row_description.go

package pgproto3

import (
	"bytes"
	"encoding/binary"

	"github.com/jackc/pgio"
)

const (
	TextFormat   = 0
	BinaryFormat = 1
)

type FieldDescription struct {
	Name                 []byte `json:"name" yaml:"name,omitempty"`
	FieldName            string `json:"field_name" yaml:"field_name"`
	TableOID             uint32 `json:"table_oid" yaml:"table_oid"`
	TableAttributeNumber uint16 `json:"table_attribute_number" yaml:"table_attribute_number"`
	DataTypeOID          uint32 `json:"data_type_oid" yaml:"data_type_oid"`
	DataTypeSize         int16  `json:"data_type_size" yaml:"data_type_size"`
	TypeModifier         int32  `json:"type_modifier" yaml:"type_modifier"`
	Format               int16  `json:"format" yaml:"format"`
}

// // MarshalJSON implements encoding/json.Marshaler.
// func (fd FieldDescription) MarshalJSON() ([]byte, error) {
// 	return json.Marshal(struct {
// 		Name                 string
// 		TableOID             uint32
// 		TableAttributeNumber uint16
// 		DataTypeOID          uint32
// 		DataTypeSize         int16
// 		TypeModifier         int32
// 		Format               int16
// 	}{
// 		Name:                 string(fd.Name),
// 		TableOID:             fd.TableOID,
// 		TableAttributeNumber: fd.TableAttributeNumber,
// 		DataTypeOID:          fd.DataTypeOID,
// 		DataTypeSize:         fd.DataTypeSize,
// 		TypeModifier:         fd.TypeModifier,
// 		Format:               fd.Format,
// 	})
// }

type RowDescription struct {
	Fields []FieldDescription
}

// Backend identifies this message as sendable by the PostgreSQL backend.
func (*RowDescription) Backend() {}

// Decode decodes src into dst. src must contain the complete message with the exception of the initial 1 byte message
// type identifier and 4 byte message length.
func (dst *RowDescription) Decode(src []byte) error {
	//println("RowDescription.Decode")
	if len(src) < 2 {
		return &invalidMessageFormatErr{messageType: "RowDescription"}
	}
	fieldCount := int(binary.BigEndian.Uint16(src))
	rp := 2

	dst.Fields = dst.Fields[0:0]

	for i := 0; i < fieldCount; i++ {
		var fd FieldDescription

		idx := bytes.IndexByte(src[rp:], 0)
		if idx < 0 {
			return &invalidMessageFormatErr{messageType: "RowDescription"}
		}
		fd.Name = src[rp : rp+idx]
		fd.FieldName = string(fd.Name)
		// now empty the buffer
		fd.Name = []byte{}
		rp += idx + 1

		// Since buf.Next() doesn't return an error if we hit the end of the buffer
		// check Len ahead of time
		if len(src[rp:]) < 18 {
			return &invalidMessageFormatErr{messageType: "RowDescription"}
		}

		fd.TableOID = binary.BigEndian.Uint32(src[rp:])
		rp += 4
		fd.TableAttributeNumber = binary.BigEndian.Uint16(src[rp:])
		rp += 2
		fd.DataTypeOID = binary.BigEndian.Uint32(src[rp:])
		rp += 4
		fd.DataTypeSize = int16(binary.BigEndian.Uint16(src[rp:]))
		rp += 2
		fd.TypeModifier = int32(binary.BigEndian.Uint32(src[rp:]))
		rp += 4
		fd.Format = int16(binary.BigEndian.Uint16(src[rp:]))
		rp += 2

		dst.Fields = append(dst.Fields, fd)
	}

	return nil
}

// Encode encodes src into dst. dst will include the 1 byte message type identifier and the 4 byte message length.
func (src *RowDescription) Encode(dst []byte) []byte {
	//println("RowDescription.Encode")
	dst = append(dst, 'T')
	sp := len(dst)
	dst = pgio.AppendInt32(dst, -1)

	dst = pgio.AppendUint16(dst, uint16(len(src.Fields)))
	for _, fd := range src.Fields {
		if len(fd.Name) == 0 {
			fd.Name = []byte(fd.FieldName)
		}

		dst = append(dst, fd.Name...)
		dst = append(dst, 0)

		dst = pgio.AppendUint32(dst, fd.TableOID)
		dst = pgio.AppendUint16(dst, fd.TableAttributeNumber)
		dst = pgio.AppendUint32(dst, fd.DataTypeOID)
		dst = pgio.AppendInt16(dst, fd.DataTypeSize)
		dst = pgio.AppendInt32(dst, fd.TypeModifier)
		dst = pgio.AppendInt16(dst, fd.Format)
	}

	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))

	return dst
}

// MarshalJSON implements encoding/json.Marshaler.
// func (src RowDescription) MarshalJSON() ([]byte, error) {
// 	return json.Marshal(struct {
// 		Type   string
// 		Fields []FieldDescription
// 	}{
// 		Type:   "RowDescription",
// 		Fields: src.Fields,
// 	})
// }

// UnmarshalJSON implements encoding/json.Unmarshaler.
// func (dst *RowDescription) UnmarshalJSON(data []byte) error {
// 	var msg struct {
// 		Fields []struct {
// 			Name                 string
// 			TableOID             uint32
// 			TableAttributeNumber uint16
// 			DataTypeOID          uint32
// 			DataTypeSize         int16
// 			TypeModifier         int32
// 			Format               int16
// 		}
// 	}
// 	if err := json.Unmarshal(data, &msg); err != nil {
// 		return err
// 	}
// 	dst.Fields = make([]FieldDescription, len(msg.Fields))
// 	for n, field := range msg.Fields {
// 		dst.Fields[n] = FieldDescription{
// 			Name:                 []byte(field.Name),
// 			TableOID:             field.TableOID,
// 			TableAttributeNumber: field.TableAttributeNumber,
// 			DataTypeOID:          field.DataTypeOID,
// 			DataTypeSize:         field.DataTypeSize,
// 			TypeModifier:         field.TypeModifier,
// 			Format:               field.Format,
// 		}
// 	}
// 	return nil
// }