mirror of
https://github.com/gohugoio/hugo.git
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129 lines
3.3 KiB
Go
129 lines
3.3 KiB
Go
// Copyright 2018 The Hugo Authors. All rights reserved.
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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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// 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 pageparser provides a parser for Hugo content files (Markdown, HTML etc.) in Hugo.
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// This implementation is highly inspired by the great talk given by Rob Pike called "Lexical Scanning in Go"
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// It's on YouTube, Google it!.
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// See slides here: http://cuddle.googlecode.com/hg/talk/lex.html
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package pageparser
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import (
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"bytes"
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"io"
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"io/ioutil"
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"github.com/pkg/errors"
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)
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// Result holds the parse result.
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type Result interface {
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// Iterator returns a new Iterator positioned at the benning of the parse tree.
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Iterator() *Iterator
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// Input returns the input to Parse.
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Input() []byte
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}
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var _ Result = (*pageLexer)(nil)
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// Parse parses the page in the given reader.
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func Parse(r io.Reader) (Result, error) {
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b, err := ioutil.ReadAll(r)
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if err != nil {
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return nil, errors.Wrap(err, "failed to read page content")
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}
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lexer := newPageLexer(b, 0, lexIntroSection)
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lexer.run()
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return lexer, nil
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}
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func parseMainSection(input []byte, from int) Result {
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lexer := newPageLexer(input, from, lexMainSection)
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lexer.run()
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return lexer
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}
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// An Iterator has methods to iterate a parsed page with support going back
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// if needed.
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type Iterator struct {
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l *pageLexer
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lastPos int // position of the last item returned by nextItem
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}
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// consumes and returns the next item
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func (t *Iterator) Next() Item {
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t.lastPos++
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return t.current()
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}
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// Input returns the input source.
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func (t *Iterator) Input() []byte {
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return t.l.Input()
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}
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var errIndexOutOfBounds = Item{tError, 0, []byte("no more tokens")}
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func (t *Iterator) current() Item {
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if t.lastPos >= len(t.l.items) {
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return errIndexOutOfBounds
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}
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return t.l.items[t.lastPos]
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}
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// backs up one token.
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func (t *Iterator) Backup() {
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if t.lastPos < 0 {
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panic("need to go forward before going back")
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}
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t.lastPos--
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}
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// check for non-error and non-EOF types coming next
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func (t *Iterator) IsValueNext() bool {
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i := t.Peek()
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return i.Type != tError && i.Type != tEOF
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}
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// look at, but do not consume, the next item
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// repeated, sequential calls will return the same item
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func (t *Iterator) Peek() Item {
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return t.l.items[t.lastPos+1]
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}
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// PeekWalk will feed the next items in the iterator to walkFn
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// until it returns false.
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func (t *Iterator) PeekWalk(walkFn func(item Item) bool) {
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for i := t.lastPos + 1; i < len(t.l.items); i++ {
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item := t.l.items[i]
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if !walkFn(item) {
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break
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}
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}
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}
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// Consume is a convencience method to consume the next n tokens,
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// but back off Errors and EOF.
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func (t *Iterator) Consume(cnt int) {
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for i := 0; i < cnt; i++ {
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token := t.Next()
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if token.Type == tError || token.Type == tEOF {
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t.Backup()
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break
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}
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}
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}
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// LineNumber returns the current line number. Used for logging.
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func (t *Iterator) LineNumber() int {
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return bytes.Count(t.l.input[:t.current().Pos], lf) + 1
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}
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