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//! Get the current size of the terminal
//!
//! NOTE: This is a copy and adaptation of the original mod `size` from the crate `termion`.
//!
//! The original `termion::terminal_size` function only checks the size against `STDOUT`,
//! but to interact with the user we use a custom tty (`/dev/tty` to be precise), so we need
//! to use a different file descriptor.
use libc::{c_int, c_ushort};
use std::io;

#[cfg(target_os = "linux")]
pub const TIOCGWINSZ: usize = 0x0000_5413;

#[cfg(not(target_os = "linux"))]
pub const TIOCGWINSZ: usize = 0x4008_7468;

#[repr(C)]
struct TermSize {
    row: c_ushort,
    col: c_ushort,
    _x: c_ushort,
    _y: c_ushort,
}

#[cfg(target_env = "musl")]
fn tiocgwinsz() -> i32 {
    TIOCGWINSZ as i32
}

#[cfg(all(not(target_env = "musl"), target_pointer_width = "64"))]
fn tiocgwinsz() -> u64 {
    TIOCGWINSZ as u64
}

#[cfg(all(not(target_env = "musl"), target_pointer_width = "32"))]
fn tiocgwinsz() -> u32 {
    TIOCGWINSZ as u32
}

/// Get the size of the terminal for the given file descriptor
pub fn terminal_size(fileno: c_int) -> io::Result<(u16, u16)> {
    use libc::ioctl;
    use std::mem;

    unsafe {
        let mut size: TermSize = mem::zeroed();

        if ioctl(fileno, tiocgwinsz(), &mut size as *mut _) == 0 {
            Ok((size.col as u16, size.row as u16))
        } else {
            Err(io::Error::new(
                io::ErrorKind::Other,
                "Unable to get the terminal size.",
            ))
        }
    }
}