Implement a generic Stack API to deal with OpenSSL stacks

1 files changed, 319 insertions, 0 deletions

diff --git a/openssl/src/stack.rs b/openssl/src/stack.rs
new file mode 100644
index 00000000..2cc53b5f
--- /dev/null
+++ b/openssl/src/stack.rs
@@ -0,0 +1,319 @@
+use std::ops::{Deref, DerefMut, Index, IndexMut};
+use std::iter;
+use std::borrow::Borrow;
+use std::convert::AsRef;
+
+#[cfg(ossl110)]
+use libc::c_int;
+
+use ffi;
+use types::{OpenSslType, Ref};
+
+/// Trait implemented by stackable types. This must *only* be
+/// implemented on opaque types that can be directly casted into their
+/// `CType`.
+pub trait Stackable: OpenSslType {
+    /// C stack type for this element. Generally called
+    /// `stack_st_{ELEMENT_TYPE}`, normally hidden by the
+    /// `STACK_OF(ELEMENT_TYPE)` macro in the OpenSSL API.
+    type StackType;
+}
+
+/// An owned stack of `T`.
+pub struct Stack<T: Stackable>(*mut T::StackType);
+
+impl<T: Stackable> Stack<T> {
+    /// Return a new Stack<T>, taking ownership of the handle
+    pub unsafe fn from_ptr(stack: *mut T::StackType) -> Stack<T> {
+        Stack(stack)
+    }
+}
+
+impl<T: Stackable> Drop for Stack<T> {
+    #[cfg(ossl10x)]
+    fn drop(&mut self) {
+        unsafe {
+            loop {
+                let ptr = ffi::sk_pop(self.as_stack());
+
+                if ptr.is_null() {
+                    break;
+                }
+
+                // Build the owned version of the object just to run
+                // its `drop` implementation and delete the item.
+                T::from_ptr(ptr as *mut _);
+            }
+
+            ffi::sk_free(self.0 as *mut _);
+        }
+    }
+
+    #[cfg(ossl110)]
+    fn drop(&mut self) {
+        unsafe {
+            loop {
+                let ptr = ffi::OPENSSL_sk_pop(self.as_stack());
+
+                if ptr.is_null() {
+                    break;
+                }
+
+                // Build the owned version of the object just to run
+                // its `drop` implementation and delete the item.
+                T::from_ptr(ptr as *mut _);
+            }
+
+            ffi::OPENSSL_sk_free(self.0 as *mut _);
+        }
+    }
+}
+
+impl<T: Stackable> AsRef<Ref<Stack<T>>> for Stack<T> {
+    fn as_ref(&self) -> &Ref<Stack<T>> {
+        &*self
+    }
+}
+
+impl<T: Stackable> Borrow<Ref<Stack<T>>> for Stack<T> {
+    fn borrow(&self) -> &Ref<Stack<T>> {
+        &*self
+    }
+}
+
+unsafe impl<T: Stackable> OpenSslType for Stack<T> {
+    type CType = T::StackType;
+
+    unsafe fn from_ptr(ptr: *mut T::StackType) -> Stack<T> {
+        Stack(ptr)
+    }
+
+    fn as_ptr(&self) -> *mut T::StackType {
+        self.0
+    }
+}
+
+impl<T: Stackable> Deref for Stack<T> {
+    type Target = Ref<Stack<T>>;
+
+    fn deref(&self) -> &Ref<Stack<T>> {
+        unsafe { Ref::from_ptr(self.0) }
+    }
+}
+
+impl<T: Stackable> DerefMut for Stack<T> {
+    fn deref_mut(&mut self) -> &mut ::types::Ref<Stack<T>> {
+        unsafe { Ref::from_ptr_mut(self.0) }
+    }
+}
+
+impl<T: Stackable> Ref<Stack<T>> {
+    /// OpenSSL stack types are just a (kinda) typesafe wrapper around
+    /// a `_STACK` object. We can therefore safely cast it and access
+    /// the `_STACK` members without having to worry about the real
+    /// layout of `T::StackType`.
+    ///
+    /// If that sounds unsafe then keep in mind that's exactly how the
+    /// OpenSSL 1.1.0 new C stack code works.
+    #[cfg(ossl10x)]
+    fn as_stack(&self) -> *mut ffi::_STACK {
+        self.as_ptr() as *mut _
+    }
+
+    /// OpenSSL 1.1.0 replaced the stack macros with a functions and
+    /// only exposes an opaque OPENSSL_STACK struct
+    /// publicly.
+    #[cfg(ossl110)]
+    fn as_stack(&self) -> *mut ffi::OPENSSL_STACK {
+        self.as_ptr() as *mut _
+    }
+
+    /// Returns the number of items in the stack
+    pub fn len(&self) -> usize {
+        self._len()
+    }
+
+    #[cfg(ossl10x)]
+    fn _len(&self) -> usize {
+        unsafe { (*self.as_stack()).num as usize }
+    }
+
+    #[cfg(ossl110)]
+    fn _len(&self) -> usize {
+        unsafe { ffi::OPENSSL_sk_num(self.as_stack()) as usize }
+    }
+
+    pub fn iter(&self) -> Iter<T> {
+        // Unfortunately we can't simply convert the stack into a
+        // slice and use that because OpenSSL 1.1.0 doesn't directly
+        // expose the stack data (we have to use `OPENSSL_sk_value`
+        // instead). We have to rewrite the entire iteration framework
+        // instead.
+
+        Iter {
+            stack: self,
+            pos: 0,
+        }
+    }
+
+    pub fn iter_mut(&mut self) -> IterMut<T> {
+        IterMut {
+            stack: self,
+            pos: 0,
+        }
+    }
+
+    /// Returns a reference to the element at the given index in the
+    /// stack or `None` if the index is out of bounds
+    pub fn get(&self, idx: usize) -> Option<&Ref<T>> {
+        if idx >= self.len() {
+            return None;
+        }
+
+        unsafe {
+            let r = Ref::from_ptr(self._get(idx));
+
+            Some(r)
+        }
+    }
+
+    /// Returns a mutable reference to the element at the given index in the
+    /// stack or `None` if the index is out of bounds
+    pub fn get_mut(&mut self, idx: usize) -> Option<&mut Ref<T>> {
+        if idx >= self.len() {
+            return None;
+        }
+
+        unsafe {
+            Some(Ref::from_ptr_mut(self._get(idx)))
+        }
+    }
+
+    #[cfg(ossl10x)]
+    unsafe fn _get(&self, idx: usize) -> *mut T::CType {
+        *(*self.as_stack()).data.offset(idx as isize) as *mut _
+    }
+
+    #[cfg(ossl110)]
+    unsafe fn _get(&self, idx: usize) -> *mut T::CType {
+        ffi::OPENSSL_sk_value(self.as_stack(), idx as c_int) as *mut _
+    }
+}
+
+impl<T: Stackable> Index<usize> for Ref<Stack<T>> {
+    type Output = Ref<T>;
+
+    fn index(&self, index: usize) -> &Ref<T> {
+        self.get(index).unwrap()
+    }
+}
+
+impl<T: Stackable> IndexMut<usize> for Ref<Stack<T>> {
+    fn index_mut(&mut self, index: usize) -> &mut Ref<T> {
+        self.get_mut(index).unwrap()
+    }
+}
+
+impl<'a, T: Stackable> iter::IntoIterator for &'a Ref<Stack<T>> {
+    type Item = &'a Ref<T>;
+    type IntoIter = Iter<'a, T>;
+
+    fn into_iter(self) -> Iter<'a, T> {
+        self.iter()
+    }
+}
+
+impl<'a, T: Stackable> iter::IntoIterator for &'a mut Ref<Stack<T>> {
+    type Item = &'a mut Ref<T>;
+    type IntoIter = IterMut<'a, T>;
+
+    fn into_iter(self) -> IterMut<'a, T> {
+        self.iter_mut()
+    }
+}
+
+impl<'a, T: Stackable> iter::IntoIterator for &'a Stack<T> {
+    type Item = &'a Ref<T>;
+    type IntoIter = Iter<'a, T>;
+
+    fn into_iter(self) -> Iter<'a, T> {
+        self.iter()
+    }
+}
+
+impl<'a, T: Stackable> iter::IntoIterator for &'a mut Stack<T> {
+    type Item = &'a mut Ref<T>;
+    type IntoIter = IterMut<'a, T>;
+
+    fn into_iter(self) -> IterMut<'a, T> {
+        self.iter_mut()
+    }
+}
+
+/// An iterator over the stack's contents.
+pub struct Iter<'a, T: Stackable>
+    where T: 'a {
+    stack: &'a Ref<Stack<T>>,
+    pos: usize,
+}
+
+impl<'a, T: Stackable> iter::Iterator for Iter<'a, T> {
+    type Item = &'a Ref<T>;
+
+    fn next(&mut self) -> Option<&'a Ref<T>> {
+        let n = self.stack.get(self.pos);
+
+        if n.is_some() {
+            self.pos += 1;
+        }
+
+        n
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let rem = self.stack.len() - self.pos;
+
+        (rem, Some(rem))
+    }
+}
+
+impl<'a, T: Stackable> iter::ExactSizeIterator for Iter<'a, T> {
+}
+
+/// A mutable iterator over the stack's contents.
+pub struct IterMut<'a, T: Stackable + 'a> {
+    stack: &'a mut Ref<Stack<T>>,
+    pos: usize,
+}
+
+impl<'a, T: Stackable> iter::Iterator for IterMut<'a, T> {
+    type Item = &'a mut Ref<T>;
+
+    fn next(&mut self) -> Option<&'a mut Ref<T>> {
+        if self.pos >= self.stack.len() {
+            None
+        } else {
+            // Rust won't allow us to get a mutable reference into
+            // `stack` in this situation since it can't statically
+            // guarantee that we won't return several references to
+            // the same object, so we have to use unsafe code for
+            // mutable iterators.
+            let n = unsafe {
+                Some(Ref::from_ptr_mut(self.stack._get(self.pos)))
+            };
+
+            self.pos += 1;
+
+            n
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let rem = self.stack.len() - self.pos;
+
+        (rem, Some(rem))
+    }
+}
+
+impl<'a, T: Stackable> iter::ExactSizeIterator for IterMut<'a, T> {
+}