#[unsafe(no_mangle)]
extern "C" fn panic() -> ! {
    panic!("Called panic from external code.");
}

#[repr(C)]
#[derive(Debug, PartialEq, Eq)]
pub struct FFISlice {
    pub ptr: *const u8,
    pub len: usize,
}

#[repr(transparent)]
#[derive(Debug, PartialEq, Eq)]
pub struct MaybeFFISlice {
    inner: FFISlice,
}

impl MaybeFFISlice {
    pub fn is_none(&self) -> bool {
        self.inner.ptr.is_null()
    }

    pub fn into_option(self) -> Option<FFISlice> {
        if self.is_none() {
            None
        } else {
            Some(self.inner)
        }
    }
}

impl FFISlice {
    pub fn as_slice(&self) -> &[u8] {
        unsafe { core::slice::from_raw_parts(self.ptr, self.len) }
    }
    pub fn as_str(&self) -> &str {
        unsafe { core::str::from_utf8_unchecked(self.as_slice()) }
    }
}