Source: reader.go in package github.com/yuin/goldmark/text

package text

import (
	"io"
	"regexp"
	"unicode/utf8"

	"github.com/yuin/goldmark/util"
)

const invalidValue = -1

EOF indicates the end of file.

const EOF = byte(0xff)

A Reader interface provides abstracted method for reading text.

type Reader interface {
	io.RuneReader

Source returns a source of the reader.

	Source() []byte

ResetPosition resets positions.

	ResetPosition()

Peek returns a byte at current position without advancing the internal pointer.

	Peek() byte

PeekLine returns the current line without advancing the internal pointer.

	PeekLine() ([]byte, Segment)

PrecendingCharacter returns a character just before current internal pointer.

	PrecendingCharacter() rune

Value returns a value of the given segment.

	Value(Segment) []byte

LineOffset returns a distance from the line head to current position.

	LineOffset() int

Position returns current line number and position.

	Position() (int, Segment)

SetPosition sets current line number and position.

	SetPosition(int, Segment)

SetPadding sets padding to the reader.

	SetPadding(int)

Advance advances the internal pointer.

	Advance(int)

AdvanceAndSetPadding advances the internal pointer and add padding to the reader.

	AdvanceAndSetPadding(int, int)

AdvanceLine advances the internal pointer to the next line head.

	AdvanceLine()

SkipSpaces skips space characters and returns a non-blank line. If it reaches EOF, returns false.

	SkipSpaces() (Segment, int, bool)

SkipSpaces skips blank lines and returns a non-blank line. If it reaches EOF, returns false.

	SkipBlankLines() (Segment, int, bool)

Match performs regular expression matching to current line.

	Match(reg *regexp.Regexp) bool

Match performs regular expression searching to current line.

	FindSubMatch(reg *regexp.Regexp) [][]byte
}

type reader struct {
	source       []byte
	sourceLength int
	line         int
	peekedLine   []byte
	pos          Segment
	head         int
	lineOffset   int
}

NewReader return a new Reader that can read UTF-8 bytes .

func NewReader(source []byte) Reader {
	r := &reader{
		source:       source,
		sourceLength: len(source),
	}
	r.ResetPosition()
	return r
}

func (r *reader) ResetPosition() {
	r.line = -1
	r.head = 0
	r.lineOffset = -1
	r.AdvanceLine()
}

func (r *reader) Source() []byte {
	return r.source
}

func (r *reader) Value(seg Segment) []byte {
	return seg.Value(r.source)
}

func (r *reader) Peek() byte {
	if r.pos.Start >= 0 && r.pos.Start < r.sourceLength {
		if r.pos.Padding != 0 {
			return space[0]
		}
		return r.source[r.pos.Start]
	}
	return EOF
}

func (r *reader) PeekLine() ([]byte, Segment) {
	if r.pos.Start >= 0 && r.pos.Start < r.sourceLength {
		if r.peekedLine == nil {
			r.peekedLine = r.pos.Value(r.Source())
		}
		return r.peekedLine, r.pos
	}
	return nil, r.pos
}

io.RuneReader interface

func (r *reader) ReadRune() (rune, int, error) {
	return readRuneReader(r)
}

func (r *reader) LineOffset() int {
	if r.lineOffset < 0 {
		v := 0
		for i := r.head; i < r.pos.Start; i++ {
			if r.source[i] == '\t' {
				v += util.TabWidth(v)
			} else {
				v++
			}
		}
		r.lineOffset = v - r.pos.Padding
	}
	return r.lineOffset
}

func (r *reader) PrecendingCharacter() rune {
	if r.pos.Start <= 0 {
		if r.pos.Padding != 0 {
			return rune(' ')
		}
		return rune('\n')
	}
	i := r.pos.Start - 1
	for ; i >= 0; i-- {
		if utf8.RuneStart(r.source[i]) {
			break
		}
	}
	rn, _ := utf8.DecodeRune(r.source[i:])
	return rn
}

func (r *reader) Advance(n int) {
	r.lineOffset = -1
	if n < len(r.peekedLine) && r.pos.Padding == 0 {
		r.pos.Start += n
		r.peekedLine = nil
		return
	}
	r.peekedLine = nil
	l := r.sourceLength
	for ; n > 0 && r.pos.Start < l; n-- {
		if r.pos.Padding != 0 {
			r.pos.Padding--
			continue
		}
		if r.source[r.pos.Start] == '\n' {
			r.AdvanceLine()
			continue
		}
		r.pos.Start++
	}
}

func (r *reader) AdvanceAndSetPadding(n, padding int) {
	r.Advance(n)
	if padding > r.pos.Padding {
		r.SetPadding(padding)
	}
}

func (r *reader) AdvanceLine() {
	r.lineOffset = -1
	r.peekedLine = nil
	r.pos.Start = r.pos.Stop
	r.head = r.pos.Start
	if r.pos.Start < 0 {
		return
	}
	r.pos.Stop = r.sourceLength
	for i := r.pos.Start; i < r.sourceLength; i++ {
		c := r.source[i]
		if c == '\n' {
			r.pos.Stop = i + 1
			break
		}
	}
	r.line++
	r.pos.Padding = 0
}

func (r *reader) Position() (int, Segment) {
	return r.line, r.pos
}

func (r *reader) SetPosition(line int, pos Segment) {
	r.lineOffset = -1
	r.line = line
	r.pos = pos
}

func (r *reader) SetPadding(v int) {
	r.pos.Padding = v
}

func (r *reader) SkipSpaces() (Segment, int, bool) {
	return skipSpacesReader(r)
}

func (r *reader) SkipBlankLines() (Segment, int, bool) {
	return skipBlankLinesReader(r)
}

func (r *reader) Match(reg *regexp.Regexp) bool {
	return matchReader(r, reg)
}

func (r *reader) FindSubMatch(reg *regexp.Regexp) [][]byte {
	return findSubMatchReader(r, reg)
}

A BlockReader interface is a reader that is optimized for Blocks.

type BlockReader interface {

Reset resets current state and sets new segments to the reader.

	Reset(segment *Segments)
}

type blockReader struct {
	source         []byte
	segments       *Segments
	segmentsLength int
	line           int
	pos            Segment
	head           int
	last           int
	lineOffset     int
}

NewBlockReader returns a new BlockReader.

func NewBlockReader(source []byte, segments *Segments) BlockReader {
	r := &blockReader{
		source: source,
	}
	if segments != nil {
		r.Reset(segments)
	}
	return r
}

func (r *blockReader) ResetPosition() {
	r.line = -1
	r.head = 0
	r.last = 0
	r.lineOffset = -1
	r.pos.Start = -1
	r.pos.Stop = -1
	r.pos.Padding = 0
	if r.segmentsLength > 0 {
		last := r.segments.At(r.segmentsLength - 1)
		r.last = last.Stop
	}
	r.AdvanceLine()
}

func (r *blockReader) Reset(segments *Segments) {
	r.segments = segments
	r.segmentsLength = segments.Len()
	r.ResetPosition()
}

func (r *blockReader) Source() []byte {
	return r.source
}

func (r *blockReader) Value(seg Segment) []byte {
	line := r.segmentsLength - 1
	ret := make([]byte, 0, seg.Stop-seg.Start+1)
	for ; line >= 0; line-- {
		if seg.Start >= r.segments.At(line).Start {
			break
		}
	}
	i := seg.Start
	for ; line < r.segmentsLength; line++ {
		s := r.segments.At(line)
		if i < 0 {
			i = s.Start
		}
		ret = s.ConcatPadding(ret)
		for ; i < seg.Stop && i < s.Stop; i++ {
			ret = append(ret, r.source[i])
		}
		i = -1
		if s.Stop > seg.Stop {
			break
		}
	}
	return ret
}

io.RuneReader interface

func (r *blockReader) ReadRune() (rune, int, error) {
	return readRuneReader(r)
}

func (r *blockReader) PrecendingCharacter() rune {
	if r.pos.Padding != 0 {
		return rune(' ')
	}
	if r.segments.Len() < 1 {
		return rune('\n')
	}
	firstSegment := r.segments.At(0)
	if r.line == 0 && r.pos.Start <= firstSegment.Start {
		return rune('\n')
	}
	l := len(r.source)
	i := r.pos.Start - 1
	for ; i < l && i >= 0; i-- {
		if utf8.RuneStart(r.source[i]) {
			break
		}
	}
	if i < 0 || i >= l {
		return rune('\n')
	}
	rn, _ := utf8.DecodeRune(r.source[i:])
	return rn
}

func (r *blockReader) LineOffset() int {
	if r.lineOffset < 0 {
		v := 0
		for i := r.head; i < r.pos.Start; i++ {
			if r.source[i] == '\t' {
				v += util.TabWidth(v)
			} else {
				v++
			}
		}
		r.lineOffset = v - r.pos.Padding
	}
	return r.lineOffset
}

func (r *blockReader) Peek() byte {
	if r.line < r.segmentsLength && r.pos.Start >= 0 && r.pos.Start < r.last {
		if r.pos.Padding != 0 {
			return space[0]
		}
		return r.source[r.pos.Start]
	}
	return EOF
}

func (r *blockReader) PeekLine() ([]byte, Segment) {
	if r.line < r.segmentsLength && r.pos.Start >= 0 && r.pos.Start < r.last {
		return r.pos.Value(r.source), r.pos
	}
	return nil, r.pos
}

func (r *blockReader) Advance(n int) {
	r.lineOffset = -1

	if n < r.pos.Stop-r.pos.Start && r.pos.Padding == 0 {
		r.pos.Start += n
		return
	}

	for ; n > 0; n-- {
		if r.pos.Padding != 0 {
			r.pos.Padding--
			continue
		}
		if r.pos.Start >= r.pos.Stop-1 && r.pos.Stop < r.last {
			r.AdvanceLine()
			continue
		}
		r.pos.Start++
	}
}

func (r *blockReader) AdvanceAndSetPadding(n, padding int) {
	r.Advance(n)
	if padding > r.pos.Padding {
		r.SetPadding(padding)
	}
}

func (r *blockReader) AdvanceLine() {
	r.SetPosition(r.line+1, NewSegment(invalidValue, invalidValue))
	r.head = r.pos.Start
}

func (r *blockReader) Position() (int, Segment) {
	return r.line, r.pos
}

func (r *blockReader) SetPosition(line int, pos Segment) {
	r.lineOffset = -1
	r.line = line
	if pos.Start == invalidValue {
		if r.line < r.segmentsLength {
			s := r.segments.At(line)
			r.head = s.Start
			r.pos = s
		}
	} else {
		r.pos = pos
		if r.line < r.segmentsLength {
			s := r.segments.At(line)
			r.head = s.Start
		}
	}
}

func (r *blockReader) SetPadding(v int) {
	r.lineOffset = -1
	r.pos.Padding = v
}

func (r *blockReader) SkipSpaces() (Segment, int, bool) {
	return skipSpacesReader(r)
}

func (r *blockReader) SkipBlankLines() (Segment, int, bool) {
	return skipBlankLinesReader(r)
}

func (r *blockReader) Match(reg *regexp.Regexp) bool {
	return matchReader(r, reg)
}

func (r *blockReader) FindSubMatch(reg *regexp.Regexp) [][]byte {
	return findSubMatchReader(r, reg)
}

func skipBlankLinesReader(r Reader) (Segment, int, bool) {
	lines := 0
	for {
		line, seg := r.PeekLine()
		if line == nil {
			return seg, lines, false
		}
		if util.IsBlank(line) {
			lines++
			r.AdvanceLine()
		} else {
			return seg, lines, true
		}
	}
}

func skipSpacesReader(r Reader) (Segment, int, bool) {
	chars := 0
	for {
		line, segment := r.PeekLine()
		if line == nil {
			return segment, chars, false
		}
		for i, c := range line {
			if util.IsSpace(c) {
				chars++
				r.Advance(1)
				continue
			}
			return segment.WithStart(segment.Start + i + 1), chars, true
		}
	}
}

func matchReader(r Reader, reg *regexp.Regexp) bool {
	oldline, oldseg := r.Position()
	match := reg.FindReaderSubmatchIndex(r)
	r.SetPosition(oldline, oldseg)
	if match == nil {
		return false
	}
	r.Advance(match[1] - match[0])
	return true
}

func findSubMatchReader(r Reader, reg *regexp.Regexp) [][]byte {
	oldline, oldseg := r.Position()
	match := reg.FindReaderSubmatchIndex(r)
	r.SetPosition(oldline, oldseg)
	if match == nil {
		return nil
	}
	runes := make([]rune, 0, match[1]-match[0])
	for i := 0; i < match[1]; {
		r, size, _ := readRuneReader(r)
		i += size
		runes = append(runes, r)
	}
	result := [][]byte{}
	for i := 0; i < len(match); i += 2 {
		result = append(result, []byte(string(runes[match[i]:match[i+1]])))
	}

	r.SetPosition(oldline, oldseg)
	r.Advance(match[1] - match[0])
	return result
}

func readRuneReader(r Reader) (rune, int, error) {
	line, _ := r.PeekLine()
	if line == nil {
		return 0, 0, io.EOF
	}
	rn, size := utf8.DecodeRune(line)
	if rn == utf8.RuneError {
		return 0, 0, io.EOF
	}
	r.Advance(size)
	return rn, size, nil