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go/printer, gofmt: more performance tweaks

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Removed more string conversions and streamlined bottleneck
printing interface by removing unnecessary tests where possible.
About 6% faster AST printing.

Before:
- printer.BenchmarkPrint		50	32056640 ns/op

After:
- printer.BenchmarkPrint		50	30138440 ns/op (-6%)

R=r
CC=golang-dev
https://golang.org/cl/5431047
This commit is contained in:
Robert Griesemer 2011-11-23 09:27:38 -08:00
parent 8362ee99b0
commit b3923a27dd
1 changed files with 101 additions and 100 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

173
src/pkg/go/printer/printer.go
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@ -21,7 +21,7 @@ import (
const debug = false // enable for debugging
const infinity = 1 << 30
type whiteSpace int
type whiteSpace byte
const (
ignore = whiteSpace(0)
@ -40,24 +40,20 @@ var ignoreMultiLine = new(bool)
type pmode int
const (
inLiteral pmode = 1 << iota
noExtraLinebreak
noExtraLinebreak pmode = 1 << iota
)
type printer struct {
// Configuration (does not change after initialization)
Config
fset *token.FileSet
output bytes.Buffer
// Current state
output bytes.Buffer // raw printer result
indent int // current indentation
mode pmode // current printer mode
lastTok token.Token // the last token printed (token.ILLEGAL if it's whitespace)
// Reused buffers
wsbuf []whiteSpace // delayed white space
litbuf bytes.Buffer // for creation of escaped literals and comments
// The (possibly estimated) position in the generated output;
// in AST space (i.e., pos is set whenever a token position is
@ -93,19 +89,6 @@ func (p *printer) internalError(msg ...interface{}) {
}
}
// escape escapes string s by bracketing it with tabwriter.Escape.
// Escaped strings pass through tabwriter unchanged. (Note that
// valid Go programs cannot contain tabwriter.Escape bytes since
// they do not appear in legal UTF-8 sequences).
//
func (p *printer) escape(s string) string {
p.litbuf.Reset()
p.litbuf.WriteByte(tabwriter.Escape)
p.litbuf.WriteString(s)
p.litbuf.WriteByte(tabwriter.Escape)
return p.litbuf.String()
}
// nlines returns the adjusted number of linebreaks given the desired number
// of breaks n such that min <= result <= max.
//
@ -120,69 +103,78 @@ func (p *printer) nlines(n, min int) int {
return n
}
// write interprets data and writes it to p.output. It inserts indentation
// after a line break unless in a tabwriter escape sequence.
// It updates p.pos as a side-effect.
//
func (p *printer) write(data string) {
i0 := 0
for i := 0; i < len(data); i++ {
switch data[i] {
case '\n', '\f':
// write segment ending in data[i]
p.output.WriteString(data[i0 : i+1])
// writeByte writes a single byte to p.output and updates p.pos.
func (p *printer) writeByte(ch byte) {
p.output.WriteByte(ch)
p.pos.Offset++
p.pos.Column++
// update p.pos
p.pos.Offset += i + 1 - i0
p.pos.Line++
p.pos.Column = 1
if p.mode&inLiteral == 0 {
if ch == '\n' || ch == '\f' {
// write indentation
const htabs = "\t\t\t\t\t\t\t\t"
// use "hard" htabs - indentation columns
// must not be discarded by the tabwriter
const htabs = "\t\t\t\t\t\t\t\t"
j := p.indent
for ; j > len(htabs); j -= len(htabs) {
for j > len(htabs) {
p.output.WriteString(htabs)
j -= len(htabs)
}
p.output.WriteString(htabs[0:j])
// update p.pos
p.pos.Line++
p.pos.Offset += p.indent
p.pos.Column += p.indent
p.pos.Column = 1 + p.indent
}
// next segment start
i0 = i + 1
case tabwriter.Escape:
p.mode ^= inLiteral
// ignore escape chars introduced by printer - they are
// invisible and must not affect p.pos (was issue #1089)
p.pos.Offset--
p.pos.Column--
}
}
// write remaining segment
p.output.WriteString(data[i0:])
// update p.pos
d := len(data) - i0
p.pos.Offset += d
p.pos.Column += d
}
func (p *printer) writeNewlines(n int, useFF bool) {
if n > 0 {
n = p.nlines(n, 0)
if useFF {
p.write("\f\f\f\f"[0:n])
} else {
p.write("\n\n\n\n"[0:n])
// writeNewlines writes up to n newlines to p.output and updates p.pos.
// The actual number of newlines written is limited by nlines.
// nl must be one of '\n' or '\f'.
//
func (p *printer) writeNewlines(n int, nl byte) {
for n = p.nlines(n, 0); n > 0; n-- {
p.writeByte(nl)
}
}
// writeString writes the string s to p.output and updates p.pos.
// If isLit is set, s is escaped w/ tabwriter.Escape characters
// to protect s from being interpreted by the tabwriter.
//
// Note: writeString is only used to write Go tokens, literals, and
// comments, all of which must be written literally. Thus, it is correct
// to always set isLit = true. However, setting it explicitly only when
// needed (i.e., when we don't know that s contains no tabs or line breaks)
// avoids processing extra escape characters and reduces run time of the
// printer benchmark by up to 10%.
//
func (p *printer) writeString(s string, isLit bool) {
if isLit {
// Protect s such that is passes through the tabwriter
// unchanged. Note that valid Go programs cannot contain
// tabwriter.Escape bytes since they do not appear in legal
// UTF-8 sequences.
p.output.WriteByte(tabwriter.Escape)
}
p.output.WriteString(s)
// update p.pos
nlines := 0
column := p.pos.Column + len(s)
for i := 0; i < len(s); i++ {
if s[i] == '\n' {
nlines++
column = len(s) - i
}
}
p.pos.Offset += len(s)
p.pos.Line += nlines
p.pos.Column = column
if isLit {
p.output.WriteByte(tabwriter.Escape)
}
}
@ -192,7 +184,7 @@ func (p *printer) writeNewlines(n int, useFF bool) {
// source text. writeItem updates p.last to the position immediately following
// the data.
//
func (p *printer) writeItem(pos token.Position, data string) {
func (p *printer) writeItem(pos token.Position, data string, isLit bool) {
if pos.IsValid() {
// continue with previous position if we don't have a valid pos
if p.last.IsValid() && p.last.Filename != pos.Filename {
@ -210,7 +202,7 @@ func (p *printer) writeItem(pos token.Position, data string) {
_, filename := filepath.Split(pos.Filename)
fmt.Fprintf(&p.output, "[%s:%d:%d]", filename, pos.Line, pos.Column)
}
p.write(data)
p.writeString(data, isLit)
p.last = p.pos
}
@ -232,7 +224,7 @@ func (p *printer) writeCommentPrefix(pos, next token.Position, prev, comment *as
if pos.IsValid() && pos.Filename != p.last.Filename {
// comment in a different file - separate with newlines (writeNewlines will limit the number)
p.writeNewlines(10, true)
p.writeNewlines(10, '\f')
return
}
@ -265,14 +257,14 @@ func (p *printer) writeCommentPrefix(pos, next token.Position, prev, comment *as
}
// make sure there is at least one separator
if !hasSep {
sep := byte('\t')
if pos.Line == next.Line {
// next item is on the same line as the comment
// (which must be a /*-style comment): separate
// with a blank instead of a tab
p.write(" ")
} else {
p.write("\t")
sep = ' '
}
p.writeByte(sep)
}
} else {
@ -325,7 +317,9 @@ func (p *printer) writeCommentPrefix(pos, next token.Position, prev, comment *as
if n <= 0 && prev != nil && prev.Text[1] == '/' {
n = 1
}
p.writeNewlines(n, true)
if n > 0 {
p.writeNewlines(n, '\f')
}
p.indent = indent
}
}
@ -530,7 +524,7 @@ func (p *printer) writeComment(comment *ast.Comment) {
// shortcut common case of //-style comments
if text[1] == '/' {
p.writeItem(p.fset.Position(comment.Pos()), p.escape(text))
p.writeItem(p.fset.Position(comment.Pos()), text, true)
return
}
@ -544,11 +538,11 @@ func (p *printer) writeComment(comment *ast.Comment) {
pos := p.fset.Position(comment.Pos())
for i, line := range lines {
if i > 0 {
p.write("\f")
p.writeByte('\f')
pos = p.pos
}
if len(line) > 0 {
p.writeItem(pos, p.escape(line))
p.writeItem(pos, line, true)
}
}
}
@ -584,7 +578,7 @@ func (p *printer) writeCommentSuffix(needsLinebreak bool) (droppedFF bool) {
// make sure we have a line break
if needsLinebreak {
p.write("\n")
p.writeByte('\n')
}
return
@ -610,7 +604,7 @@ func (p *printer) intersperseComments(next token.Position, tok token.Token) (dro
if last.Text[1] == '*' && p.fset.Position(last.Pos()).Line == next.Line {
// the last comment is a /*-style comment and the next item
// follows on the same line: separate with an extra blank
p.write(" ")
p.writeByte(' ')
}
// ensure that there is a line break after a //-style comment,
// before a closing '}' unless explicitly disabled, or at eof
@ -661,7 +655,7 @@ func (p *printer) writeWhitespace(n int) {
}
fallthrough
default:
p.write(string(ch))
p.writeByte(byte(ch))
}
}
@ -709,7 +703,8 @@ func mayCombine(prev token.Token, next byte) (b bool) {
func (p *printer) print(args ...interface{}) {
for _, f := range args {
next := p.pos // estimated position of next item
var data string
data := ""
isLit := false
var tok token.Token
switch x := f.(type) {
@ -737,7 +732,8 @@ func (p *printer) print(args ...interface{}) {
data = x.Name
tok = token.IDENT
case *ast.BasicLit:
data = p.escape(x.Value)
data = x.Value
isLit = true
tok = x.Kind
case token.Token:
s := x.String()
@ -769,15 +765,20 @@ func (p *printer) print(args ...interface{}) {
p.pos = next
if data != "" {
droppedFF := p.flush(next, tok)
nl := byte('\n')
if p.flush(next, tok) {
nl = '\f' // dropped formfeed before
}
// intersperse extra newlines if present in the source
// (don't do this in flush as it will cause extra newlines
// at the end of a file) - use formfeeds if we dropped one
// before
p.writeNewlines(next.Line-p.pos.Line, droppedFF)
if n := next.Line - p.pos.Line; n > 0 {
p.writeNewlines(n, nl)
}
p.writeItem(next, data)
p.writeItem(next, data, isLit)
}
}
}