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package pgproto3
import (
"bytes"
"encoding/json"
"errors"
"github.com/jackc/pgio"
)
type Describe struct {
ObjectType byte // 'S' = prepared statement, 'P' = portal
Name string
}
// Frontend identifies this message as sendable by a PostgreSQL frontend.
func (*Describe) Frontend() {}
// 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 *Describe) Decode(src []byte) error {
if len(src) < 2 {
return &invalidMessageFormatErr{messageType: "Describe"}
}
dst.ObjectType = src[0]
rp := 1
idx := bytes.IndexByte(src[rp:], 0)
if idx != len(src[rp:])-1 {
return &invalidMessageFormatErr{messageType: "Describe"}
}
dst.Name = string(src[rp : len(src)-1])
return nil
}
// Encode encodes src into dst. dst will include the 1 byte message type identifier and the 4 byte message length.
func (src *Describe) Encode(dst []byte) []byte {
dst = append(dst, 'D')
sp := len(dst)
dst = pgio.AppendInt32(dst, -1)
dst = append(dst, src.ObjectType)
dst = append(dst, src.Name...)
dst = append(dst, 0)
pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
return dst
}
// MarshalJSON implements encoding/json.Marshaler.
func (src Describe) MarshalJSON() ([]byte, error) {
return json.Marshal(struct {
Type string
ObjectType string
Name string
}{
Type: "Describe",
ObjectType: string(src.ObjectType),
Name: src.Name,
})
}
// UnmarshalJSON implements encoding/json.Unmarshaler.
func (dst *Describe) UnmarshalJSON(data []byte) error {
// Ignore null, like in the main JSON package.
if string(data) == "null" {
return nil
}
var msg struct {
ObjectType string
Name string
}
if err := json.Unmarshal(data, &msg); err != nil {
return err
}
if len(msg.ObjectType) != 1 {
return errors.New("invalid length for Describe.ObjectType")
}
dst.ObjectType = byte(msg.ObjectType[0])
dst.Name = msg.Name
return nil
}
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