Switch X509Name over to new borrow setup

The use of actual references enables us to be correct with respect to
mutability without needing two structs for the mutable and immutable
cases and more deref impls.

openssl/src/lib.rs

@@ -32,6 +32,7 @@ pub mod nid;
 pub mod ssl;
 pub mod version;
 pub mod x509;
+mod opaque;
 
 pub fn cvt_p<T>(r: *mut T) -> Result<*mut T, ErrorStack> {
     if r.is_null() {

openssl/src/opaque.rs

@@ -0,0 +1,6 @@
+use std::cell::UnsafeCell;
+
+/// This is intended to be used as the inner type for types designed to be pointed to by references
+/// converted from raw C pointers. It has an `UnsafeCell` internally to inform the compiler about
+/// aliasability and doesn't implement `Copy`, so it can't be dereferenced.
+pub struct Opaque(UnsafeCell<()>);

openssl/src/x509/mod.rs

@@ -18,9 +18,10 @@ use bio::{MemBio, MemBioSlice};
 use crypto::hash::MessageDigest;
 use crypto::pkey::PKey;
 use crypto::rand::rand_bytes;
+use error::ErrorStack;
 use ffi;
 use nid::Nid;
-use error::ErrorStack;
+use opaque::Opaque;
 
 #[cfg(ossl10x)]
 use ffi::{
@@ -401,9 +402,11 @@ impl<'a> X509Ref<'a> {
         self.0
     }
 
-    pub fn subject_name<'b>(&'b self) -> X509Name<'b> {
+    pub fn subject_name(&self) -> &X509NameRef {
-        let name = unsafe { ffi::X509_get_subject_name(self.0) };
+        unsafe {
-        X509Name(name, PhantomData)
+            let name = ffi::X509_get_subject_name(self.0);
+            X509NameRef::from_ptr(name)
+        }
     }
 
     /// Returns this certificate's SAN entries, if they exist.
@@ -534,17 +537,25 @@ impl Drop for X509 {
     }
 }
 
-pub struct X509Name<'x>(*mut ffi::X509_NAME, PhantomData<&'x ()>);
+pub struct X509NameRef(Opaque);
+
+impl X509NameRef {
+    pub unsafe fn from_ptr<'a>(ptr: *mut ffi::X509_NAME) -> &'a X509NameRef {
+        &*(ptr as *mut _)
+    }
+
+    pub fn as_ptr(&self) -> *mut ffi::X509_NAME {
+        self as *const _ as *mut _
+    }
 
-impl<'x> X509Name<'x> {
     pub fn text_by_nid(&self, nid: Nid) -> Option<SslString> {
         unsafe {
-            let loc = ffi::X509_NAME_get_index_by_NID(self.0, nid as c_int, -1);
+            let loc = ffi::X509_NAME_get_index_by_NID(self.as_ptr(), nid as c_int, -1);
             if loc == -1 {
                 return None;
             }
 
-            let ne = ffi::X509_NAME_get_entry(self.0, loc);
+            let ne = ffi::X509_NAME_get_entry(self.as_ptr(), loc);
             if ne.is_null() {
                 return None;
             }