rust: clean up other slice casts involved in FFI

This is decided in the previous code reviews, that we adopt a unified
"calling convention" for slices.

Signed-off-by: Xiangfei Ding <xfding@google.com>
Change-Id: I6d4696e4585b076b226e442d31747ea26a6a6964
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/88847
Reviewed-by: Adam Langley <agl@google.com>

rust/bssl-crypto/src/hpke.rs

diff --git a/rust/bssl-crypto/src/hpke.rs b/rust/bssl-crypto/src/hpke.rs
index bf50759..1e29bd7 100644
--- a/rust/bssl-crypto/src/hpke.rs
+++ b/rust/bssl-crypto/src/hpke.rs
@@ -149,7 +149,7 @@
             bssl_sys::EVP_HPKE_KEY_init(
                 key.as_mut_ffi_ptr(),
                 self.as_ffi_ptr(),
-                priv_key.as_ptr(),
+                priv_key.as_ffi_ptr(),
                 priv_key.len(),
             )
         };

rust/bssl-crypto/src/slhdsa.rs

diff --git a/rust/bssl-crypto/src/slhdsa.rs b/rust/bssl-crypto/src/slhdsa.rs
index dd822b5..8b1de1e 100644
--- a/rust/bssl-crypto/src/slhdsa.rs
+++ b/rust/bssl-crypto/src/slhdsa.rs
@@ -91,7 +91,7 @@
         unsafe {
             bssl_sys::SLHDSA_SHA2_128S_public_from_private(
                 public_key.as_mut_ptr(),
-                self.0.as_ptr(),
+                self.0.as_ffi_ptr(),
             );
         }
 
@@ -116,7 +116,7 @@
             with_output_vec_fallible(SIGNATURE_BYTES, |signature| {
                 if bssl_sys::SLHDSA_SHA2_128S_sign(
                     signature,
-                    self.0.as_ptr(),
+                    self.0.as_ffi_ptr(),
                     msg.as_ffi_ptr(),
                     msg.len(),
                     context.as_ffi_ptr(),
@@ -163,7 +163,7 @@
             bssl_sys::SLHDSA_SHA2_128S_verify(
                 signature.as_ffi_ptr(),
                 signature.len(),
-                self.0.as_ptr(),
+                self.0.as_ffi_ptr(),
                 msg.as_ffi_ptr(),
                 msg.len(),
                 context.as_ffi_ptr(),