godoc/format.go - tools - Git at Google

 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // This file implements FormatSelections and FormatText.
 // FormatText is used to HTML-format Go and non-Go source
 // text with line numbers and highlighted sections. It is
 // built on top of FormatSelections, a generic formatter
 // for "selected" text.

 package godoc

 import (
 	"fmt"
 	"go/scanner"
 	"go/token"
 	"io"
 	"regexp"
 	"strconv"
 	"text/template"
 )

 // ----------------------------------------------------------------------------
 // Implementation of FormatSelections

 // A Segment describes a text segment [start, end).
 // The zero value of a Segment is a ready-to-use empty segment.
 type Segment struct {
 	start, end int
 }

 func (seg *Segment) isEmpty() bool { return seg.start >= seg.end }

 // A Selection is an "iterator" function returning a text segment.
 // Repeated calls to a selection return consecutive, non-overlapping,
 // non-empty segments, followed by an infinite sequence of empty
 // segments. The first empty segment marks the end of the selection.
 type Selection func() Segment

 // A LinkWriter writes some start or end "tag" to w for the text offset offs.
 // It is called by FormatSelections at the start or end of each link segment.
 type LinkWriter func(w io.Writer, offs int, start bool)

 // A SegmentWriter formats a text according to selections and writes it to w.
 // The selections parameter is a bit set indicating which selections provided
 // to FormatSelections overlap with the text segment: If the n'th bit is set
 // in selections, the n'th selection provided to FormatSelections is overlapping
 // with the text.
 type SegmentWriter func(w io.Writer, text []byte, selections int)

 // FormatSelections takes a text and writes it to w using link and segment
 // writers lw and sw as follows: lw is invoked for consecutive segment starts
 // and ends as specified through the links selection, and sw is invoked for
 // consecutive segments of text overlapped by the same selections as specified
 // by selections. The link writer lw may be nil, in which case the links
 // Selection is ignored.
 func FormatSelections(w io.Writer, text []byte, lw LinkWriter, links Selection, sw SegmentWriter, selections ...Selection) {
 	// If we have a link writer, make the links
 	// selection the last entry in selections
 	if lw != nil {
 		selections = append(selections, links)
 	}

 	// compute the sequence of consecutive segment changes
 	changes := newMerger(selections)

 	// The i'th bit in bitset indicates that the text
 	// at the current offset is covered by selections[i].
 	bitset := 0
 	lastOffs := 0

 	// Text segments are written in a delayed fashion
 	// such that consecutive segments belonging to the
 	// same selection can be combined (peephole optimization).
 	// last describes the last segment which has not yet been written.
 	var last struct {
 		begin, end int // valid if begin < end
 		bitset     int
 	}

 	// flush writes the last delayed text segment
 	flush := func() {
 		if last.begin < last.end {
 			sw(w, text[last.begin:last.end], last.bitset)
 		}
 		last.begin = last.end // invalidate last
 	}

 	// segment runs the segment [lastOffs, end) with the selection
 	// indicated by bitset through the segment peephole optimizer.
 	segment := func(end int) {
 		if lastOffs < end { // ignore empty segments
 			if last.end != lastOffs || last.bitset != bitset {
 				// the last segment is not adjacent to or
 				// differs from the new one
 				flush()
 				// start a new segment
 				last.begin = lastOffs
 			}
 			last.end = end
 			last.bitset = bitset
 		}
 	}

 	for {
 		// get the next segment change
 		index, offs, start := changes.next()
 		if index < 0 || offs > len(text) {
 			// no more segment changes or the next change
 			// is past the end of the text - we're done
 			break
 		}
 		// determine the kind of segment change
 		if lw != nil && index == len(selections)-1 {
 			// we have a link segment change (see start of this function):
 			// format the previous selection segment, write the
 			// link tag and start a new selection segment
 			segment(offs)
 			flush()
 			lastOffs = offs
 			lw(w, offs, start)
 		} else {
 			// we have a selection change:
 			// format the previous selection segment, determine
 			// the new selection bitset and start a new segment
 			segment(offs)
 			lastOffs = offs
 			mask := 1 << uint(index)
 			if start {
 				bitset |= mask
 			} else {
 				bitset &^= mask
 			}
 		}
 	}
 	segment(len(text))
 	flush()
 }

 // A merger merges a slice of Selections and produces a sequence of
 // consecutive segment change events through repeated next() calls.
 type merger struct {
 	selections []Selection
 	segments   []Segment // segments[i] is the next segment of selections[i]
 }

 const infinity int = 2e9

 func newMerger(selections []Selection) *merger {
 	segments := make([]Segment, len(selections))
 	for i, sel := range selections {
 		segments[i] = Segment{infinity, infinity}
 		if sel != nil {
 			if seg := sel(); !seg.isEmpty() {
 				segments[i] = seg
 			}
 		}
 	}
 	return &merger{selections, segments}
 }

 // next returns the next segment change: index specifies the Selection
 // to which the segment belongs, offs is the segment start or end offset
 // as determined by the start value. If there are no more segment changes,
 // next returns an index value < 0.
 func (m *merger) next() (index, offs int, start bool) {
 	// find the next smallest offset where a segment starts or ends
 	offs = infinity
 	index = -1
 	for i, seg := range m.segments {
 		switch {
 		case seg.start < offs:
 			offs = seg.start
 			index = i
 			start = true
 		case seg.end < offs:
 			offs = seg.end
 			index = i
 			start = false
 		}
 	}
 	if index < 0 {
 		// no offset found => all selections merged
 		return
 	}
 	// offset found - it's either the start or end offset but
 	// either way it is ok to consume the start offset: set it
 	// to infinity so it won't be considered in the following
 	// next call
 	m.segments[index].start = infinity
 	if start {
 		return
 	}
 	// end offset found - consume it
 	m.segments[index].end = infinity
 	// advance to the next segment for that selection
 	seg := m.selections[index]()
 	if !seg.isEmpty() {
 		m.segments[index] = seg
 	}
 	return
 }

 // ----------------------------------------------------------------------------
 // Implementation of FormatText

 // lineSelection returns the line segments for text as a Selection.
 func lineSelection(text []byte) Selection {
 	i, j := 0, 0
 	return func() (seg Segment) {
 		// find next newline, if any
 		for j < len(text) {
 			j++
 			if text[j-1] == '\n' {
 				break
 			}
 		}
 		if i < j {
 			// text[i:j] constitutes a line
 			seg = Segment{i, j}
 			i = j
 		}
 		return
 	}
 }

 // tokenSelection returns, as a selection, the sequence of
 // consecutive occurrences of token sel in the Go src text.
 func tokenSelection(src []byte, sel token.Token) Selection {
 	var s scanner.Scanner
 	fset := token.NewFileSet()
 	file := fset.AddFile("", fset.Base(), len(src))
 	s.Init(file, src, nil, scanner.ScanComments)
 	return func() (seg Segment) {
 		for {
 			pos, tok, lit := s.Scan()
 			if tok == token.EOF {
 				break
 			}
 			offs := file.Offset(pos)
 			if tok == sel {
 				seg = Segment{offs, offs + len(lit)}
 				break
 			}
 		}
 		return
 	}
 }

 // makeSelection is a helper function to make a Selection from a slice of pairs.
 // Pairs describing empty segments are ignored.
 func makeSelection(matches [][]int) Selection {
 	i := 0
 	return func() Segment {
 		for i < len(matches) {
 			m := matches[i]
 			i++
 			if m[0] < m[1] {
 				// non-empty segment
 				return Segment{m[0], m[1]}
 			}
 		}
 		return Segment{}
 	}
 }

 // regexpSelection computes the Selection for the regular expression expr in text.
 func regexpSelection(text []byte, expr string) Selection {
 	var matches [][]int
 	if rx, err := regexp.Compile(expr); err == nil {
 		matches = rx.FindAllIndex(text, -1)
 	}
 	return makeSelection(matches)
 }

 var selRx = regexp.MustCompile(`^([0-9]+):([0-9]+)`)

 // RangeSelection computes the Selection for a text range described
 // by the argument str; the range description must match the selRx
 // regular expression.
 func RangeSelection(str string) Selection {
 	m := selRx.FindStringSubmatch(str)
 	if len(m) >= 2 {
 		from, _ := strconv.Atoi(m[1])
 		to, _ := strconv.Atoi(m[2])
 		if from < to {
 			return makeSelection([][]int{{from, to}})
 		}
 	}
 	return nil
 }

 // Span tags for all the possible selection combinations that may
 // be generated by FormatText. Selections are indicated by a bitset,
 // and the value of the bitset specifies the tag to be used.
 //
 // bit 0: comments
 // bit 1: highlights
 // bit 2: selections
 var startTags = [][]byte{
 	/* 000 */ []byte(``),
 	/* 001 */ []byte(`<span class="comment">`),
 	/* 010 */ []byte(`<span class="highlight">`),
 	/* 011 */ []byte(`<span class="highlight-comment">`),
 	/* 100 */ []byte(`<span class="selection">`),
 	/* 101 */ []byte(`<span class="selection-comment">`),
 	/* 110 */ []byte(`<span class="selection-highlight">`),
 	/* 111 */ []byte(`<span class="selection-highlight-comment">`),
 }

 var endTag = []byte(`</span>`)

 func selectionTag(w io.Writer, text []byte, selections int) {
 	if selections < len(startTags) {
 		if tag := startTags[selections]; len(tag) > 0 {
 			w.Write(tag)
 			template.HTMLEscape(w, text)
 			w.Write(endTag)
 			return
 		}
 	}
 	template.HTMLEscape(w, text)
 }

 // FormatText HTML-escapes text and writes it to w.
 // Consecutive text segments are wrapped in HTML spans (with tags as
 // defined by startTags and endTag) as follows:
 //
 //   - if line >= 0, line number (ln) spans are inserted before each line,
 //     starting with the value of line
 //   - if the text is Go source, comments get the "comment" span class
 //   - each occurrence of the regular expression pattern gets the "highlight"
 //     span class
 //   - text segments covered by selection get the "selection" span class
 //
 // Comments, highlights, and selections may overlap arbitrarily; the respective
 // HTML span classes are specified in the startTags variable.
 func FormatText(w io.Writer, text []byte, line int, goSource bool, pattern string, selection Selection) {
 	var comments, highlights Selection
 	if goSource {
 		comments = tokenSelection(text, token.COMMENT)
 	}
 	if pattern != "" {
 		highlights = regexpSelection(text, pattern)
 	}
 	if line >= 0 || comments != nil || highlights != nil || selection != nil {
 		var lineTag LinkWriter
 		if line >= 0 {
 			lineTag = func(w io.Writer, _ int, start bool) {
 				if start {
 					fmt.Fprintf(w, "<span id=\"L%d\" class=\"ln\">%6d</span>", line, line)
 					line++
 				}
 			}
 		}
 		FormatSelections(w, text, lineTag, lineSelection(text), selectionTag, comments, highlights, selection)
 	} else {
 		template.HTMLEscape(w, text)
 	}
 }
	// Copyright 2011 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// This file implements FormatSelections and FormatText.
	// FormatText is used to HTML-format Go and non-Go source
	// text with line numbers and highlighted sections. It is
	// built on top of FormatSelections, a generic formatter
	// for "selected" text.

	package godoc

	import (
	"fmt"
	"go/scanner"
	"go/token"
	"io"
	"regexp"
	"strconv"
	"text/template"
	)

	// ----------------------------------------------------------------------------
	// Implementation of FormatSelections

	// A Segment describes a text segment [start, end).
	// The zero value of a Segment is a ready-to-use empty segment.
	type Segment struct {
	start, end int
	}

	func (seg *Segment) isEmpty() bool { return seg.start >= seg.end }

	// A Selection is an "iterator" function returning a text segment.
	// Repeated calls to a selection return consecutive, non-overlapping,
	// non-empty segments, followed by an infinite sequence of empty
	// segments. The first empty segment marks the end of the selection.
	type Selection func() Segment

	// A LinkWriter writes some start or end "tag" to w for the text offset offs.
	// It is called by FormatSelections at the start or end of each link segment.
	type LinkWriter func(w io.Writer, offs int, start bool)

	// A SegmentWriter formats a text according to selections and writes it to w.
	// The selections parameter is a bit set indicating which selections provided
	// to FormatSelections overlap with the text segment: If the n'th bit is set
	// in selections, the n'th selection provided to FormatSelections is overlapping
	// with the text.
	type SegmentWriter func(w io.Writer, text []byte, selections int)

	// FormatSelections takes a text and writes it to w using link and segment
	// writers lw and sw as follows: lw is invoked for consecutive segment starts
	// and ends as specified through the links selection, and sw is invoked for
	// consecutive segments of text overlapped by the same selections as specified
	// by selections. The link writer lw may be nil, in which case the links
	// Selection is ignored.
	func FormatSelections(w io.Writer, text []byte, lw LinkWriter, links Selection, sw SegmentWriter, selections ...Selection) {
	// If we have a link writer, make the links
	// selection the last entry in selections
	if lw != nil {
	selections = append(selections, links)
	}

	// compute the sequence of consecutive segment changes
	changes := newMerger(selections)

	// The i'th bit in bitset indicates that the text
	// at the current offset is covered by selections[i].
	bitset := 0
	lastOffs := 0

	// Text segments are written in a delayed fashion
	// such that consecutive segments belonging to the
	// same selection can be combined (peephole optimization).
	// last describes the last segment which has not yet been written.
	var last struct {
	begin, end int // valid if begin < end
	bitset int
	}

	// flush writes the last delayed text segment
	flush := func() {
	if last.begin < last.end {
	sw(w, text[last.begin:last.end], last.bitset)
	}
	last.begin = last.end // invalidate last
	}

	// segment runs the segment [lastOffs, end) with the selection
	// indicated by bitset through the segment peephole optimizer.
	segment := func(end int) {
	if lastOffs < end { // ignore empty segments
	if last.end != lastOffs \|\| last.bitset != bitset {
	// the last segment is not adjacent to or
	// differs from the new one
	flush()
	// start a new segment
	last.begin = lastOffs
	}
	last.end = end
	last.bitset = bitset
	}
	}

	for {
	// get the next segment change
	index, offs, start := changes.next()
	if index < 0 \|\| offs > len(text) {
	// no more segment changes or the next change
	// is past the end of the text - we're done
	break
	}
	// determine the kind of segment change
	if lw != nil && index == len(selections)-1 {
	// we have a link segment change (see start of this function):
	// format the previous selection segment, write the
	// link tag and start a new selection segment
	segment(offs)
	flush()
	lastOffs = offs
	lw(w, offs, start)
	} else {
	// we have a selection change:
	// format the previous selection segment, determine
	// the new selection bitset and start a new segment
	segment(offs)
	lastOffs = offs
	mask := 1 << uint(index)
	if start {
	bitset \|= mask
	} else {
	bitset &^= mask
	}
	}
	}
	segment(len(text))
	flush()
	}

	// A merger merges a slice of Selections and produces a sequence of
	// consecutive segment change events through repeated next() calls.
	type merger struct {
	selections []Selection
	segments []Segment // segments[i] is the next segment of selections[i]
	}

	const infinity int = 2e9

	func newMerger(selections []Selection) *merger {
	segments := make([]Segment, len(selections))
	for i, sel := range selections {
	segments[i] = Segment{infinity, infinity}
	if sel != nil {
	if seg := sel(); !seg.isEmpty() {
	segments[i] = seg
	}
	}
	}
	return &merger{selections, segments}
	}

	// next returns the next segment change: index specifies the Selection
	// to which the segment belongs, offs is the segment start or end offset
	// as determined by the start value. If there are no more segment changes,
	// next returns an index value < 0.
	func (m *merger) next() (index, offs int, start bool) {
	// find the next smallest offset where a segment starts or ends
	offs = infinity
	index = -1
	for i, seg := range m.segments {
	switch {
	case seg.start < offs:
	offs = seg.start
	index = i
	start = true
	case seg.end < offs:
	offs = seg.end
	index = i
	start = false
	}
	}
	if index < 0 {
	// no offset found => all selections merged
	return
	}
	// offset found - it's either the start or end offset but
	// either way it is ok to consume the start offset: set it
	// to infinity so it won't be considered in the following
	// next call
	m.segments[index].start = infinity
	if start {
	return
	}
	// end offset found - consume it
	m.segments[index].end = infinity
	// advance to the next segment for that selection
	seg := m.selections[index]()
	if !seg.isEmpty() {
	m.segments[index] = seg
	}
	return
	}

	// ----------------------------------------------------------------------------
	// Implementation of FormatText

	// lineSelection returns the line segments for text as a Selection.
	func lineSelection(text []byte) Selection {
	i, j := 0, 0
	return func() (seg Segment) {
	// find next newline, if any
	for j < len(text) {
	j++
	if text[j-1] == '\n' {
	break
	}
	}
	if i < j {
	// text[i:j] constitutes a line
	seg = Segment{i, j}
	i = j
	}
	return
	}
	}

	// tokenSelection returns, as a selection, the sequence of
	// consecutive occurrences of token sel in the Go src text.
	func tokenSelection(src []byte, sel token.Token) Selection {
	var s scanner.Scanner
	fset := token.NewFileSet()
	file := fset.AddFile("", fset.Base(), len(src))
	s.Init(file, src, nil, scanner.ScanComments)
	return func() (seg Segment) {
	for {
	pos, tok, lit := s.Scan()
	if tok == token.EOF {
	break
	}
	offs := file.Offset(pos)
	if tok == sel {
	seg = Segment{offs, offs + len(lit)}
	break
	}
	}
	return
	}
	}

	// makeSelection is a helper function to make a Selection from a slice of pairs.
	// Pairs describing empty segments are ignored.
	func makeSelection(matches [][]int) Selection {
	i := 0
	return func() Segment {
	for i < len(matches) {
	m := matches[i]
	i++
	if m[0] < m[1] {
	// non-empty segment
	return Segment{m[0], m[1]}
	}
	}
	return Segment{}
	}
	}

	// regexpSelection computes the Selection for the regular expression expr in text.
	func regexpSelection(text []byte, expr string) Selection {
	var matches [][]int
	if rx, err := regexp.Compile(expr); err == nil {
	matches = rx.FindAllIndex(text, -1)
	}
	return makeSelection(matches)
	}

	var selRx = regexp.MustCompile(`^([0-9]+):([0-9]+)`)

	// RangeSelection computes the Selection for a text range described
	// by the argument str; the range description must match the selRx
	// regular expression.
	func RangeSelection(str string) Selection {
	m := selRx.FindStringSubmatch(str)
	if len(m) >= 2 {
	from, _ := strconv.Atoi(m[1])
	to, _ := strconv.Atoi(m[2])
	if from < to {
	return makeSelection([][]int{{from, to}})
	}
	}
	return nil
	}

	// Span tags for all the possible selection combinations that may
	// be generated by FormatText. Selections are indicated by a bitset,
	// and the value of the bitset specifies the tag to be used.
	//
	// bit 0: comments
	// bit 1: highlights
	// bit 2: selections
	var startTags = [][]byte{
	/* 000 */ []byte(``),
	/* 001 */ []byte(`<span class="comment">`),
	/* 010 */ []byte(`<span class="highlight">`),
	/* 011 */ []byte(`<span class="highlight-comment">`),
	/* 100 */ []byte(`<span class="selection">`),
	/* 101 */ []byte(`<span class="selection-comment">`),
	/* 110 */ []byte(`<span class="selection-highlight">`),
	/* 111 */ []byte(`<span class="selection-highlight-comment">`),
	}

	var endTag = []byte(`</span>`)

	func selectionTag(w io.Writer, text []byte, selections int) {
	if selections < len(startTags) {
	if tag := startTags[selections]; len(tag) > 0 {
	w.Write(tag)
	template.HTMLEscape(w, text)
	w.Write(endTag)
	return
	}
	}
	template.HTMLEscape(w, text)
	}

	// FormatText HTML-escapes text and writes it to w.
	// Consecutive text segments are wrapped in HTML spans (with tags as
	// defined by startTags and endTag) as follows:
	//
	// - if line >= 0, line number (ln) spans are inserted before each line,
	// starting with the value of line
	// - if the text is Go source, comments get the "comment" span class
	// - each occurrence of the regular expression pattern gets the "highlight"
	// span class
	// - text segments covered by selection get the "selection" span class
	//
	// Comments, highlights, and selections may overlap arbitrarily; the respective
	// HTML span classes are specified in the startTags variable.
	func FormatText(w io.Writer, text []byte, line int, goSource bool, pattern string, selection Selection) {
	var comments, highlights Selection
	if goSource {
	comments = tokenSelection(text, token.COMMENT)
	}
	if pattern != "" {
	highlights = regexpSelection(text, pattern)
	}
	if line >= 0 \|\| comments != nil \|\| highlights != nil \|\| selection != nil {
	var lineTag LinkWriter
	if line >= 0 {
	lineTag = func(w io.Writer, _ int, start bool) {
	if start {
	fmt.Fprintf(w, "<span id=\"L%d\" class=\"ln\">%6d</span>", line, line)
	line++
	}
	}
	}
	FormatSelections(w, text, lineTag, lineSelection(text), selectionTag, comments, highlights, selection)
	} else {
	template.HTMLEscape(w, text)
	}
	}