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https://github.com/denoland/deno.git
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289 lines
8.3 KiB
Rust
289 lines
8.3 KiB
Rust
// Copyright 2018 the Deno authors. All rights reserved. MIT license.
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/*
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SharedQueue Binary Layout
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+-------------------------------+-------------------------------+
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| NUM_RECORDS (32) |
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+---------------------------------------------------------------+
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| NUM_SHIFTED_OFF (32) |
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+---------------------------------------------------------------+
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| HEAD (32) |
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+---------------------------------------------------------------+
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| OFFSETS (32) |
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+---------------------------------------------------------------+
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| RECORD_ENDS (*MAX_RECORDS) ...
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+---------------------------------------------------------------+
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| RECORDS (*MAX_RECORDS) ...
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+---------------------------------------------------------------+
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*/
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use crate::libdeno::deno_buf;
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use crate::libdeno::OpId;
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const MAX_RECORDS: usize = 100;
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/// Total number of records added.
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const INDEX_NUM_RECORDS: usize = 0;
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/// Number of records that have been shifted off.
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const INDEX_NUM_SHIFTED_OFF: usize = 1;
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/// The head is the number of initialized bytes in SharedQueue.
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/// It grows monotonically.
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const INDEX_HEAD: usize = 2;
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const INDEX_OFFSETS: usize = 3;
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const INDEX_RECORDS: usize = INDEX_OFFSETS + 2 * MAX_RECORDS;
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/// Byte offset of where the records begin. Also where the head starts.
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const HEAD_INIT: usize = 4 * INDEX_RECORDS;
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/// A rough guess at how big we should make the shared buffer in bytes.
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pub const RECOMMENDED_SIZE: usize = 128 * MAX_RECORDS;
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pub struct SharedQueue {
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bytes: Vec<u8>,
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}
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impl SharedQueue {
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pub fn new(len: usize) -> Self {
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let mut bytes = Vec::new();
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bytes.resize(HEAD_INIT + len, 0);
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let mut q = Self { bytes };
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q.reset();
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q
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}
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pub fn as_deno_buf(&self) -> deno_buf {
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let ptr = self.bytes.as_ptr();
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let len = self.bytes.len();
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unsafe { deno_buf::from_raw_parts(ptr, len) }
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}
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fn reset(&mut self) {
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debug!("rust:shared_queue:reset");
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let s: &mut [u32] = self.as_u32_slice_mut();
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s[INDEX_NUM_RECORDS] = 0;
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s[INDEX_NUM_SHIFTED_OFF] = 0;
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s[INDEX_HEAD] = HEAD_INIT as u32;
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}
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fn as_u32_slice(&self) -> &[u32] {
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let p = self.bytes.as_ptr();
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// Assert pointer is 32 bit aligned before casting.
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assert_eq!((p as usize) % std::mem::align_of::<u32>(), 0);
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#[allow(clippy::cast_ptr_alignment)]
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let p32 = p as *const u32;
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unsafe { std::slice::from_raw_parts(p32, self.bytes.len() / 4) }
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}
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fn as_u32_slice_mut(&mut self) -> &mut [u32] {
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let p = self.bytes.as_mut_ptr();
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// Assert pointer is 32 bit aligned before casting.
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assert_eq!((p as usize) % std::mem::align_of::<u32>(), 0);
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#[allow(clippy::cast_ptr_alignment)]
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let p32 = p as *mut u32;
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unsafe { std::slice::from_raw_parts_mut(p32, self.bytes.len() / 4) }
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}
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pub fn size(&self) -> usize {
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let s = self.as_u32_slice();
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(s[INDEX_NUM_RECORDS] - s[INDEX_NUM_SHIFTED_OFF]) as usize
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}
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fn num_records(&self) -> usize {
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let s = self.as_u32_slice();
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s[INDEX_NUM_RECORDS] as usize
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}
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fn head(&self) -> usize {
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let s = self.as_u32_slice();
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s[INDEX_HEAD] as usize
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}
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fn num_shifted_off(&self) -> usize {
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let s = self.as_u32_slice();
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s[INDEX_NUM_SHIFTED_OFF] as usize
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}
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fn set_meta(&mut self, index: usize, end: usize, op_id: OpId) {
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let s = self.as_u32_slice_mut();
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s[INDEX_OFFSETS + 2 * index] = end as u32;
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s[INDEX_OFFSETS + 2 * index + 1] = op_id;
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}
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#[cfg(test)]
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fn get_meta(&self, index: usize) -> Option<(OpId, usize)> {
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if index < self.num_records() {
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let s = self.as_u32_slice();
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let end = s[INDEX_OFFSETS + 2 * index] as usize;
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let op_id = s[INDEX_OFFSETS + 2 * index + 1];
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Some((op_id, end))
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} else {
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None
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}
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}
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#[cfg(test)]
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fn get_offset(&self, index: usize) -> Option<usize> {
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if index < self.num_records() {
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Some(if index == 0 {
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HEAD_INIT
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} else {
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let s = self.as_u32_slice();
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s[INDEX_OFFSETS + 2 * (index - 1)] as usize
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})
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} else {
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None
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}
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}
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/// Returns none if empty.
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#[cfg(test)]
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pub fn shift(&mut self) -> Option<(OpId, &[u8])> {
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let u32_slice = self.as_u32_slice();
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let i = u32_slice[INDEX_NUM_SHIFTED_OFF] as usize;
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if self.size() == 0 {
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assert_eq!(i, 0);
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return None;
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}
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let off = self.get_offset(i).unwrap();
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let (op_id, end) = self.get_meta(i).unwrap();
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if self.size() > 1 {
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let u32_slice = self.as_u32_slice_mut();
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u32_slice[INDEX_NUM_SHIFTED_OFF] += 1;
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} else {
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self.reset();
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}
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println!(
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"rust:shared_queue:shift: num_records={}, num_shifted_off={}, head={}",
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self.num_records(),
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self.num_shifted_off(),
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self.head()
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);
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Some((op_id, &self.bytes[off..end]))
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}
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/// Because JS-side may cast `record` to Int32Array it is required
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/// that `record`'s length is divisible by 4.
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pub fn push(&mut self, op_id: OpId, record: &[u8]) -> bool {
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let off = self.head();
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let end = off + record.len();
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debug!(
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"rust:shared_queue:pre-push: op={}, off={}, end={}, len={}",
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op_id,
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off,
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end,
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record.len()
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);
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assert_eq!(record.len() % 4, 0);
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let index = self.num_records();
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if end > self.bytes.len() || index >= MAX_RECORDS {
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debug!("WARNING the sharedQueue overflowed");
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return false;
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}
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self.set_meta(index, end, op_id);
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assert_eq!(end - off, record.len());
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self.bytes[off..end].copy_from_slice(record);
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let u32_slice = self.as_u32_slice_mut();
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u32_slice[INDEX_NUM_RECORDS] += 1;
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u32_slice[INDEX_HEAD] = end as u32;
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debug!(
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"rust:shared_queue:push: num_records={}, num_shifted_off={}, head={}",
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self.num_records(),
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self.num_shifted_off(),
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self.head()
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);
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true
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::ops::Buf;
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#[test]
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fn basic() {
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let mut q = SharedQueue::new(RECOMMENDED_SIZE);
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let h = q.head();
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assert!(h > 0);
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let r = vec![1u8, 2, 3, 4].into_boxed_slice();
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let len = r.len() + h;
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assert!(q.push(0, &r));
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assert_eq!(q.head(), len);
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let r = vec![5, 6, 7, 8].into_boxed_slice();
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assert!(q.push(0, &r));
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let r = vec![9, 10, 11, 12].into_boxed_slice();
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assert!(q.push(0, &r));
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assert_eq!(q.num_records(), 3);
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assert_eq!(q.size(), 3);
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let (_op_id, r) = q.shift().unwrap();
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assert_eq!(r, vec![1, 2, 3, 4].as_slice());
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assert_eq!(q.num_records(), 3);
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assert_eq!(q.size(), 2);
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let (_op_id, r) = q.shift().unwrap();
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assert_eq!(r, vec![5, 6, 7, 8].as_slice());
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assert_eq!(q.num_records(), 3);
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assert_eq!(q.size(), 1);
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let (_op_id, r) = q.shift().unwrap();
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assert_eq!(r, vec![9, 10, 11, 12].as_slice());
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assert_eq!(q.num_records(), 0);
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assert_eq!(q.size(), 0);
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assert!(q.shift().is_none());
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assert!(q.shift().is_none());
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assert_eq!(q.num_records(), 0);
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assert_eq!(q.size(), 0);
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}
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fn alloc_buf(byte_length: usize) -> Buf {
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let mut v = Vec::new();
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v.resize(byte_length, 0);
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v.into_boxed_slice()
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}
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#[test]
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fn overflow() {
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let mut q = SharedQueue::new(RECOMMENDED_SIZE);
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assert!(q.push(0, &alloc_buf(RECOMMENDED_SIZE - 4)));
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assert_eq!(q.size(), 1);
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assert!(!q.push(0, &alloc_buf(8)));
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assert_eq!(q.size(), 1);
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assert!(q.push(0, &alloc_buf(4)));
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assert_eq!(q.size(), 2);
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let (_op_id, buf) = q.shift().unwrap();
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assert_eq!(buf.len(), RECOMMENDED_SIZE - 4);
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assert_eq!(q.size(), 1);
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assert!(!q.push(0, &alloc_buf(4)));
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let (_op_id, buf) = q.shift().unwrap();
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assert_eq!(buf.len(), 4);
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assert_eq!(q.size(), 0);
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}
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#[test]
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fn full_records() {
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let mut q = SharedQueue::new(RECOMMENDED_SIZE);
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for _ in 0..MAX_RECORDS {
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assert!(q.push(0, &alloc_buf(4)))
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}
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assert_eq!(q.push(0, &alloc_buf(4)), false);
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// Even if we shift one off, we still cannot push a new record.
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let _ignored = q.shift().unwrap();
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assert_eq!(q.push(0, &alloc_buf(4)), false);
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}
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#[test]
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#[should_panic]
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fn bad_buf_length() {
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let mut q = SharedQueue::new(RECOMMENDED_SIZE);
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// check that `record` that has length not a multiple of 4 will cause panic
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q.push(0, &alloc_buf(3));
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}
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}
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