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// Copyright 2009 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 a simple printer performance benchmark:
// go test -bench=BenchmarkPrint
package printer
import (
"bytes"
"go/ast"
"go/parser"
"go/token"
"io"
"log"
"os"
"testing"
)
var (
fileNode *ast.File
fileSize int64
declNode ast.Decl
declSize int64
)
func testprint(out io.Writer, node ast.Node) {
if err := (&Config{TabIndent | UseSpaces | normalizeNumbers, 8, 0}).Fprint(out, fset, node); err != nil {
log.Fatalf("print error: %s", err)
}
}
// cannot initialize in init because (printer) Fprint launches goroutines.
func initialize() {
const filename = "testdata/parser.go"
src, err := os.ReadFile(filename)
if err != nil {
log.Fatalf("%s", err)
}
file, err := parser.ParseFile(fset, filename, src, parser.ParseComments)
if err != nil {
log.Fatalf("%s", err)
}
var buf bytes.Buffer
testprint(&buf, file)
if !bytes.Equal(buf.Bytes(), src) {
log.Fatalf("print error: %s not idempotent", filename)
}
fileNode = file
fileSize = int64(len(src))
for _, decl := range file.Decls {
// The first global variable, which is pretty short:
//
// var unresolved = new(ast.Object)
if decl, ok := decl.(*ast.GenDecl); ok && decl.Tok == token.VAR {
declNode = decl
declSize = int64(fset.Position(decl.End()).Offset - fset.Position(decl.Pos()).Offset)
break
}
}
}
func BenchmarkPrintFile(b *testing.B) {
if fileNode == nil {
initialize()
}
b.ReportAllocs()
b.SetBytes(fileSize)
for i := 0; i < b.N; i++ {
testprint(io.Discard, fileNode)
}
}
func BenchmarkPrintDecl(b *testing.B) {
if declNode == nil {
initialize()
}
b.ReportAllocs()
b.SetBytes(declSize)
for i := 0; i < b.N; i++ {
testprint(io.Discard, declNode)
}
}