Update upstream source from tag 'upstream/1.52.1+dfsg1'

[rustc.git] / vendor / rustc-ap-rustc_data_structures / src / const_cstr.rs

diff --git a/vendor/rustc-ap-rustc_data_structures/src/const_cstr.rs b/vendor/rustc-ap-rustc_data_structures/src/const_cstr.rs
new file mode 100644 (file)
index 0000000..1ebcb87
--- /dev/null
+++ b/vendor/rustc-ap-rustc_data_structures/src/const_cstr.rs
@@ -0,0 +1,30 @@
+/// This macro creates a zero-overhead &CStr by adding a NUL terminator to
+/// the string literal passed into it at compile-time. Use it like:
+///
+/// ```
+///     let some_const_cstr = const_cstr!("abc");
+/// ```
+///
+/// The above is roughly equivalent to:
+///
+/// ```
+///     let some_const_cstr = CStr::from_bytes_with_nul(b"abc\0").unwrap()
+/// ```
+///
+/// Note that macro only checks the string literal for internal NULs if
+/// debug-assertions are enabled in order to avoid runtime overhead in release
+/// builds.
+#[macro_export]
+macro_rules! const_cstr {
+    ($s:expr) => {{
+        use std::ffi::CStr;
+
+        let str_plus_nul = concat!($s, "\0");
+
+        if cfg!(debug_assertions) {
+            CStr::from_bytes_with_nul(str_plus_nul.as_bytes()).unwrap()
+        } else {
+            unsafe { CStr::from_bytes_with_nul_unchecked(str_plus_nul.as_bytes()) }
+        }
+    }};
+}