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