From 67cdcc2e12118becb823e20a40cc2687f2b8425a Mon Sep 17 00:00:00 2001
From: Adam Carpenter <53hornet@gmail.com>
Date: Wed, 27 Mar 2019 15:32:37 -0400
Subject: Started Rust in Action MEAP.
---
meap/meap-code/ch10/ch10-sjlj/src/main.rs | 105 ++++++++++++++++++++++++++++++
1 file changed, 105 insertions(+)
create mode 100644 meap/meap-code/ch10/ch10-sjlj/src/main.rs
(limited to 'meap/meap-code/ch10/ch10-sjlj/src')
diff --git a/meap/meap-code/ch10/ch10-sjlj/src/main.rs b/meap/meap-code/ch10/ch10-sjlj/src/main.rs
new file mode 100644
index 0000000..baac669
--- /dev/null
+++ b/meap/meap-code/ch10/ch10-sjlj/src/main.rs
@@ -0,0 +1,105 @@
+#![feature(link_llvm_intrinsics)]
+#![allow(non_camel_case_types)]
+#![cfg(not(windows))]
+
+extern crate libc;
+
+use libc::{SIGUSR1, SIGALRM, SIGHUP, SIGQUIT, SIGTERM};
+use std::mem;
+
+const JMP_BUF_WIDTH: usize = mem::size_of::<usize>() * 8;
+type jmp_buf = [i8; JMP_BUF_WIDTH];
+
+static mut SHUT_DOWN: bool = false;
+static mut RETURN_HERE: jmp_buf = [0; JMP_BUF_WIDTH];
+const MOCK_SIGNAL_AT: usize = 3;
+
+extern "C" {
+ #[link_name = "llvm.setjmp"]
+ pub fn setjmp(a: *mut i8) -> i32;
+
+ #[link_name = "llvm.longjmp"]
+ pub fn longjmp(a: *mut i8, b: i32) -> ();
+}
+
+#[inline]
+fn ptr_to_jmp_buf() -> *mut i8 {
+ unsafe { &RETURN_HERE as *const i8 as *mut i8 }
+}
+
+#[inline]
+fn return_early() {
+ let franken_pointer = ptr_to_jmp_buf();
+ unsafe { longjmp(franken_pointer, 1) };
+}
+
+fn register_signal_handler() {
+ unsafe {
+ libc::signal(SIGUSR1, handle_signals as usize); // <4>
+ }
+}
+
+#[allow(dead_code)] // <5>
+fn handle_signals(sig: i32) {
+ register_signal_handler(); // Immediately re-registering the signal handler minimizes the chances of a missing a signal.
+
+ let should_shut_down = match sig {
+ SIGHUP => false, // <7>
+ SIGALRM => false, // <7>
+ SIGTERM => true, // <7>
+ SIGQUIT => true, // <7>
+ SIGUSR1 => true,
+ _ => false, // <7>
+ };
+
+ unsafe {
+ // This unsafe block is required because we are modifying a global static variable.
+ SHUT_DOWN = should_shut_down;
+ }
+
+ return_early();
+}
+
+fn print_depth(depth: usize) {
+ for _ in 0..depth {
+ print!("#");
+ }
+ println!("");
+}
+
+fn dive(depth: usize, max_depth: usize) {
+ unsafe {
+ if SHUT_DOWN == true {
+ println!("!");
+ return;
+ }
+ }
+ print_depth(depth);
+
+ if depth >= max_depth {
+ return;
+ } else if depth == MOCK_SIGNAL_AT {
+ unsafe {
+ libc::raise(SIGUSR1);
+ }
+ } else {
+ dive(depth + 1, max_depth);
+ }
+ print_depth(depth);
+}
+
+fn main() {
+ const JUMP_SET: i32 = 0;
+
+ register_signal_handler();
+
+ let return_point = ptr_to_jmp_buf();
+ let rc = unsafe { setjmp(return_point) };
+ if rc == JUMP_SET {
+ dive(0, 10);
+ } else {
+ println!("early return!");
+ }
+
+ println!("finishing!")
+}
--
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