What's the fastest way to convert base-10 64 bit signed integer to []byte?

I want to use it to persist many counters on the disk.

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评论：

TheMerovius:

n, _ := strconv.ParseInt("12345678901234", 10, 64)
b := make([]byte, 8)
binary.LittleEndian.PutUint64(b, n)

andreasblixt:

Note that you'd have to turn the int64 into a uint64 before PutUint64 will work.

But – if writing to disk anyway:

n, _ := strconv.ParseInt("12345678901234", 10, 64)
binary.Write(w, binary.LittleEndian, n)

TheMerovius:

Note that you'd have to turn the int64 into a uint64 before PutUint64 will work.

Ah, right, forgot that part. But doesn't matter, just convert, it'll do the right thing.

But – if writing to disk anyway:

binary.Write uses reflection, so I avoided it intentionally due to the "fastest way" in the question (whether this actually needs to be the fastest way is a different question - probably not).

andreasblixt:

I would measure before deciding which way is faster. For example, if the b slice is recreated for every value instead of being reused, then it might very well be slower than binary.Write. And if done perfectly (by which I mean writing more complex code), it might still only be faster on the order of nanoseconds per value, at which point the disk writes will overweigh the speed difference so much it might not even be measurable.

dcormier:

Or, if you're not writing to disk:
n, _ := strconv.ParseInt("12345678901234", 10, 64)
buf := &bytes.Buffer{}
binary.Write(buf, binary.LittleEndian, n)
// buf.Bytes() has your []byte

drvd:

func convert(s string) []byte {return nil}

Is the fastest way. Albeit not the most correct one. (Paraphrasing Russ).
func convert(s string) []byte {return []byte(s)}

Is an other candidate which turns a base-10 64 bit signed integer string to a byte slice. It is very fast and correct and converts any string to a byte slice.
Your use case seems like speed of conversion won't be the problem: Writing to disk is presumably slower than strconv + bitfidling.