On Tuesday, January 24, 2012 23:02:18 Mantis wrote:
24.01.2012 22:48, Mars пишет:
Hello everybody.
I have to convert a char* (from a C function) to long. At the moment
I'm using
long foo = to!long( to!string(bar) );
but this doesn't feel right... with 2 to calls. Is this the way to go?
Or is there something better?
Mars
This seems to work:
char[] c = 123\0.dup;
auto l = parse!long(c);
writeln( l );
Yeah, but note that that's really equivalent to
auto foo = to!long(to!(char[])(bar));
except that you're creating an extra variable and using parse with its
somewhat different semantics. In either case, you need to convert it from a
char* to an actual character array of some kind before converting it to a
long, and that means that you're allocating memory. In general, I would
recommend just doing what the OP said
auto foo = to!long(to!string(bar));
It's the cleanest solution IMHO, and in general, that extra bit of memory
allocation isn't a big deal. However, if you know the length of the char*,
then you can slice it and pass that to std.conv.to. e.g.
auto foo = to!long(bar[0 .. 3]);
But you have to know the length of the string already - or use strlen on it to
get its length. e.g.
auto foo = to!long(bar[0 .. strlen(bar)]);
It's quite doable and probably faster than converting to string and then to
long, but it's certainly uglier code. This should only be a problem when
interfacing with C though, since you really shouldn't be using char*'s or
null-terminated strings otherwise.
- Jonathan M Davis
