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 example:

------
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.


T

-- 
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