Write UTF-8 bytes directly to stack buffer

H. S. Teoh hsteoh at quickfur.ath.cx
Thu Mar 10 17:59:33 UTC 2022

On Thu, Mar 10, 2022 at 05:39:34PM +0000, Chris Piker via Digitalmars-d-learn wrote:
> Hi D
> There are quite a few string, array and range functions in phobos so
> I'm getting confused as to the right way to encode string data as
> UTF-8 directly into a stack buffer while keeping track of the write
> point.
> I have some output packets I'm building up in a tight loop.  For speed
> I'm using the a priori knowledge that output packets will never be
> larger then 64K.   So what's the best way to do this:
> ```d
> ubyte[65536] buf;
> ubyte[] usable_buf = buf;
>   // part of some tight loop, how to create function writef_utf8 ?
>   foreach(input_thing; things){
>      usable_buf.writef_utf8!"format str"(input_thing.fieldA, input_thing.fieldB);
>   }
> size_t used = buf.length - usable_buf.length;
> stdout.write(buf[0.. used]);
> ```

Probably what you're looking for is std.format.formattedWrite. For

import std;
void main() {
	ubyte[65536] buf;
	char[] usable_buf = cast(char[]) buf[];
	usable_buf.formattedWrite!"Blah %d blah %s"(123, "Это UTF-8 строка.");
	auto used = buf.length - usable_buf.length;
	writefln("%(%02X %)", buf[0 .. used]);

D strings are UTF-8 by default, so for the most part, you don't need to
worry about it.


Guns don't kill people. Bullets do.

More information about the Digitalmars-d-learn mailing list