GoToSocial/vendor/gopkg.in/mcuadros/go-syslog.v2/format/automatic.go

105 lines
3.2 KiB
Go

package format
import (
"bufio"
"bytes"
"strconv"
"gopkg.in/mcuadros/go-syslog.v2/internal/syslogparser/rfc3164"
"gopkg.in/mcuadros/go-syslog.v2/internal/syslogparser/rfc5424"
)
/* Selecting an 'Automatic' format detects incoming format (i.e. RFC3164 vs RFC5424) and Framing
* (i.e. RFC6587 s3.4.1 octet counting as described here as RFC6587, and either no framing or
* RFC6587 s3.4.2 octet stuffing / non-transparent framing, described here as either RFC3164
* or RFC6587).
*
* In essence if you don't know which format to select, or have multiple incoming formats, this
* is the one to go for. There is a theoretical performance penalty (it has to look at a few bytes
* at the start of the frame), and a risk that you may parse things you don't want to parse
* (rogue syslog clients using other formats), so if you can be absolutely sure of your syslog
* format, it would be best to select it explicitly.
*/
type Automatic struct{}
const (
detectedUnknown = iota
detectedRFC3164 = iota
detectedRFC5424 = iota
detectedRFC6587 = iota
)
/*
* Will always fallback to rfc3164 (see section 4.3.3)
*/
func detect(data []byte) int {
// all formats have a sapce somewhere
if i := bytes.IndexByte(data, ' '); i > 0 {
pLength := data[0:i]
if _, err := strconv.Atoi(string(pLength)); err == nil {
return detectedRFC6587
}
// are we starting with <
if data[0] != '<' {
return detectedRFC3164
}
// is there a close angle bracket before the ' '? there should be
angle := bytes.IndexByte(data, '>')
if (angle < 0) || (angle >= i) {
return detectedRFC3164
}
// if a single digit immediately follows the angle bracket, then a space
// it is RFC5424, as RFC3164 must begin with a letter (month name)
if (angle+2 == i) && (data[angle+1] >= '0') && (data[angle+1] <= '9') {
return detectedRFC5424
} else {
return detectedRFC3164
}
}
// fallback to rfc 3164 section 4.3.3
return detectedRFC3164
}
func (f *Automatic) GetParser(line []byte) LogParser {
switch format := detect(line); format {
case detectedRFC3164:
return &parserWrapper{rfc3164.NewParser(line)}
case detectedRFC5424:
return &parserWrapper{rfc5424.NewParser(line)}
default:
// If the line was an RFC6587 line, the splitter should already have removed the length,
// so one of the above two will be chosen if the line is correctly formed. However, it
// may have a second length illegally placed at the start, in which case the detector
// will return detectedRFC6587. The line may also simply be malformed after the length in
// which case we will have detectedUnknown. In this case we return the simplest parser so
// the illegally formatted line is properly handled
return &parserWrapper{rfc3164.NewParser(line)}
}
}
func (f *Automatic) GetSplitFunc() bufio.SplitFunc {
return f.automaticScannerSplit
}
func (f *Automatic) automaticScannerSplit(data []byte, atEOF bool) (advance int, token []byte, err error) {
if atEOF && len(data) == 0 {
return 0, nil, nil
}
switch format := detect(data); format {
case detectedRFC6587:
return rfc6587ScannerSplit(data, atEOF)
case detectedRFC3164, detectedRFC5424:
// the default
return bufio.ScanLines(data, atEOF)
default:
if err != nil {
return 0, nil, err
}
// Request more data
return 0, nil, nil
}
}