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package pgproto3
import (
"encoding/hex"
"errors"
"fmt"
"github.com/jackc/pgx/v5/internal/pgio"
)
// maxMessageBodyLen is the maximum length of a message body in bytes. See PG_LARGE_MESSAGE_LIMIT in the PostgreSQL
// source. It is defined as (MaxAllocSize - 1). MaxAllocSize is defined as 0x3fffffff.
const maxMessageBodyLen = (0x3fffffff - 1)
// Message is the interface implemented by an object that can decode and encode
// a particular PostgreSQL message.
type Message interface {
// Decode is allowed and expected to retain a reference to data after
// returning (unlike encoding.BinaryUnmarshaler).
Decode(data []byte) error
// Encode appends itself to dst and returns the new buffer.
Encode(dst []byte) ([]byte, error)
}
// FrontendMessage is a message sent by the frontend (i.e. the client).
type FrontendMessage interface {
Message
Frontend() // no-op method to distinguish frontend from backend methods
}
// BackendMessage is a message sent by the backend (i.e. the server).
type BackendMessage interface {
Message
Backend() // no-op method to distinguish frontend from backend methods
}
type AuthenticationResponseMessage interface {
BackendMessage
AuthenticationResponse() // no-op method to distinguish authentication responses
}
type invalidMessageLenErr struct {
messageType string
expectedLen int
actualLen int
}
func (e *invalidMessageLenErr) Error() string {
return fmt.Sprintf("%s body must have length of %d, but it is %d", e.messageType, e.expectedLen, e.actualLen)
}
type invalidMessageFormatErr struct {
messageType string
details string
}
func (e *invalidMessageFormatErr) Error() string {
return fmt.Sprintf("%s body is invalid %s", e.messageType, e.details)
}
type writeError struct {
err error
safeToRetry bool
}
func (e *writeError) Error() string {
return fmt.Sprintf("write failed: %s", e.err.Error())
}
func (e *writeError) SafeToRetry() bool {
return e.safeToRetry
}
func (e *writeError) Unwrap() error {
return e.err
}
type ExceededMaxBodyLenErr struct {
MaxExpectedBodyLen int
ActualBodyLen int
}
func (e *ExceededMaxBodyLenErr) Error() string {
return fmt.Sprintf("invalid body length: expected at most %d, but got %d", e.MaxExpectedBodyLen, e.ActualBodyLen)
}
// getValueFromJSON gets the value from a protocol message representation in JSON.
func getValueFromJSON(v map[string]string) ([]byte, error) {
if v == nil {
return nil, nil
}
if text, ok := v["text"]; ok {
return []byte(text), nil
}
if binary, ok := v["binary"]; ok {
return hex.DecodeString(binary)
}
return nil, errors.New("unknown protocol representation")
}
// beginMessage begins a new message of type t. It appends the message type and a placeholder for the message length to
// dst. It returns the new buffer and the position of the message length placeholder.
func beginMessage(dst []byte, t byte) ([]byte, int) {
dst = append(dst, t)
sp := len(dst)
dst = pgio.AppendInt32(dst, -1)
return dst, sp
}
// finishMessage finishes a message that was started with beginMessage. It computes the message length and writes it to
// dst[sp]. If the message length is too large it returns an error. Otherwise it returns the final message buffer.
func finishMessage(dst []byte, sp int) ([]byte, error) {
messageBodyLen := len(dst[sp:])
if messageBodyLen > maxMessageBodyLen {
return nil, errors.New("message body too large")
}
pgio.SetInt32(dst[sp:], int32(messageBodyLen))
return dst, nil
}
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