[64]byte()[:]

[Gert]

Is it possible to write this without creating a separate var b64 first? Basically just write it in one line?

var b64 [64]byte // 64 zero bytes

if bytes.Equal(b64[:], x) {}

[Aston Motes]

https://play.golang.org/p/LNP6SK1J02V

var b64 [64]byte // 64 zero bytes

var x = make([]byte, 64)
fmt.Println(bytes.Equal(b64[:], x))

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[Gert]

if bytes.Equal(make([]byte, 64), x) {}

answer from slack (Dorian Thiessen)

 

[Kevin Malachowski]

"make"ing a byre slice every time you call Equal is not likely as efficient; surely it will put pressure on the garbage collector, assuming it's not just called a few times.

Writing something in less lines is not strictly better. I'd probably just make package level variable and reuse it among multiple calls to that function.

[Marcin Romaszewicz]

It's not even worth calling bytes.Equal to see if a bunch of bytes is zero. A more efficient way would be to simply loop over them and check for non-zero.

-- Marcin

On Sat, Nov 16, 2019 at 4:00 PM Kevin Malachowski <nifta...@gmail.com> wrote:

"make"ing a byre slice every time you call Equal is not likely as efficient; surely it will put pressure on the garbage collector, assuming it's not just called a few times.

Writing something in less lines is not strictly better. I'd probably just make package level variable and reuse it among multiple calls to that function.

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[Axel Wagner]

On Sun, Nov 17, 2019 at 1:00 AM Kevin Malachowski <nifta...@gmail.com> wrote:

"make"ing a byre slice every time you call Equal is not likely as efficient; surely it will put pressure on the garbage collector, assuming it's not just called a few times.

AFAICT the compiler correctly deduces that the slice doesn't escape and puts it on the stack. So, no, it doesn't :)

 

Writing something in less lines is not strictly better. I'd probably just make package level variable and reuse it among multiple calls to that function.

[Ren Thraysk]

Trick is knowing the compiler can optimize string(b) away. 

const z8 = "\x00\x00\x00\x00\x00\x00\x00\x00"

const z64 = z8 + z8 + z8 + z8 + z8 + z8 + z8 + z8

if string(b64) == z64 {

}

Ren

[Kevin Malachowski]

Good call, I don't know why I didn't think of the stack allocation.

The conversion to string first is also quite interesting. If bytes.Equal is inlined in practice, profiling is probably the only way to tell which is faster.

[Ren Thraysk]

Or look at the source of bytes.Equal() first. :)

https://golang.org/src/bytes/bytes.go?s=505:533#L8

Ren

On Sunday, 17 November 2019 17:54:47 UTC, Kevin Malachowski wrote:

Good call, I don't know why I didn't think of the stack allocation.

The conversion to string first is also quite interesting. If bytes.Equal is inlined in practice, profiling is probably the only way to tell which is faster.

On Sun, Nov 17, 2019, 2:48 AM Axel Wagner <axel.w...@googlemail.com> wrote:

On Sun, Nov 17, 2019 at 1:00 AM Kevin Malachowski <nifta...@gmail.com> wrote:

"make"ing a byre slice every time you call Equal is not likely as efficient; surely it will put pressure on the garbage collector, assuming it's not just called a few times.

AFAICT the compiler correctly deduces that the slice doesn't escape and puts it on the stack. So, no, it doesn't :)

 

Writing something in less lines is not strictly better. I'd probably just make package level variable and reuse it among multiple calls to that function.

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