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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));
}
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