digitalmars.D.learn - Receiving data into a type using sockets
- Jonathan Sternberg <jonathansternberg gmail.com> Jun 05 2011
- David Nadlinger <see klickverbot.at> Jun 05 2011
- Jonathan Sternberg <jonathansternberg gmail.com> Jun 05 2011
- David Nadlinger <see klickverbot.at> Jun 05 2011
- Andrew Wiley <wiley.andrew.j gmail.com> Jun 05 2011
I'm trying to learn how to do some networking code in D. In C, if I wanted to read 4 bytes into an integer, I could just do (ignoring any error detection): int foo; recv(sockfd, &foo, sizeof(int), 0); How do I do this with D? The receive function takes in a void [] parameter and doesn't take in a number of bytes to read. Is there anyway to accomplish this in D?
Jun 05 2011
On 6/5/11 8:51 PM, Jonathan Sternberg wrote:I'm trying to learn how to do some networking code in D. In C, if I wanted to read 4 bytes into an integer, I could just do (ignoring any error detection): int foo; recv(sockfd,&foo, sizeof(int), 0); How do I do this with D? The receive function takes in a void [] parameter and doesn't take in a number of bytes to read. Is there anyway to accomplish this in D?
auto socket = new Socket(…); … int foo; socket.receive((&foo)[0..1]); --- void[] is like an array of bytes, with the difference to ubyte[] being that it can contain pointers which must be taken into account by the GC, and implicit convertibility. However, all the socket functions should operate on ubyte[] instead of void[] by current guidelines – the socket module is really old, this will definitely be changed when it will be overhauled/replaced. David
Jun 05 2011
Cool. It compiles, but it doesn't seem to be doing exactly what I want. Say I
send
2 integers from the server to the client. When I do this on the client, it seems
to do the wrong thing.
int first, second;
auto sock = new TcpSocket();
sock.connect(new InternetAddress("localhost", 10000));
writeln( sock.receive((&first)[0..int.sizeof]) );
writeln( sock.receive((&second)[0..int.sizeof] );
This seems to print 8 and then block on the second call to receive. I thought
that
D was supposed to recognize that the array was only 4 bytes long and read only
that much. (note: on a 32-bit machine, so int comes out to 4 bytes)
When I do:
writeln( (&first)[0..int.sizeof].length );
It prints 4 as it's supposed to.
Jun 05 2011
David Nadlinger <see klickverbot.at> On 6/5/11 9:49 PM, Jonathan Sternberg wrote:Cool. It compiles, but it doesn't seem to be doing exactly what I want. Say I send 2 integers from the server to the client. When I do this on the client, it seems to do the wrong thing. int first, second; auto sock = new TcpSocket(); sock.connect(new InternetAddress("localhost", 10000)); writeln( sock.receive((&first)[0..int.sizeof]) ); writeln( sock.receive((&second)[0..int.sizeof] ); This seems to print 8 and then block on the second call to receive. I thought that D was supposed to recognize that the array was only 4 bytes long and read only that much. (note: on a 32-bit machine, so int comes out to 4 bytes) When I do: writeln( (&first)[0..int.sizeof].length ); It prints 4 as it's supposed to.
&first is of type int*, so (&first)[0..int.sizeof] returns a slice pointing to int.sizeof (i.e. 4) ints, not a single one as you intend to. Just use »(&first)[0..1]« as per my original reply, and you should be fine. David
Jun 05 2011
--001636c5c006685bd004a4fc91b7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On Sun, Jun 5, 2011 at 12:55 PM, David Nadlinger <see klickverbot.at> wrote= :On 6/5/11 9:49 PM, Jonathan Sternberg wrote:Cool. It compiles, but it doesn't seem to be doing exactly what I want. Say I send 2 integers from the server to the client. When I do this on the client, =
seems to do the wrong thing. int first, second; auto sock =3D new TcpSocket(); sock.connect(new InternetAddress("localhost", 10000)); writeln( sock.receive((&first)[0..int.sizeof]) ); writeln( sock.receive((&second)[0..int.sizeof] ); This seems to print 8 and then block on the second call to receive. I thought that D was supposed to recognize that the array was only 4 bytes long and rea=
only that much. (note: on a 32-bit machine, so int comes out to 4 bytes) When I do: writeln( (&first)[0..int.sizeof].length ); It prints 4 as it's supposed to.
&first is of type int*, so (&first)[0..int.sizeof] returns a slice pointi=
to int.sizeof (i.e. 4) ints, not a single one as you intend to. Just use =BB(&first)[0..1]=AB as per my original reply, and you should be fine.
Also, note that receive is basically a direct call to C's receive, which means that it has the same behavior with regards to buffer filling. Calling sock.receive((&first)[0..1]) returns the number of bytes read, which may be less than 4. I've handled this in the past by writing a template function that takes a primitive type and loops until it has read all the bytes it needs. Oh, and D's int is always 32 bits, on 32 bit or 64 bit platforms. size_t is an alias that switches from uint on 32 bit to ulong on 64 bit, and there's another alias somewhere for signed types (ssize_t, I believe). The primitiv= e types always have the same sizes until you get into things like cent. --001636c5c006685bd004a4fc91b7 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <div class=3D"gmail_quote">On Sun, Jun 5, 2011 at 12:55 PM, David Nadlinger= <span dir=3D"ltr"><<a href=3D"mailto:see klickverbot.at">see klickverbo= t.at</a>></span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"ma= rgin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"> <div><div></div><div class=3D"h5">On 6/5/11 9:49 PM, Jonathan Sternberg wro= te:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex"> Cool. It compiles, but it doesn't seem to be doing exactly what I want.= Say I send<br> 2 integers from the server to the client. When I do this on the client, it = seems<br> to do the wrong thing.<br> <br> int first, second;<br> auto sock =3D new TcpSocket();<br> sock.connect(new InternetAddress("localhost", 10000));<br> <br> writeln( sock.receive((&first)[0..int.sizeof]) );<br> writeln( sock.receive((&second)[0..int.sizeof] );<br> <br> This seems to print 8 and then block on the second call to receive. I thoug= ht that<br> D was supposed to recognize that the array was only 4 bytes long and read o= nly<br> that much. (note: on a 32-bit machine, so int comes out to 4 bytes)<br> <br> When I do:<br> <br> writeln( (&first)[0..int.sizeof].length );<br> <br> It prints 4 as it's supposed to.<br> </blockquote> <br></div></div> &first is of type int*, so (&first)[0..int.sizeof] returns a slice = pointing to int.sizeof (i.e. 4) ints, not a single one as you intend to. Ju= st use =BB(&first)[0..1]=AB as per my original reply, and you should be= fine.<br> </blockquote><div><br></div><div>Also, note that receive is basically a dir= ect call to C's receive, which means that it has the same behavior with= regards to buffer filling. Calling sock.receive((&first)[0..1]) return= s the number of bytes read, which may be less than 4. I've handled this= in the past by writing a template function that takes a primitive type and= loops until it has read all the bytes it needs.</div> <div>Oh, and D's int is always 32 bits, on 32 bit or 64 bit platforms. = size_t is an alias that switches from uint on 32 bit to ulong on 64 bit, an= d there's another alias somewhere for signed types (ssize_t, I believe)= . The primitive types always have the same sizes until you get into things = like cent.</div> </div><br> --001636c5c006685bd004a4fc91b7--
Jun 05 2011