use std::io::Write;
use deno_core::{JsRuntimeForSnapshot, RuntimeOptions};
use deno_core::v8;
fn main() {
// Box::leak pattern: RuntimeOptions::startup_snapshot requires &'static [u8].
// We leak the dynamically-loaded snapshot data, then reclaim after snapshot()
// consumes the runtime.
let leaked_snapshot: Option<(*mut [u8], &'static [u8])> =
match std::fs::read("snapshot.bin") {
Ok(snapshot) => {
eprintln!("creating isolate from snapshot...");
let ptr = Box::into_raw(snapshot.into_boxed_slice());
let static_ref: &'static [u8] = unsafe { &*ptr };
Some((ptr, static_ref))
}
Err(e) => {
if e.kind() == std::io::ErrorKind::NotFound {
eprintln!("snapshot file not found, creating new isolate...");
None
} else {
eprintln!("error: {}", e);
return;
}
}
};
let startup_snapshot = leaked_snapshot.as_ref().map(|(_, s)| *s);
let mut runtime = JsRuntimeForSnapshot::new(RuntimeOptions {
startup_snapshot,
..Default::default()
});
// Execute script and stringify result before consuming runtime for snapshot.
let code = r#"
try {
x = x + 1
} catch (e) {
x = 1
}
x;
"#;
match runtime.execute_script("<eval>", code.to_string()) {
Ok(global_value) => {
deno_core::scope!(scope, runtime);
let local = v8::Local::new(scope, global_value);
match local.to_string(scope) {
Some(s) => eprintln!("x = {}", s.to_rust_string_lossy(scope)),
None => {
eprintln!("Failed to convert result to string");
return;
}
}
}
Err(e) => {
eprintln!("eval error: {}", e);
return;
}
}
// Consume runtime to create snapshot.
let snapshot_data = runtime.snapshot();
// Reclaim leaked input snapshot memory (safe: runtime is consumed).
if let Some((ptr, _)) = leaked_snapshot {
unsafe { let _ = Box::from_raw(ptr); }
}
// Write snapshot to file
eprintln!("snapshot created");
eprintln!("writing snapshot to file snapshot.bin in current directory");
let mut file = match std::fs::File::create("snapshot.bin") {
Ok(f) => f,
Err(e) => {
eprintln!("Failed to create snapshot.bin: {}", e);
return;
}
};
if let Err(e) = file.write_all(&snapshot_data) {
eprintln!("Failed to write snapshot data: {}", e);
}
}
