Cannot read unicode data from STDIN on Windows

[Tetralux]

Tracking issue for how, on Windows, just using ReadFile will completely corrupt UTF-16 data.

Instead, you have to use ReadConsoleW.

For example:

extern "kernel32" fn ReadConsoleW(handle: os.fd_t, buffer: [*]u16, len: os.windows.DWORD, read: *os.windows.DWORD, input_ctrl: ?*c_void) i32;
extern "kernel32" fn SetConsoleOutputCP(cp: os.windows.UINT) i32;

// ...

assert(SetConsoleOutputCP(65001) != 0); // display outputted utf8 correctly in the console
    
var stdin = io.getStdIn().handle;
var data: [256]u16 = undefined;
var read: u32 = undefined;
const ok = ReadConsoleW(stdin, &data, data.len, &read, null); // type in '안녕'
assert(ok != 0);

var utf8: [1024]u8 = undefined;
const utf8_len = try unicode.utf16leToUtf8(&utf8, data[0..read]);
const s = utf8[0..utf8_len];

print("'{}'\n", .{s});  // prints out '안녕
                        //            '

As noted by @fengb, this may mean Zig needs to have a special InStream for the console.

[doongjohn]

maybe we can solve this without using ReadConsoleW?
https://forum.nim-lang.org/t/5874#38898

edit: using ReadConsoleW seems cleaner