From 38c6d942b7c1bd8b01a66bbcd8f9757ce0b6180b Mon Sep 17 00:00:00 2001
From: ijl <ijl@mailbox.org>
Date: Fri, 28 Sep 2018 22:01:04 +0000
Subject: [PATCH] Document UTF-8 FFI assumptions

---
 src/types/string.rs  | 2 ++
 src/types/string2.rs | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/src/types/string.rs b/src/types/string.rs
index b5d4d7d7..da7b75de 100644
--- a/src/types/string.rs
+++ b/src/types/string.rs
@@ -56,6 +56,8 @@ impl PyString {
         unsafe {
             let mut size: ffi::Py_ssize_t = mem::uninitialized();
             let data = ffi::PyUnicode_AsUTF8AndSize(self.0.as_ptr(), &mut size) as *const u8;
+            // PyUnicode_AsUTF8AndSize would return null if the pointer did not reference a valid
+            // unicode object, but because we have a valid PyString, assume success
             debug_assert!(!data.is_null());
             std::slice::from_raw_parts(data, size as usize)
         }
diff --git a/src/types/string2.rs b/src/types/string2.rs
index 2a95f3f2..88a7f4c1 100644
--- a/src/types/string2.rs
+++ b/src/types/string2.rs
@@ -154,6 +154,8 @@ impl PyUnicode {
     #[inline]
     pub fn as_bytes(&self) -> &[u8] {
         unsafe {
+            // PyUnicode_AsUTF8String would return null if the pointer did not reference a valid
+            // unicode object, but because we have a valid PyUnicode, assume success
             let data: Py<PyBytes> = Py::from_owned_ptr(
                 ffi::PyUnicode_AsUTF8String(self.0.as_ptr()),
             );