performance_test.go

Documentation: go/printer

     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  	"go/token"
    15  	"io"
    16  	"log"
    17  	"os"
    18  	"testing"
    19  )
    20  
    21  var (
    22  	fileNode *ast.File
    23  	fileSize int64
    24  
    25  	declNode ast.Decl
    26  	declSize int64
    27  )
    28  
    29  func testprint(out io.Writer, node ast.Node) {
    30  	if err := (&Config{TabIndent | UseSpaces | normalizeNumbers, 8, 0}).Fprint(out, fset, node); err != nil {
    31  		log.Fatalf("print error: %s", err)
    32  	}
    33  }
    34  
    35  // cannot initialize in init because (printer) Fprint launches goroutines.
    36  func initialize() {
    37  	const filename = "testdata/parser.go"
    38  
    39  	src, err := os.ReadFile(filename)
    40  	if err != nil {
    41  		log.Fatalf("%s", err)
    42  	}
    43  
    44  	file, err := parser.ParseFile(fset, filename, src, parser.ParseComments)
    45  	if err != nil {
    46  		log.Fatalf("%s", err)
    47  	}
    48  
    49  	var buf bytes.Buffer
    50  	testprint(&buf, file)
    51  	if !bytes.Equal(buf.Bytes(), src) {
    52  		log.Fatalf("print error: %s not idempotent", filename)
    53  	}
    54  
    55  	fileNode = file
    56  	fileSize = int64(len(src))
    57  
    58  	for _, decl := range file.Decls {
    59  		// The first global variable, which is pretty short:
    60  		//
    61  		//	var unresolved = new(ast.Object)
    62  		if decl, ok := decl.(*ast.GenDecl); ok && decl.Tok == token.VAR {
    63  			declNode = decl
    64  			declSize = int64(fset.Position(decl.End()).Offset - fset.Position(decl.Pos()).Offset)
    65  			break
    66  		}
    67  
    68  	}
    69  }
    70  
    71  func BenchmarkPrintFile(b *testing.B) {
    72  	if fileNode == nil {
    73  		initialize()
    74  	}
    75  	b.ReportAllocs()
    76  	b.SetBytes(fileSize)
    77  	for i := 0; i < b.N; i++ {
    78  		testprint(io.Discard, fileNode)
    79  	}
    80  }
    81  
    82  func BenchmarkPrintDecl(b *testing.B) {
    83  	if declNode == nil {
    84  		initialize()
    85  	}
    86  	b.ReportAllocs()
    87  	b.SetBytes(declSize)
    88  	for i := 0; i < b.N; i++ {
    89  		testprint(io.Discard, declNode)
    90  	}
    91  }
    92
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