Adds Cid/NullCid type

values.go

@@ -23,6 +23,7 @@ const (
 	TextOid             = 25
 	OidOid              = 26
 	XidOid              = 28
+	CidOid              = 29
 	JsonOid             = 114
 	CidrOid             = 650
 	CidrArrayOid        = 651
@@ -95,6 +96,7 @@ func init() {
 		"int8":         BinaryFormatCode,
 		"oid":          BinaryFormatCode,
 		"xid":          BinaryFormatCode,
+		"cid":          BinaryFormatCode,
 		"record":       BinaryFormatCode,
 		"text":         BinaryFormatCode,
 		"timestamp":    BinaryFormatCode,
@@ -384,6 +386,58 @@ func (n NullXid) Encode(w *WriteBuf, oid Oid) error {
 	return encodeXid(w, oid, n.Xid)
 }
 
+// Cid is PostgreSQL's Command Identifier type.
+//
+// When one does
+//
+// 	select cmin, cmax, * from some_table;
+//
+// it is the data type of the cmin and cmax hidden system columns.
+//
+// It is currently implemented as an unsigned for byte integer.
+// Its definition can be found in src/include/c.h as CommandId
+// in the PostgreSQL sources.
+type Cid uint32
+
+// NullCid represents a Command Identifier (Cid) that may be null. NullCid implements the
+// Scanner and Encoder interfaces so it may be used both as an argument to
+// Query[Row] and a destination for Scan.
+//
+// If Valid is false then the value is NULL.
+type NullCid struct {
+	Cid   Cid
+	Valid bool // Valid is true if Int32 is not NULL
+}
+
+func (n *NullCid) Scan(vr *ValueReader) error {
+	if vr.Type().DataType != CidOid {
+		return SerializationError(fmt.Sprintf("NullCid.Scan cannot decode OID %d", vr.Type().DataType))
+	}
+
+	if vr.Len() == -1 {
+		n.Cid, n.Valid = 0, false
+		return nil
+	}
+	n.Valid = true
+	n.Cid = decodeCid(vr)
+	return vr.Err()
+}
+
+func (n NullCid) FormatCode() int16 { return BinaryFormatCode }
+
+func (n NullCid) Encode(w *WriteBuf, oid Oid) error {
+	if oid != CidOid {
+		return SerializationError(fmt.Sprintf("NullCid.Encode cannot encode into OID %d", oid))
+	}
+
+	if !n.Valid {
+		w.WriteInt32(-1)
+		return nil
+	}
+
+	return encodeCid(w, oid, n.Cid)
+}
+
 // NullInt64 represents an bigint that may be null. NullInt64 implements the
 // Scanner and Encoder interfaces so it may be used both as an argument to
 // Query[Row] and a destination for Scan.
@@ -750,6 +804,8 @@ func Encode(wbuf *WriteBuf, oid Oid, arg interface{}) error {
 		return encodeOid(wbuf, oid, arg)
 	case Xid:
 		return encodeXid(wbuf, oid, arg)
+	case Cid:
+		return encodeCid(wbuf, oid, arg)
 	default:
 		if strippedArg, ok := stripNamedType(&refVal); ok {
 			return Encode(wbuf, oid, strippedArg)
@@ -876,6 +932,8 @@ func Decode(vr *ValueReader, d interface{}) error {
 		*v = decodeOid(vr)
 	case *Xid:
 		*v = decodeXid(vr)
+	case *Cid:
+		*v = decodeCid(vr)
 	case *string:
 		*v = decodeText(vr)
 	case *float32:
@@ -1443,6 +1501,49 @@ func encodeXid(w *WriteBuf, oid Oid, value Xid) error {
 	return nil
 }
 
+func decodeCid(vr *ValueReader) Cid {
+	if vr.Len() == -1 {
+		vr.Fatal(ProtocolError("Cannot decode null into Cid"))
+		return Cid(0)
+	}
+
+	if vr.Type().DataType != CidOid {
+		vr.Fatal(ProtocolError(fmt.Sprintf("Cannot decode oid %v into pgx.Cid", vr.Type().DataType)))
+		return Cid(0)
+	}
+
+	// Unlikely Cid will ever go over the wire as text format, but who knows?
+	switch vr.Type().FormatCode {
+	case TextFormatCode:
+		s := vr.ReadString(vr.Len())
+		n, err := strconv.ParseUint(s, 10, 32)
+		if err != nil {
+			vr.Fatal(ProtocolError(fmt.Sprintf("Received invalid Oid: %v", s)))
+		}
+		return Cid(n)
+	case BinaryFormatCode:
+		if vr.Len() != 4 {
+			vr.Fatal(ProtocolError(fmt.Sprintf("Received an invalid size for an Oid: %d", vr.Len())))
+			return Cid(0)
+		}
+		return Cid(vr.ReadUint32())
+	default:
+		vr.Fatal(ProtocolError(fmt.Sprintf("Unknown field description format code: %v", vr.Type().FormatCode)))
+		return Cid(0)
+	}
+}
+
+func encodeCid(w *WriteBuf, oid Oid, value Cid) error {
+	if oid != CidOid {
+		return fmt.Errorf("cannot encode Go %s into oid %d", "pgx.Cid", oid)
+	}
+
+	w.WriteInt32(4)
+	w.WriteUint32(uint32(value))
+
+	return nil
+}
+
 func decodeFloat4(vr *ValueReader) float32 {
 	if vr.Len() == -1 {
 		vr.Fatal(ProtocolError("Cannot decode null into float32"))

values_test.go

@@ -595,6 +595,7 @@ func TestNullX(t *testing.T) {
 		i16 pgx.NullInt16
 		i32 pgx.NullInt32
 		xid pgx.NullXid
+		cid pgx.NullCid
 		i64 pgx.NullInt64
 		f32 pgx.NullFloat32
 		f64 pgx.NullFloat64
@@ -619,6 +620,9 @@ func TestNullX(t *testing.T) {
 		{"select $1::xid", []interface{}{pgx.NullXid{Xid: 1, Valid: true}}, []interface{}{&actual.xid}, allTypes{xid: pgx.NullXid{Xid: 1, Valid: true}}},
 		{"select $1::xid", []interface{}{pgx.NullXid{Xid: 1, Valid: false}}, []interface{}{&actual.xid}, allTypes{xid: pgx.NullXid{Xid: 0, Valid: false}}},
 		{"select $1::xid", []interface{}{pgx.NullXid{Xid: 4294967295, Valid: true}}, []interface{}{&actual.xid}, allTypes{xid: pgx.NullXid{Xid: 4294967295, Valid: true}}},
+		{"select $1::cid", []interface{}{pgx.NullCid{Cid: 1, Valid: true}}, []interface{}{&actual.cid}, allTypes{cid: pgx.NullCid{Cid: 1, Valid: true}}},
+		{"select $1::cid", []interface{}{pgx.NullCid{Cid: 1, Valid: false}}, []interface{}{&actual.cid}, allTypes{cid: pgx.NullCid{Cid: 0, Valid: false}}},
+		{"select $1::cid", []interface{}{pgx.NullCid{Cid: 4294967295, Valid: true}}, []interface{}{&actual.cid}, allTypes{cid: pgx.NullCid{Cid: 4294967295, Valid: true}}},
 		{"select $1::int8", []interface{}{pgx.NullInt64{Int64: 1, Valid: true}}, []interface{}{&actual.i64}, allTypes{i64: pgx.NullInt64{Int64: 1, Valid: true}}},
 		{"select $1::int8", []interface{}{pgx.NullInt64{Int64: 1, Valid: false}}, []interface{}{&actual.i64}, allTypes{i64: pgx.NullInt64{Int64: 0, Valid: false}}},
 		{"select $1::float4", []interface{}{pgx.NullFloat32{Float32: 1.23, Valid: true}}, []interface{}{&actual.f32}, allTypes{f32: pgx.NullFloat32{Float32: 1.23, Valid: true}}},