builder_test.go

var someBytes = []byte("some bytes sdljlk jsklj3lkjlk djlkjw")

var sinkS string

func benchmarkBuilder(b *testing.B, f func(b *testing.B, numWrite int, grow bool)) {
	b.Run("1Write_NoGrow", func(b *testing.B) {
		b.ReportAllocs()
		f(b, 1, false)
	})
	b.Run("3Write_NoGrow", func(b *testing.B) {
		b.ReportAllocs()
		f(b, 3, false)
	})
	b.Run("3Write_Grow", func(b *testing.B) {
		b.ReportAllocs()
		f(b, 3, true)
	})
}

func BenchmarkBuildString_Builder(b *testing.B) {
	benchmarkBuilder(b, func(b *testing.B, numWrite int, grow bool) {
		for i := 0; i < b.N; i++ {
			var buf Builder
			if grow {
				buf.Grow(len(someBytes) * numWrite)
			}
			for i := 0; i < numWrite; i++ {
				buf.Write(someBytes)
			}
			sinkS = buf.String()
		}
	})
}

func BenchmarkBuildString_ByteBuffer(b *testing.B) {
	benchmarkBuilder(b, func(b *testing.B, numWrite int, grow bool) {
		for i := 0; i < b.N; i++ {
			var buf bytes.Buffer
			if grow {
				buf.Grow(len(someBytes) * numWrite)
			}
			for i := 0; i < numWrite; i++ {
				buf.Write(someBytes)
			}
			sinkS = buf.String()
		}
	})
}

// 以下是性能测试的运行结果，可以看到 strings.Builder 的运行时间和所用空间都比 bytes.Buffer 要小
// 而且可以看到，用户主动执行 Grow 后，程序分配内存的次数少了，时间也大大加快

//>>> go test -v -bench=BenchmarkBuild -run='^$' builder_test.go                                                                                                                                                               22:11:37 (04-26)
//goos: darwin
//goarch: amd64
//BenchmarkBuildString_Builder/1Write_NoGrow-4            20000000                78.2 ns/op            48 B/op          1 allocs/op
//BenchmarkBuildString_Builder/3Write_NoGrow-4             5000000               305 ns/op             336 B/op          3 allocs/op
//BenchmarkBuildString_Builder/3Write_Grow-4              10000000               112 ns/op             112 B/op          1 allocs/op
//BenchmarkBuildString_ByteBuffer/1Write_NoGrow-4         10000000               139 ns/op             112 B/op          2 allocs/op
//BenchmarkBuildString_ByteBuffer/3Write_NoGrow-4          3000000               438 ns/op             352 B/op          3 allocs/op
//BenchmarkBuildString_ByteBuffer/3Write_Grow-4            5000000               324 ns/op             224 B/op          2 allocs/op
//PASS
//ok      command-line-arguments  9.987s