well-goknown/vendor/github.com/gobwas/httphead/lexer.go

361 lines
6.7 KiB
Go
Raw Permalink Normal View History

package httphead
import (
"bytes"
)
// ItemType encodes type of the lexing token.
type ItemType int
const (
// ItemUndef reports that token is undefined.
ItemUndef ItemType = iota
// ItemToken reports that token is RFC2616 token.
ItemToken
// ItemSeparator reports that token is RFC2616 separator.
ItemSeparator
// ItemString reports that token is RFC2616 quouted string.
ItemString
// ItemComment reports that token is RFC2616 comment.
ItemComment
// ItemOctet reports that token is octet slice.
ItemOctet
)
// Scanner represents header tokens scanner.
// See https://tools.ietf.org/html/rfc2616#section-2
type Scanner struct {
data []byte
pos int
itemType ItemType
itemBytes []byte
err bool
}
// NewScanner creates new RFC2616 data scanner.
func NewScanner(data []byte) *Scanner {
return &Scanner{data: data}
}
// Next scans for next token. It returns true on successful scanning, and false
// on error or EOF.
func (l *Scanner) Next() bool {
c, ok := l.nextChar()
if !ok {
return false
}
switch c {
case '"': // quoted-string;
return l.fetchQuotedString()
case '(': // comment;
return l.fetchComment()
case '\\', ')': // unexpected chars;
l.err = true
return false
default:
return l.fetchToken()
}
}
// FetchUntil fetches ItemOctet from current scanner position to first
// occurence of the c or to the end of the underlying data.
func (l *Scanner) FetchUntil(c byte) bool {
l.resetItem()
if l.pos == len(l.data) {
return false
}
return l.fetchOctet(c)
}
// Peek reads byte at current position without advancing it. On end of data it
// returns 0.
func (l *Scanner) Peek() byte {
if l.pos == len(l.data) {
return 0
}
return l.data[l.pos]
}
// Peek2 reads two first bytes at current position without advancing it.
// If there not enough data it returs 0.
func (l *Scanner) Peek2() (a, b byte) {
if l.pos == len(l.data) {
return 0, 0
}
if l.pos+1 == len(l.data) {
return l.data[l.pos], 0
}
return l.data[l.pos], l.data[l.pos+1]
}
// Buffered reporst how many bytes there are left to scan.
func (l *Scanner) Buffered() int {
return len(l.data) - l.pos
}
// Advance moves current position index at n bytes. It returns true on
// successful move.
func (l *Scanner) Advance(n int) bool {
l.pos += n
if l.pos > len(l.data) {
l.pos = len(l.data)
return false
}
return true
}
// Skip skips all bytes until first occurence of c.
func (l *Scanner) Skip(c byte) {
if l.err {
return
}
// Reset scanner state.
l.resetItem()
if i := bytes.IndexByte(l.data[l.pos:], c); i == -1 {
// Reached the end of data.
l.pos = len(l.data)
} else {
l.pos += i + 1
}
}
// SkipEscaped skips all bytes until first occurence of non-escaped c.
func (l *Scanner) SkipEscaped(c byte) {
if l.err {
return
}
// Reset scanner state.
l.resetItem()
if i := ScanUntil(l.data[l.pos:], c); i == -1 {
// Reached the end of data.
l.pos = len(l.data)
} else {
l.pos += i + 1
}
}
// Type reports current token type.
func (l *Scanner) Type() ItemType {
return l.itemType
}
// Bytes returns current token bytes.
func (l *Scanner) Bytes() []byte {
return l.itemBytes
}
func (l *Scanner) nextChar() (byte, bool) {
// Reset scanner state.
l.resetItem()
if l.err {
return 0, false
}
l.pos += SkipSpace(l.data[l.pos:])
if l.pos == len(l.data) {
return 0, false
}
return l.data[l.pos], true
}
func (l *Scanner) resetItem() {
l.itemType = ItemUndef
l.itemBytes = nil
}
func (l *Scanner) fetchOctet(c byte) bool {
i := l.pos
if j := bytes.IndexByte(l.data[l.pos:], c); j == -1 {
// Reached the end of data.
l.pos = len(l.data)
} else {
l.pos += j
}
l.itemType = ItemOctet
l.itemBytes = l.data[i:l.pos]
return true
}
func (l *Scanner) fetchToken() bool {
n, t := ScanToken(l.data[l.pos:])
if n == -1 {
l.err = true
return false
}
l.itemType = t
l.itemBytes = l.data[l.pos : l.pos+n]
l.pos += n
return true
}
func (l *Scanner) fetchQuotedString() (ok bool) {
l.pos++
n := ScanUntil(l.data[l.pos:], '"')
if n == -1 {
l.err = true
return false
}
l.itemType = ItemString
l.itemBytes = RemoveByte(l.data[l.pos:l.pos+n], '\\')
l.pos += n + 1
return true
}
func (l *Scanner) fetchComment() (ok bool) {
l.pos++
n := ScanPairGreedy(l.data[l.pos:], '(', ')')
if n == -1 {
l.err = true
return false
}
l.itemType = ItemComment
l.itemBytes = RemoveByte(l.data[l.pos:l.pos+n], '\\')
l.pos += n + 1
return true
}
// ScanUntil scans for first non-escaped character c in given data.
// It returns index of matched c and -1 if c is not found.
func ScanUntil(data []byte, c byte) (n int) {
for {
i := bytes.IndexByte(data[n:], c)
if i == -1 {
return -1
}
n += i
if n == 0 || data[n-1] != '\\' {
break
}
n++
}
return
}
// ScanPairGreedy scans for complete pair of opening and closing chars in greedy manner.
// Note that first opening byte must not be present in data.
func ScanPairGreedy(data []byte, open, close byte) (n int) {
var m int
opened := 1
for {
i := bytes.IndexByte(data[n:], close)
if i == -1 {
return -1
}
n += i
// If found index is not escaped then it is the end.
if n == 0 || data[n-1] != '\\' {
opened--
}
for m < i {
j := bytes.IndexByte(data[m:i], open)
if j == -1 {
break
}
m += j + 1
opened++
}
if opened == 0 {
break
}
n++
m = n
}
return
}
// RemoveByte returns data without c. If c is not present in data it returns
// the same slice. If not, it copies data without c.
func RemoveByte(data []byte, c byte) []byte {
j := bytes.IndexByte(data, c)
if j == -1 {
return data
}
n := len(data) - 1
// If character is present, than allocate slice with n-1 capacity. That is,
// resulting bytes could be at most n-1 length.
result := make([]byte, n)
k := copy(result, data[:j])
for i := j + 1; i < n; {
j = bytes.IndexByte(data[i:], c)
if j != -1 {
k += copy(result[k:], data[i:i+j])
i = i + j + 1
} else {
k += copy(result[k:], data[i:])
break
}
}
return result[:k]
}
// SkipSpace skips spaces and lws-sequences from p.
// It returns number ob bytes skipped.
func SkipSpace(p []byte) (n int) {
for len(p) > 0 {
switch {
case len(p) >= 3 &&
p[0] == '\r' &&
p[1] == '\n' &&
OctetTypes[p[2]].IsSpace():
p = p[3:]
n += 3
case OctetTypes[p[0]].IsSpace():
p = p[1:]
n++
default:
return
}
}
return
}
// ScanToken scan for next token in p. It returns length of the token and its
// type. It do not trim p.
func ScanToken(p []byte) (n int, t ItemType) {
if len(p) == 0 {
return 0, ItemUndef
}
c := p[0]
switch {
case OctetTypes[c].IsSeparator():
return 1, ItemSeparator
case OctetTypes[c].IsToken():
for n = 1; n < len(p); n++ {
c := p[n]
if !OctetTypes[c].IsToken() {
break
}
}
return n, ItemToken
default:
return -1, ItemUndef
}
}