"John Colvin" <john.loughran.col...@gmail.com> schrieb im Newsbeitrag news:zjsykclxreagfhqsq...@forum.dlang.org... > On Monday, 3 March 2014 at 22:22:06 UTC, Christof Schardt wrote: >> "John Colvin" <john.loughran.col...@gmail.com> schrieb im Newsbeitrag >> news:dyfkblqonigrtmkwt...@forum.dlang.org... >>> On Monday, 3 March 2014 at 21:44:16 UTC, Christof Schardt wrote: >>>> I'm evaluating D and try to write a binary io class. >>>> I got stuck with strings: >>>> >>>> void rw(ref string x) >>>> { >>>> if(_isWriting) >>>> { >>>> int size = x.length; >>>> _f.rawWrite((&size)[0..1]); >>>> _f.rawWrite(x); >>>> } >>>> else >>>> { >>>> int size; >>>> _f.rawRead((&size)[0..1]); >>>> >>>> ... what now? >>>> } >>>> } >>>> >>>> Writing is ok, but how do I read the bytes to the >>>> string x after having its size? >>> >>> >>> Assuming you're not expecting pre-allocation (which I infer from your >>> choice of "ref string" instead of "char[]"), you could do this: >>> >>>> void rw(ref string x) >>>> { >>>> if(_isWriting) >>>> { >>>> size_t size = x.length; >>>> _f.rawWrite((&size)[0..1]); >>>> _f.rawWrite(x); >>>> } >>>> else >>>> { >>>> size_t size; >>>> _f.rawRead((&size)[0..1]); >>>> auto tmp = new char[size]; >>>> _f.rawRead(tmp); >>>> import std.exception : assumeUnique; >>>> x = tmp.assumeUnique; >>>> } >>>> } >> >> Thanks, John, this works. >> >> Though it feels a bit strange, that one has to do such trickery in order >> to >> perform basic things like binary io of strings. > > Doesn't seem like trickery to me; you just make a new array of the correct > size and then fill it from the file. Is that not what you expected to do? > > The only thing that is unusual is assumeUnique, but if you understand that > string is an alias to immutable(char)[] then it should be apparent why > it's there. You could just write "x = cast(string)tmp;" instead, it's the > same.
By "trickery" I meant having to know about things like "import std.exception : assumeUnique" for this basic kind of task. Anyway, since D has an incredible community, which answers questions like mine within minutes, this is not really an obstacle.
