154 lines
3.0 KiB
Go
154 lines
3.0 KiB
Go
// Copyright 2015 Light Code Labs, LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package caddyfile
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import (
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"bufio"
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"io"
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"unicode"
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)
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type (
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// lexer is a utility which can get values, token by
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// token, from a Reader. A token is a word, and tokens
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// are separated by whitespace. A word can be enclosed
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// in quotes if it contains whitespace.
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lexer struct {
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reader *bufio.Reader
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token Token
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line int
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}
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// Token represents a single parsable unit.
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Token struct {
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File string
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Line int
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Text string
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}
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)
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// load prepares the lexer to scan an input for tokens.
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// It discards any leading byte order mark.
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func (l *lexer) load(input io.Reader) error {
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l.reader = bufio.NewReader(input)
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l.line = 1
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// discard byte order mark, if present
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firstCh, _, err := l.reader.ReadRune()
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if err != nil {
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if err == io.EOF {
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return nil
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}
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return err
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}
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if firstCh != 0xFEFF {
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err := l.reader.UnreadRune()
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if err != nil {
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return err
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}
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}
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return nil
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}
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// next loads the next token into the lexer.
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// A token is delimited by whitespace, unless
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// the token starts with a quotes character (")
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// in which case the token goes until the closing
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// quotes (the enclosing quotes are not included).
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// Inside quoted strings, quotes may be escaped
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// with a preceding \ character. No other chars
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// may be escaped. The rest of the line is skipped
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// if a "#" character is read in. Returns true if
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// a token was loaded; false otherwise.
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func (l *lexer) next() bool {
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var val []rune
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var comment, quoted, escaped bool
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makeToken := func() bool {
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l.token.Text = string(val)
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return true
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}
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for {
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ch, _, err := l.reader.ReadRune()
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if err != nil {
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if len(val) > 0 {
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return makeToken()
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}
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if err == io.EOF {
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return false
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}
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panic(err)
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}
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if quoted {
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if !escaped {
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if ch == '\\' {
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escaped = true
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continue
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} else if ch == '"' {
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quoted = false
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return makeToken()
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}
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}
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if ch == '\n' {
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l.line++
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}
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if escaped {
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// only escape quotes
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if ch != '"' {
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val = append(val, '\\')
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}
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}
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val = append(val, ch)
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escaped = false
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continue
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}
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if unicode.IsSpace(ch) {
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if ch == '\r' {
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continue
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}
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if ch == '\n' {
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l.line++
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comment = false
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}
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if len(val) > 0 {
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return makeToken()
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}
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continue
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}
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if ch == '#' {
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comment = true
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}
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if comment {
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continue
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}
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if len(val) == 0 {
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l.token = Token{Line: l.line}
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if ch == '"' {
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quoted = true
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continue
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}
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}
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val = append(val, ch)
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}
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}
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