libgo/go/go/printer/performance_test.go

   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
   8 package printer
   9
  10 import (
  11         "bytes"
  12         "go/ast"
  13         "go/parser"
  14         "io"
  15         "io/ioutil"
  16         "log"
  17         "testing"
  18 )
  19
  20 var testfile *ast.File
  21
  22 func 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.
  29 func 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
  51 func 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 }