Difference between chunks(stdin, 1) and stdin.rawRead?

[jms]

On Thursday, 28 March 2024 at 02:30:11 UTC, jms wrote:
> Why in the below silly program am I reading both the \r and \n 
> characters when using rawRead in block a, but when looping by 1 
> byte chunks in block b only appear to be reading the \n 
> characters?
>
> I'm on Windows 11 using DMD64 D Compiler v2.107.1 if that 
> matters, but I'm thinking this maybe has something to do with 
> stdin in general that I'm not aware of. Any pointers to 
> understanding what's going on would be appreciated.
>
> import std.stdio;
>
> void main() {
>     int i;
> a: {
>         i = 0;
>         writeln("\nin a");
>         ubyte[1] buffer;
>         while (true) {
>             i++;
>             stdin.rawRead(buffer);
>             if (buffer[0] == 13) {
>                 write("CR");
>             } else if (buffer[0] == 10) {
>                 write("LF");
>             }
>             if (i > 5) {
>                 goto b;
>             }
>
>         }
>     }
> b: {
>
>         writeln("\n\nin b");
>         i = 0;
>         foreach (ubyte[] buffer; chunks(stdin, 1)) {
>             i++;
>             if (buffer[0] == 13) {
>                 write("cr");
>             } else if (buffer[0] == 10) {
>                 write("lf");
>             }
>             if (i > 5) {
>                 goto a;
>             }
>         }
>     }
>
> }
>
>
>
> Output:
> in a
>
> CRLF
> CRLF
> CRLF
>
> in b
>
> lf
> lf
> lf
> lf
> lf
> lf
> in a

I think I figured it out and the difference is probably in the 
mode. This documentation 
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/fread?view=msvc-170 mentions that "If the given stream is opened in text mode, Windows-style newlines are converted into Unix-style newlines. That is, carriage return-line feed (CRLF) pairs are replaced by single line feed (LF) characters."

And rawRead's documention mentions that "rawRead always reads in 
binary mode on Windows.", which I guess should have given me a 
clue. chunks must be using text-mode.