Adds binary tid decode

msg_reader.go

@@ -137,6 +137,34 @@ func (r *msgReader) readInt32() int32 {
 	return n
 }
 
+func (r *msgReader) readUint16() uint16 {
+	if r.err != nil {
+		return 0
+	}
+
+	r.msgBytesRemaining -= 2
+	if r.msgBytesRemaining < 0 {
+		r.fatal(errors.New("read past end of message"))
+		return 0
+	}
+
+	b, err := r.reader.Peek(2)
+	if err != nil {
+		r.fatal(err)
+		return 0
+	}
+
+	n := uint16(binary.BigEndian.Uint16(b))
+
+	r.reader.Discard(2)
+
+	if r.shouldLog(LogLevelTrace) {
+		r.log(LogLevelTrace, "msgReader.readUint16", "value", n, "msgBytesRemaining", r.msgBytesRemaining)
+	}
+
+	return n
+}
+
 func (r *msgReader) readUint32() uint32 {
 	if r.err != nil {
 		return 0

values.go

@@ -344,7 +344,7 @@ func (n NullInt32) Encode(w *WriteBuf, oid Oid) error {
 //
 // it is the data type of the xmin and xmax hidden system columns.
 //
-// It is currently implemented as an unsigned for byte integer.
+// 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 uint32
@@ -396,7 +396,7 @@ func (n NullXid) Encode(w *WriteBuf, oid Oid) error {
 //
 // it is the data type of the cmin and cmax hidden system columns.
 //
-// It is currently implemented as an unsigned for byte integer.
+// It is currently implemented as an unsigned four byte integer.
 // Its definition can be found in src/include/c.h as CommandId
 // in the PostgreSQL sources.
 type Cid uint32
@@ -440,6 +440,61 @@ func (n NullCid) Encode(w *WriteBuf, oid Oid) error {
 	return encodeCid(w, oid, n.Cid)
 }
 
+// Tid is PostgreSQL's Tuple Identifier type.
+//
+// When one does
+//
+// 	select ctid, * from some_table;
+//
+// it is the data type of the ctid hidden system column.
+//
+// It is currently implemented as a pair unsigned two byte integers.
+// Its conversion functions can be found in src/backend/utils/adt/tid.c
+// in the PostgreSQL sources.
+type Tid struct {
+	BlockNumber  uint16
+	OffsetNumber uint16
+}
+
+// NullTid represents a Tuple Identifier (Tid) that may be null. NullTid 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 NullTid struct {
+	Tid   Tid
+	Valid bool // Valid is true if Int32 is not NULL
+}
+
+func (n *NullTid) Scan(vr *ValueReader) error {
+	if vr.Type().DataType != TidOid {
+		return SerializationError(fmt.Sprintf("NullTid.Scan cannot decode OID %d", vr.Type().DataType))
+	}
+
+	if vr.Len() == -1 {
+		n.Tid, n.Valid = 0, false
+		return nil
+	}
+	n.Valid = true
+	n.Tid = decodeTid(vr)
+	return vr.Err()
+}
+
+func (n NullTid) FormatCode() int16 { return BinaryFormatCode }
+
+func (n NullTid) Encode(w *WriteBuf, oid Oid) error {
+	if oid != TidOid {
+		return SerializationError(fmt.Sprintf("NullTid.Encode cannot encode into OID %d", oid))
+	}
+
+	if !n.Valid {
+		w.WriteInt32(-1)
+		return nil
+	}
+
+	return encodeTid(w, oid, n.Tid)
+}
+
 // 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.
@@ -934,6 +989,8 @@ func Decode(vr *ValueReader, d interface{}) error {
 		*v = decodeOid(vr)
 	case *Xid:
 		*v = decodeXid(vr)
+	case *Tid:
+		*v = decodeTid(vr)
 	case *Cid:
 		*v = decodeCid(vr)
 	case *string:
@@ -1546,6 +1603,49 @@ func encodeCid(w *WriteBuf, oid Oid, value Cid) error {
 	return nil
 }
 
+func decodeTid(vr *ValueReader) Tid {
+	if vr.Len() == -1 {
+		vr.Fatal(ProtocolError("Cannot decode null into Tid"))
+		return Tid{BlockNumber: 0, OffsetNumber: 0}
+	}
+
+	if vr.Type().DataType != TidOid {
+		vr.Fatal(ProtocolError(fmt.Sprintf("Cannot decode oid %v into pgx.Tid", vr.Type().DataType)))
+		return Tid{BlockNumber: 0, OffsetNumber: 0}
+	}
+
+	// Unlikely Tid will ever go over the wire as text format, but who knows?
+	switch vr.Type().FormatCode {
+	case TextFormatCode: // XXX: not done yet src/backend/utils/adt/tid.c for hints; s already contains the string, so we just have to parse out (uint16,uint16)
+		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 Tid(n)
+	case BinaryFormatCode:
+		if vr.Len() != 4 {
+			vr.Fatal(ProtocolError(fmt.Sprintf("Received an invalid size for an Oid: %d", vr.Len())))
+			return Tid{BlockNumber: 0, OffsetNumber: 0}
+		}
+		return Tid{BlockNumber: vr.ReadUint16(), OffsetNumber: vr.ReadUint16()}
+	default:
+		vr.Fatal(ProtocolError(fmt.Sprintf("Unknown field description format code: %v", vr.Type().FormatCode)))
+		return Tid{BlockNumber: 0, OffsetNumber: 0}
+	}
+}
+
+func encodeTid(w *WriteBuf, oid Oid, value Tid) error {
+	if oid != TidOid {
+		return fmt.Errorf("cannot encode Go %s into oid %d", "pgx.Tid", 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"))