From 8922421ad60854c5387cd7a863b1a1d0b21b0e14 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Sun, 5 Mar 2017 09:07:07 -0600
Subject: [PATCH] Move XID to pgypte

---
 pgtype.go   |  2 +-
 xid.go      | 45 +++++++++++++++++++++++++
 xid_test.go | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 140 insertions(+), 1 deletion(-)
 create mode 100644 xid.go
 create mode 100644 xid_test.go

diff --git a/pgtype.go b/pgtype.go
index 1200bf12..15c0cc76 100644
--- a/pgtype.go
+++ b/pgtype.go
@@ -19,7 +19,7 @@ const (
 	TextOID             = 25
 	OIDOID              = 26
 	TidOID              = 27
-	XidOID              = 28
+	XIDOID              = 28
 	CIDOID              = 29
 	JSONOID             = 114
 	CidrOID             = 650
diff --git a/xid.go b/xid.go
new file mode 100644
index 00000000..f4d087a5
--- /dev/null
+++ b/xid.go
@@ -0,0 +1,45 @@
+package pgtype
+
+import (
+	"io"
+)
+
+// Xid is PostgreSQL's Transaction ID type.
+//
+// In later versions of PostgreSQL, it is the type used for the backend_xid
+// and backend_xmin columns of the pg_stat_activity system view.
+//
+// Also, when one does
+//
+//  select xmin, xmax, * from some_table;
+//
+// it is the data type of the xmin and xmax hidden system columns.
+//
+// It is currently implemented as an unsigned four byte integer.
+// Its definition can be found in src/include/postgres_ext.h as TransactionId
+// in the PostgreSQL sources.
+type XID CID
+
+func (dst *XID) ConvertFrom(src interface{}) error {
+	return (*CID)(dst).ConvertFrom(src)
+}
+
+func (src *XID) AssignTo(dst interface{}) error {
+	return (*CID)(src).AssignTo(dst)
+}
+
+func (dst *XID) DecodeText(r io.Reader) error {
+	return (*CID)(dst).DecodeText(r)
+}
+
+func (dst *XID) DecodeBinary(r io.Reader) error {
+	return (*CID)(dst).DecodeBinary(r)
+}
+
+func (src XID) EncodeText(w io.Writer) error {
+	return (CID)(src).EncodeText(w)
+}
+
+func (src XID) EncodeBinary(w io.Writer) error {
+	return (CID)(src).EncodeBinary(w)
+}
diff --git a/xid_test.go b/xid_test.go
new file mode 100644
index 00000000..664920bc
--- /dev/null
+++ b/xid_test.go
@@ -0,0 +1,94 @@
+package pgtype_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/jackc/pgx/pgtype"
+)
+
+func TestXIDTranscode(t *testing.T) {
+	testSuccessfulTranscode(t, "xid", []interface{}{
+		pgtype.XID{Uint: 42, Status: pgtype.Present},
+		pgtype.XID{Status: pgtype.Null},
+	})
+}
+
+func TestXIDConvertFrom(t *testing.T) {
+	successfulTests := []struct {
+		source interface{}
+		result pgtype.XID
+	}{
+		{source: uint32(1), result: pgtype.XID{Uint: 1, Status: pgtype.Present}},
+	}
+
+	for i, tt := range successfulTests {
+		var r pgtype.XID
+		err := r.ConvertFrom(tt.source)
+		if err != nil {
+			t.Errorf("%d: %v", i, err)
+		}
+
+		if r != tt.result {
+			t.Errorf("%d: expected %v to convert to %v, but it was %v", i, tt.source, tt.result, r)
+		}
+	}
+}
+
+func TestXIDAssignTo(t *testing.T) {
+	var ui32 uint32
+	var pui32 *uint32
+
+	simpleTests := []struct {
+		src      pgtype.XID
+		dst      interface{}
+		expected interface{}
+	}{
+		{src: pgtype.XID{Uint: 42, Status: pgtype.Present}, dst: &ui32, expected: uint32(42)},
+		{src: pgtype.XID{Status: pgtype.Null}, dst: &pui32, expected: ((*uint32)(nil))},
+	}
+
+	for i, tt := range simpleTests {
+		err := tt.src.AssignTo(tt.dst)
+		if err != nil {
+			t.Errorf("%d: %v", i, err)
+		}
+
+		if dst := reflect.ValueOf(tt.dst).Elem().Interface(); dst != tt.expected {
+			t.Errorf("%d: expected %v to assign %v, but result was %v", i, tt.src, tt.expected, dst)
+		}
+	}
+
+	pointerAllocTests := []struct {
+		src      pgtype.XID
+		dst      interface{}
+		expected interface{}
+	}{
+		{src: pgtype.XID{Uint: 42, Status: pgtype.Present}, dst: &pui32, expected: uint32(42)},
+	}
+
+	for i, tt := range pointerAllocTests {
+		err := tt.src.AssignTo(tt.dst)
+		if err != nil {
+			t.Errorf("%d: %v", i, err)
+		}
+
+		if dst := reflect.ValueOf(tt.dst).Elem().Elem().Interface(); dst != tt.expected {
+			t.Errorf("%d: expected %v to assign %v, but result was %v", i, tt.src, tt.expected, dst)
+		}
+	}
+
+	errorTests := []struct {
+		src pgtype.XID
+		dst interface{}
+	}{
+		{src: pgtype.XID{Status: pgtype.Null}, dst: &ui32},
+	}
+
+	for i, tt := range errorTests {
+		err := tt.src.AssignTo(tt.dst)
+		if err == nil {
+			t.Errorf("%d: expected error but none was returned (%v -> %v)", i, tt.src, tt.dst)
+		}
+	}
+}