grb 1.3.0

use grb_sys2 as ffi;
use std::ffi::CStr;

/// Copy a raw C-string into a String
///
/// To quote the Gurobi docs:
/// Note that all interface routines that return string-valued attributes are returning pointers
/// into internal Gurobi data structures. The user should copy the contents of the pointer to a
/// different data structure before the next call to a Gurobi library routine. The user should
/// also be careful to never modify the data pointed to by the returned character pointer.
pub(crate) unsafe fn copy_c_str(s: ffi::c_str) -> String {
  debug_assert!(!s.is_null());
  CStr::from_ptr(s).to_string_lossy().into_owned() // to_string_lossy().into_owned() ALWAYS clones
}

#[test]
fn conversion_must_succeed() {
    use std::ffi::CString;
    let s1 = "mip1.log";
    let cs = CString::new(s1).unwrap();
    let s2 = unsafe { copy_c_str(cs.as_ptr()) };
    assert!(s1 == s2);
}

pub(crate) trait AsPtr {
    type Ptr;
    /// Return the underlying Gurobi pointer for [`Model`] and [`Env`] objects
    ///
    /// # Safety
    /// One of the following conditions must hold
    /// - self is mutable
    /// - the resulting pointer is passed only to Gurobi C routines
    unsafe fn as_mut_ptr(&self) -> *mut Self::Ptr;

    /// Return the underling Gurobi pointer
    fn as_ptr(&self) -> *const Self::Ptr {
        (unsafe { self.as_mut_ptr() }) as *const Self::Ptr
    }
}