--- /dev/null
+// 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)
+ }
+}
projects / dotfiles / .git / blobdiff