On Thu, Mar 28, 2013 at 09:24:49PM +0100, Vidar Wahlberg wrote:
> To follow up with some new woes I'm currently struggling with: I'm
> storing some various values in an ubyte array. I discovered that it's
> probably std.bitmanip I wish to use in order to "convert" i.e. an int
> to 4 bytes (although I went first to std.conv looking for this
> feature).
[...]
There are several ways to convert an int into 4 bytes:
1) Use a union:
static assert(int.sizeof==4);
ubyte[4] intToUbytes(int x) {
union U {
int i;
ubyte[4] b;
}
U u;
u.i = x;
return u.b;
}
2) Use bit operators:
ubyte[4] intToUbytes(int x) {
ubyte[4] bytes;
// Note: this assumes little-endian. For big-endian,
// reverse the order below.
bytes[0] = x & 0xFF;
bytes[1] = (x >> 8) & 0xFF;
bytes[2] = (x >> 16) & 0xFF;
bytes[3] = (x >> 24) & 0xFF;
return bytes;
}
3) Use a pointer cast (warning: un-@safe):
ubyte[4] intToUbytes(int x) @system {
ubyte[4] b;
ubyte* ptr = cast(ubyte*)&x;
b[0] = *ptr++;
b[1] = *ptr++;
b[2] = *ptr++;
b[3] = *ptr;
return b;
}
4) Reinterpret a pointer (warning: un-@safe):
ubyte[4] intToUbytes(int x) @system {
return *cast(ubyte[4]*)&x;
}
I'm sure there are several other ways to do it.
You don't need to use appender unless you're doing a lot of conversions
in one go.
--T
