github.com/jackc/pgx/v5@v5.5.5/pgproto3/parameter_description.go (about)

     1  package pgproto3
     2  
     3  import (
     4  	"bytes"
     5  	"encoding/binary"
     6  	"encoding/json"
     7  	"errors"
     8  	"math"
     9  
    10  	"github.com/jackc/pgx/v5/internal/pgio"
    11  )
    12  
    13  type ParameterDescription struct {
    14  	ParameterOIDs []uint32
    15  }
    16  
    17  // Backend identifies this message as sendable by the PostgreSQL backend.
    18  func (*ParameterDescription) Backend() {}
    19  
    20  // Decode decodes src into dst. src must contain the complete message with the exception of the initial 1 byte message
    21  // type identifier and 4 byte message length.
    22  func (dst *ParameterDescription) Decode(src []byte) error {
    23  	buf := bytes.NewBuffer(src)
    24  
    25  	if buf.Len() < 2 {
    26  		return &invalidMessageFormatErr{messageType: "ParameterDescription"}
    27  	}
    28  
    29  	// Reported parameter count will be incorrect when number of args is greater than uint16
    30  	buf.Next(2)
    31  	// Instead infer parameter count by remaining size of message
    32  	parameterCount := buf.Len() / 4
    33  
    34  	*dst = ParameterDescription{ParameterOIDs: make([]uint32, parameterCount)}
    35  
    36  	for i := 0; i < parameterCount; i++ {
    37  		dst.ParameterOIDs[i] = binary.BigEndian.Uint32(buf.Next(4))
    38  	}
    39  
    40  	return nil
    41  }
    42  
    43  // Encode encodes src into dst. dst will include the 1 byte message type identifier and the 4 byte message length.
    44  func (src *ParameterDescription) Encode(dst []byte) ([]byte, error) {
    45  	dst, sp := beginMessage(dst, 't')
    46  
    47  	if len(src.ParameterOIDs) > math.MaxUint16 {
    48  		return nil, errors.New("too many parameter oids")
    49  	}
    50  	dst = pgio.AppendUint16(dst, uint16(len(src.ParameterOIDs)))
    51  	for _, oid := range src.ParameterOIDs {
    52  		dst = pgio.AppendUint32(dst, oid)
    53  	}
    54  
    55  	return finishMessage(dst, sp)
    56  }
    57  
    58  // MarshalJSON implements encoding/json.Marshaler.
    59  func (src ParameterDescription) MarshalJSON() ([]byte, error) {
    60  	return json.Marshal(struct {
    61  		Type          string
    62  		ParameterOIDs []uint32
    63  	}{
    64  		Type:          "ParameterDescription",
    65  		ParameterOIDs: src.ParameterOIDs,
    66  	})
    67  }