isCygwinPty

fn isCygwinPty(file: File) Io.Cancelable!bool

File

Code

fn isCygwinPty(file: File) Io.Cancelable!bool {
    if (!is_windows) return false;

    const handle = file.handle;

    // If this is a MSYS2/cygwin pty, then it will be a named pipe with a name in one of these formats:
    //   msys-[...]-ptyN-[...]
    //   cygwin-[...]-ptyN-[...]
    //
    // Example: msys-1888ae32e00d56aa-pty0-to-master

    // First, just check that the handle is a named pipe.
    // This allows us to avoid the more costly NtQueryInformationFile call
    // for handles that aren't named pipes.
    {
        var io_status: windows.IO_STATUS_BLOCK = undefined;
        var device_info: windows.FILE.FS_DEVICE_INFORMATION = undefined;
        const syscall: Syscall = try .start();
        while (true) switch (windows.ntdll.NtQueryVolumeInformationFile(
            handle,
            &io_status,
            &device_info,
            @sizeOf(windows.FILE.FS_DEVICE_INFORMATION),
            .Device,
        )) {
            .SUCCESS => break syscall.finish(),
            .CANCELLED => {
                try syscall.checkCancel();
                continue;
            },
            else => {
                syscall.finish();
                return false;
            },
        };
        if (device_info.DeviceType.FileDevice != .NAMED_PIPE) return false;
    }

    const name_bytes_offset = @offsetOf(windows.FILE.NAME_INFORMATION, "FileName");
    // `NAME_MAX` UTF-16 code units (2 bytes each)
    // This buffer may not be long enough to handle *all* possible paths
    // (PATH_MAX_WIDE would be necessary for that), but because we only care
    // about certain paths and we know they must be within a reasonable length,
    // we can use this smaller buffer and just return false on any error from
    // NtQueryInformationFile.
    const num_name_bytes = windows.MAX_PATH * 2;
    var name_info_bytes: [name_bytes_offset + num_name_bytes]u8 align(@alignOf(windows.FILE.NAME_INFORMATION)) = @splat(0);

    var io_status_block: windows.IO_STATUS_BLOCK = undefined;
    const syscall: Syscall = try .start();
    while (true) switch (windows.ntdll.NtQueryInformationFile(
        handle,
        &io_status_block,
        &name_info_bytes,
        @intCast(name_info_bytes.len),
        .Name,
    )) {
        .SUCCESS => break syscall.finish(),
        .CANCELLED => {
            try syscall.checkCancel();
            continue;
        },
        .INVALID_PARAMETER => unreachable,
        else => {
            syscall.finish();
            return false;
        },
    };

    const name_info: *const windows.FILE.NAME_INFORMATION = @ptrCast(&name_info_bytes);
    const name_bytes = name_info_bytes[name_bytes_offset .. name_bytes_offset + name_info.FileNameLength];
    const name_wide = std.mem.bytesAsSlice(u16, name_bytes);
    // The name we get from NtQueryInformationFile will be prefixed with a '\', e.g. \msys-1888ae32e00d56aa-pty0-to-master
    return (std.mem.startsWith(u16, name_wide, &[_]u16{ '\\', 'm', 's', 'y', 's', '-' }) or
        std.mem.startsWith(u16, name_wide, &[_]u16{ '\\', 'c', 'y', 'g', 'w', 'i', 'n', '-' })) and
        std.mem.indexOf(u16, name_wide, &[_]u16{ '-', 'p', 't', 'y' }) != null;
}