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|
package robotstxt
import (
"bytes"
"fmt"
"go/token"
"os"
"sync"
"unicode/utf8"
)
type byteScanner struct {
pos token.Position
buf []byte
ErrorCount int
ch rune
Quiet bool
keyTokenFound bool
lastChunk bool
}
const tokEOL = "\n"
var WhitespaceChars = []rune{' ', '\t', '\v'}
var tokBuffers = sync.Pool{New: func() interface{} { return bytes.NewBuffer(make([]byte, 32)) }}
func newByteScanner(srcname string, quiet bool) *byteScanner {
return &byteScanner{
Quiet: quiet,
ch: -1,
pos: token.Position{Filename: srcname},
}
}
func (s *byteScanner) feed(input []byte, end bool) {
s.buf = input
s.pos.Offset = 0
s.pos.Line = 1
s.pos.Column = 1
s.lastChunk = end
// Read first char into look-ahead buffer `s.ch`.
if !s.nextChar() {
return
}
// Skip UTF-8 byte order mark
if s.ch == 65279 {
s.nextChar()
s.pos.Column = 1
}
}
func (s *byteScanner) GetPosition() token.Position {
return s.pos
}
func (s *byteScanner) scan() string {
// Note Offset > len, not >=, so we can scan last character.
if s.lastChunk && s.pos.Offset > len(s.buf) {
return ""
}
s.skipSpace()
if s.ch == -1 {
return ""
}
// EOL
if s.isEol() {
s.keyTokenFound = false
// skip subsequent newline chars
for s.ch != -1 && s.isEol() {
s.nextChar()
}
// emit newline as separate token
return tokEOL
}
// skip comments
if s.ch == '#' {
s.keyTokenFound = false
s.skipUntilEol()
if s.ch == -1 {
return ""
}
// emit newline as separate token
return tokEOL
}
// else we found something
tok := tokBuffers.Get().(*bytes.Buffer)
defer tokBuffers.Put(tok)
tok.Reset()
tok.WriteRune(s.ch)
s.nextChar()
for s.ch != -1 && !s.isSpace() && !s.isEol() {
// Do not consider ":" to be a token separator if a first key token
// has already been found on this line (avoid cutting an absolute URL
// after the "http:")
if s.ch == ':' && !s.keyTokenFound {
s.nextChar()
s.keyTokenFound = true
break
}
tok.WriteRune(s.ch)
s.nextChar()
}
return tok.String()
}
func (s *byteScanner) scanAll() []string {
results := make([]string, 0, 64) // random guess of average tokens length
for {
token := s.scan()
if token != "" {
results = append(results, token)
} else {
break
}
}
return results
}
func (s *byteScanner) error(pos token.Position, msg string) {
s.ErrorCount++
if !s.Quiet {
fmt.Fprintf(os.Stderr, "robotstxt from %s: %s\n", pos.String(), msg)
}
}
func (s *byteScanner) isEol() bool {
return s.ch == '\n' || s.ch == '\r'
}
func (s *byteScanner) isSpace() bool {
for _, r := range WhitespaceChars {
if s.ch == r {
return true
}
}
return false
}
func (s *byteScanner) skipSpace() {
for s.ch != -1 && s.isSpace() {
s.nextChar()
}
}
func (s *byteScanner) skipUntilEol() {
for s.ch != -1 && !s.isEol() {
s.nextChar()
}
// skip subsequent newline chars
for s.ch != -1 && s.isEol() {
s.nextChar()
}
}
// Reads next Unicode char.
func (s *byteScanner) nextChar() bool {
if s.pos.Offset >= len(s.buf) {
s.ch = -1
return false
}
s.pos.Column++
if s.ch == '\n' {
s.pos.Line++
s.pos.Column = 1
}
r, w := rune(s.buf[s.pos.Offset]), 1
if r >= 0x80 {
r, w = utf8.DecodeRune(s.buf[s.pos.Offset:])
if r == utf8.RuneError && w == 1 {
s.error(s.pos, "illegal UTF-8 encoding")
}
}
s.pos.Column++
s.pos.Offset += w
s.ch = r
return true
}
|
