Move internal-only but kernel-agnostic paths into an `__internal` module
Add some documentation along the way.
PiperOrigin-RevId: 540311409
diff --git a/rust/internal.rs b/rust/internal.rs
new file mode 100644
index 0000000..ae07849
--- /dev/null
+++ b/rust/internal.rs
@@ -0,0 +1,71 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2023 Google Inc. All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//! Kernel-agnostic logic for the Rust Protobuf runtime that should not be
+//! exposed to through the `protobuf` path but must be public for use by
+//! generated code.
+
+use std::slice;
+
+/// Represents an ABI-stable version of `NonNull<[u8]>`/`string_view` (a
+/// borrowed slice of bytes) for FFI use only.
+///
+/// Has semantics similar to `std::string_view` in C++ and `&[u8]` in Rust,
+/// but is not ABI-compatible with either.
+///
+/// If `len` is 0, then `ptr` can be null or dangling. C++ considers a dangling
+/// 0-len `std::string_view` to be invalid, and Rust considers a `&[u8]` with a
+/// null data pointer to be invalid.
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct PtrAndLen {
+ /// Pointer to the first byte.
+ /// Borrows the memory.
+ pub ptr: *const u8,
+
+ /// Length of the `[u8]` pointed to by `ptr`.
+ pub len: usize,
+}
+
+impl PtrAndLen {
+ /// Unsafely dereference this slice.
+ ///
+ /// # Safety
+ /// - `ptr` must be valid for `len` bytes. It can be null or dangling if
+ /// `self.len == 0`.
+ pub unsafe fn as_ref<'a>(self) -> &'a [u8] {
+ if self.ptr.is_null() {
+ assert_eq!(self.len, 0, "Non-empty slice with null data pointer");
+ &[]
+ } else {
+ slice::from_raw_parts(self.ptr, self.len)
+ }
+ }
+}
