time_to_string_without_allocs.go

package main

import (
	"strings"
	"testing"
	"time"
)

func timeIntToString(val int) string {
	switch val {
	case 0:
		return "0"
	case 1:
		return "1"
	case 2:
		return "2"
	case 3:
		return "3"
	case 4:
		return "4"
	case 5:
		return "5"
	case 6:
		return "6"
	case 7:
		return "7"
	case 8:
		return "8"
	case 9:
		return "9"
	case 10:
		return "10"
	case 11:
		return "11"
	case 12:
		return "12"
	case 13:
		return "13"
	case 14:
		return "14"
	case 15:
		return "15"
	case 16:
		return "16"
	case 17:
		return "17"
	case 18:
		return "18"
	case 19:
		return "19"
	case 20:
		return "20"
	case 21:
		return "21"
	case 22:
		return "22"
	case 23:
		return "23"
	case 24:
		return "24"
	case 25:
		return "25"
	case 26:
		return "26"
	case 27:
		return "27"
	case 28:
		return "28"
	case 29:
		return "29"
	case 30:
		return "30"
	case 31:
		return "31"
	case 32:
		return "32"
	case 33:
		return "33"
	case 34:
		return "34"
	case 35:
		return "35"
	case 36:
		return "36"
	case 37:
		return "37"
	case 38:
		return "38"
	case 39:
		return "39"
	case 40:
		return "40"
	case 41:
		return "41"
	case 42:
		return "42"
	case 43:
		return "43"
	case 44:
		return "44"
	case 45:
		return "45"
	case 46:
		return "46"
	case 47:
		return "47"
	case 48:
		return "48"
	case 49:
		return "49"
	case 50:
		return "50"
	case 51:
		return "51"
	case 52:
		return "52"
	case 53:
		return "53"
	case 54:
		return "54"
	case 55:
		return "55"
	case 56:
		return "56"
	case 57:
		return "57"
	case 58:
		return "58"
	case 59:
		return "59"
	case 60:
		return "60"
	case 2022:
		return "2022"
	case 2023:
		return "2023"
	case 2024:
		return "2024"
	case 2025:
		return "2025"
	case 2026:
		return "2026"
	case 2027:
		return "2027"
	case 2028:
		return "2028"
	case 2029:
		return "2029"
	case 2030:
		return "2030"
	case 2031:
		return "2031"
	case 2032:
		return "2032"
	default:
		return "0"
	}
}

func timeFormat(nn time.Time, sb strings.Builder) strings.Builder {
	sb.WriteString(timeIntToString(nn.Year()) + "-")
	sb.WriteString(timeIntToString(int(nn.Month())) + "-")
	sb.WriteString(timeIntToString(nn.Day()) + " ")
	sb.WriteString(timeIntToString(nn.Hour()) + ":")
	sb.WriteString(timeIntToString(nn.Minute()))
	return sb
}

// BenchmarkTimeFormatFast-8   	 3 899 320	       277.8 ns/op	      64 B/op	       0 allocs/op
func BenchmarkTimeFormatFast(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()

	now := time.Now()
	var strBuilder strings.Builder
	for i := 0; i < b.N; i++ {
		strBuilder = timeFormat(now, strBuilder)
		_ = strBuilder.String()
	}
}

// BenchmarkTimeFormat2-8   	 9 556 900	       122.4 ns/op	      16 B/op	       1 allocs/op
func BenchmarkTimeFormatStandard(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()

	now := time.Now()
	for i := 0; i < b.N; i++ {
		_ = now.Format("2006-01-02")
	}
}

// BenchmarkStr-8   	1000000000	         0.8312 ns/op	       0 B/op	       0 allocs/op
func BenchmarkStr(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()

	var y, m, r string
	for i := 0; i < b.N; i++ {
		y = "111"
		m = "222"
		r = y
	}
	_, _ = y, m
	_ = r
}

// BenchmarkStrWithConcat-8   	31274161	        36.73 ns/op	       8 B/op	       1 allocs/op
func BenchmarkStrWithConcat(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()

	var y, m, r string
	for i := 0; i < b.N; i++ {
		y = "111"
		m = "222"
		r = y + m
	}
	_, _ = y, m
	_ = r
}