niki/vendor/github.com/go-sql-driver/mysql/conncheck.go

// Go MySQL Driver - A MySQL-Driver for Go's database/sql package

//

// Copyright 2019 The Go-MySQL-Driver Authors. All rights reserved.

//

// This Source Code Form is subject to the terms of the Mozilla Public

// License, v. 2.0. If a copy of the MPL was not distributed with this file,

// You can obtain one at http://mozilla.org/MPL/2.0/.

//go:build linux || darwin || dragonfly || freebsd || netbsd || openbsd || solaris || illumos
// +build linux darwin dragonfly freebsd netbsd openbsd solaris illumos

package mysql

import (
	"errors"
	"io"
	"net"
	"syscall"
)

var errUnexpectedRead = errors.New("unexpected read from socket")

func connCheck(conn net.Conn) error {

	var sysErr error

	sysConn, ok := conn.(syscall.Conn)

	if !ok {

		return nil

	}

	rawConn, err := sysConn.SyscallConn()

	if err != nil {

		return err

	}

	err = rawConn.Read(func(fd uintptr) bool {

		var buf [1]byte

		n, err := syscall.Read(int(fd), buf[:])

		switch {

		case n == 0 && err == nil:

			sysErr = io.EOF

		case n > 0:

			sysErr = errUnexpectedRead

		case err == syscall.EAGAIN || err == syscall.EWOULDBLOCK:

			sysErr = nil

		default:

			sysErr = err

		}

		return true

	})

	if err != nil {

		return err

	}

	return sysErr

}