Add gen_random_uuid() to contrib/pgcrypto.

This function provides a way of generating version 4 (pseudorandom) UUIDs
based on pgcrypto's PRNG.  The main reason for doing this is that the
OSSP UUID library depended on by contrib/uuid-ossp is becoming more and
more of a porting headache, so we need an alternative for people who can't
install that.  A nice side benefit though is that this implementation is
noticeably faster than uuid-ossp's uuid_generate_v4() function.

Oskari Saarenmaa, reviewed by Emre Hasegeli

contrib/pgcrypto/Makefile

@@ -26,7 +26,7 @@ MODULE_big	= pgcrypto
 OBJS		= $(SRCS:.c=.o)
 
 EXTENSION = pgcrypto
-DATA = pgcrypto--1.0.sql pgcrypto--unpackaged--1.0.sql
+DATA = pgcrypto--1.1.sql pgcrypto--1.0--1.1.sql pgcrypto--unpackaged--1.0.sql
 
 REGRESS = init md5 sha1 hmac-md5 hmac-sha1 blowfish rijndael \
 	$(CF_TESTS) \

contrib/pgcrypto/pgcrypto--1.0--1.1.sql

@@ -0,0 +1,9 @@
+/* contrib/pgcrypto/pgcrypto--1.0--1.1.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pgcrypto UPDATE TO '1.1'" to load this file. \quit
+
+CREATE FUNCTION gen_random_uuid()
+RETURNS uuid
+AS 'MODULE_PATHNAME', 'pg_random_uuid'
+LANGUAGE C VOLATILE;

contrib/pgcrypto/pgcrypto--1.1.sql

@@ -1,4 +1,4 @@
-/* contrib/pgcrypto/pgcrypto--1.0.sql */
+/* contrib/pgcrypto/pgcrypto--1.1.sql */
 
 -- complain if script is sourced in psql, rather than via CREATE EXTENSION
 \echo Use "CREATE EXTENSION pgcrypto" to load this file. \quit
@@ -63,6 +63,11 @@ RETURNS bytea
 AS 'MODULE_PATHNAME', 'pg_random_bytes'
 LANGUAGE C VOLATILE STRICT;
 
+CREATE FUNCTION gen_random_uuid()
+RETURNS uuid
+AS 'MODULE_PATHNAME', 'pg_random_uuid'
+LANGUAGE C VOLATILE;
+
 --
 -- pgp_sym_encrypt(data, key)
 --

contrib/pgcrypto/pgcrypto.c

@@ -35,6 +35,7 @@
 
 #include "parser/scansup.h"
 #include "utils/builtins.h"
+#include "utils/uuid.h"
 
 #include "px.h"
 #include "px-crypt.h"
@@ -443,6 +444,32 @@ pg_random_bytes(PG_FUNCTION_ARGS)
 	PG_RETURN_BYTEA_P(res);
 }
 
+/* SQL function: gen_random_uuid() returns uuid */
+PG_FUNCTION_INFO_V1(pg_random_uuid);
+
+Datum
+pg_random_uuid(PG_FUNCTION_ARGS)
+{
+	uint8	   *buf = (uint8 *) palloc(UUID_LEN);
+	int			err;
+
+	/* generate random bits */
+	err = px_get_pseudo_random_bytes(buf, UUID_LEN);
+	if (err < 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_EXTERNAL_ROUTINE_INVOCATION_EXCEPTION),
+				 errmsg("Random generator error: %s", px_strerror(err))));
+
+	/*
+	 * Set magic numbers for a "version 4" (pseudorandom) UUID, see
+	 * http://tools.ietf.org/html/rfc4122#section-4.4
+	 */
+	buf[6] = (buf[6] & 0x0f) | 0x40;	/* "version" field */
+	buf[8] = (buf[8] & 0x3f) | 0x80;	/* "variant" field */
+
+	PG_RETURN_UUID_P((pg_uuid_t *) buf);
+}
+
 static void *
 find_provider(text *name,
 			  PFN provider_lookup,

contrib/pgcrypto/pgcrypto.control

@@ -1,5 +1,5 @@
 # pgcrypto extension
 comment = 'cryptographic functions'
-default_version = '1.0'
+default_version = '1.1'
 module_pathname = '$libdir/pgcrypto'
 relocatable = true

contrib/pgcrypto/pgcrypto.h

@@ -45,5 +45,6 @@ Datum		pg_decrypt(PG_FUNCTION_ARGS);
 Datum		pg_encrypt_iv(PG_FUNCTION_ARGS);
 Datum		pg_decrypt_iv(PG_FUNCTION_ARGS);
 Datum		pg_random_bytes(PG_FUNCTION_ARGS);
+Datum		pg_random_uuid(PG_FUNCTION_ARGS);
 
 #endif

doc/src/sgml/datatype.sgml

@@ -4015,6 +4015,8 @@ a0ee-bc99-9c0b-4ef8-bb6d-6bb9-bd38-0a11
     suited for every application.  The <xref
     linkend="uuid-ossp"> module
     provides functions that implement several standard algorithms.
+    The <xref linkend="pgcrypto"> module also provides a generation
+    function for random UUIDs.
     Alternatively, UUIDs could be generated by client applications or
     other libraries invoked through a server-side function.
    </para>

doc/src/sgml/pgcrypto.sgml

@@ -1084,6 +1084,17 @@ gen_random_bytes(count integer) returns bytea
    At most 1024 bytes can be extracted at a time.  This is to avoid
    draining the randomness generator pool.
   </para>
+
+  <indexterm>
+   <primary>gen_random_uuid</primary>
+  </indexterm>
+
+<synopsis>
+gen_random_uuid() returns uuid
+</synopsis>
+  <para>
+   Returns a version 4 (random) UUID.
+  </para>
  </sect2>
 
  <sect2>

doc/src/sgml/uuid-ossp.sgml

@@ -18,6 +18,15 @@
   <ulink url="http://www.ossp.org/pkg/lib/uuid/"></ulink>.
  </para>
 
+ <note>
+  <para>
+   The OSSP UUID library is not well maintained, and is becoming increasingly
+   difficult to port to newer platforms.  If you only need randomly-generated
+   (version 4) UUIDs, consider using the <function>gen_random_uuid()</>
+   function from the <xref linkend="pgcrypto"> module instead.
+  </para>
+ </note>
+
  <sect2>
   <title><literal>uuid-ossp</literal> Functions</title>