implement get_servers()

build.rs

@@ -34,6 +34,11 @@ fn main() {
             println!("cargo:rustc-cfg=cares1_23");
         }
 
+        println!("cargo::rustc-check-cfg=cfg(cares1_24)");
+        if version >= 0x1_18_00 {
+            println!("cargo:rustc-cfg=cares1_24");
+        }
+
         println!("cargo::rustc-check-cfg=cfg(cares1_29)");
         if version >= 0x1_1d_00 {
             println!("cargo:rustc-cfg=cares1_29");

src/channel.rs

@@ -25,6 +25,8 @@ use crate::ptr::{query_ptr_callback, PTRResults};
 use crate::query::query_callback;
 use crate::soa::{query_soa_callback, SOAResult};
 use crate::srv::{query_srv_callback, SRVResults};
+#[cfg(cares1_24)]
+use crate::string::AresString;
 use crate::txt::{query_txt_callback, TXTResults};
 use crate::types::{AddressFamily, DnsClass, QueryType, Socket};
 use crate::uri::{query_uri_callback, URIResults};
@@ -479,6 +481,13 @@ impl Channel {
         }
     }
 
+    /// Retrieves the list of servers in comma delimited format.
+    #[cfg(cares1_24)]
+    pub fn get_servers(&self) -> AresString {
+        let servers = unsafe { c_ares_sys::ares_get_servers_csv(self.ares_channel) };
+        AresString::new(servers)
+    }
+
     /// Set the local IPv4 address from which to make queries.
     pub fn set_local_ipv4(&mut self, ipv4: Ipv4Addr) -> &mut Self {
         unsafe { c_ares_sys::ares_set_local_ip4(self.ares_channel, u32::from(ipv4)) }

src/lib.rs

@@ -58,6 +58,7 @@ mod query;
 mod server_state_flags;
 mod soa;
 mod srv;
+mod string;
 mod txt;
 mod types;
 mod uri;
@@ -89,6 +90,7 @@ pub use crate::ptr::PTRResults;
 pub use crate::server_state_flags::ServerStateFlags;
 pub use crate::soa::SOAResult;
 pub use crate::srv::{SRVResult, SRVResults, SRVResultsIter};
+pub use crate::string::AresString;
 pub use crate::txt::{TXTResult, TXTResults, TXTResultsIter};
 pub use crate::types::{AddressFamily, Socket, SOCKET_BAD};
 pub use crate::uri::{URIResult, URIResults, URIResultsIter};

src/string.rs

@@ -0,0 +1,34 @@
+use std::ffi::CStr;
+use std::ops::Deref;
+use std::os::raw::c_char;
+
+/// A smart pointer wrapping a string as allocated by c-ares.
+pub struct AresString {
+    ares_string: *mut c_char,
+    rust_str: &'static str,
+}
+
+impl AresString {
+    #[allow(dead_code)]
+    pub(crate) fn new(ares_string: *mut c_char) -> Self {
+        let c_str = unsafe { CStr::from_ptr(ares_string) };
+        let rust_str = c_str.to_str().unwrap();
+        AresString {
+            ares_string,
+            rust_str,
+        }
+    }
+}
+
+impl Deref for AresString {
+    type Target = str;
+    fn deref(&self) -> &str {
+        self.rust_str
+    }
+}
+
+impl Drop for AresString {
+    fn drop(&mut self) {
+        unsafe { c_ares_sys::ares_free_string(self.ares_string.cast()) }
+    }
+}