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use crate::node::{BinEntry, Node, TreeNode};
use crate::raw::Table;
use crate::reclaim::{Guard, Linked, Shared};
use std::sync::atomic::Ordering;
#[derive(Debug)]
pub(crate) struct NodeIter<'g, K, V> {
/// Current table; update if resized
table: Option<&'g Linked<Table<K, V>>>,
stack: Option<Box<TableStack<'g, K, V>>>,
spare: Option<Box<TableStack<'g, K, V>>>,
/// The last bin entry iterated over
prev: Option<&'g Node<K, V>>,
/// Index of bin to use next
index: usize,
/// Current index of initial table
base_index: usize,
/// Index bound for inital table
base_limit: usize,
/// Initial table size
base_size: usize,
guard: &'g Guard<'g>,
}
impl<'g, K, V> NodeIter<'g, K, V> {
pub(crate) fn new(table: Shared<'g, Table<K, V>>, guard: &'g Guard<'_>) -> Self {
let (table, len) = if table.is_null() {
(None, 0)
} else {
// safety: flurry guarantees that a table read under a guard is never dropped or moved
// until after that guard is dropped.
let table = unsafe { table.deref() };
(Some(table), table.len())
};
Self {
table,
stack: None,
spare: None,
prev: None,
base_size: len,
base_index: 0,
index: 0,
base_limit: len,
guard,
}
}
fn push_state(&mut self, t: &'g Linked<Table<K, V>>, i: usize, n: usize) {
let mut s = self.spare.take();
if let Some(ref mut s) = s {
self.spare = s.next.take();
}
let target = TableStack {
table: t,
length: n,
index: i,
next: self.stack.take(),
};
self.stack = if let Some(mut s) = s {
*s = target;
Some(s)
} else {
Some(Box::new(target))
};
}
fn recover_state(&mut self, mut n: usize) {
while let Some(ref mut s) = self.stack {
if self.index + s.length < n {
// if we haven't checked the high "side" of this bucket,
// then do _not_ pop the stack frame,
// and instead moveon to that bin.
self.index += s.length;
break;
}
// we _are_ popping the stack
let mut s = self.stack.take().expect("while let Some");
n = s.length;
self.index = s.index;
self.table = Some(s.table);
self.stack = s.next.take();
// save stack frame for re-use
s.next = self.spare.take();
self.spare = Some(s);
}
if self.stack.is_none() {
// move to next "part" of the top-level bin in the largest table
self.index += self.base_size;
if self.index >= n {
// we've gone past the last part of this top-level bin,
// so move to the _next_ top-level bin.
self.base_index += 1;
self.index = self.base_index;
}
}
}
}
impl<'g, K, V> Iterator for NodeIter<'g, K, V> {
type Item = &'g Node<K, V>;
fn next(&mut self) -> Option<Self::Item> {
let mut e = None;
if let Some(prev) = self.prev {
let next = prev.next.load(Ordering::SeqCst, self.guard);
if !next.is_null() {
// we have to check if we are iterating over a regular bin or a
// TreeBin. the Java code gets away without this due to
// inheritance (everything is a node), but we have to explicitly
// check
// safety: flurry does not drop or move until after guard drop
match **unsafe { next.deref() } {
BinEntry::Node(ref node) => {
e = Some(node);
}
BinEntry::TreeNode(ref tree_node) => {
e = Some(&tree_node.node);
}
BinEntry::Moved | BinEntry::Tree(_) => {
unreachable!("Nodes can only point to Nodes or TreeNodes")
}
}
}
}
loop {
if e.is_some() {
self.prev = e;
return e;
}
// safety: flurry does not drop or move until after guard drop
if self.base_index >= self.base_limit
|| self.table.is_none()
|| self.table.as_ref().unwrap().len() <= self.index
{
self.prev = None;
return None;
}
let t = self.table.expect("is_none in if above");
let i = self.index;
let n = t.len();
let bin = t.bin(i, self.guard);
if !bin.is_null() {
// safety: flurry does not drop or move until after guard drop
let bin = unsafe { bin.deref() };
match **bin {
BinEntry::Moved => {
// recurse down into the target table
// safety: same argument as for following Moved in Table::find
self.table = Some(unsafe { t.next_table(self.guard).deref() });
self.prev = None;
// make sure we can get back "up" to where we're at
self.push_state(t, i, n);
continue;
}
BinEntry::Node(ref node) => {
e = Some(node);
}
BinEntry::Tree(ref tree_bin) => {
// since we want to iterate over all entries, TreeBins
// are also traversed via the `next` pointers of their
// contained node
e = Some(
// safety: `bin` was read under our guard, at which
// point the tree was valid. Since our guard marks
// the current thread as active, the TreeNodes remain valid for
// at least as long as we hold onto the guard.
// Structurally, TreeNodes always point to TreeNodes, so this is sound.
&unsafe {
TreeNode::get_tree_node(
tree_bin.first.load(Ordering::SeqCst, self.guard),
)
}
.node,
);
}
BinEntry::TreeNode(_) => unreachable!(
"The head of a bin cannot be a TreeNode directly without BinEntry::Tree"
),
}
}
if self.stack.is_some() {
self.recover_state(n);
} else {
self.index = i + self.base_size;
if self.index >= n {
self.base_index += 1;
self.index = self.base_index;
}
}
}
}
}
#[derive(Debug)]
struct TableStack<'g, K, V> {
length: usize,
index: usize,
table: &'g Linked<Table<K, V>>,
next: Option<Box<TableStack<'g, K, V>>>,
}
#[cfg(test)]
mod tests {
use super::*;
use crate::raw::Table;
use crate::reclaim::Atomic;
use parking_lot::Mutex;
#[test]
fn iter_new() {
let guard = unsafe { seize::Guard::unprotected() };
let iter = NodeIter::<usize, usize>::new(Shared::null(), &guard);
assert_eq!(iter.count(), 0);
}
#[test]
fn iter_empty() {
let collector = seize::Collector::new();
let table = Shared::boxed(Table::<usize, usize>::new(16, &collector), &collector);
let guard = collector.enter();
let iter = NodeIter::new(table, &guard);
assert_eq!(iter.count(), 0);
// safety: nothing holds on to references into the table any more
let mut t = unsafe { table.into_box() };
t.drop_bins();
}
#[test]
fn iter_simple() {
let collector = seize::Collector::new();
let mut bins = vec![Atomic::null(); 16];
bins[8] = Atomic::from(Shared::boxed(
BinEntry::Node(Node {
hash: 0,
key: 0usize,
value: Atomic::from(Shared::boxed(0usize, &collector)),
next: Atomic::null(),
lock: Mutex::new(()),
}),
&collector,
));
let table = Shared::boxed(Table::from(bins, &collector), &collector);
let guard = collector.enter();
{
let mut iter = NodeIter::new(table, &guard);
let e = iter.next().unwrap();
assert_eq!(e.key, 0);
assert!(iter.next().is_none());
}
// safety: nothing holds on to references into the table any more
let mut t = unsafe { table.into_box() };
t.drop_bins();
}
#[test]
fn iter_fw() {
// construct the forwarded-to table
let collector = seize::Collector::new();
let mut deep_bins = vec![Atomic::null(); 16];
deep_bins[8] = Atomic::from(Shared::boxed(
BinEntry::Node(Node {
hash: 0,
key: 0usize,
value: Atomic::from(Shared::boxed(0usize, &collector)),
next: Atomic::null(),
lock: Mutex::new(()),
}),
&collector,
));
let guard = collector.enter();
let deep_table = Shared::boxed(Table::from(deep_bins, &collector), &collector);
// construct the forwarded-from table
let mut bins = vec![Shared::null(); 16];
let table = Table::<usize, usize>::new(bins.len(), &collector);
for bin in &mut bins[8..] {
// this also sets table.next_table to deep_table
*bin = table.get_moved(deep_table, &guard);
}
// this cannot use Table::from(bins), since we need the table to get
// the Moved and set its next_table
for i in 0..bins.len() {
table.store_bin(i, bins[i]);
}
let table = Shared::boxed(table, &collector);
{
let mut iter = NodeIter::new(table, &guard);
let e = iter.next().unwrap();
assert_eq!(e.key, 0);
assert!(iter.next().is_none());
}
// safety: nothing holds on to references into the table any more
let mut t = unsafe { table.into_box() };
t.drop_bins();
// no one besides this test case uses deep_table
unsafe { deep_table.into_box() }.drop_bins();
}
}