Alloc enough space is better than multi append

[cloudaice]

I do some benchmark for this:

Code:

var (
        v1 = []byte("hello")
        v2 = []byte("world")
)

func Append() {
        v := append([]byte{}, v1...)
        v = append(v, v2...)
}

func Copy() {
        v := make([]byte, len(v1)+len(v2))
        n := copy(v, v1)
        copy(v[n:], v2)
}

Bench Code:

func BenchmarkAppend(b *testing.B) {
        for i := 0; i < b.N; i++ {
                Append()
        }
}

func BenchmarkCopy(b *testing.B) {
        for i := 0; i < b.N; i++ {
                Copy()
        }
}

Bench Reusult:

BenchmarkAppend-32      20000000                77.0 ns/op            24 B/op          2 allocs/op
BenchmarkCopy-32        50000000                37.5 ns/op            16 B/op          1 allocs/op
PASS
ok      demo/append     3.537s

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[cloudaice]

Something wrong happend