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//! Forward batch iteration methods for maximum performance.
use std::mem::MaybeUninit;
use crate::alloc_trait::TreeAllocator;
use crate::leaf15::LeafNode15;
use crate::policy::LeafPolicy;
use crate::policy::RefPolicy as RefLeafPolicy;
use super::RangeIter;
use crate::tree::range::forward_ctx::{
IntraLeafCopyStrategy, IntraLeafRefStrategy, ValuesOnlyStrategy,
};
use crate::tree::range::scan_state::{ScanState, StepResult};
impl<P, A> RangeIter<'_, '_, P, A>
where
P: LeafPolicy,
A: TreeAllocator<P>,
{
/// Zero-allocation iteration with a visitor closure.
#[inline]
#[must_use = "returns the number of entries visited"]
pub fn for_each<F>(mut self, mut visitor: F) -> usize
where
F: FnMut(&[u8], P::Output) -> bool,
{
if self.fwd.flags.exhausted() {
return 0;
}
if !self.fwd.flags.initialized() {
self.initialize();
if self.fwd.flags.exhausted() {
return 0;
}
}
let mut count: usize = 0;
'l: loop {
if let Some(entry) = self.fwd.advance_no_alloc(&self.end_bound, self.guard) {
count += 1;
if !visitor(entry.0, entry.1) {
break 'l;
}
} else {
break 'l;
}
}
count
}
/// Zero-copy iteration with borrowed `&P::Value` references.
///
/// Eliminates Arc increment per entry vs [`for_each`](Self::for_each).
/// References are valid only within the callback scope.
#[inline]
#[must_use = "returns the number of entries visited"]
pub fn for_each_ref<F>(mut self, mut visitor: F) -> usize
where
P: RefLeafPolicy,
F: FnMut(&[u8], &P::Value) -> bool,
{
if self.fwd.flags.exhausted() {
return 0;
}
if !self.fwd.flags.initialized() {
self.initialize();
if self.fwd.flags.exhausted() {
return 0;
}
}
let mut count: usize = 0;
'l: loop {
if let Some((key, value_ref)) =
self.fwd.advance_no_alloc_ref(&self.end_bound, self.guard)
{
count += 1;
if !visitor(key, value_ref) {
break 'l;
}
} else {
break 'l;
}
}
count
}
/// Batch scan with zero-copy references and reduced dispatch overhead.
///
/// Inlines the `FindNext` -> `Emit` hot path, eliminating `match state {}`
/// dispatch. Uses per-entry OCC validation and handles layer transitions
/// by dynamically switching to multi-layer mode on `Down`.
#[inline]
#[must_use = "returns the number of entries visited"]
pub fn for_each_batch_ref<F>(mut self, mut visitor: F) -> usize
where
P: RefLeafPolicy,
F: FnMut(&[u8], &P::Value) -> bool,
{
if self.fwd.flags.exhausted() {
return 0;
}
if !self.fwd.flags.initialized() {
self.initialize();
if self.fwd.flags.exhausted() {
return 0;
}
}
let mut count: usize = 0;
// Handle initial Emit state from initialize() if present
if self.fwd.state == ScanState::Emit {
if let Some(snapshot) = self.fwd.snapshot.take() {
// SAFETY: CursorKey invariant guarantees offset + len <= MAX_KEY_LENGTH
let key: &[u8] = unsafe { self.fwd.cursor_key.full_key_unchecked() };
if !self.end_bound.contains(key) {
self.fwd.flags.mark_exhausted();
return 0;
}
// SAFETY: Guard protects the output. output_as_ref_sound
// uses atomic read for write-through types, avoiding
// aliasing violation with concurrent write_through_update.
let mut scratch: MaybeUninit<P::Value> = MaybeUninit::uninit();
let value_ref: &P::Value =
unsafe { P::output_as_ref_sound(&snapshot.value, &mut scratch) };
count += 1;
let should_continue: bool = visitor(key, value_ref);
if !should_continue {
return count;
}
}
self.fwd.state = ScanState::FindNext;
}
// Main batch loop
loop {
// Handle rare states (layer transitions, retries, exhaustion)
match self.fwd.step_transitions(self.guard) {
StepResult::Exhausted => return count,
StepResult::Continue => continue,
StepResult::Ready => {}
}
if self.fwd.stack.is_null() {
if self.fwd.layer_stack.is_empty() {
self.fwd.flags.mark_exhausted();
return count;
}
self.fwd.state = ScanState::Up;
continue;
}
let leaf: &LeafNode15<P> = unsafe { self.fwd.stack.leaf_ref() };
if leaf.version().is_deleted() {
self.fwd.state = ScanState::Retry;
continue;
}
// Hot path: FindNext -> Emit (inlined)
let (new_state, snapshot_ptr) = if self.fwd.flags.needs_duplicate_check() {
self.fwd.flags.clear_duplicate_check();
self.fwd.find_next_with_dup_check_ptr(self.guard)
} else {
self.fwd.find_next_ptr(self.guard)
};
self.fwd.state = new_state;
match new_state {
ScanState::Emit => {
if let Some(snap) = snapshot_ptr {
// SAFETY: CursorKey invariant guarantees offset + len <= MAX_KEY_LENGTH
let key: &[u8] = unsafe { self.fwd.cursor_key.full_key_unchecked() };
if !self.end_bound.contains(key) {
self.fwd.flags.mark_exhausted();
return count;
}
count += 1;
self.fwd.state = ScanState::FindNext;
// SAFETY: Version validated, guard held, snap pointer valid.
let mut scratch: MaybeUninit<P::Value> = MaybeUninit::uninit();
let value_ref: &P::Value =
unsafe { snap.resolve_value_ref::<P>(&mut scratch) };
let should_continue: bool = visitor(key, value_ref);
if !should_continue {
return count;
}
}
}
ScanState::FindNext | ScanState::Down | ScanState::Up | ScanState::Retry => {}
}
}
}
/// Intra-leaf batch iteration with zero-copy references.
///
/// Processes entire leaves in tight loops with single OCC validation per
/// leaf. Falls back to state machine for sublayer transitions.
#[inline]
#[must_use = "returns the number of entries visited"]
pub fn for_each_intra_leaf_batch_ref<F>(mut self, mut visitor: F) -> usize
where
P: RefLeafPolicy,
F: FnMut(&[u8], &P::Value) -> bool,
{
if self.fwd.flags.exhausted() {
return 0;
}
if !self.fwd.flags.initialized() {
self.initialize();
if self.fwd.flags.exhausted() {
return 0;
}
}
let end_bound_ikey: Option<u64> = self.end_bound.extract_ikey();
self.fwd.run_batch(
&mut IntraLeafRefStrategy::new(&mut visitor, end_bound_ikey),
&self.end_bound,
self.guard,
)
}
/// Intra-leaf batch iteration returning values by copy.
///
/// Works for ALL `LeafPolicy` types including true-inline storage.
/// Same leaf-level batching as `for_each_intra_leaf_batch_ref` but returns
/// `P::Output` by value. For Arc storage where zero-copy matters, prefer
/// the `_ref` variant.
#[inline]
#[must_use = "returns the number of entries visited"]
pub fn for_each_intra_leaf_batch<F>(mut self, mut visitor: F) -> usize
where
F: FnMut(&[u8], P::Output) -> bool,
{
if self.fwd.flags.exhausted() {
return 0;
}
if !self.fwd.flags.initialized() {
self.initialize();
if self.fwd.flags.exhausted() {
return 0;
}
}
let end_bound_ikey: Option<u64> = self.end_bound.extract_ikey();
self.fwd.run_batch(
&mut IntraLeafCopyStrategy::new(&mut visitor, end_bound_ikey),
&self.end_bound,
self.guard,
)
}
/// Value-only batch iteration.
///
/// ```no_run
/// use masstree::MassTree;
/// let tree: MassTree<u64> = MassTree::new();
/// let guard = tree.guard();
/// let mut sum = 0u64;
/// tree.iter(&guard).for_each_values_batch(|value| {
/// sum += value;
/// true
/// });
/// ```
#[inline]
#[must_use = "returns the number of entries visited"]
pub fn for_each_values_batch<F>(mut self, mut visitor: F) -> usize
where
F: FnMut(P::Output) -> bool,
{
if self.fwd.flags.exhausted() {
return 0;
}
if !self.fwd.flags.initialized() {
self.initialize();
if self.fwd.flags.exhausted() {
return 0;
}
}
self.fwd.run_batch(
&mut ValuesOnlyStrategy::new(&mut visitor),
&self.end_bound,
self.guard,
)
}
/// Fallible iteration with zero-copy references.
///
/// ```ignore
/// let result = tree.iter(&guard).try_for_each_ref(|key, value| {
/// writer.write_entry(key, value)?;
/// Ok(true)
/// });
/// ```
///
/// # Errors
///
/// Returns the visitor's error.
#[inline]
#[must_use = "returns the count or error - check the result"]
pub fn try_for_each_ref<F, E>(mut self, mut visitor: F) -> Result<usize, E>
where
P: RefLeafPolicy,
F: FnMut(&[u8], &P::Value) -> Result<bool, E>,
{
if self.fwd.flags.exhausted() {
return Ok(0);
}
if !self.fwd.flags.initialized() {
self.initialize();
if self.fwd.flags.exhausted() {
return Ok(0);
}
}
let mut count: usize = 0;
loop {
if let Some((key, value_ref)) =
self.fwd.advance_no_alloc_ref(&self.end_bound, self.guard)
{
count += 1;
match visitor(key, value_ref) {
Ok(true) => {}
Ok(false) => return Ok(count),
Err(e) => return Err(e),
}
} else {
return Ok(count);
}
}
}
}