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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
// Do not add flatbuffer dependencies to this module.
//! Connects to js/dispatch_minimal.ts sendAsyncMinimal This acts as a faster
//! alternative to flatbuffers using a very simple list of int32s to lay out
//! messages. The first i32 is used to determine if a message a flatbuffer
//! message or a "minimal" message.
use deno::Buf;
use deno::CoreOp;
use deno::ErrBox;
use deno::Op;
use deno::PinnedBuf;
use futures::Future;
pub type MinimalOp = dyn Future<Item = i32, Error = ErrBox> + Send;
pub type Dispatcher = fn(i32, Option<PinnedBuf>) -> Box<MinimalOp>;
#[derive(Copy, Clone, Debug, PartialEq)]
// This corresponds to RecordMinimal on the TS side.
pub struct Record {
pub promise_id: i32,
pub arg: i32,
pub result: i32,
}
impl Into<Buf> for Record {
fn into(self) -> Buf {
let vec = vec![self.promise_id, self.arg, self.result];
let buf32 = vec.into_boxed_slice();
let ptr = Box::into_raw(buf32) as *mut [u8; 3 * 4];
unsafe { Box::from_raw(ptr) }
}
}
pub fn parse_min_record(bytes: &[u8]) -> Option<Record> {
if bytes.len() % std::mem::size_of::<i32>() != 0 {
return None;
}
let p = bytes.as_ptr();
#[allow(clippy::cast_ptr_alignment)]
let p32 = p as *const i32;
let s = unsafe { std::slice::from_raw_parts(p32, bytes.len() / 4) };
if s.len() != 3 {
return None;
}
let ptr = s.as_ptr();
let ints = unsafe { std::slice::from_raw_parts(ptr, 3) };
Some(Record {
promise_id: ints[0],
arg: ints[1],
result: ints[2],
})
}
#[test]
fn test_parse_min_record() {
let buf = vec![1, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0];
assert_eq!(
parse_min_record(&buf),
Some(Record {
promise_id: 1,
arg: 3,
result: 4,
})
);
let buf = vec![];
assert_eq!(parse_min_record(&buf), None);
let buf = vec![5];
assert_eq!(parse_min_record(&buf), None);
}
pub fn minimal_op(
d: Dispatcher,
) -> impl Fn(&[u8], Option<PinnedBuf>) -> CoreOp {
move |control: &[u8], zero_copy: Option<PinnedBuf>| {
let mut record = parse_min_record(control).unwrap();
let is_sync = record.promise_id == 0;
let rid = record.arg;
let min_op = d(rid, zero_copy);
// Convert to CoreOp
let fut = Box::new(min_op.then(move |result| -> Result<Buf, ()> {
match result {
Ok(r) => {
record.result = r;
}
Err(err) => {
// TODO(ry) The dispatch_minimal doesn't properly pipe errors back to
// the caller.
debug!("swallowed err {}", err);
record.result = -1;
}
}
Ok(record.into())
}));
if is_sync {
// Warning! Possible deadlocks can occur if we try to wait for a future
// while in a future. The safe but expensive alternative is to use
// tokio_util::block_on.
// This block is only exercised for readSync and writeSync, which I think
// works since they're simple polling futures.
Op::Sync(fut.wait().unwrap())
} else {
Op::Async(fut)
}
}
}
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