, and
+--	will be implicitly defined when those are, further down.
+--
+
+create operator < (
+	leftarg = issn,
+	rightarg = issn,
+--	negator = >=,
+	procedure = issn_lt
+);
+
+create operator <= (
+	leftarg = issn,
+	rightarg = issn,
+--	negator = >,
+	procedure = issn_le
+);
+
+create operator = (
+	leftarg = issn,
+	rightarg = issn,
+	commutator = =,
+--	negator = <>,
+	procedure = issn_eq
+);
+
+create operator >= (
+	leftarg = issn,
+	rightarg = issn,
+	negator = <,
+	procedure = issn_ge
+);
+
+create operator > (
+	leftarg = issn,
+	rightarg = issn,
+	negator = <=,
+	procedure = issn_gt
+);
+
+create operator <> (
+	leftarg = issn,
+	rightarg = issn,
+	negator = =,
+	procedure = issn_ne
+);
+
+--
+--	eof
+--