ValueTranscoder uses new interfaces

array_type.go

@@ -129,12 +129,44 @@ func (src *ArrayType) AssignTo(dst interface{}) error {
 	}
 }
 
-func (dst *ArrayType) DecodeText(ci *ConnInfo, src []byte) error {
+func (ArrayType) BinaryFormatSupported() bool {
+	return true
+}
+
+func (ArrayType) TextFormatSupported() bool {
+	return true
+}
+
+func (ArrayType) PreferredFormat() int16 {
+	return TextFormatCode
+}
+
+func (dst *ArrayType) DecodeResult(ci *ConnInfo, oid uint32, format int16, src []byte) error {
 	if src == nil {
 		dst.setNil()
 		return nil
 	}
 
+	switch format {
+	case BinaryFormatCode:
+		return dst.DecodeBinary(ci, src)
+	case TextFormatCode:
+		return dst.DecodeText(ci, src)
+	}
+	return fmt.Errorf("unknown format code %d", format)
+}
+
+func (src ArrayType) EncodeParam(ci *ConnInfo, oid uint32, format int16, buf []byte) (newBuf []byte, err error) {
+	switch format {
+	case BinaryFormatCode:
+		return src.EncodeBinary(ci, buf)
+	case TextFormatCode:
+		return src.EncodeText(ci, buf)
+	}
+	return nil, fmt.Errorf("unknown format code %d", format)
+}
+
+func (dst *ArrayType) DecodeText(ci *ConnInfo, src []byte) error {
 	uta, err := ParseUntypedTextArray(string(src))
 	if err != nil {
 		return err
@@ -151,7 +183,7 @@ func (dst *ArrayType) DecodeText(ci *ConnInfo, src []byte) error {
 			if s != "NULL" {
 				elemSrc = []byte(s)
 			}
-			err = elem.DecodeText(ci, elemSrc)
+			err = elem.DecodeResult(ci, dst.elementOID, TextFormatCode, elemSrc)
 			if err != nil {
 				return err
 			}
@@ -168,11 +200,6 @@ func (dst *ArrayType) DecodeText(ci *ConnInfo, src []byte) error {
 }
 
 func (dst *ArrayType) DecodeBinary(ci *ConnInfo, src []byte) error {
-	if src == nil {
-		dst.setNil()
-		return nil
-	}
-
 	var arrayHeader ArrayHeader
 	rp, err := arrayHeader.DecodeBinary(ci, src)
 	if err != nil {
@@ -204,7 +231,7 @@ func (dst *ArrayType) DecodeBinary(ci *ConnInfo, src []byte) error {
 			elemSrc = src[rp : rp+elemLen]
 			rp += elemLen
 		}
-		err = elem.DecodeBinary(ci, elemSrc)
+		err = elem.DecodeResult(ci, dst.elementOID, BinaryFormatCode, elemSrc)
 		if err != nil {
 			return err
 		}
@@ -253,7 +280,7 @@ func (src ArrayType) EncodeText(ci *ConnInfo, buf []byte) ([]byte, error) {
 			}
 		}
 
-		elemBuf, err := elem.EncodeText(ci, inElemBuf)
+		elemBuf, err := elem.EncodeParam(ci, src.elementOID, TextFormatCode, inElemBuf)
 		if err != nil {
 			return nil, err
 		}
@@ -296,7 +323,7 @@ func (src ArrayType) EncodeBinary(ci *ConnInfo, buf []byte) ([]byte, error) {
 		sp := len(buf)
 		buf = pgio.AppendInt32(buf, -1)
 
-		elemBuf, err := src.elements[i].EncodeBinary(ci, buf)
+		elemBuf, err := src.elements[i].EncodeParam(ci, src.elementOID, BinaryFormatCode, buf)
 		if err != nil {
 			return nil, err
 		}

composite_fields.go

@@ -59,8 +59,8 @@ func (cf CompositeFields) EncodeText(ci *ConnInfo, buf []byte) ([]byte, error) {
 	b := NewCompositeTextBuilder(ci, buf)
 
 	for _, f := range cf {
-		if textEncoder, ok := f.(TextEncoder); ok {
+		if paramEncoder, ok := f.(ParamEncoder); ok {
-			b.AppendEncoder(textEncoder)
+			b.AppendEncoder(paramEncoder)
 		} else {
 			b.AppendValue(f)
 		}
@@ -88,15 +88,15 @@ func (cf CompositeFields) EncodeBinary(ci *ConnInfo, buf []byte) ([]byte, error)
 			return nil, fmt.Errorf("Unknown OID for %#v", f)
 		}
 
-		if binaryEncoder, ok := f.(BinaryEncoder); ok {
+		if paramEncoder, ok := f.(ParamEncoder); ok {
-			b.AppendEncoder(dt.OID, binaryEncoder)
+			b.AppendEncoder(dt.OID, paramEncoder)
 		} else {
 			err := dt.Value.Set(f)
 			if err != nil {
 				return nil, err
 			}
-			if binaryEncoder, ok := dt.Value.(BinaryEncoder); ok {
+			if paramEncoder, ok := dt.Value.(ParamEncoder); ok {
-				b.AppendEncoder(dt.OID, binaryEncoder)
+				b.AppendEncoder(dt.OID, paramEncoder)
 			} else {
 				return nil, fmt.Errorf("Cannot encode binary format for %v", f)
 			}

composite_type.go

@@ -91,9 +91,13 @@ func (ct *CompositeType) Fields() []CompositeTypeField {
 	return ct.fields
 }
 
+func (dst *CompositeType) setNil() {
+	dst.valid = false
+}
+
 func (dst *CompositeType) Set(src interface{}) error {
 	if src == nil {
-		dst.valid = false
+		dst.setNil()
 		return nil
 	}
 
@@ -110,7 +114,7 @@ func (dst *CompositeType) Set(src interface{}) error {
 		dst.valid = true
 	case *[]interface{}:
 		if value == nil {
-			dst.valid = false
+			dst.setNil()
 			return nil
 		}
 		return dst.Set(*value)
@@ -213,6 +217,56 @@ func (src CompositeType) assignToPtrStruct(dst interface{}) (bool, error) {
 	return true, nil
 }
 
+func (ct *CompositeType) BinaryFormatSupported() bool {
+	for _, vt := range ct.valueTranscoders {
+		if !vt.BinaryFormatSupported() {
+			return false
+		}
+	}
+	return true
+}
+
+func (ct *CompositeType) TextFormatSupported() bool {
+	for _, vt := range ct.valueTranscoders {
+		if !vt.TextFormatSupported() {
+			return false
+		}
+	}
+	return true
+}
+
+func (ct *CompositeType) PreferredFormat() int16 {
+	if ct.BinaryFormatSupported() {
+		return BinaryFormatCode
+	}
+	return TextFormatCode
+}
+
+func (dst *CompositeType) DecodeResult(ci *ConnInfo, oid uint32, format int16, src []byte) error {
+	if src == nil {
+		dst.setNil()
+		return nil
+	}
+
+	switch format {
+	case BinaryFormatCode:
+		return dst.DecodeBinary(ci, src)
+	case TextFormatCode:
+		return dst.DecodeText(ci, src)
+	}
+	return fmt.Errorf("unknown format code %d", format)
+}
+
+func (src CompositeType) EncodeParam(ci *ConnInfo, oid uint32, format int16, buf []byte) (newBuf []byte, err error) {
+	switch format {
+	case BinaryFormatCode:
+		return src.EncodeBinary(ci, buf)
+	case TextFormatCode:
+		return src.EncodeText(ci, buf)
+	}
+	return nil, fmt.Errorf("unknown format code %d", format)
+}
+
 func (src CompositeType) EncodeBinary(ci *ConnInfo, buf []byte) (newBuf []byte, err error) {
 	if !src.valid {
 		return nil, nil
@@ -231,11 +285,6 @@ func (src CompositeType) EncodeBinary(ci *ConnInfo, buf []byte) (newBuf []byte,
 // and decoding fails if SQL value can't be assigned due to
 // type mismatch
 func (dst *CompositeType) DecodeBinary(ci *ConnInfo, buf []byte) error {
-	if buf == nil {
-		dst.valid = false
-		return nil
-	}
-
 	scanner := NewCompositeBinaryScanner(ci, buf)
 
 	for _, f := range dst.valueTranscoders {
@@ -252,11 +301,6 @@ func (dst *CompositeType) DecodeBinary(ci *ConnInfo, buf []byte) error {
 }
 
 func (dst *CompositeType) DecodeText(ci *ConnInfo, buf []byte) error {
-	if buf == nil {
-		dst.valid = false
-		return nil
-	}
-
 	scanner := NewCompositeTextScanner(ci, buf)
 
 	for _, f := range dst.valueTranscoders {
@@ -315,13 +359,13 @@ func NewCompositeBinaryScanner(ci *ConnInfo, src []byte) *CompositeBinaryScanner
 }
 
 // ScanDecoder calls Next and decodes the result with d.
-func (cfs *CompositeBinaryScanner) ScanDecoder(d BinaryDecoder) {
+func (cfs *CompositeBinaryScanner) ScanDecoder(d ResultDecoder) {
 	if cfs.err != nil {
 		return
 	}
 
 	if cfs.Next() {
-		cfs.err = d.DecodeBinary(cfs.ci, cfs.fieldBytes)
+		cfs.err = d.DecodeResult(cfs.ci, 0, BinaryFormatCode, cfs.fieldBytes)
 	} else {
 		cfs.err = errors.New("read past end of composite")
 	}
@@ -425,13 +469,13 @@ func NewCompositeTextScanner(ci *ConnInfo, src []byte) *CompositeTextScanner {
 }
 
 // ScanDecoder calls Next and decodes the result with d.
-func (cfs *CompositeTextScanner) ScanDecoder(d TextDecoder) {
+func (cfs *CompositeTextScanner) ScanDecoder(d ResultDecoder) {
 	if cfs.err != nil {
 		return
 	}
 
 	if cfs.Next() {
-		cfs.err = d.DecodeText(cfs.ci, cfs.fieldBytes)
+		cfs.err = d.DecodeResult(cfs.ci, 0, TextFormatCode, cfs.fieldBytes)
 	} else {
 		cfs.err = errors.New("read past end of composite")
 	}
@@ -547,16 +591,16 @@ func (b *CompositeBinaryBuilder) AppendValue(oid uint32, field interface{}) {
 		return
 	}
 
-	binaryEncoder, ok := dt.Value.(BinaryEncoder)
+	paramEncoder, ok := dt.Value.(ParamEncoder)
 	if !ok {
-		b.err = fmt.Errorf("unable to encode binary for OID: %d", oid)
+		b.err = fmt.Errorf("unable to encode for OID: %d", oid)
 		return
 	}
 
-	b.AppendEncoder(oid, binaryEncoder)
+	b.AppendEncoder(oid, paramEncoder)
 }
 
-func (b *CompositeBinaryBuilder) AppendEncoder(oid uint32, field BinaryEncoder) {
+func (b *CompositeBinaryBuilder) AppendEncoder(oid uint32, field ParamEncoder) {
 	if b.err != nil {
 		return
 	}
@@ -564,7 +608,7 @@ func (b *CompositeBinaryBuilder) AppendEncoder(oid uint32, field BinaryEncoder)
 	b.buf = pgio.AppendUint32(b.buf, oid)
 	lengthPos := len(b.buf)
 	b.buf = pgio.AppendInt32(b.buf, -1)
-	fieldBuf, err := field.EncodeBinary(b.ci, b.buf)
+	fieldBuf, err := field.EncodeParam(b.ci, oid, BinaryFormatCode, b.buf)
 	if err != nil {
 		b.err = err
 		return
@@ -622,21 +666,21 @@ func (b *CompositeTextBuilder) AppendValue(field interface{}) {
 		return
 	}
 
-	textEncoder, ok := dt.Value.(TextEncoder)
+	paramEncoder, ok := dt.Value.(ParamEncoder)
 	if !ok {
-		b.err = fmt.Errorf("unable to encode text for value: %v", field)
+		b.err = fmt.Errorf("unable to encode for value: %v", field)
 		return
 	}
 
-	b.AppendEncoder(textEncoder)
+	b.AppendEncoder(paramEncoder)
 }
 
-func (b *CompositeTextBuilder) AppendEncoder(field TextEncoder) {
+func (b *CompositeTextBuilder) AppendEncoder(field ParamEncoder) {
 	if b.err != nil {
 		return
 	}
 
-	fieldBuf, err := field.EncodeText(b.ci, b.fieldBuf[0:0])
+	fieldBuf, err := field.EncodeParam(b.ci, 0, TextFormatCode, b.fieldBuf[0:0])
 	if err != nil {
 		b.err = err
 		return

pgtype.go

@@ -147,10 +147,9 @@ type TypeValue interface {
 // ValueTranscoder is a value that implements the text and binary encoding and decoding interfaces.
 type ValueTranscoder interface {
 	Value
-	TextEncoder
+	FormatSupport
-	BinaryEncoder
+	ParamEncoder
-	TextDecoder
+	ResultDecoder
-	BinaryDecoder
 }
 
 type FormatSupport interface {
@@ -160,12 +159,17 @@ type FormatSupport interface {
 }
 
 type ParamEncoder interface {
-	FormatSupport
+	// EncodeParam should append the encoded value of self to buf. If self is the
+	// SQL value NULL then append nothing and return (nil, nil). The caller of
+	// EncodeText is responsible for writing the correct NULL value or the
+	// length of the data written.
 	EncodeParam(ci *ConnInfo, oid uint32, format int16, buf []byte) (newBuf []byte, err error)
 }
 
 type ResultDecoder interface {
-	FormatSupport
+	// DecodeResult decodes src into ResultDecoder. If src is nil then the
+	// original SQL value is NULL. ResultDecoder takes ownership of src. The
+	// caller MUST not use it again.
 	DecodeResult(ci *ConnInfo, oid uint32, format int16, src []byte) error
 }