Add unstable_static_encoding_str feature

madsmtm · Nov 3, 2021 · 19e9e4e · 19e9e4e
1 parent 10b7550
commit 19e9e4e
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Showing 3 changed files with 48 additions and 5 deletions.
diff --git a/objc2-encode/Cargo.toml b/objc2-encode/Cargo.toml
@@ -17,3 +17,7 @@ readme = "README.md"
 repository = "https://github.com/madsmtm/objc2"
 documentation = "https://docs.rs/objc2-encode/"
 license = "MIT"
+
+[features]
+# Requires the `generic_const_exprs` feature
+unstable_static_encoding_str = []
diff --git a/objc2-encode/src/lib.rs b/objc2-encode/src/lib.rs
@@ -10,6 +10,8 @@
 #![deny(unsafe_op_in_unsafe_fn)]
 // Update in Cargo.toml as well.
 #![doc(html_root_url = "https://docs.rs/objc2-encode/1.1.0")]
+#![cfg_attr(feature = "unstable_static_encoding_str", allow(incomplete_features))]
+#![cfg_attr(feature = "unstable_static_encoding_str", feature(generic_const_exprs))]
 
 #[cfg(doctest)]
 #[doc = include_str!("../README.md")]
@@ -21,9 +23,11 @@ extern crate alloc;
 mod encode;
 mod encoding;
 mod parse;
-#[allow(dead_code)]
+#[cfg_attr(not(feature = "unstable_static_encoding_str"), allow(dead_code))]
 mod static_encoding_str;
 mod static_int_str;
 
 pub use self::encode::{Encode, EncodeArguments, RefEncode};
 pub use self::encoding::Encoding;
+#[cfg(feature = "unstable_static_encoding_str")]
+pub use self::static_encoding_str::EncodingHelper;
diff --git a/objc2-encode/src/static_encoding_str.rs b/objc2-encode/src/static_encoding_str.rs
@@ -1,8 +1,11 @@
 use super::static_int_str;
+#[cfg(feature = "unstable_static_encoding_str")]
+use super::Encode;
 use super::Encoding;
 
 impl<'a> Encoding<'a> {
-    const fn end_str_len(self) -> usize {
+    #[doc(hidden)]
+    pub const fn end_str_len(self) -> usize {
         use Encoding::*;
 
         match self {
@@ -26,7 +29,8 @@ impl<'a> Encoding<'a> {
         }
     }
 
-    const fn get_str_array<const LEN: usize>(self) -> [u8; LEN] {
+    #[doc(hidden)]
+    pub const fn get_str_array<const LEN: usize>(self) -> [u8; LEN] {
         use Encoding::*;
 
         let mut res: [u8; LEN] = [0; LEN];
@@ -156,16 +160,47 @@ impl<'a> Encoding<'a> {
         res
     }
 
-    const fn end_cstr_len(self) -> usize {
+    #[doc(hidden)]
+    pub const fn end_cstr_len(self) -> usize {
         self.end_str_len() + 1
     }
 
-    const fn get_cstr_array<const RES: usize>(self) -> [u8; RES] {
+    #[doc(hidden)]
+    pub const fn get_cstr_array<const RES: usize>(self) -> [u8; RES] {
         // Contains nul byte at the end
         self.get_str_array()
     }
 }
 
+/// Workaround since we can't specify the correct `where` bound on `Encode`.
+#[cfg(feature = "unstable_static_encoding_str")]
+pub struct EncodingHelper<T>(T);
+
+#[cfg(feature = "unstable_static_encoding_str")]
+impl<T: super::Encode> EncodingHelper<T>
+where
+    [u8; T::ENCODING.end_cstr_len()]: Sized,
+{
+    #[doc(hidden)]
+    const __ENCODING_CSTR_BYTES: [u8; T::ENCODING.end_cstr_len()] = T::ENCODING.get_cstr_array();
+
+    /// TODO
+    pub const ENCODING_CSTR: *const u8 = Self::__ENCODING_CSTR_BYTES.as_ptr();
+}
+
+#[cfg(feature = "unstable_static_encoding_str")]
+impl<T: Encode> EncodingHelper<T>
+where
+    [u8; T::ENCODING.end_str_len()]: Sized,
+{
+    #[doc(hidden)]
+    const __ENCODING_STR_BYTES: [u8; T::ENCODING.end_str_len()] = T::ENCODING.get_str_array();
+
+    /// TODO
+    pub const ENCODING_STR: &'static str =
+        unsafe { core::mem::transmute::<&[u8], &str>(&Self::__ENCODING_STR_BYTES) };
+}
+
 #[cfg(test)]
 mod tests {
     use super::Encoding;