slice 复制

slice_test.go

package utils

import "testing"

// BenchmarkSliceCopy 对比 slice 通过 loop 和 copy 进行复制的性能
func BenchmarkSliceCopy(b *testing.B) {
	const length = 256
	type foo struct {
		val int
	}
	var (
		int64Src    = make([]int64, length)
		int64Src2   = make([]int64, length)
		float64Src  = make([]float64, length)
		float64Src2 = make([]float64, length)
		structSrc   = make([]*foo, length)
		byteSrc     = make([][]byte, length)

		int64Dst    = make([]int64, length)
		int64Dst2   = make([]int64, length)
		float64Dst  = make([]float64, length)
		float64Dst2 = make([]float64, length)
		structDst   = make([]*foo, length)
		byteDst     = make([][]byte, length)
	)

	for i := 0; i < length; i++ {
		int64Src[i] = int64(i)
		int64Src2[i] = int64(i)
		float64Src[i] = float64(i)
		float64Src2[i] = float64(i)
		structSrc[i] = &foo{val: i}

		byteSrc[i] = []byte{byte(i), byte(i + 1)}
	}

	b.Run("copy", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			copy(int64Dst, int64Src)
			copy(int64Dst2, int64Src2)
			copy(float64Dst, float64Src)
			copy(float64Dst2, float64Src2)
			copy(structDst, structSrc)
			copy(byteDst, byteSrc)
		}
	})
	b.Run("loop", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			byteDstLen := len(byteDst)
			structDstLen := len(structDst)
			for i := 0; i < len(int64Src); i++ {
				int64Dst[i] = int64Src[i]
				int64Dst2[i] = int64Src2[i]
				float64Dst[i] = float64Src[i]
				float64Dst2[i] = float64Src2[i]
				if structDstLen > i {
					structDst[i] = structSrc[i]
				}
				if byteDstLen > i {
					byteDst[i] = byteSrc[i]
				}
			}
		}
	})
}