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.
