368 lines
10 KiB
Go
368 lines
10 KiB
Go
package pgproto3
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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)
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// Frontend acts as a client for the PostgreSQL wire protocol version 3.
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type Frontend struct {
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cr *chunkReader
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w io.Writer
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// tracer is used to trace messages when Send or Receive is called. This means an outbound message is traced
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// before it is actually transmitted (i.e. before Flush). It is safe to change this variable when the Frontend is
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// idle. Setting and unsetting tracer provides equivalent functionality to PQtrace and PQuntrace in libpq.
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tracer *tracer
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wbuf []byte
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// Backend message flyweights
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authenticationOk AuthenticationOk
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authenticationCleartextPassword AuthenticationCleartextPassword
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authenticationMD5Password AuthenticationMD5Password
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authenticationGSS AuthenticationGSS
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authenticationGSSContinue AuthenticationGSSContinue
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authenticationSASL AuthenticationSASL
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authenticationSASLContinue AuthenticationSASLContinue
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authenticationSASLFinal AuthenticationSASLFinal
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backendKeyData BackendKeyData
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bindComplete BindComplete
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closeComplete CloseComplete
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commandComplete CommandComplete
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copyBothResponse CopyBothResponse
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copyData CopyData
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copyInResponse CopyInResponse
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copyOutResponse CopyOutResponse
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copyDone CopyDone
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dataRow DataRow
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emptyQueryResponse EmptyQueryResponse
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errorResponse ErrorResponse
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functionCallResponse FunctionCallResponse
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noData NoData
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noticeResponse NoticeResponse
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notificationResponse NotificationResponse
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parameterDescription ParameterDescription
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parameterStatus ParameterStatus
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parseComplete ParseComplete
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readyForQuery ReadyForQuery
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rowDescription RowDescription
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portalSuspended PortalSuspended
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bodyLen int
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msgType byte
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partialMsg bool
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authType uint32
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}
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// NewFrontend creates a new Frontend.
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func NewFrontend(r io.Reader, w io.Writer) *Frontend {
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cr := newChunkReader(r, 0)
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return &Frontend{cr: cr, w: w}
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}
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// Send sends a message to the backend (i.e. the server). The message is not guaranteed to be written until Flush is
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// called.
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//
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// Send can work with any FrontendMessage. Some commonly used message types such as Bind have specialized send methods
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// such as SendBind. These methods should be preferred when the type of message is known up front (e.g. when building an
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// extended query protocol query) as they may be faster due to knowing the type of msg rather than it being hidden
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// behind an interface.
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func (f *Frontend) Send(msg FrontendMessage) {
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prevLen := len(f.wbuf)
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f.wbuf = msg.Encode(f.wbuf)
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if f.tracer != nil {
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f.tracer.traceMessage('F', int32(len(f.wbuf)-prevLen), msg)
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}
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}
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// Flush writes any pending messages to the backend (i.e. the server).
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func (f *Frontend) Flush() error {
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if len(f.wbuf) == 0 {
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return nil
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}
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n, err := f.w.Write(f.wbuf)
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const maxLen = 1024
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if len(f.wbuf) > maxLen {
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f.wbuf = make([]byte, 0, maxLen)
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} else {
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f.wbuf = f.wbuf[:0]
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}
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if err != nil {
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return &writeError{err: err, safeToRetry: n == 0}
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}
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return nil
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}
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// Trace starts tracing the message traffic to w. It writes in a similar format to that produced by the libpq function
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// PQtrace.
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func (f *Frontend) Trace(w io.Writer, options TracerOptions) {
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f.tracer = &tracer{
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w: w,
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buf: &bytes.Buffer{},
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TracerOptions: options,
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}
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}
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// Untrace stops tracing.
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func (f *Frontend) Untrace() {
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f.tracer = nil
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}
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// SendBind sends a Bind message to the backend (i.e. the server). The message is not guaranteed to be written until
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// Flush is called.
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func (f *Frontend) SendBind(msg *Bind) {
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prevLen := len(f.wbuf)
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f.wbuf = msg.Encode(f.wbuf)
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if f.tracer != nil {
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f.tracer.traceBind('F', int32(len(f.wbuf)-prevLen), msg)
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}
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}
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// SendParse sends a Parse message to the backend (i.e. the server). The message is not guaranteed to be written until
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// Flush is called.
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func (f *Frontend) SendParse(msg *Parse) {
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prevLen := len(f.wbuf)
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f.wbuf = msg.Encode(f.wbuf)
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if f.tracer != nil {
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f.tracer.traceParse('F', int32(len(f.wbuf)-prevLen), msg)
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}
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}
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// SendClose sends a Close message to the backend (i.e. the server). The message is not guaranteed to be written until
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// Flush is called.
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func (f *Frontend) SendClose(msg *Close) {
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prevLen := len(f.wbuf)
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f.wbuf = msg.Encode(f.wbuf)
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if f.tracer != nil {
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f.tracer.traceClose('F', int32(len(f.wbuf)-prevLen), msg)
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}
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}
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// SendDescribe sends a Describe message to the backend (i.e. the server). The message is not guaranteed to be written until
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// Flush is called.
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func (f *Frontend) SendDescribe(msg *Describe) {
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prevLen := len(f.wbuf)
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f.wbuf = msg.Encode(f.wbuf)
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if f.tracer != nil {
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f.tracer.traceDescribe('F', int32(len(f.wbuf)-prevLen), msg)
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}
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}
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// SendExecute sends a Execute message to the backend (i.e. the server). The message is not guaranteed to be written until
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// Flush is called.
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func (f *Frontend) SendExecute(msg *Execute) {
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prevLen := len(f.wbuf)
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f.wbuf = msg.Encode(f.wbuf)
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if f.tracer != nil {
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f.tracer.TraceQueryute('F', int32(len(f.wbuf)-prevLen), msg)
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}
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}
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// SendSync sends a Sync message to the backend (i.e. the server). The message is not guaranteed to be written until
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// Flush is called.
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func (f *Frontend) SendSync(msg *Sync) {
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prevLen := len(f.wbuf)
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f.wbuf = msg.Encode(f.wbuf)
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if f.tracer != nil {
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f.tracer.traceSync('F', int32(len(f.wbuf)-prevLen), msg)
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}
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}
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// SendQuery sends a Query message to the backend (i.e. the server). The message is not guaranteed to be written until
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// Flush is called.
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func (f *Frontend) SendQuery(msg *Query) {
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prevLen := len(f.wbuf)
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f.wbuf = msg.Encode(f.wbuf)
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if f.tracer != nil {
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f.tracer.traceQuery('F', int32(len(f.wbuf)-prevLen), msg)
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}
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}
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// SendUnbufferedEncodedCopyData immediately sends an encoded CopyData message to the backend (i.e. the server). This method
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// is more efficient than sending a CopyData message with Send as the message data is not copied to the internal buffer
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// before being written out. The internal buffer is flushed before the message is sent.
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func (f *Frontend) SendUnbufferedEncodedCopyData(msg []byte) error {
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err := f.Flush()
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if err != nil {
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return err
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}
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n, err := f.w.Write(msg)
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if err != nil {
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return &writeError{err: err, safeToRetry: n == 0}
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}
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if f.tracer != nil {
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f.tracer.traceCopyData('F', int32(len(msg)-1), &CopyData{})
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}
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return nil
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}
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func translateEOFtoErrUnexpectedEOF(err error) error {
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if err == io.EOF {
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return io.ErrUnexpectedEOF
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}
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return err
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}
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// Receive receives a message from the backend. The returned message is only valid until the next call to Receive.
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func (f *Frontend) Receive() (BackendMessage, error) {
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if !f.partialMsg {
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header, err := f.cr.Next(5)
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if err != nil {
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return nil, translateEOFtoErrUnexpectedEOF(err)
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}
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f.msgType = header[0]
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msgLength := int(binary.BigEndian.Uint32(header[1:]))
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if msgLength < 4 {
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return nil, fmt.Errorf("invalid message length: %d", msgLength)
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}
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f.bodyLen = msgLength - 4
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f.partialMsg = true
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}
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msgBody, err := f.cr.Next(f.bodyLen)
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if err != nil {
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return nil, translateEOFtoErrUnexpectedEOF(err)
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}
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f.partialMsg = false
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var msg BackendMessage
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switch f.msgType {
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case '1':
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msg = &f.parseComplete
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case '2':
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msg = &f.bindComplete
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case '3':
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msg = &f.closeComplete
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case 'A':
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msg = &f.notificationResponse
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case 'c':
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msg = &f.copyDone
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case 'C':
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msg = &f.commandComplete
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case 'd':
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msg = &f.copyData
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case 'D':
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msg = &f.dataRow
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case 'E':
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msg = &f.errorResponse
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case 'G':
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msg = &f.copyInResponse
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case 'H':
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msg = &f.copyOutResponse
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case 'I':
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msg = &f.emptyQueryResponse
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case 'K':
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msg = &f.backendKeyData
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case 'n':
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msg = &f.noData
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case 'N':
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msg = &f.noticeResponse
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case 'R':
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var err error
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msg, err = f.findAuthenticationMessageType(msgBody)
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if err != nil {
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return nil, err
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}
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case 's':
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msg = &f.portalSuspended
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case 'S':
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msg = &f.parameterStatus
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case 't':
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msg = &f.parameterDescription
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case 'T':
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msg = &f.rowDescription
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case 'V':
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msg = &f.functionCallResponse
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case 'W':
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msg = &f.copyBothResponse
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case 'Z':
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msg = &f.readyForQuery
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default:
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return nil, fmt.Errorf("unknown message type: %c", f.msgType)
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}
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err = msg.Decode(msgBody)
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if err != nil {
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return nil, err
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}
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if f.tracer != nil {
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f.tracer.traceMessage('B', int32(5+len(msgBody)), msg)
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}
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return msg, nil
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}
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// Authentication message type constants.
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// See src/include/libpq/pqcomm.h for all
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// constants.
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const (
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AuthTypeOk = 0
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AuthTypeCleartextPassword = 3
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AuthTypeMD5Password = 5
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AuthTypeSCMCreds = 6
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AuthTypeGSS = 7
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AuthTypeGSSCont = 8
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AuthTypeSSPI = 9
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AuthTypeSASL = 10
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AuthTypeSASLContinue = 11
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AuthTypeSASLFinal = 12
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)
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func (f *Frontend) findAuthenticationMessageType(src []byte) (BackendMessage, error) {
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if len(src) < 4 {
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return nil, errors.New("authentication message too short")
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}
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f.authType = binary.BigEndian.Uint32(src[:4])
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switch f.authType {
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case AuthTypeOk:
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return &f.authenticationOk, nil
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case AuthTypeCleartextPassword:
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return &f.authenticationCleartextPassword, nil
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case AuthTypeMD5Password:
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return &f.authenticationMD5Password, nil
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case AuthTypeSCMCreds:
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return nil, errors.New("AuthTypeSCMCreds is unimplemented")
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case AuthTypeGSS:
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return &f.authenticationGSS, nil
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case AuthTypeGSSCont:
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return &f.authenticationGSSContinue, nil
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case AuthTypeSSPI:
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return nil, errors.New("AuthTypeSSPI is unimplemented")
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case AuthTypeSASL:
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return &f.authenticationSASL, nil
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case AuthTypeSASLContinue:
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return &f.authenticationSASLContinue, nil
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case AuthTypeSASLFinal:
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return &f.authenticationSASLFinal, nil
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default:
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return nil, fmt.Errorf("unknown authentication type: %d", f.authType)
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}
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}
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// GetAuthType returns the authType used in the current state of the frontend.
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// See SetAuthType for more information.
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func (f *Frontend) GetAuthType() uint32 {
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return f.authType
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}
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func (f *Frontend) ReadBufferLen() int {
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return f.cr.wp - f.cr.rp
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}
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