func bytesToString(b []byte) string {
return *(*string)(unsafe.Pointer(&b))
}
https://play.golang.org/p/azJPbl946zj
On Fri, 2019-09-20 at 13:30 -0700, Francis wrote:
> Thanks Ian, that's a very interesting solution.
>
> Is there a solution for going in the other direction? Although I
> excluded
> it from the initial post, it was only to reduce the size of the
> discussion.
> I would also like to implement
>
> func BytesToString(b []byte) string {
>
> I don't clearly see how to avoid using the StringHeader in this case.
>
> F
>
> On Wednesday, 18 September 2019 22:46:44 UTC+2, Ian Lance Taylor
> wrote:
> >
> > On Wed, Sep 18, 2019 at 2:42 AM Francis <[email protected]
> > <javascript:>> wrote:
> > >
> > > I am looking at the correct way to convert from a byte slice to a
> > > string
> >
> > and back with no allocations. All very unsafe.
> > >
> > > I think these two cases are fairly symmetrical. So to simplify
> > > the
> >
> > discussion below I will only talk about converting from a string to
> > []byte.
> > >
> > > func StringToBytes(s string) (b []byte)
> >
> > No reason to use SliceHeader, and avoiding SliceHeader avoids the
> > problems you discuss.
> >
> > func StringToBytes(s string) []byte {
> > const max = 0x7fff0000
> > if len(s) > max {
> > panic("string too long")
> > }
> > return
> > (*[max]byte)(unsafe.Pointer((*reflect.StringHeader)(unsafe.Pointer(
> > &s)).Data))[:len(s):len(s)]
> >
> > }
> >
> > Of course, as you say, you must not mutate the returned []byte.
> >
> > Ian
> >
>
>
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