1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137

use std::ffi::CStr;
use std::fmt;
use std::marker::PhantomData;
use std::os::raw::{c_int, c_uchar, c_void};
use std::ptr;
use std::slice;

use itertools::Itertools;

use crate::error::{Error, Result};
use crate::panic;

/// The result of a successful MX lookup.
#[derive(Debug)]
pub struct MXResults {
    mx_reply: *mut c_ares_sys::ares_mx_reply,
    phantom: PhantomData<c_ares_sys::ares_mx_reply>,
}

/// The contents of a single MX record.
#[derive(Clone, Copy)]
pub struct MXResult<'a> {
    mx_reply: &'a c_ares_sys::ares_mx_reply,
}

impl MXResults {
    /// Obtain an `MXResults` from the response to an MX lookup.
    pub fn parse_from(data: &[u8]) -> Result<MXResults> {
        let mut mx_reply: *mut c_ares_sys::ares_mx_reply = ptr::null_mut();
        let parse_status = unsafe {
            c_ares_sys::ares_parse_mx_reply(data.as_ptr(), data.len() as c_int, &mut mx_reply)
        };
        if parse_status == c_ares_sys::ares_status_t::ARES_SUCCESS as i32 {
            let result = MXResults::new(mx_reply);
            Ok(result)
        } else {
            Err(Error::from(parse_status))
        }
    }

    fn new(mx_reply: *mut c_ares_sys::ares_mx_reply) -> Self {
        MXResults {
            mx_reply,
            phantom: PhantomData,
        }
    }

    /// Returns an iterator over the `MXResult` values in this `MXResults`.
    pub fn iter(&self) -> MXResultsIter {
        MXResultsIter {
            next: unsafe { self.mx_reply.as_ref() },
        }
    }
}

impl fmt::Display for MXResults {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        let results = self.iter().format("}, {");
        write!(fmt, "[{{{results}}}]")
    }
}

/// Iterator of `MXResult`s.
#[derive(Clone, Copy)]
pub struct MXResultsIter<'a> {
    next: Option<&'a c_ares_sys::ares_mx_reply>,
}

impl<'a> Iterator for MXResultsIter<'a> {
    type Item = MXResult<'a>;
    fn next(&mut self) -> Option<Self::Item> {
        let opt_reply = self.next;
        self.next = opt_reply.and_then(|reply| unsafe { reply.next.as_ref() });
        opt_reply.map(|reply| MXResult { mx_reply: reply })
    }
}

impl<'a> IntoIterator for &'a MXResults {
    type Item = MXResult<'a>;
    type IntoIter = MXResultsIter<'a>;

    fn into_iter(self) -> Self::IntoIter {
        self.iter()
    }
}

impl Drop for MXResults {
    fn drop(&mut self) {
        unsafe { c_ares_sys::ares_free_data(self.mx_reply.cast()) }
    }
}

unsafe impl Send for MXResults {}
unsafe impl Sync for MXResults {}
unsafe impl<'a> Send for MXResult<'a> {}
unsafe impl<'a> Sync for MXResult<'a> {}
unsafe impl<'a> Send for MXResultsIter<'a> {}
unsafe impl<'a> Sync for MXResultsIter<'a> {}

impl<'a> MXResult<'a> {
    /// Returns the hostname in this `MXResult`.
    ///
    /// In practice this is very likely to be a valid UTF-8 string, but the underlying `c-ares`
    /// library does not guarantee this - so we leave it to users to decide whether they prefer a
    /// fallible conversion, a lossy conversion, or something else altogether.
    pub fn host(self) -> &'a CStr {
        unsafe { CStr::from_ptr(self.mx_reply.host) }
    }

    /// Returns the priority from this `MXResult`.
    pub fn priority(self) -> u16 {
        self.mx_reply.priority
    }
}

impl<'a> fmt::Display for MXResult<'a> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(
            fmt,
            "Hostname: {}, ",
            self.host().to_str().unwrap_or("<not utf8>")
        )?;
        write!(fmt, "Priority: {}", self.priority())
    }
}

pub(crate) unsafe extern "C" fn query_mx_callback<F>(
    arg: *mut c_void,
    status: c_int,
    _timeouts: c_int,
    abuf: *mut c_uchar,
    alen: c_int,
) where
    F: FnOnce(Result<MXResults>) + Send + 'static,
{
    ares_callback!(arg.cast::<F>(), status, abuf, alen, MXResults::parse_from);
}