1 files changed, 101 insertions, 0 deletions
diff --git a/mozglue/static/rust/lib.rs b/mozglue/static/rust/lib.rs
new file mode 100644
index 0000000000..7faf9d3873
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+++ b/mozglue/static/rust/lib.rs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use arrayvec::{Array, ArrayString};
+use std::cmp;
+use std::ops::Deref;
+use std::os::raw::c_char;
+use std::os::raw::c_int;
+use std::panic;
+
+#[link(name = "wrappers")]
+extern "C" {
+    // We can't use MOZ_Crash directly because it may be weakly linked
+    // and rust can't handle that.
+    fn RustMozCrash(filename: *const c_char, line: c_int, reason: *const c_char) -> !;
+}
+
+/// Truncate a string at the closest unicode character boundary
+/// ```
+/// assert_eq!(str_truncate_valid("éà", 3), "é");
+/// assert_eq!(str_truncate_valid("éà", 4), "éè");
+/// ```
+fn str_truncate_valid(s: &str, mut mid: usize) -> &str {
+    loop {
+        if let Some(res) = s.get(..mid) {
+            return res;
+        }
+        mid -= 1;
+    }
+}
+
+/// Similar to ArrayString, but with terminating nul character.
+#[derive(Debug, PartialEq)]
+struct ArrayCString<A: Array<Item = u8> + Copy> {
+    inner: ArrayString<A>,
+}
+
+impl<S: AsRef<str>, A: Array<Item = u8> + Copy> From<S> for ArrayCString<A> {
+    /// Contrary to ArrayString::from, truncates at the closest unicode
+    /// character boundary.
+    /// ```
+    /// assert_eq!(ArrayCString::<[_; 4]>::from("éà"),
+    ///            ArrayCString::<[_; 4]>::from("é"));
+    /// assert_eq!(&*ArrayCString::<[_; 4]>::from("éà"), "é\0");
+    /// ```
+    fn from(s: S) -> Self {
+        let s = s.as_ref();
+        let len = cmp::min(s.len(), A::CAPACITY - 1);
+        let mut result = Self {
+            inner: ArrayString::from(str_truncate_valid(s, len)).unwrap(),
+        };
+        result.inner.push('\0');
+        result
+    }
+}
+
+impl<A: Array<Item = u8> + Copy> Deref for ArrayCString<A> {
+    type Target = str;
+
+    fn deref(&self) -> &str {
+        self.inner.as_str()
+    }
+}
+
+fn panic_hook(info: &panic::PanicInfo) {
+    // Try to handle &str/String payloads, which should handle 99% of cases.
+    let payload = info.payload();
+    let message = if let Some(s) = payload.downcast_ref::<&str>() {
+        s
+    } else if let Some(s) = payload.downcast_ref::<String>() {
+        s.as_str()
+    } else {
+        // Not the most helpful thing, but seems unlikely to happen
+        // in practice.
+        "Unhandled rust panic payload!"
+    };
+    let (filename, line) = if let Some(loc) = info.location() {
+        (loc.file(), loc.line())
+    } else {
+        ("unknown.rs", 0)
+    };
+    // Copy the message and filename to the stack in order to safely add
+    // a terminating nul character (since rust strings don't come with one
+    // and RustMozCrash wants one).
+    let message = ArrayCString::<[_; 512]>::from(message);
+    let filename = ArrayCString::<[_; 512]>::from(filename);
+    unsafe {
+        RustMozCrash(
+            filename.as_ptr() as *const c_char,
+            line as c_int,
+            message.as_ptr() as *const c_char,
+        );
+    }
+}
+
+/// Configure a panic hook to redirect rust panics to MFBT's MOZ_Crash.
+#[no_mangle]
+pub extern "C" fn install_rust_panic_hook() {
+    panic::set_hook(Box::new(panic_hook));
+}