1// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// This file implements a simple printer performance benchmark:
6// go test -bench=BenchmarkPrint
7
8package printer
9
10import (
11	"bytes"
12	"go/ast"
13	"go/parser"
14	"io"
15	"io/ioutil"
16	"log"
17	"testing"
18)
19
20var testfile *ast.File
21
22func testprint(out io.Writer, file *ast.File) {
23	if err := (&Config{TabIndent | UseSpaces, 8, 0}).Fprint(out, fset, file); err != nil {
24		log.Fatalf("print error: %s", err)
25	}
26}
27
28// cannot initialize in init because (printer) Fprint launches goroutines.
29func initialize() {
30	const filename = "testdata/parser.go"
31
32	src, err := ioutil.ReadFile(filename)
33	if err != nil {
34		log.Fatalf("%s", err)
35	}
36
37	file, err := parser.ParseFile(fset, filename, src, parser.ParseComments)
38	if err != nil {
39		log.Fatalf("%s", err)
40	}
41
42	var buf bytes.Buffer
43	testprint(&buf, file)
44	if !bytes.Equal(buf.Bytes(), src) {
45		log.Fatalf("print error: %s not idempotent", filename)
46	}
47
48	testfile = file
49}
50
51func BenchmarkPrint(b *testing.B) {
52	if testfile == nil {
53		initialize()
54	}
55	for i := 0; i < b.N; i++ {
56		testprint(ioutil.Discard, testfile)
57	}
58}
59