Jack Christensen
118 lines
2.3 KiB
Go
118 lines
2.3 KiB
Go
package pgproto3
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import (
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"encoding/binary"
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"io"
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"github.com/pkg/errors"
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)
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// Backend acts as a server for the PostgreSQL wire protocol version 3.
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type Backend struct {
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cr ChunkReader
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w io.Writer
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// Frontend message flyweights
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bind Bind
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_close Close
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copyFail CopyFail
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describe Describe
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execute Execute
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flush Flush
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parse Parse
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passwordMessage PasswordMessage
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query Query
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startupMessage StartupMessage
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sync Sync
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terminate Terminate
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bodyLen int
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msgType byte
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partialMsg bool
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}
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// NewBackend creates a new Backend.
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func NewBackend(cr ChunkReader, w io.Writer) (*Backend, error) {
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return &Backend{cr: cr, w: w}, nil
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}
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// Send sends a message to the frontend.
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func (b *Backend) Send(msg BackendMessage) error {
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_, err := b.w.Write(msg.Encode(nil))
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return err
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}
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// ReceiveStartupMessage receives the initial startup message. This method is used of the normal Receive method
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// because StartupMessage and SSLRequest are "special" and do not include the message type as the first byte.
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func (b *Backend) ReceiveStartupMessage() (*StartupMessage, error) {
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buf, err := b.cr.Next(4)
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if err != nil {
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return nil, err
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}
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msgSize := int(binary.BigEndian.Uint32(buf) - 4)
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buf, err = b.cr.Next(msgSize)
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if err != nil {
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return nil, err
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}
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err = b.startupMessage.Decode(buf)
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if err != nil {
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return nil, err
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}
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return &b.startupMessage, nil
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}
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// Receive receives a message from the frontend.
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func (b *Backend) Receive() (FrontendMessage, error) {
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if !b.partialMsg {
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header, err := b.cr.Next(5)
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if err != nil {
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return nil, err
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}
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b.msgType = header[0]
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b.bodyLen = int(binary.BigEndian.Uint32(header[1:])) - 4
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b.partialMsg = true
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}
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var msg FrontendMessage
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switch b.msgType {
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case 'B':
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msg = &b.bind
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case 'C':
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msg = &b._close
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case 'D':
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msg = &b.describe
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case 'E':
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msg = &b.execute
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case 'f':
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msg = &b.copyFail
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case 'H':
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msg = &b.flush
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case 'P':
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msg = &b.parse
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case 'p':
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msg = &b.passwordMessage
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case 'Q':
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msg = &b.query
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case 'S':
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msg = &b.sync
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case 'X':
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msg = &b.terminate
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default:
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return nil, errors.Errorf("unknown message type: %c", b.msgType)
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}
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msgBody, err := b.cr.Next(b.bodyLen)
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if err != nil {
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return nil, err
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}
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b.partialMsg = false
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err = msg.Decode(msgBody)
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return msg, err
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}
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