startup_message.go

Documentation: github.com/jackc/pgx/v5/pgproto3

     1  package pgproto3
     2  
     3  import (
     4  	"bytes"
     5  	"encoding/binary"
     6  	"encoding/json"
     7  	"errors"
     8  	"fmt"
     9  
    10  	"github.com/jackc/pgx/v5/internal/pgio"
    11  )
    12  
    13  const ProtocolVersionNumber = 196608 // 3.0
    14  
    15  type StartupMessage struct {
    16  	ProtocolVersion uint32
    17  	Parameters      map[string]string
    18  }
    19  
    20  // Frontend identifies this message as sendable by a PostgreSQL frontend.
    21  func (*StartupMessage) Frontend() {}
    22  
    23  // Decode decodes src into dst. src must contain the complete message with the exception of the initial 1 byte message
    24  // type identifier and 4 byte message length.
    25  func (dst *StartupMessage) Decode(src []byte) error {
    26  	if len(src) < 4 {
    27  		return errors.New("startup message too short")
    28  	}
    29  
    30  	dst.ProtocolVersion = binary.BigEndian.Uint32(src)
    31  	rp := 4
    32  
    33  	if dst.ProtocolVersion != ProtocolVersionNumber {
    34  		return fmt.Errorf("Bad startup message version number. Expected %d, got %d", ProtocolVersionNumber, dst.ProtocolVersion)
    35  	}
    36  
    37  	dst.Parameters = make(map[string]string)
    38  	for {
    39  		idx := bytes.IndexByte(src[rp:], 0)
    40  		if idx < 0 {
    41  			return &invalidMessageFormatErr{messageType: "StartupMessage"}
    42  		}
    43  		key := string(src[rp : rp+idx])
    44  		rp += idx + 1
    45  
    46  		idx = bytes.IndexByte(src[rp:], 0)
    47  		if idx < 0 {
    48  			return &invalidMessageFormatErr{messageType: "StartupMessage"}
    49  		}
    50  		value := string(src[rp : rp+idx])
    51  		rp += idx + 1
    52  
    53  		dst.Parameters[key] = value
    54  
    55  		if len(src[rp:]) == 1 {
    56  			if src[rp] != 0 {
    57  				return fmt.Errorf("Bad startup message last byte. Expected 0, got %d", src[rp])
    58  			}
    59  			break
    60  		}
    61  	}
    62  
    63  	return nil
    64  }
    65  
    66  // Encode encodes src into dst. dst will include the 1 byte message type identifier and the 4 byte message length.
    67  func (src *StartupMessage) Encode(dst []byte) ([]byte, error) {
    68  	sp := len(dst)
    69  	dst = pgio.AppendInt32(dst, -1)
    70  
    71  	dst = pgio.AppendUint32(dst, src.ProtocolVersion)
    72  	for k, v := range src.Parameters {
    73  		dst = append(dst, k...)
    74  		dst = append(dst, 0)
    75  		dst = append(dst, v...)
    76  		dst = append(dst, 0)
    77  	}
    78  	dst = append(dst, 0)
    79  
    80  	return finishMessage(dst, sp)
    81  }
    82  
    83  // MarshalJSON implements encoding/json.Marshaler.
    84  func (src StartupMessage) MarshalJSON() ([]byte, error) {
    85  	return json.Marshal(struct {
    86  		Type            string
    87  		ProtocolVersion uint32
    88  		Parameters      map[string]string
    89  	}{
    90  		Type:            "StartupMessage",
    91  		ProtocolVersion: src.ProtocolVersion,
    92  		Parameters:      src.Parameters,
    93  	})
    94  }
    95
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