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godoc: peephole optimization for generated HTML

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When searching for regular expressions such as
".", there are many consecutive matches.
In the generated HTML, combine them instead of
generating a new <span> for each adjacent text
segment highlighting a match.

Massively reduces the size of the generated
HTML in those cases.

R=r, rsc
CC=golang-dev
https://golang.org/cl/3971041
This commit is contained in:
Robert Griesemer 2011-01-13 10:23:42 -08:00
parent 6f788e784e
commit d4bdaf11d9
1 changed files with 48 additions and 12 deletions
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60
src/cmd/godoc/format.go
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@ -62,12 +62,48 @@ func FormatSelections(w io.Writer, text []byte, lw LinkWriter, links Selection,
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 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()
@ -81,14 +117,15 @@ func FormatSelections(w io.Writer, text []byte, lw LinkWriter, links Selection,
// we have a link segment change:
// format the previous selection segment, write the
// link tag and start a new selection segment
sw(w, text[lastOffs:offs], bitset)
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
sw(w, text[lastOffs:offs], bitset)
segment(offs)
lastOffs = offs
mask := 1 << uint(index)
if start {
@ -98,7 +135,8 @@ func FormatSelections(w io.Writer, text []byte, lw LinkWriter, links Selection,
}
}
}
sw(w, text[lastOffs:], bitset)
segment(len(text))
flush()
}
@ -283,17 +321,15 @@ var endTag = []byte(`</span>`)
func selectionTag(w io.Writer, text []byte, selections int) {
if len(text) > 0 {
if selections < len(startTags) {
if tag := startTags[selections]; len(tag) > 0 {
w.Write(tag)
template.HTMLEscape(w, text)
w.Write(endTag)
return
}
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)
}
template.HTMLEscape(w, text)
}