Add static encoding strings

madsmtm · madsmtm · commit c5ad3ce1070d · 2022-08-09T21:48:42.000+02:00
diff --git a/objc2-encode/CHANGELOG.md b/objc2-encode/CHANGELOG.md
@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased - YYYY-MM-DD
 
+### Added
+* Added `Encode::ENCODING_CSTR` for statically generating an encoding string.
+
 ### Fixed
 * Fixed the encoding output and comparison of structs behind pointers.
 
diff --git a/objc2-encode/src/encode.rs b/objc2-encode/src/encode.rs
@@ -6,7 +6,11 @@ use core::num::{
 };
 use core::ptr::NonNull;
 use core::sync::atomic;
+#[cfg(feature = "std")] // TODO: Use `core`
+use std::ffi::CStr;
 
+use crate::helper::NestingLevel;
+use crate::static_str::{static_encoding_str_array, static_encoding_str_len};
 use crate::Encoding;
 
 /// Types that have an Objective-C type-encoding.
@@ -16,6 +20,7 @@ use crate::Encoding;
 /// If your type is an opaque type you should not need to implement this;
 /// there you will only need [`RefEncode`].
 ///
+///
 /// # Safety
 ///
 /// The type must be FFI-safe, meaning a C-compatible `repr` (`repr(C)`,
@@ -33,6 +38,9 @@ use crate::Encoding;
 /// passed to Objective-C via. `objc2::msg_send!` their destructor will not be
 /// called!
 ///
+/// Finally, you must not override [`ENCODING_CSTR`][Self::ENCODING_CSTR].
+///
+///
 /// # Examples
 ///
 /// Implementing for a struct:
@@ -69,6 +77,43 @@ use crate::Encoding;
 pub unsafe trait Encode {
     /// The Objective-C type-encoding for this type.
     const ENCODING: Encoding<'static>;
+
+    #[doc(hidden)]
+    const __ENCODING_CSTR_LEN: usize = static_encoding_str_len(Self::ENCODING, NestingLevel::new());
+
+    #[doc(hidden)]
+    const __ENCODING_CSTR_ARRAY: [u8; 128] = {
+        if Self::__ENCODING_CSTR_LEN >= 127 {
+            panic!("encoding string was too long! The maximum supported length is 1023.");
+        }
+
+        static_encoding_str_array(Self::ENCODING, NestingLevel::new())
+    };
+
+    /// The encoding as a static [`CStr`].
+    ///
+    /// This has the same output as `Encoding::to_string`, but it is created
+    /// at compile-time instead.
+    ///
+    /// The encoding is guaranteed to be a pure ASCII string.
+    #[cfg(feature = "std")]
+    const ENCODING_CSTR: &'static CStr = {
+        let mut slice: &[u8] = &Self::__ENCODING_CSTR_ARRAY;
+        // Cut down to desired size (length + 1 for NUL byte)
+        // Equivalent to:
+        // slice[0..Self::__ENCODING_CSTR_LEN + 1]
+        while slice.len() > Self::__ENCODING_CSTR_LEN + 1 {
+            if let Some(res) = slice.split_last() {
+                slice = res.1;
+            } else {
+                unreachable!();
+            }
+        }
+        // SAFETY: `static_encoding_str_array` is guaranteed to not contain
+        // any NULL bytes (the only place those could appear would be in a
+        // struct or union name, and that case is checked).
+        unsafe { CStr::from_bytes_with_nul_unchecked(slice) }
+    };
 }
 
 /// Types whoose references has an Objective-C type-encoding.
@@ -736,4 +781,39 @@ mod tests {
         assert_eq!(<(i8,)>::ENCODINGS, &[i8::ENCODING]);
         assert_eq!(<(i8, u32)>::ENCODINGS, &[i8::ENCODING, u32::ENCODING]);
     }
+
+    #[test]
+    #[cfg(feature = "std")]
+    fn test_cstr_simple() {
+        assert_eq!(i8::__ENCODING_CSTR_LEN, 1);
+
+        let mut array = [0; 1024];
+        array[0] = b'c';
+        assert_eq!(i8::__ENCODING_CSTR_ARRAY, array);
+
+        let cstr = CStr::from_bytes_with_nul(b"c\0").unwrap();
+        assert_eq!(i8::ENCODING_CSTR, cstr);
+    }
+
+    #[test]
+    #[cfg(feature = "std")]
+    fn test_cstr() {
+        struct X;
+
+        unsafe impl Encode for X {
+            const ENCODING: Encoding<'static> = Encoding::Struct(
+                "abc",
+                &[
+                    Encoding::Union("def", &[Encoding::Char]),
+                    <*const *const i8>::ENCODING,
+                    <AtomicPtr<AtomicI16>>::ENCODING,
+                    <extern "C" fn()>::ENCODING,
+                ],
+            );
+        }
+
+        let s = b"{abc=(def=c)^*A^As^?}\0";
+
+        assert_eq!(X::ENCODING_CSTR.to_bytes_with_nul(), s);
+    }
 }
diff --git a/objc2-encode/src/lib.rs b/objc2-encode/src/lib.rs
@@ -110,9 +110,6 @@ mod encode;
 mod encoding;
 mod helper;
 mod parse;
-
-// Will be used at some point when generic constants are available
-#[allow(dead_code)]
 mod static_str;
 
 pub use self::encode::{Encode, EncodeArguments, RefEncode};
diff --git a/test-assembly/crates/test_encoding_cstr/Cargo.toml b/test-assembly/crates/test_encoding_cstr/Cargo.toml
@@ -0,0 +1,26 @@
+[package]
+name = "test_encoding_cstr"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[lib]
+path = "lib.rs"
+
+[dependencies]
+objc2-encode = { path = "../../../objc2-encode", default-features = false }
+
+[features]
+default = ["apple", "std"]
+std = ["objc2-encode/std"]
+
+# Runtime
+apple = []
+gnustep-1-7 = []
+gnustep-1-8 = ["gnustep-1-7"]
+gnustep-1-9 = ["gnustep-1-8"]
+gnustep-2-0 = ["gnustep-1-9"]
+gnustep-2-1 = ["gnustep-2-0"]
+
+# Hack
+assembly-features = ["std"]
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-aarch64.s b/test-assembly/crates/test_encoding_cstr/expected/apple-aarch64.s
@@ -0,0 +1,13 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	3
+_ENC:
+	.quad	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000\000\000\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-armv7.s b/test-assembly/crates/test_encoding_cstr/expected/apple-armv7.s
@@ -0,0 +1,14 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.syntax unified
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	2
+_ENC:
+	.long	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-armv7s.s b/test-assembly/crates/test_encoding_cstr/expected/apple-armv7s.s
@@ -0,0 +1,14 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.syntax unified
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	2
+_ENC:
+	.long	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-x86.s b/test-assembly/crates/test_encoding_cstr/expected/apple-x86.s
@@ -0,0 +1,14 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.intel_syntax noprefix
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	2
+_ENC:
+	.long	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-x86_64.s b/test-assembly/crates/test_encoding_cstr/expected/apple-x86_64.s
@@ -0,0 +1,14 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.intel_syntax noprefix
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	3
+_ENC:
+	.quad	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000\000\000\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86.s b/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86.s
@@ -0,0 +1,18 @@
+	.text
+	.intel_syntax noprefix
+	.type	.Lanon.a88231c846af3b75605317c1ca346ede.0,@object
+	.section	.rodata..Lanon.a88231c846af3b75605317c1ca346ede.0,"a",@progbits
+.Lanon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+	.size	.Lanon.a88231c846af3b75605317c1ca346ede.0, 128
+
+	.type	ENC,@object
+	.section	.data.rel.ro.ENC,"aw",@progbits
+	.globl	ENC
+	.p2align	2
+ENC:
+	.long	.Lanon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000"
+	.size	ENC, 8
+
+	.section	".note.GNU-stack","",@progbits
diff --git a/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86_64.s b/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86_64.s
@@ -0,0 +1,18 @@
+	.text
+	.intel_syntax noprefix
+	.type	.Lanon.a88231c846af3b75605317c1ca346ede.0,@object
+	.section	.rodata..Lanon.a88231c846af3b75605317c1ca346ede.0,"a",@progbits
+.Lanon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+	.size	.Lanon.a88231c846af3b75605317c1ca346ede.0, 128
+
+	.type	ENC,@object
+	.section	.data.rel.ro.ENC,"aw",@progbits
+	.globl	ENC
+	.p2align	3
+ENC:
+	.quad	.Lanon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000\000\000\000\000"
+	.size	ENC, 16
+
+	.section	".note.GNU-stack","",@progbits
diff --git a/test-assembly/crates/test_encoding_cstr/lib.rs b/test-assembly/crates/test_encoding_cstr/lib.rs
@@ -0,0 +1,7 @@
+//! Test that the encoding string that we output is not full length.
+use std::ffi::CStr;
+
+use objc2_encode::Encode;
+
+#[no_mangle]
+static ENC: &CStr = i8::ENCODING_CSTR;
diff --git a/test-ui/src/main.rs b/test-ui/src/main.rs
@@ -14,10 +14,16 @@
 #[cfg(feature = "run")]
 fn main() {
     let t = trybuild::TestCases::new();
+
     let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
         .join("ui")
         .join("*.rs");
     t.compile_fail(path);
+
+    let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("ui-ignore")
+        .join("*.rs");
+    t.pass(path);
 }
 
 #[cfg(not(feature = "run"))]
diff --git a/test-ui/ui-ignore/encode_cstr_not_ident.rs b/test-ui/ui-ignore/encode_cstr_not_ident.rs
@@ -0,0 +1,15 @@
+//! Test that compilation fails when the struct name is invalid.
+//!
+//! Ideally, this should be tested by `trybuild`, but it doesn't work at the
+//! moment (`cargo check` doesn't catch the error).
+use objc2::{Encode, Encoding};
+
+struct X;
+
+unsafe impl Encode for X {
+    const ENCODING: Encoding<'static> = Encoding::Struct("-", &[]);
+}
+
+fn main() {
+    let _ = X::ENCODING_CSTR;
+}
diff --git a/test-ui/ui-ignore/encode_cstr_too_long.rs b/test-ui/ui-ignore/encode_cstr_too_long.rs
@@ -0,0 +1,17 @@
+//! Test that compilation fails when the encoding is too long.
+//!
+//! Ideally, this should be tested by `trybuild`, but it doesn't work at the
+//! moment (`cargo check` doesn't catch the error).
+use objc2::{Encode, Encoding};
+
+struct X;
+
+const S: &str = unsafe { std::str::from_utf8_unchecked(&[b'a'; 1020]) };
+
+unsafe impl Encode for X {
+    const ENCODING: Encoding<'static> = Encoding::Struct(S, &[]);
+}
+
+fn main() {
+    let _ = X::ENCODING_CSTR;
+}
diff --git a/tests/src/test_encode_utils.rs b/tests/src/test_encode_utils.rs
@@ -20,6 +20,12 @@ unsafe fn assert_encoding(s: *const c_char, e: Encoding) {
     assert_eq!(e.to_string(), s.trim_start_matches('r'));
 }
 
+unsafe fn assert_ty<T: Encode>(s: *const c_char) {
+    assert_encoding(s, T::ENCODING);
+    // To ensure ENCODING_CSTR is implemented correctly
+    assert_eq!(T::ENCODING_CSTR.to_str().unwrap(), T::ENCODING.to_string());
+}
+
 #[allow(unused)]
 unsafe fn assert_str<T: Display>(s: *const c_char, expected: T) {
     let s = CStr::from_ptr(s).to_str().unwrap();
@@ -39,6 +45,16 @@ macro_rules! assert_inner {
             unsafe { assert_encoding($stat, $expected) };
         }
     };
+    (ty $(#[$m:meta])* $stat:ident => $expected:ty) => {
+        $(#[$m])*
+        #[test]
+        fn $stat() {
+            extern "C" {
+                static $stat: *const c_char;
+            }
+            unsafe { assert_ty::<$expected>($stat) };
+        }
+    };
     (str $(#[$m:meta])* $stat:ident => $expected:expr) => {
         $(#[$m])*
         #[test]
@@ -78,10 +94,10 @@ macro_rules! assert_types {
         $stat:ident $($should_atomic:ident)? => $type:ident
     ) => {
         paste! {
-            assert_inner!(enc $(#[$m])* [<ENCODING_ $stat>] => <$type>::ENCODING);
-            assert_inner!(enc $(#[$m])* [<ENCODING_ $stat _POINTER>] => <*const $type>::ENCODING);
-            assert_inner!(enc $(#[$m])* [<ENCODING_ $stat _POINTER_POINTER>] => <*const *const $type>::ENCODING);
-            assert_inner!(enc $(#[$m])* [<ENCODING_ $stat _POINTER_POINTER_POINTER>] => <*const *const *const $type>::ENCODING);
+            assert_inner!(ty $(#[$m])* [<ENCODING_ $stat>] => $type);
+            assert_inner!(ty $(#[$m])* [<ENCODING_ $stat _POINTER>] => *const $type);
+            assert_inner!(ty $(#[$m])* [<ENCODING_ $stat _POINTER_POINTER>] => *const *const $type);
+            assert_inner!(ty $(#[$m])* [<ENCODING_ $stat _POINTER_POINTER_POINTER>] => *const *const *const $type);
             $(assert_types!(#$should_atomic);)?
             assert_inner!(enc $(#[$m])* $(#[cfg($should_atomic)])? [<ENCODING_ $stat _ATOMIC>] => Encoding::Atomic(&<$type>::ENCODING));
             assert_inner!(enc $(#[$m])* $(#[cfg($should_atomic)])? [<ENCODING_ $stat _ATOMIC_POINTER>] => Encoding::Pointer(&Encoding::Atomic(&<$type>::ENCODING)));
