Re: Is there any way for non-blocking IO with phobos?
On Tuesday, 13 November 2018 at 13:52:57 UTC, Sobaya wrote:
I want to connect to a server and communicate with ssh.
So I tried to spawn the process of ssh using pipeProcess
function, and read/write with its pipe's stdin and stdout.
But I don't know how many lines are sent from the server for an
input, so readln function blocks.
I think this can be solved with non-blocking IO, but I cannot
find how do I use non-blocking IO with phobos.
Please give me any ideas.
Thanks.
I had some success with the "hasdata" package available on
code.dlang.org:
https://code.dlang.org/packages/hasdata
Below is a sample program that I have tested on Linux:
--
/+ dub.sdl:
name "non-blocking-io"
description "A non blocking IO example using hasdata."
authors "Rémy J. A. Mouëza"
license "MIT"
dependency "hasdata" version="~>1.1.0"
-- sourcePaths "."
configuration "application" {
targetType "executable"
}
+/
// Written in the D programming language: http://dlang.org
import std.process;
import std.string;
import std.range;
import std.stdio;
import core.thread;
import hasdata;
struct NonBlockingPs {
/// The underlying vlc process.
ProcessPipes ps;
alias ps this;
immutable bufsize = 8;
this (string [] args...) {
this.ps = pipeProcess (args,
Redirect.stdin |
Redirect.stdout |
Redirect.stderrToStdout);
}
~this () {
if (! ps.pid.tryWait.terminated) {
ps.pid.kill ();
}
}
string [] readlines () {
string lines;
string line;
char [bufsize] buffer;
try {
int loop = 16;
while (loop -- > 0 && ps.stdout.hasData) {
line = cast (string) ps.stdout.rawRead (buffer);
if (! line.empty) {
lines ~= line;
}
}
}
catch (Exception e) {
"Exception: %s".writeln (e);
}
return lines.splitLines ();
}
}
void main () {
NonBlockingPs ps = NonBlockingPs ("bash", "-c", `
for i in {1..10}; do
printf "hello %02d" $i
sleep 1
done
`);
while (! ps.pid.tryWait.terminated) {
string [] text = ps.readlines ();
if (text.empty) {
"Nothing to read for now".writeln;
}
else {
"=> %s".writefln (text.join ("\n => "));
}
Thread.getThis ().sleep (500.dur!"msecs");
}
}
--
And here is the output of its execution (launched with `dub
nbio.d` -- as I named the file `nbio.d`):
Nothing to read for now
=> hello 01
Nothing to read for now
=> hello 02
Nothing to read for now
=> hello 03
Nothing to read for now
=> hello 04
Nothing to read for now
=> hello 05
Nothing to read for now
=> hello 06
Nothing to read for now
=> hello 07
Nothing to read for now
=> hello 08
Nothing to read for now
=> hello 09
Nothing to read for now
=> hello 10
Nothing to read for now
Re: Is there any way for non-blocking IO with phobos?
On 11/13/18 8:52 AM, Sobaya wrote: I want to connect to a server and communicate with ssh. So I tried to spawn the process of ssh using pipeProcess function, and read/write with its pipe's stdin and stdout. But I don't know how many lines are sent from the server for an input, so readln function blocks. I think this can be solved with non-blocking IO, but I cannot find how do I use non-blocking IO with phobos. Please give me any ideas. Phobos process pipes use std.stdio.File and therefore FILE * as underlying mechanism. I don't think you can do this non-blocking. You could extract the FILE *, and extract the file descriptor, and do it manually. Only way I can think of. -Steve
Is there any way for non-blocking IO with phobos?
I want to connect to a server and communicate with ssh. So I tried to spawn the process of ssh using pipeProcess function, and read/write with its pipe's stdin and stdout. But I don't know how many lines are sent from the server for an input, so readln function blocks. I think this can be solved with non-blocking IO, but I cannot find how do I use non-blocking IO with phobos. Please give me any ideas. Thanks.
Re: Inherit from class based on bool value
On Tuesday, 13 November 2018 at 07:10:26 UTC, Jamie wrote:
I would like my class to inherit from one of two classes based
on a boolean value known at compile time. Something like this:
void main()
{
Top!(OPTION.FALSE) top = new Top!(OPTION.FALSE);
}
enum OPTION
{
FALSE = 0.,
TRUE = 1.
}
class One
{}
class Two
{}
class Top(OPTION option) : option ? One : Two
{}
Is this possible? I can't get it to work in the way I'm showing
above.
Cheers
You can use an alias seq :
void main()
{
Top!(OPTION.FALSE) top = new Top!(OPTION.FALSE);
}
enum OPTION
{
FALSE = 0,
TRUE = 1
}
class One
{}
class Two
{}
import std.meta : AliasSeq;
alias Bases = AliasSeq!(One, Two);
class Top(OPTION option) : Bases[option]
{}
Re: Inherit from class based on bool value
On Tuesday, 13 November 2018 at 07:29:30 UTC, Ali Çehreli wrote:
On 11/12/2018 11:10 PM, Jamie wrote:
> I would like my class to inherit from one of two classes ...
> Is this possible? I can't get it to work in the way I'm
showing above.
> Cheers
I got it working inside an eponymous template. D is pretty cool
actually. :)
enum OPTION
{
FALSE = 0.,
TRUE = 1.
}
class One
{}
class Two
{}
template Top(OPTION option) {
static if (option == OPTION.TRUE) {
alias Base = One;
} else {
alias Base = Two;
}
class Top : Base
{}
}
void main() {
auto a = new Top!(OPTION.FALSE);
auto b = new Top!(OPTION.TRUE);
}
Ali
Wow that's nifty, thanks very much! And thanks for the speedy
response
Re: Inherit from class based on bool value
On Tuesday, 13 November 2018 at 07:10:26 UTC, Jamie wrote:
Is this possible? I can't get it to work in the way I'm showing
above.
...or abstract away Ali's solution:
enum OPTION {
FALSE,
TRUE,
}
template Select(OPTION opt, IfTrue, IfFalse) {
static if (opt == OPTION.TRUE) alias Select = IfTrue;
else alias Select = IfFalse;
}
class One {}
class Two {}
class Top(OPTION opt) : Select!(opt, One, Two) {}
void main() {
import std.traits : BaseClassesTuple;
auto t1 = new Top!(OPTION.TRUE);
static assert(is(BaseClassesTuple!(typeof(t1))[0] == One));
auto t2 = new Top!(OPTION.FALSE);
static assert(is(BaseClassesTuple!(typeof(t2))[0] == Two));
}
