Hi y'all,
given that the concern here seems to be performance (though, TBH, I doubt
this particular case is much of a bottleneck), this seems to be far simpler
to address as a compiler optimization - if the compiler can prove there are
no other references to a `[]byte`, it can do the conversion cheaply. You
need to implement that check anyway, and optimizations are transparent to
the user, so the hurdle for them is lower.
The only problem with that is that it would need to happen cross-package.
That's where the type-system might help. AFAICT however, if you're willing
to change the API anyway, the simpler fix here would be to take an
`io.Writer` instead of returning a `[]byte`. The user is then free to pass
a `*bytes.Buffer` or a `*strings.Builder`, depending on which of the two
they need. And if the wins of this optimization are large enough to justify
changing the language (which, again, remains to be proven) they certainly
are large enough to justify this slightly less user-friendly API.
So, really, IMO the case for language changes here is pretty weak.
On Sat, Sep 12, 2020 at 9:46 AM tapi...@gmail.com <tapir....@gmail.com>
wrote:
> There is a prerequisite to transfer ownership: it must be proved that
> no other values share ownership of the byte slice returned by
> ioutil.ReadFile.
>
> On Saturday, September 12, 2020 at 3:42:14 AM UTC-4 tapi...@gmail.com
> wrote:
>
>> Is it good to introduce owner transfer based string<->[]byte conversions?
>> After the conversion, the being converted string/[]byte values mustn't be
>> used any more.
>> Such as
>>
>> tlsCertData, _ = ioutil.ReadFile("/etc/ssl/mycert")
>> var tlsCert string = bultin.ByteSlice2String(tlsCertData)
>>
>> // forbid using tlsCertData any more
>> _ = tlsCertData // error: tlsCertData can only used after a re-assignment.
>>
>> On Friday, September 11, 2020 at 3:09:57 PM UTC-4 Ian Lance Taylor wrote:
>>
>>> On Fri, Sep 11, 2020 at 9:45 AM Kevin Chadwick <m8il...@gmail.com>
>>> wrote:
>>> >
>>> > I apologise if this has already been discussed. Google didn't turn up
>>> anything
>>> > directly related.
>>> >
>>> > If you read a file using the following that returns a byte slice.
>>> >
>>> > tlsCertb, err := ioutil.ReadFile("/etc/ssl/mycert")
>>> > if err != nil {
>>> > log.Fatal(err)
>>> > }
>>> > tlsCert = string(tlsCertb)
>>> >
>>> > Is there a way to get a string without the cast.
>>> >
>>> > Otherwise couldn't the language automatically return a string rather
>>> than a byte
>>> > slice in these cases if the receiving var is already a string?
>>> >
>>> > e.g.
>>> >
>>> > var string tlsCert
>>> > tlsCert, err = ioutil.ReadFile("/etc/ssl/mycert")
>>> > if err != nil {
>>> > log.Fatal(err)
>>> > }
>>>
>>> The way Go works, ioutil.ReadFile is compiled with the io/ioutil
>>> package. It can't change based on how it is called. So it is always
>>> going to return []byte.
>>>
>>> The only way to implement what you suggest would be to add an implicit
>>> conversion from []byte to string. But that seems problematic. In
>>> general Go avoids implicit conversions except to interface types. And
>>> a conversion to string does require a copy, so it doesn't seem like a
>>> great idea to do that implicitly.
>>>
>>> If this happens a lot in your code, it seems easy enough to use a tiny
>>> helper function.
>>>
>>> Ian
>>>
>> --
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