Merge Windows helper module into the verifier impl

There is no longer enough code to justify it being split up

rustls-platform-verifier/src/lib.rs

@@ -15,9 +15,6 @@ pub use verification::Verifier;
 #[cfg_attr(docsrs, doc(cfg(target_os = "android")))]
 pub mod android;
 
-#[cfg(windows)]
-mod windows;
-
 /// Fixures and data to support testing the server
 /// certificate verifier.
 #[cfg(any(test, feature = "ffi-testing"))]

rustls-platform-verifier/src/verification/windows.rs

@@ -19,7 +19,6 @@
 //! [Microsoft's Example]: <https://docs.microsoft.com/en-us/windows/win32/seccrypto/example-c-program-creating-a-certificate-chain>
 
 use super::{log_server_cert, ALLOWED_EKUS};
-use crate::windows::{nonnull_from_const_ptr, ZeroedWithSize};
 use once_cell::sync::OnceCell;
 use rustls::client::danger::{HandshakeSignatureValid, ServerCertVerifier};
 use rustls::crypto::{verify_tls12_signature, verify_tls13_signature, CryptoProvider};
@@ -630,3 +629,33 @@ impl Default for Verifier {
         Self::new()
     }
 }
+
+/// A trait to represent an object that can be safely created with all zero values
+/// and have a size assigned to it.
+///
+/// # Safety
+///
+/// This has the same safety requirements as [std::mem::zeroed].
+unsafe trait ZeroedWithSize: Sized {
+    const SIZE: u32 = {
+        let size = core::mem::size_of::<Self>();
+
+        // NB: `TryInto` isn't stable in const yet.
+        #[allow(clippy::as_conversions)]
+        if size <= u32::MAX as usize {
+            size as u32
+        } else {
+            panic!("structure was larger then DWORD")
+        }
+    };
+
+    /// Returns a zeroed structure with its structure size (`cbSize`) field set to the correct value.
+    fn zeroed_with_size() -> Self;
+}
+
+/// Returns `p` as a `NonNull<T>`, erasing its `const`-ness.
+///
+/// The conversion is done in the most type-safe way possible.
+fn nonnull_from_const_ptr<T>(p: *const T) -> Option<NonNull<T>> {
+    NonNull::new(p as *mut T)
+}