As long as no one modifies the bytes in the byteslice. Go can no longer
enforce that the string is immutable with this hack.
On Mon, Sep 19, 2016 at 2:35 PM, <badrel...@gmail.com> wrote:
> I don't like the extra allocation and copies involved when casting from
> byte slice to string or vice versa just because one type or the other is
> required. The code below reuses the data pointer and as far as I can tell
> in my tests so far, it even works well with garbage collection. My question
> is... why shouldn't I do this?
>
>
> func fastStringToBytes(str string) []byte {
> var b []byte
>
> strhdr := (*reflect.StringHeader)(unsafe.Pointer(&str))
> bythdr := (*reflect.SliceHeader)(unsafe.Pointer(&b))
>
> d := strhdr.Data
> l := strhdr.Len
>
> // strhdr.Data = bythdr.Data
> // strhdr.Len = bythdr.Len
>
> bythdr.Data = d
> bythdr.Len = l
> bythdr.Cap = l
>
> return b
> }
>
> func fastBytesToString(b []byte) string {
> var str string
>
> strhdr := (*reflect.StringHeader)(unsafe.Pointer(&str))
> bythdr := (*reflect.SliceHeader)(unsafe.Pointer(&b))
>
> // d := strhdr.Data
> // l := strhdr.Len
>
> strhdr.Data = bythdr.Data
> strhdr.Len = bythdr.Len
>
> // bythdr.Data = d
> // bythdr.Len = l
> // bythdr.Cap = l
>
> return str
> }
>
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