1 files changed, 81 insertions, 0 deletions
diff --git a/compiler/rustc_data_structures/src/small_c_str.rs b/compiler/rustc_data_structures/src/small_c_str.rs
new file mode 100644
index 000000000..3a8ab8ff9
--- /dev/null
+++ b/compiler/rustc_data_structures/src/small_c_str.rs
@@ -0,0 +1,81 @@
+use std::ffi;
+use std::ops::Deref;
+
+use smallvec::SmallVec;
+
+#[cfg(test)]
+mod tests;
+
+const SIZE: usize = 36;
+
+/// Like SmallVec but for C strings.
+#[derive(Clone)]
+pub struct SmallCStr {
+    data: SmallVec<[u8; SIZE]>,
+}
+
+impl SmallCStr {
+    #[inline]
+    pub fn new(s: &str) -> SmallCStr {
+        let len = s.len();
+        let len1 = len + 1;
+        let data = if len < SIZE {
+            let mut buf = [0; SIZE];
+            buf[..len].copy_from_slice(s.as_bytes());
+            SmallVec::from_buf_and_len(buf, len1)
+        } else {
+            let mut data = Vec::with_capacity(len1);
+            data.extend_from_slice(s.as_bytes());
+            data.push(0);
+            SmallVec::from_vec(data)
+        };
+        if let Err(e) = ffi::CStr::from_bytes_with_nul(&data) {
+            panic!("The string \"{}\" cannot be converted into a CStr: {}", s, e);
+        }
+        SmallCStr { data }
+    }
+
+    #[inline]
+    pub fn new_with_nul(s: &str) -> SmallCStr {
+        let b = s.as_bytes();
+        if let Err(e) = ffi::CStr::from_bytes_with_nul(b) {
+            panic!("The string \"{}\" cannot be converted into a CStr: {}", s, e);
+        }
+        SmallCStr { data: SmallVec::from_slice(s.as_bytes()) }
+    }
+
+    #[inline]
+    pub fn as_c_str(&self) -> &ffi::CStr {
+        unsafe { ffi::CStr::from_bytes_with_nul_unchecked(&self.data) }
+    }
+
+    #[inline]
+    pub fn len_with_nul(&self) -> usize {
+        self.data.len()
+    }
+
+    pub fn spilled(&self) -> bool {
+        self.data.spilled()
+    }
+}
+
+impl Deref for SmallCStr {
+    type Target = ffi::CStr;
+
+    #[inline]
+    fn deref(&self) -> &ffi::CStr {
+        self.as_c_str()
+    }
+}
+
+impl<'a> FromIterator<&'a str> for SmallCStr {
+    fn from_iter<T: IntoIterator<Item = &'a str>>(iter: T) -> Self {
+        let mut data =
+            iter.into_iter().flat_map(|s| s.as_bytes()).copied().collect::<SmallVec<_>>();
+        data.push(0);
+        if let Err(e) = ffi::CStr::from_bytes_with_nul(&data) {
+            panic!("The iterator {:?} cannot be converted into a CStr: {}", data, e);
+        }
+        Self { data }
+    }
+}