Go語言如何高效的進行字串拼接(6種方式對比分析)

// string is the set of all strings of 8-bit bytes, conventionally but not
// necessarily representing UTF-8-encoded text. A string may be empty, but
// not nil. Values of string type are immutable.
type string string

type stringStruct struct {
    str unsafe.Pointer
    len int
}

//go:nosplit
func gostringnocopy(str *byte) string {
	ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)}
	s := *(*string)(unsafe.Pointer(&ss))
	return s
}

var s string
s += "asong"
s += "真帥"

str := "asong"
str = fmt.Sprintf("%s%s", str, str)

var builder strings.Builder
builder.WriteString("asong")
builder.String()

type Builder struct {
    addr *Builder // of receiver, to detect copies by value
    buf  []byte // 1
}

func (b *Builder) WriteString(s string) (int, error) {
	b.copyCheck()
	b.buf = append(b.buf, s...)
	return len(s), nil
}

func (b *Builder) String() string {
	return *(*string)(unsafe.Pointer(&b.buf))
}

buf := new(bytes.Buffer)
buf.WriteString("asong")
buf.String()

type Buffer struct {
	buf      []byte // contents are the bytes buf[off : len(buf)]
	off      int    // read at &buf[off], write at &buf[len(buf)]
	lastRead readOp // last read operation, so that Unread* can work correctly.
}

func (b *Buffer) WriteString(s string) (n int, err error) {
	b.lastRead = opInvalid
	m, ok := b.tryGrowByReslice(len(s))
	if !ok {
		m = b.grow(len(s))
	}
	return copy(b.buf[m:], s), nil
}

func (b *Buffer) String() string {
	if b == nil {
		// Special case, useful in debugging.
		return "<nil>"
	}
	return string(b.buf[b.off:])
}

baseSlice := []string{"asong", "真帥"}
strings.Join(baseSlice, "")

func Join(elems []string, sep string) string {
	switch len(elems) {
	case 0:
		return ""
	case 1:
		return elems[0]
	}
	n := len(sep) * (len(elems) - 1)
	for i := 0; i < len(elems); i++ {
		n += len(elems[i])
	}

	var b Builder
	b.Grow(n)
	b.WriteString(elems[0])
	for _, s := range elems[1:] {
		b.WriteString(sep)
		b.WriteString(s)
	}
	return b.String()
}

buf := make([]byte, 0)
base = "asong"
buf = append(buf, base...)
string(base)

var base  = "123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASFGHJKLZXCVBNM"

goos: darwin
goarch: amd64
pkg: asong.cloud/Golang_Dream/code_demo/string_join/once
cpu: Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
BenchmarkSumString-16           21338802                49.19 ns/op          128 B/op          1 allocs/op
BenchmarkSprintfString-16        7887808               140.5 ns/op           160 B/op          3 allocs/op
BenchmarkBuilderString-16       27084855                41.39 ns/op          128 B/op          1 allocs/op
BenchmarkBytesBuffString-16      9546277               126.0 ns/op           384 B/op          3 allocs/op
BenchmarkJoinstring-16          24617538                48.21 ns/op          128 B/op          1 allocs/op
BenchmarkByteSliceString-16     10347416               112.7 ns/op           320 B/op          3 allocs/op
PASS
ok      asong.cloud/Golang_Dream/code_demo/string_join/once     8.412s

var baseSlice []string
for i := 0; i < 200; i++ {
		baseSlice = append(baseSlice, base)
}

goos: darwin
goarch: amd64
pkg: asong.cloud/Golang_Dream/code_demo/string_join/muliti
cpu: Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
BenchmarkSumString-16                       7396            163612 ns/op         1277713 B/op        199 allocs/op
BenchmarkSprintfString-16                   5946            202230 ns/op         1288552 B/op        600 allocs/op
BenchmarkBuilderString-16                 262525              4638 ns/op           40960 B/op          1 allocs/op
BenchmarkBytesBufferString-16             183492              6568 ns/op           44736 B/op          9 allocs/op
BenchmarkJoinstring-16                    398923              3035 ns/op           12288 B/op          1 allocs/op
BenchmarkByteSliceString-16               144554              8205 ns/op           60736 B/op         15 allocs/op
PASS
ok      asong.cloud/Golang_Dream/code_demo/string_join/muliti   10.699s